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diff --git a/doc/html/chrono/users_guide.html b/doc/html/chrono/users_guide.html new file mode 100755 index 0000000000..1f849880e0 --- /dev/null +++ b/doc/html/chrono/users_guide.html @@ -0,0 +1,2251 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> +<title>User's Guide</title> +<link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> +<meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> +<link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> +<link rel="up" href="../chrono.html" title="Chapter 4. Boost.Chrono 1.2.1"> +<link rel="prev" href="../chrono.html" title="Chapter 4. Boost.Chrono 1.2.1"> +<link rel="next" href="reference.html" title="Reference"> +</head> +<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> +<table cellpadding="2" width="100%"><tr> +<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../boost.png"></td> +<td align="center"><a href="../../../index.html">Home</a></td> +<td align="center"><a href="../../../libs/libraries.htm">Libraries</a></td> +<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> +<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> +<td align="center"><a href="../../../more/index.htm">More</a></td> +</tr></table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="../chrono.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../chrono.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="reference.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> +</div> +<div class="section"> +<div class="titlepage"><div><div><h2 class="title" style="clear: both"> +<a name="chrono.users_guide"></a><a class="link" href="users_guide.html" title="User's Guide">User's Guide</a> +</h2></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.getting_started">Getting Started</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial">Tutorial</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples">Examples</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.ext_references">External Resources</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="chrono.users_guide.getting_started"></a><a class="link" href="users_guide.html#chrono.users_guide.getting_started" title="Getting Started">Getting Started</a> +</h3></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.getting_started.install">Installing + Chrono</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.getting_started.hello_world__">Hello + World! </a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.getting_started.install"></a><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install" title="Installing Chrono">Installing + Chrono</a> +</h4></div></div></div> +<h6> +<a name="chrono.users_guide.getting_started.install.h0"></a> + <span><a name="chrono.users_guide.getting_started.install.getting__emphasis_role__bold__boost_chrono__emphasis__"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.getting__emphasis_role__bold__boost_chrono__emphasis__">Getting + <span class="bold"><strong>Boost.Chrono</strong></span> </a> + </h6> +<p> + <span class="bold"><strong>Boost.Chrono</strong></span> is in the latest Boost release + in the folder <code class="computeroutput"><span class="special">/</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span></code>. + Documentation, tests and examples folder are at <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">libs</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span></code>. + </p> +<p> + You can also access the latest (unstable?) state from the <a href="https://svn.boost.org/svn/boost-trunk" target="_top">Boost + trunk</a> directories boost/chrono and libs/chrono. Just go to <a href="http://svn.boost.org/trac/boost/wiki/BoostSubversion" target="_top">here</a> + and follow the instructions there for anonymous SVN access. + </p> +<h6> +<a name="chrono.users_guide.getting_started.install.h1"></a> + <span><a name="chrono.users_guide.getting_started.install.where_to_install_boost_chrono__"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.where_to_install_boost_chrono__">Where + to install Boost.Chrono? </a> + </h6> +<p> + The simple way is to decompress (or checkout from SVN) the files in your + BOOST_ROOT directory. + </p> +<h6> +<a name="chrono.users_guide.getting_started.install.h2"></a> + <span><a name="chrono.users_guide.getting_started.install.building_boost_chrono_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.building_boost_chrono_">Building + Boost.Chrono </a> + </h6> +<p> + <span class="bold"><strong>Boost.Chrono</strong></span> can be configured as a header-only + library. When <a class="link" href="reference.html#chrono.reference.cpp0x.chrono_chrono_hpp.conf.header_only" title="How to Build Boost.Chrono as a Header Only Library?"><code class="computeroutput"><span class="identifier">BOOST_CHRONO_HEADER_ONLY</span></code></a> is defined + the Boost.Chrono is a header-only library. Otherwise is not a header only + library and you need to compile it and build the library before use, for + example using: + </p> +<pre class="programlisting"><span class="identifier">bjam</span> <span class="identifier">libs</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">build</span> +</pre> +<h6> +<a name="chrono.users_guide.getting_started.install.h3"></a> + <span><a name="chrono.users_guide.getting_started.install.requirements"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.requirements">Requirements</a> + </h6> +<p> + In particular, <span class="bold"><strong>Boost.Chrono</strong></span> depends on: + </p> +<div class="variablelist"> +<p class="title"><b></b></p> +<dl> +<dt><span class="term"><a href="http://www.boost.org/libs/config" target="_top"><span class="bold"><strong>Boost.Config</strong></span></a></span></dt> +<dd><p> + for configuration purposes, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/exception" target="_top"><span class="bold"><strong>Boost.Exception</strong></span></a></span></dt> +<dd><p> + for throw_exception, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/integer" target="_top"><span class="bold"><strong>Boost.Integer</strong></span></a></span></dt> +<dd><p> + for cstdint conformance, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/mpl" target="_top"><span class="bold"><strong>Boost.MPL</strong></span></a></span></dt> +<dd><p> + for MPL Assert and bool, logical ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/operators" target="_top"><span class="bold"><strong>Boost.Operators</strong></span></a></span></dt> +<dd><p> + for operators, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/ratio" target="_top"><span class="bold"><strong>Boost.Ratio</strong></span></a></span></dt> +<dd><p> + for ratio, milli, micro, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/system" target="_top"><span class="bold"><strong>Boost.System</strong></span></a></span></dt> +<dd><p> + for error_code, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/type_traits" target="_top"><span class="bold"><strong>Boost.TypeTraits</strong></span></a></span></dt> +<dd><p> + for is_base, is_convertible, common_type, ... + </p></dd> +<dt><span class="term"><a href="http://www.boost.org/libs/utility" target="_top"><span class="bold"><strong>Boost.Utility/EnableIf</strong></span></a></span></dt> +<dd><p> + for enable_if, ... + </p></dd> +</dl> +</div> +<h6> +<a name="chrono.users_guide.getting_started.install.h4"></a> + <span><a name="chrono.users_guide.getting_started.install.building_an_executable_that_uses_boost_chrono_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.building_an_executable_that_uses_boost_chrono_">Building + an Executable that Uses Boost.Chrono </a> + </h6> +<p> + In addition to link with the <span class="bold"><strong>Boost.Chrono</strong></span> + library you need also to link with the <span class="bold"><strong>Boost.System</strong></span> + library. Once <span class="bold"><strong>Boost.System</strong></span> will be configurable + to be a header only using <code class="computeroutput"><span class="identifier">BOOST_SYSTEM_INLINED</span></code> + you will no need to link with it. + </p> +<h6> +<a name="chrono.users_guide.getting_started.install.h5"></a> + <span><a name="chrono.users_guide.getting_started.install.exception_safety_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.exception_safety_">Exception + safety </a> + </h6> +<p> + All functions in the library are exception-neutral and provide strong guarantee + of exception safety as long as the underlying parameters provide it. + </p> +<h6> +<a name="chrono.users_guide.getting_started.install.h6"></a> + <span><a name="chrono.users_guide.getting_started.install.thread_safety_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.thread_safety_">Thread + safety </a> + </h6> +<p> + All functions in the library are thread-unsafe except when noted explicitly. + </p> +<p> + As Boost.Chrono doesn't use mutable global variables the thread-safety + analysis is limited to the access to each instance variable. It is not + thread safe to use a function that modifies the access to a user variable + if another can be reading or writing it. + </p> +<h6> +<a name="chrono.users_guide.getting_started.install.h7"></a> + <span><a name="chrono.users_guide.getting_started.install.tested_compilers_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.tested_compilers_">Tested + compilers </a> + </h6> +<p> + The implementation will eventually work with most C++03 conforming compilers. + Currently I use to test with on: + </p> +<p> + Windows with + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + MSVC 10.0 + </li></ul></div> +<p> + Cygwin 1.7 with + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + GCC 4.3.4 + </li></ul></div> +<p> + MinGW with + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + GCC 4.5.0 + </li> +<li class="listitem"> + GCC 4.5.0 -std=c++0x + </li> +<li class="listitem"> + GCC 4.5.2 + </li> +<li class="listitem"> + GCC 4.5.2 -std=c++0x + </li> +<li class="listitem"> + GCC 4.6.0 + </li> +<li class="listitem"> + GCC 4.6.0 -std=c++0x + </li> +</ul></div> +<p> + OsX with + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + GCC 4.1.2 + </li> +<li class="listitem"> + clang 1.6 + </li> +<li class="listitem"> + clang 2.9 + </li> +<li class="listitem"> + clang 2.9 -std=c++0x + </li> +</ul></div> +<p> + The committed code is tested with much more compilers. There are two compilers + (VACPP and Borland) that don't provide the needed features. Other as Intel + and Sun have some issues with i/o. While everything compiles and link correctly, + there are some runtime issues I have not cached yet. See the regression + tests for details. + </p> +<div class="note"><table border="0" summary="Note"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> +<th align="left">Note</th> +</tr> +<tr><td align="left" valign="top"><p> + Please let us know how this works on other platforms/compilers. + </p></td></tr> +</table></div> +<div class="note"><table border="0" summary="Note"> +<tr> +<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> +<th align="left">Note</th> +</tr> +<tr><td align="left" valign="top"><p> + Please send any questions, comments and bug reports to boost <at> + lists <dot> boost <dot> org. + </p></td></tr> +</table></div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.getting_started.hello_world__"></a><a class="link" href="users_guide.html#chrono.users_guide.getting_started.hello_world__" title="Hello World!">Hello + World! </a> +</h4></div></div></div> +<p> + If all you want to do is to time a program's execution, here is a complete + program: + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cmath</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + + <span class="keyword">for</span> <span class="special">(</span> <span class="keyword">long</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">10000000</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span> <span class="special">)</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">sqrt</span><span class="special">(</span> <span class="number">123.456L</span> <span class="special">);</span> <span class="comment">// burn some time</span> + + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"took "</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Output was: + </p> +<pre class="programlisting"><span class="identifier">took</span> <span class="number">0.832</span> <span class="identifier">seconds</span> +</pre> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="chrono.users_guide.tutorial"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial" title="Tutorial">Tutorial</a> +</h3></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration">Duration</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.clocks">Clocks</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.time_point">Time Point</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks">Specific + Clocks</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.i_o">I/O</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.tutorial.duration"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration" title="Duration">Duration</a> +</h4></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.so_what_exactly_is_a__duration__and_how_do_i_use_one_">So + What Exactly is a <code class="computeroutput"><span class="identifier">duration</span></code> + and How Do I Use One?</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.what_happens_if_i_assign__m3___us3__to__minutes__instead_of__microseconds__">What + Happens if I Assign <code class="computeroutput"><span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span></code> + to <code class="computeroutput"><span class="identifier">minutes</span></code> Instead of + <code class="computeroutput"><span class="identifier">microseconds</span></code>?</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.but_what_if_the_truncation_behavior_is_what_i_want_to_do_">But + What if the Truncation Behavior is What I Want to Do?</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.round">Rounding + functions</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.trafficking_in_floating_point_durations">Trafficking + in floating-point Durations</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.how_expensive_is_all_of_this_">How + Expensive is All of this?</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.how_complicated_is_it_to_build_a_function_taking_a__duration__parameter_">How + Complicated is it to Build a Function Taking a <code class="computeroutput"><span class="identifier">duration</span></code> + Parameter?</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.is_it_possible_for_the_user_to_pass_a___duration_to_a_function_with_the_units_being_ambiguous_">Is + it possible for the user to pass a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to a function with the + units being ambiguous?</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.can_durations_overflow_">Can + Durations Overflow?</a></span></dt> +</dl></div> +<p> + The <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> is the heart of this + library. The interface that the user will see in everyday use is nearly + identical to that of <span class="bold"><strong>Boost.DateTime</strong></span> time + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s authored by Jeff Garland, + both in syntax and in behavior. This has been a very popular boost library + for 7 years. There is an enormous positive history with this interface. + </p> +<p> + The library consists of six units of time <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>: + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">hours</span></code></a> + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a> + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a> + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> + </li> +</ul></div> +<p> + These units were chosen as a subset of the boost library because they are + the most common units used when sleeping, waiting on a condition variable, + or waiting to obtain the lock on a mutex. Each of these units is nothing + but a thin wrapper around a signed integral count. That is, when you construct + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a><code class="computeroutput"><span class="special">(</span><span class="number">3</span><span class="special">)</span></code>, all that + happens is a <code class="computeroutput"><span class="number">3</span></code> is stored inside + <code class="computeroutput"><span class="identifier">minutes</span></code>. When you construct + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><code class="computeroutput"><span class="special">(</span><span class="number">3</span><span class="special">)</span></code>, all that + happens is a <code class="computeroutput"><span class="number">3</span></code> is stored inside + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a>. + </p> +<p> + The only context in which these different types differ is when being converted + to one another. At this time, unit-specific compile-time conversion constants + are used to convert the source unit to the target unit. Only conversions + from coarser units to finer units are allowed (in Boost). This restriction + ensures that all conversions are always exact. That is, <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> can always represent + any value <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a> has. + </p> +<p> + In <span class="bold"><strong>Boost.DateTime</strong></span>, these units are united + via inheritance. <span class="bold"><strong>Boost.Chrono</strong></span> instead + unites these units through the class template <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. That is, in <span class="bold"><strong>Boost.Chrono</strong></span> all six of the above units are nothing + but typedefs to different instantiations of <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. This change from Boost.DateTime + has a far reaching positive impact, while not changing the syntax of the + everyday use at all. + </p> +<p> + The most immediate positive impact is that the library can immediately + generate any unit, with any precision it needs. This is sometimes necessary + when doing comparisons or arithmetic between <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s of differing precision, + assuming one wants the comparison and arithmetic to be exact. + </p> +<p> + A secondary benefit is that by publishing the class template <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> interface, user code + can very easily create <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s with any precision they + desire. The <code class="computeroutput"><span class="identifier">ratio</span></code> utility + is used to specify the precision, so as long as the precision can be expressed + by a rational constant with respect to seconds, this framework can exactly + represent it (one third of a second is no problem, and neither is one third + of a <code class="computeroutput"><span class="identifier">femto</span></code> second). All + of this utility and flexibility comes at no cost just by making use of + the no-run-time-overhead <code class="computeroutput"><span class="identifier">ratio</span></code> + facility. + </p> +<p> + In Boost.DateTime, <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">hours</span></code></a> does not have the same representation + as <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a>. The former is usually + represented with a <code class="computeroutput"><span class="keyword">long</span></code> whereas + a <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">long</span></code> + is required for the latter. The reason for this is simply range. You don't + need many hours to cover an extremely large range of time. But this isn't + true of nanoseconds. Being able to reduce the sizeof overhead for some + units when possible, can be a significant performance advantage. + </p> +<p> + <span class="bold"><strong>Boost.Chrono</strong></span> continues, and generalizes + that philosophy. Not only can one specify the precision of a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, one can also specify + its representation. This can be any integral type, or even a floating-point + type. Or it can be a user-defined type which emulates an arithmetic type. + The six predefined units all use signed integral types as their representation. + And they all have a minimum range of ± 292 years. <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> needs 64 bits to cover + that range. <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">hours</span></code></a> needs only 23 bits to cover + that range. + </p> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.so_what_exactly_is_a__duration__and_how_do_i_use_one_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.so_what_exactly_is_a__duration__and_how_do_i_use_one_" title="So What Exactly is a duration and How Do I Use One?">So + What Exactly is a <code class="computeroutput"><span class="identifier">duration</span></code> + and How Do I Use One?</a> +</h5></div></div></div> +<p> + A <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> has a representation + and a tick period (precision). + </p> +<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span> <span class="special">=</span> <code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="number">1</span><span class="special">></span> <span class="special">></span> <span class="keyword">class</span> <span class="identifier">duration</span><span class="special">;</span> +</pre> +<p> + The representation is simply any arithmetic type, or an emulation of + such a type. The representation stores a count of ticks. This count is + the only data member stored in a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. If the representation + is floating-point, it can store fractions of a tick to the precision + of the representation. The tick period is represented by a <code class="computeroutput"><span class="identifier">ratio</span></code> and is encoded into the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>'s type, instead of + stored. The tick period only has an impact on the behavior of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> when a conversion between + different <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s is attempted. The + tick period is completely ignored when simply doing arithmetic among + like <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s. + </p> +<p> + <span class="bold"><strong>Example:</strong></span> + </p> +<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">60</span><span class="special">></span> <span class="special">></span> <span class="identifier">minutes</span><span class="special">;</span> +<span class="identifier">minutes</span> <span class="identifier">m1</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// m1 stores 3</span> +<span class="identifier">minutes</span> <span class="identifier">m2</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="comment">// m2 stores 2</span> +<span class="identifier">minutes</span> <span class="identifier">m3</span> <span class="special">=</span> <span class="identifier">m1</span> <span class="special">+</span> <span class="identifier">m2</span><span class="special">;</span> <span class="comment">// m3 stores 5</span> + +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">micro</span><span class="special">></span> <span class="identifier">microseconds</span><span class="special">;</span> +<span class="identifier">microseconds</span> <span class="identifier">us1</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// us1 stores 3</span> +<span class="identifier">microseconds</span> <span class="identifier">us2</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="comment">// us2 stores 2</span> +<span class="identifier">microseconds</span> <span class="identifier">us3</span> <span class="special">=</span> <span class="identifier">us1</span> <span class="special">+</span> <span class="identifier">us2</span><span class="special">;</span> <span class="comment">// us3 stores 5</span> + +<span class="identifier">microseconds</span> <span class="identifier">us4</span> <span class="special">=</span> <span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">;</span> <span class="comment">// us4 stores 300000005</span> +</pre> +<p> + In the final line of code above, there is an implicit conversion from + minutes to microseconds, resulting in a relatively large number of microseconds. + </p> +<p> + If you need to access the tick count within a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, there is a member + <code class="computeroutput"><span class="identifier">count</span><span class="special">()</span></code> + which simply returns the stored tick count. + </p> +<pre class="programlisting"><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">tc</span> <span class="special">=</span> <span class="identifier">us4</span><span class="special">.</span><span class="identifier">count</span><span class="special">();</span> <span class="comment">// tc is 300000005</span> +</pre> +<p> + These <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>'s have very simple, + very predictable, and very observable behavior. After all, this is really + nothing but the time-tested interface of Jeff's boost time <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> library (unified with + templates instead of inheritance). + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.what_happens_if_i_assign__m3___us3__to__minutes__instead_of__microseconds__"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.what_happens_if_i_assign__m3___us3__to__minutes__instead_of__microseconds__" title="What Happens if I Assign m3 + us3 to minutes Instead of microseconds?">What + Happens if I Assign <code class="computeroutput"><span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span></code> + to <code class="computeroutput"><span class="identifier">minutes</span></code> Instead of + <code class="computeroutput"><span class="identifier">microseconds</span></code>?</a> +</h5></div></div></div> +<pre class="programlisting"><span class="identifier">minutes</span> <span class="identifier">m4</span> <span class="special">=</span> <span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">;</span> +</pre> +<p> + It won't compile! The rationale is that implicit truncation error should + not be allowed to happen. If this were to compile, then <code class="computeroutput"><span class="identifier">m4</span></code> would hold <code class="computeroutput"><span class="number">5</span></code>, + the same value as <code class="computeroutput"><span class="identifier">m3</span></code>. + The value associated with <code class="computeroutput"><span class="identifier">us3</span></code> + has been effectively ignored. This is similar to the problem of assigning + a double to an <code class="computeroutput"><span class="keyword">int</span></code>: the + fractional part gets silently discarded. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.but_what_if_the_truncation_behavior_is_what_i_want_to_do_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.but_what_if_the_truncation_behavior_is_what_i_want_to_do_" title="But What if the Truncation Behavior is What I Want to Do?">But + What if the Truncation Behavior is What I Want to Do?</a> +</h5></div></div></div> +<p> + There is a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> facility to explicitly + ask for this behavior: + </p> +<pre class="programlisting"><span class="identifier">minutes</span> <span class="identifier">m4</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">minutes</span><span class="special">>(</span><span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">);</span> <span class="comment">// m4.count() == 5</span> +</pre> +<p> + In general, one can perform <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> arithmetic at will. + If <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> isn't used, and + it compiles, the arithmetic is exact. If one wants to override this exact + arithmetic behavior, <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> can be used to + explicitly specify that desire. The <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> has the same efficiency + as the implicit conversion, and will even be exact as often as it can. + </p> +<p> + You can use <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code> + to convert the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> into whatever units + you desire. This facility will round down (truncate) if an exact conversion + is not possible. For example: + </p> +<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> <span class="identifier">start</span><span class="special">;</span> +<span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> <span class="identifier">end</span><span class="special">;</span> +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> <span class="identifier">ms</span><span class="special">;</span> +<span class="identifier">ms</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">ms</span><span class="special">>(</span><span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">);</span> + +<span class="comment">// d now holds the number of milliseconds from start to end.</span> + +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ms\n"</span><span class="special">;</span> +</pre> +<p> + We can convert to <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a>, or some integral-based + duration which <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> will always exactly + convert to, then <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code> + is unnecessary: + </p> +<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> <span class="identifier">ns</span><span class="special">;</span> +<span class="identifier">ns</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ns</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ns\n"</span><span class="special">;</span> +</pre> +<p> + If you need seconds with a floating-point representation you can also + eliminate the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code>: + </p> +<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span><span class="special">;</span> <span class="comment">// seconds, stored with a double</span> +<span class="identifier">sec</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"s\n"</span><span class="special">;</span> +</pre> +<p> + If you're not sure if you need <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code> + or not, feel free to try it without. If the conversion is exact, or if + the destination has a floating-point representation, it will compile: + else it will not compile. + </p> +<p> + If you need to use <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code>, + but want to round up, instead of down when the conversion is inexact, + here is a handy little helper function to do so. Writing it is actually + a good starter project for understanding <span class="bold"><strong>Boost.Chrono</strong></span>: + </p> +<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">ToDuration</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">ToDuration</span> +<span class="identifier">round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="comment">// first round down</span> + <span class="identifier">ToDuration</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">ToDuration</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">result</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> <span class="comment">// comparisons are *always* exact</span> + <span class="special">++</span><span class="identifier">result</span><span class="special">;</span> <span class="comment">// increment by one tick period</span> + <span class="keyword">return</span> <span class="identifier">result</span><span class="special">;</span> +<span class="special">}</span> + +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> <span class="identifier">ms</span><span class="special">;</span> +<span class="identifier">ms</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">round_up</span><span class="special"><</span><span class="identifier">ms</span><span class="special">>(</span><span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">);</span> +<span class="comment">// d now holds the number of milliseconds from start to end, rounded up.</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ms\n"</span><span class="special">;</span> +</pre> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.round"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.round" title="Rounding functions">Rounding + functions</a> +</h5></div></div></div> +<p> + <span class="bold"><strong>Boost.Chrono</strong></span> provides few simple rounding + utility functions for working with durations. + </p> +<pre class="programlisting"><span class="comment">// round down</span> +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">To</span> +<span class="identifier">floor</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="keyword">return</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> +<span class="special">}</span> + +<span class="comment">// round to nearest, to even on tie</span> +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">To</span> +<span class="identifier">round</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="identifier">To</span> <span class="identifier">t0</span> <span class="special">=</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="identifier">To</span> <span class="identifier">t1</span> <span class="special">=</span> <span class="identifier">t0</span><span class="special">;</span> + <span class="special">++</span><span class="identifier">t1</span><span class="special">;</span> + <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">diff0</span><span class="special">,</span> <span class="identifier">d</span> <span class="special">-</span> <span class="identifier">t0</span><span class="special">);</span> + <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">diff1</span><span class="special">,</span> <span class="identifier">t1</span> <span class="special">-</span> <span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">diff0</span> <span class="special">==</span> <span class="identifier">diff1</span><span class="special">)</span> + <span class="special">{</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t0</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special">&</span> <span class="number">1</span><span class="special">)</span> + <span class="keyword">return</span> <span class="identifier">t1</span><span class="special">;</span> + <span class="keyword">return</span> <span class="identifier">t0</span><span class="special">;</span> + <span class="special">}</span> + <span class="keyword">else</span> <span class="keyword">if</span> <span class="special">(</span><span class="identifier">diff0</span> <span class="special"><</span> <span class="identifier">diff1</span><span class="special">)</span> + <span class="keyword">return</span> <span class="identifier">t0</span><span class="special">;</span> + <span class="keyword">return</span> <span class="identifier">t1</span><span class="special">;</span> +<span class="special">}</span> +<span class="comment">// round up</span> +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">To</span> +<span class="identifier">ceil</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="identifier">To</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> + <span class="special">++</span><span class="identifier">t</span><span class="special">;</span> + <span class="keyword">return</span> <span class="identifier">t</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The beauty of the chrono library is the ease and accuracy with which + such conversions can be made. For example to convert from <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> (<code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">1000</span></code> + of a second), to <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">30</span></code> of a second, one must multiply the milliseconds + by <code class="computeroutput"><span class="number">0.03</span></code>. It is common knowledge + that you can't exactly represent <code class="computeroutput"><span class="number">0.03</span></code> + in a computer. Nevertheless round will exactly (with no round off error) + detect a tie and round to even when this happens. The differences <code class="computeroutput"><span class="identifier">diff0</span></code> and <code class="computeroutput"><span class="identifier">diff1</span></code> + are not approximate, but exact differences, even when <code class="computeroutput"><span class="identifier">d</span></code> + has the units of millisecond and <code class="computeroutput"><span class="identifier">To</span></code> + is <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">30</span></code> of a second. The unit of <code class="computeroutput"><span class="identifier">diff0</span></code> and <code class="computeroutput"><span class="identifier">diff1</span></code> + is <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">3000</span></code> of a second which both millisecond + and <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">30</span></code> of a second exactly convert to (with + no truncation error). + </p> +<p> + Similarly, the comparison <code class="computeroutput"><span class="identifier">t</span> + <span class="special"><</span> <span class="identifier">d</span></code> + in <a class="link" href="reference.html#chrono.reference.round.ceil_hpp" title="Header <boost/chrono/ceil.hpp>"><code class="computeroutput"><span class="identifier">ceil</span></code></a> + is exact, even when there is no exact conversion between <code class="computeroutput"><span class="identifier">t</span></code> and <code class="computeroutput"><span class="identifier">d</span></code>. + Example use of rounding functions + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">floor</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">round</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">ceil</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> + <span class="identifier">milliseconds</span> <span class="identifier">ms</span><span class="special">(</span><span class="number">2500</span><span class="special">);</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">floor</span><span class="special"><</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">round</span><span class="special"><</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ceil</span><span class="special"><</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">ms</span> <span class="special">=</span> <span class="identifier">milliseconds</span><span class="special">(</span><span class="number">2516</span><span class="special">);</span> + <span class="keyword">typedef</span> <span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">1</span><span class="special">,</span> <span class="number">30</span><span class="special">></span> <span class="special">></span> <span class="identifier">frame_rate</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">floor</span><span class="special"><</span><span class="identifier">frame_rate</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">round</span><span class="special"><</span><span class="identifier">frame_rate</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ceil</span><span class="special"><</span><span class="identifier">frame_rate</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The output of this program should be + </p> +<pre class="programlisting"><span class="number">2</span> <span class="identifier">seconds</span> +<span class="number">2</span> <span class="identifier">seconds</span> +<span class="number">3</span> <span class="identifier">seconds</span> +<span class="number">75</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">30</span><span class="special">]</span><span class="identifier">seconds</span> +<span class="number">75</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">30</span><span class="special">]</span><span class="identifier">seconds</span> +<span class="number">76</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">30</span><span class="special">]</span><span class="identifier">seconds</span> +</pre> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.trafficking_in_floating_point_durations"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.trafficking_in_floating_point_durations" title="Trafficking in floating-point Durations">Trafficking + in floating-point Durations</a> +</h5></div></div></div> +<p> + I don't want to deal with writing <code class="computeroutput"><span class="identifier">duration_cast</span></code> + all over the place. I'm content with the precision of my floating-point + representation. + </p> +<p> + Not a problem. When the destination of a conversion has floating-point + representation, all conversions are allowed to happen implicitly. + </p> +<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="number">60</span><span class="special">></span> <span class="special">></span> <span class="identifier">dminutes</span><span class="special">;</span> +<span class="identifier">dminutes</span> <span class="identifier">dm4</span> <span class="special">=</span> <span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">;</span> <span class="comment">// dm4.count() == 5.000000083333333</span> +</pre> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.how_expensive_is_all_of_this_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.how_expensive_is_all_of_this_" title="How Expensive is All of this?">How + Expensive is All of this?</a> +</h5></div></div></div> +<p> + If you were writing these conversions by hand, you could not make it + more efficient. The use of <code class="computeroutput"><span class="identifier">ratio</span></code> + ensures that all conversion constants are simplified as much as possible + at compile-time. This usually results in the numerator or denominator + of the conversion factor simplifying to <code class="computeroutput"><span class="number">1</span></code>, + and being subsequently ignored in converting the run-time values of the + tick counts. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.how_complicated_is_it_to_build_a_function_taking_a__duration__parameter_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.how_complicated_is_it_to_build_a_function_taking_a__duration__parameter_" title="How Complicated is it to Build a Function Taking a duration Parameter?">How + Complicated is it to Build a Function Taking a <code class="computeroutput"><span class="identifier">duration</span></code> + Parameter?</a> +</h5></div></div></div> +<p> + There are several options open to the user: + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + If the author of the function wants to accept any <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, and is willing + to work in floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s, he can simply + use any floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> as the parameter: + </li></ul></div> +<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> <span class="comment">// accept floating-point seconds</span> +<span class="special">{</span> + <span class="comment">// d.count() == 3.e-6 when passed boost::chrono::microseconds(3)</span> +<span class="special">}</span> + +<span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> +</pre> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + If the author of the function wants to traffic only in integral + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s, and is content + with handling nothing finer than say nanoseconds (just as an example), + he can simply specify nanoseconds as the parameter: + </li></ul></div> +<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="comment">// d.count() == 3000 when passed boost::chrono::microseconds(3)</span> +<span class="special">}</span> + +<span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> +</pre> +<p> + In this design, if the client wants to pass in a floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, or a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> of finer precision + than nanoseconds, then the client is responsible for choosing his own + rounding mode in the conversion to nanoseconds. + </p> +<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">s</span><span class="special">(</span><span class="number">1.</span><span class="special">/</span><span class="number">3</span><span class="special">);</span> <span class="comment">// 1/3 of a second</span> +<span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">>(</span><span class="identifier">s</span><span class="special">));</span> <span class="comment">// round towards zero in conversion to nanoseconds</span> +</pre> +<p> + In the example above, the client of f has chosen "round towards + zero" as the desired rounding mode to nanoseconds. If the client + has a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> that won't exactly + convert to nanoseconds, and fails to choose how the conversion will take + place, the compiler will refuse the call: + </p> +<pre class="programlisting"><span class="identifier">f</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span> <span class="comment">// does not compile</span> +</pre> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + If the author of the function wants to accept any <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, but wants to work + with integral representations and wants to control the rounding mode + internally, then he can template the function: + </li></ul></div> +<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="comment">// convert d to nanoseconds, rounding up if it is not an exact conversion</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span> <span class="identifier">ns</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ns</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> + <span class="special">++</span><span class="identifier">ns</span><span class="special">;</span> + <span class="comment">// ns.count() == 333333334 when passed 1/3 of a floating-point second</span> +<span class="special">}</span> + + <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">1.</span><span class="special">/</span><span class="number">3</span><span class="special">));</span> +</pre> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> + If the author in the example does not want to accept floating-point + based <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s, he can enforce + that behavior like so: + </li></ul></div> +<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="comment">// convert d to nanoseconds, rounding up if it is not an exact conversion</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span> <span class="identifier">ns</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">nanoseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ns</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> + <span class="special">++</span><span class="identifier">ns</span><span class="special">;</span> + <span class="comment">// ns.count() == 333333334 when passed 333333333333 picoseconds</span> +<span class="special">}</span> +<span class="comment">// About 1/3 of a second worth of picoseconds</span> +<span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">pico</span><span class="special">>(</span><span class="number">333333333333</span><span class="special">));</span> +</pre> +<p> + Clients with floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s who want to use f + will now have to convert to an integral <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> themselves before passing + the result to f. + </p> +<p> + In summary, the author of f has quite a bit of flexibility and control + in the interface he wants to provide his clients with, and easy options + for manipulating that <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> internal to his function. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.is_it_possible_for_the_user_to_pass_a___duration_to_a_function_with_the_units_being_ambiguous_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.is_it_possible_for_the_user_to_pass_a___duration_to_a_function_with_the_units_being_ambiguous_" title="Is it possible for the user to pass a duration to a function with the units being ambiguous?">Is + it possible for the user to pass a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to a function with the + units being ambiguous?</a> +</h5></div></div></div> +<p> + No. No matter which option the author of <code class="computeroutput"><span class="identifier">f</span></code> + chooses above, the following client code will not compile: + </p> +<pre class="programlisting"><span class="identifier">f</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// Will not compile, 3 is not implicitly convertible to any __duration</span> +</pre> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.duration.can_durations_overflow_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.can_durations_overflow_" title="Can Durations Overflow?">Can + Durations Overflow?</a> +</h5></div></div></div> +<p> + This depend on the representation. The default typedefs uses a representation + that don't handle overflows. The user can define his own representation + that manage overflow as required by its application. + </p> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.tutorial.clocks"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.clocks" title="Clocks">Clocks</a> +</h4></div></div></div> +<p> + While <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s only have precision + and representation to concern themselves, clocks and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s are intimately related + and refer to one another. Because clocks are simpler to explain, we will + do so first without fully explaining <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s. Once clocks are introduced, + it will be easier to then fill in what a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> is. + </p> +<p> + A clock is a concept which bundles 3 things: + </p> +<div class="orderedlist"><ol class="orderedlist" type="1"> +<li class="listitem"> + A concrete <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> type. + </li> +<li class="listitem"> + A concrete <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> type. + </li> +<li class="listitem"> + A function called now() which returns the concrete <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>. + </li> +</ol></div> +<p> + The standard defines three system-wide clocks that are associated to the + computer time. + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> represents system-wide + realtime clock that can be synchronized with an external clock. + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> can not be changed + explicitly and the time since the initial epoch increase in a steady + way. + </li> +<li class="listitem"> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a> intend + to use the system-wide clock provided by the platform with the highest + resolution. + </li> +</ul></div> +<p> + <span class="bold"><strong>Boost.Chrono</strong></span> provides them when supported + by the underlying platform. A given platform may not be able to supply + all three of these clocks. + </p> +<p> + The library adds some clocks that are specific to a process or a thread, + that is there is a clock per process or per thread. + </p> +<p> + The user is also able to easily create more clocks. + </p> +<p> + Given a clock named Clock, it will have: + </p> +<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">Clock</span> <span class="special">{</span> +<span class="keyword">public</span><span class="special">:</span> + <span class="keyword">typedef</span> <span class="identifier">an</span> <span class="identifier">arithmetic</span><span class="special">-</span><span class="identifier">like</span> <span class="identifier">type</span> <span class="identifier">rep</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">an</span> <span class="identifier">instantiation</span> <span class="identifier">of</span> <span class="identifier">ratio</span> <span class="identifier">period</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">rep</span><span class="special">,</span> <span class="identifier">period</span><span class="special">></span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> + <span class="keyword">static</span> <span class="identifier">constexpr</span> <span class="keyword">bool</span> <span class="identifier">is_steady</span> <span class="special">=</span> <span class="keyword">true</span> <span class="keyword">or</span> <span class="keyword">false</span><span class="special">;</span> + + <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">();</span> +<span class="special">};</span> +</pre> +<p> + One can get the current time from Clock with: + </p> +<pre class="programlisting"><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t1</span> <span class="special">=</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> +</pre> +<p> + And one can get the time <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> between two <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s associated with Clock + with: + </p> +<pre class="programlisting"><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">t1</span><span class="special">;</span> +</pre> +<p> + And one can specify a past or future <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> with: + </p> +<pre class="programlisting"><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t2</span> <span class="special">=</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">d</span><span class="special">;</span> +</pre> +<p> + Note how even if a particular clock becomes obsolete, the next clock in + line will have the same API. There is no new learning curve to come up. + The only source code changes will be simply changing the type of the clock. + The same <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> framework continues + to work as new clocks are introduced. And multiple clocks are safely and + easily handled within the same program. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.tutorial.time_point"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.time_point" title="Time Point">Time Point</a> +</h4></div></div></div> +<div class="toc"><dl><dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.time_point.so_what_exactly_is_a__time_point__and_how_do_i_use_one_">So + What Exactly is a <code class="computeroutput"><span class="identifier">time_point</span></code> + and How Do I Use One?</a></span></dt></dl></div> +<p> + A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> represents a point + in time, as opposed to a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> of time. Another way + of saying the same thing, is that a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> represents an epoch + plus or minus a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. Examples of <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s include: + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + 3 minutes after the computer booted. + </li> +<li class="listitem"> + 03:14:07 UTC on Tuesday, January 19, 2038 + </li> +<li class="listitem"> + 20 milliseconds after I started that timer. + </li> +</ul></div> +<p> + In each of the examples above, a different epoch is implied. Sometimes + an epoch has meaning for several millennia. Other times the meaning of + an epoch is lost after a while (such as the start of a timer, or when the + computer booted). However, if two <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s are known to share + the same epoch, they can be subtracted, yielding a valid <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, even if the definition + of the epoch no longer has meaning. + </p> +<p> + In <span class="bold"><strong>Boost.Chrono</strong></span>, an epoch is a purely + abstract and unspecified concept. There is no type representing an epoch. + It is simply an idea that relates (or doesn't) <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s to a clock, and in + the case that they share a clock, <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s to one another. <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s associated with different + clocks are generally not interoperable unless the relationship between + the epochs associated with each clock is known. + </p> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.time_point.so_what_exactly_is_a__time_point__and_how_do_i_use_one_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.time_point.so_what_exactly_is_a__time_point__and_how_do_i_use_one_" title="So What Exactly is a time_point and How Do I Use One?">So + What Exactly is a <code class="computeroutput"><span class="identifier">time_point</span></code> + and How Do I Use One?</a> +</h5></div></div></div> +<p> + A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> has a clock and a + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. + </p> +<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">duration</span><span class="special">></span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special">;</span> +</pre> +<p> + The <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>'s clock is not stored. + It is simply embedded into the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>'s type and serves + two purposes: + </p> +<div class="orderedlist"><ol class="orderedlist" type="1"> +<li class="listitem"> + Because <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s originating + from different clocks have different types, the compiler can be instructed + to fail if incompatible <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s are used in + inappropriate ways. + </li> +<li class="listitem"> + Given a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>, one often needs + to compare that <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> to "now". + This is very simple as long as the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> knows what clock + it is defined with respect to. + </li> +</ol></div> +<p> + A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>'s <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> is stored as the only + data member of the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>. Thus <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s and their corresponding + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> have exactly the same + layout. But they have very different meanings. For example, it is one + thing to say I want to sleep for 3 minutes. It is a completely different + thing to say I want to sleep until 3 minutes past the time I started + that timer (unless you just happened to start that timer now). Both meanings + (and options for sleeping) have great practical value in common use cases + for sleeping, waiting on a condition variable, and waiting for a mutex's + lock. These same concepts and tools are found (for example) in Ada. + </p> +<p> + A timer example: + </p> +<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">()</span> +<span class="special">{</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">g</span><span class="special">();</span> + <span class="identifier">h</span><span class="special">();</span> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"f() took "</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Note that if one is using the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> between two clock + <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s in a way where the + precision of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> matters, it is good + practice to convert the clock's <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to a known <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. This insulates the + code from future changes which may be made to the clock's precision in + the future. For example <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> could easily be + based on the clock speed of the cpu. When you upgrade to a faster machine, + you do not want your code that assumed a certain tick period of this + clock to start experiencing run-time failures because your timing code + has silently changed meaning. + </p> +<p> + A delay loop example: + </p> +<pre class="programlisting"><span class="comment">// delay for at least 500 nanoseconds:</span> +<span class="keyword">auto</span> <span class="identifier">go</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">500</span><span class="special">);</span> +<span class="keyword">while</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><</span> <span class="identifier">go</span><span class="special">)</span> + <span class="special">;</span> +</pre> +<p> + The above code will delay as close as possible to half a microsecond, + no matter what the precision of <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> is. The more precise + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> becomes, the more + accurate will be the delay to 500 nanoseconds. + </p> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.tutorial.specific_clocks"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks" title="Specific Clocks">Specific + Clocks</a> +</h4></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.system_clock">system_clock</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.steady_clock">steady_clock</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.high_resolution_clock">high_resolution_clock</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.process_cpu_clock">process_cpu_clock</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.thread_clock">thread_clock</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.specific_clocks.system_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.system_clock" title="system_clock">system_clock</a> +</h5></div></div></div> +<p> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> is useful when + you need to correlate the time with a known epoch so you can convert + it to a calendar time. Note the specific functions in the <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> class. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.specific_clocks.steady_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.steady_clock" title="steady_clock">steady_clock</a> +</h5></div></div></div> +<p> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> is useful when + you need to wait for a specific amount of time. <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> time can not be + reset. As other steady clocks, it is usually based on the processor tick. + </p> +<p> + Here is a polling solution, but it will probably be too inefficient: + </p> +<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span><span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> +<span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">delay</span><span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">);</span> +<span class="keyword">while</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span> <span class="special"><=</span> <span class="identifier">delay</span><span class="special">)</span> <span class="special">{}</span> +</pre> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.specific_clocks.high_resolution_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.high_resolution_clock" title="high_resolution_clock">high_resolution_clock</a> +</h5></div></div></div> +<p> + When available, <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a> is usually + more expensive than the other system-wide clocks, so they are used only + when the provided resolution is required to the application. + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.specific_clocks.process_cpu_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.process_cpu_clock" title="process_cpu_clock">process_cpu_clock</a> +</h5></div></div></div> +<p> + Process and thread clocks are used usually to measure the time spent + by code blocks, as a basic time-spent profiling of different blocks of + code (Boost.Stopwatch is a clear example of this use). + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.tutorial.specific_clocks.thread_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.thread_clock" title="thread_clock">thread_clock</a> +</h5></div></div></div> +<p> + You can use <a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a> whenever you want + to measure the time spent by the current thread. For example: + </p> +<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span><span class="special">=</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> +<span class="comment">// ... do something ...</span> + +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> <span class="identifier">ms</span><span class="special">;</span> +<span class="identifier">ms</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> +<span class="comment">// d now holds the number of milliseconds from start to end.</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ms\n"</span><span class="special">;</span> +</pre> +<p> + If you need seconds with a floating-point representation you can do: + </p> +<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span><span class="special">;</span> <span class="comment">// seconds, stored with a double.</span> +<span class="identifier">sec</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"s\n"</span><span class="special">;</span> +</pre> +<p> + If you would like to programmatically inspect <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">duration</span></code>, you can get the representation + type with <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">rep</span></code>, and the tick period with <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">period</span></code> (which should be a type <code class="computeroutput"><span class="identifier">ratio</span></code> which has nested values <code class="computeroutput"><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special">::</span><span class="identifier">num</span></code> and <code class="computeroutput"><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special">::</span><span class="identifier">den</span></code>). + The tick period of <a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a> is <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">num</span> <span class="special">/</span> <a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">den</span></code> seconds: <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">1000000000</span></code> + in this case (<code class="computeroutput"><span class="number">1</span></code> billionth + of a second), stored in a <code class="computeroutput"><span class="keyword">long</span> + <span class="keyword">long</span></code>. + </p> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.tutorial.i_o"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.i_o" title="I/O">I/O</a> +</h4></div></div></div> +<p> + Any <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> can be streamed out to + a <code class="computeroutput"><span class="identifier">basic_ostream</span></code>. The run-time + value of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> is formatted according + to the rules and current format settings for <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><code class="computeroutput"><span class="special">::</span><span class="identifier">rep</span></code>. This is followed by a single space + and then the compile-time unit name of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. This unit name is built + on the string returned from <code class="computeroutput"><span class="identifier">ratio_string</span><span class="special"><></span></code> and the data used to construct + the <a class="link" href="reference.html#chrono.reference.io.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> which was inserted + into the stream's locale. If a <a class="link" href="reference.html#chrono.reference.io.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> has not been inserted + into the stream's locale, a default constructed <a class="link" href="reference.html#chrono.reference.io.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> will be added to + the stream's locale. + </p> +<p> + <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> unit names come in two + varieties: long and short. The default constructed <a class="link" href="reference.html#chrono.reference.io.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> provides names + in the long format. These names are English descriptions. Other languages + are supported by constructing a <a class="link" href="reference.html#chrono.reference.io.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> with the proper + spellings for "hours", "minutes" and "seconds", + and their abbreviations (for the short format). The short or long format + can be easily chosen by streaming a <code class="computeroutput"><span class="identifier">duration_short</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">duration_long</span><span class="special">()</span></code> manipulator respectively. + </p> +<p> + A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> is formatted by outputting + its internal <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> followed by a string + that describes the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><code class="computeroutput"><span class="special">::</span><span class="identifier">clock</span></code> epoch. This string will vary for + each distinct clock, and for each implementation of the supplied clocks. + </p> +<p> + <span class="bold"><strong>Example:</strong></span> + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"milliseconds(3) + microseconds(10) = "</span> + <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"hours(3) + minutes(10) = "</span> + <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">1</span><span class="special">,</span> <span class="number">2500000000</span><span class="special">></span> <span class="special">></span> <span class="identifier">ClockTick</span><span class="special">;</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"ClockTick(3) + boost::chrono::nanoseconds(10) = "</span> + <span class="special"><<</span> <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nSet cout to use short names:\n"</span><span class="special">;</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_short</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"milliseconds(3) + microseconds(10) = "</span> + <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"hours(3) + minutes(10) = "</span> + <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"ClockTick(3) + nanoseconds(10) = "</span> + <span class="special"><<</span> <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nsystem_clock::now() = "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="preprocessor">#ifdef</span> <span class="identifier">BOOST_CHRONO_HAS_CLOCK_STEADY</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"steady_clock::now() = "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="preprocessor">#endif</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nSet cout to use long names:\n"</span> + <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_long</span> + <span class="special"><<</span> <span class="string">"high_resolution_clock::now() = "</span> + <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The output could be + </p> +<pre class="programlisting"><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">3010</span> <span class="identifier">microseconds</span> +<span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">190</span> <span class="identifier">minutes</span> +<span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">56</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">5000000000</span><span class="special">]</span><span class="identifier">seconds</span> + +<span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">short</span> <span class="identifier">names</span><span class="special">:</span> +<span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">3010</span> <span class="special">[</span><span class="identifier">mu</span><span class="special">]</span><span class="identifier">s</span> +<span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">190</span> <span class="identifier">m</span> +<span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">56</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">5000000000</span><span class="special">]</span><span class="identifier">s</span> + +<span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">129387415616250000</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">10000000</span><span class="special">]</span><span class="identifier">s</span> <span class="identifier">since</span> <span class="identifier">Jan</span> <span class="number">1</span><span class="special">,</span> <span class="number">1970</span> +<span class="identifier">monotonic_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387636417</span> <span class="identifier">ns</span> <span class="identifier">since</span> <span class="identifier">boot</span> + +<span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">long</span> <span class="identifier">names</span><span class="special">:</span> +<span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387655134</span> <span class="identifier">nanoseconds</span> <span class="identifier">since</span> <span class="identifier">boot</span> +</pre> +<p> + Parsing a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> follows rules analogous + to the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> converting constructor. + A value and a unit (short or long) are read from the <code class="computeroutput"><span class="identifier">basic_istream</span></code>. + If the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> has an integral representation, + then the value parsed must be exactly representable in the target <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> + (after conversion to the target <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> units), else <code class="computeroutput"><span class="identifier">failbit</span></code> is set. <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s based on floating-point + representations can be parsed using any units that do not cause overflow. + </p> +<p> + For example a stream containing "5000 milliseconds" can be parsed + into seconds, but if the stream contains "5001 milliseconds", + parsing into <code class="computeroutput"><span class="identifier">seconds</span></code> will + cause <code class="computeroutput"><span class="identifier">failbit</span></code> to be set. + </p> +<p> + <span class="bold"><strong>Example:</strong></span> + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">sstream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + + <span class="identifier">istringstream</span> <span class="identifier">in</span><span class="special">(</span><span class="string">"5000 milliseconds 4000 ms 3001 ms"</span><span class="special">);</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span> <span class="identifier">d</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> + <span class="identifier">in</span> <span class="special">>></span> <span class="identifier">d</span><span class="special">;</span> + <span class="identifier">assert</span><span class="special">(</span><span class="identifier">in</span><span class="special">.</span><span class="identifier">good</span><span class="special">());</span> + <span class="identifier">assert</span><span class="special">(</span><span class="identifier">d</span> <span class="special">==</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span> + <span class="identifier">in</span> <span class="special">>></span> <span class="identifier">d</span><span class="special">;</span> + <span class="identifier">assert</span><span class="special">(</span><span class="identifier">in</span><span class="special">.</span><span class="identifier">good</span><span class="special">());</span> + <span class="identifier">assert</span><span class="special">(</span><span class="identifier">d</span> <span class="special">==</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">4</span><span class="special">));</span> + <span class="identifier">in</span> <span class="special">>></span> <span class="identifier">d</span><span class="special">;</span> + <span class="identifier">assert</span><span class="special">(</span><span class="identifier">in</span><span class="special">.</span><span class="identifier">fail</span><span class="special">());</span> + <span class="identifier">assert</span><span class="special">(</span><span class="identifier">d</span> <span class="special">==</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">4</span><span class="special">));</span> + + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Note that a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> failure may occur late + in the parsing process. This means that the characters making up the failed + parse in the stream are usually consumed despite the failure to successfully + parse. + </p> +<p> + Parsing a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> involves first parsing + a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> and then parsing the + epoch string. If the epoch string does not match that associated with + <code class="computeroutput"><span class="identifier">time_point</span><span class="special">::</span><span class="identifier">clock</span></code> then failbit will be set. + </p> +<p> + <span class="bold"><strong>Example:</strong></span> + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">sstream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t0</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">stringstream</span> <span class="identifier">io</span><span class="special">;</span> + <span class="identifier">io</span> <span class="special"><<</span> <span class="identifier">t0</span><span class="special">;</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t1</span><span class="special">;</span> + <span class="identifier">io</span> <span class="special">>></span> <span class="identifier">t1</span><span class="special">;</span> + <span class="identifier">assert</span><span class="special">(!</span><span class="identifier">io</span><span class="special">.</span><span class="identifier">fail</span><span class="special">());</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">io</span><span class="special">.</span><span class="identifier">str</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t0</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t1</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"That took "</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special">-</span> <span class="identifier">t0</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"That took "</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special">-</span> <span class="identifier">t1</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The output could be: + </p> +<pre class="programlisting"><span class="number">50908679121461</span> <span class="identifier">nanoseconds</span> <span class="identifier">since</span> <span class="identifier">boot</span> +<span class="identifier">That</span> <span class="identifier">took</span> <span class="number">649630</span> <span class="identifier">nanoseconds</span> +</pre> +<p> + Here's a simple example to find out how many hours the computer has been + up (on this platform): + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> + + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">3600</span><span class="special">></span> <span class="special">></span> <span class="special">></span> <span class="identifier">T</span><span class="special">;</span> + <span class="identifier">T</span> <span class="identifier">tp</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">tp</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The output could be: + </p> +<pre class="programlisting"><span class="number">17.8666</span> <span class="identifier">hours</span> <span class="identifier">since</span> <span class="identifier">boot</span> +</pre> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="chrono.users_guide.examples"></a><a class="link" href="users_guide.html#chrono.users_guide.examples" title="Examples">Examples</a> +</h3></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration">Duration</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.clocks">Clocks</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point">Time Point</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.io">IO</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.examples.duration"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration" title="Duration">Duration</a> +</h4></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration.how_you_override_the_duration_s_default_constructor">How + you Override the Duration's Default Constructor</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration.saturating">Saturating</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration.xtime_conversions">xtime + Conversions</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.duration.how_you_override_the_duration_s_default_constructor"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration.how_you_override_the_duration_s_default_constructor" title="How you Override the Duration's Default Constructor">How + you Override the Duration's Default Constructor</a> +</h5></div></div></div> +<p> + Next we show how to override the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>'s default constructor + to do anything you want (in this case set it to zero). All we need to + do is to change the representation + </p> +<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">I_dont_like_the_default_duration_behavior</span> <span class="special">{</span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> +<span class="keyword">class</span> <span class="identifier">zero_default</span> +<span class="special">{</span> +<span class="keyword">public</span><span class="special">:</span> + <span class="keyword">typedef</span> <span class="identifier">R</span> <span class="identifier">rep</span><span class="special">;</span> + +<span class="keyword">private</span><span class="special">:</span> + <span class="identifier">rep</span> <span class="identifier">rep_</span><span class="special">;</span> +<span class="keyword">public</span><span class="special">:</span> + <span class="identifier">zero_default</span><span class="special">(</span><span class="identifier">rep</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">rep_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{}</span> + <span class="keyword">operator</span> <span class="identifier">rep</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">rep_</span><span class="special">;}</span> + + <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">+=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">+=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">-=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">-=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">*=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">/=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">/=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + + <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">+</span> <span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">-</span> <span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">zero_default</span><span class="special">(-</span><span class="identifier">rep_</span><span class="special">);}</span> + <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">++()</span> <span class="special">{++</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">++(</span><span class="keyword">int</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">zero_default</span><span class="special">(</span><span class="identifier">rep_</span><span class="special">++);}</span> + <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">--()</span> <span class="special">{--</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> + <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">--(</span><span class="keyword">int</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">zero_default</span><span class="special">(</span><span class="identifier">rep_</span><span class="special">--);}</span> + + <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">+(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">+=</span> <span class="identifier">y</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">-(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">-=</span> <span class="identifier">y</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">*(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">*=</span> <span class="identifier">y</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">/(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">/=</span> <span class="identifier">y</span><span class="special">;}</span> + + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">);}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><</span> <span class="special">(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">!(</span><span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">);}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">></span> <span class="special">(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">>=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">);}</span> +<span class="special">};</span> + +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">nano</span> <span class="special">></span> <span class="identifier">nanoseconds</span><span class="special">;</span> +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">micro</span> <span class="special">></span> <span class="identifier">microseconds</span><span class="special">;</span> +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">milli</span> <span class="special">></span> <span class="identifier">milliseconds</span><span class="special">;</span> +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">></span> <span class="special">></span> <span class="identifier">seconds</span><span class="special">;</span> +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">60</span><span class="special">></span> <span class="special">></span> <span class="identifier">minutes</span><span class="special">;</span> +<span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">3600</span><span class="special">></span> <span class="special">></span> <span class="identifier">hours</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Usage + </p> +<pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">I_dont_like_the_default_duration_behavior</span><span class="special">;</span> + +<span class="identifier">milliseconds</span> <span class="identifier">ms</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/i_dont_like_the_default_duration_behavior.cpp" target="_top">example/i_dont_like_the_default_duration_behavior.cpp</a></em></span> + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.duration.saturating"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration.saturating" title="Saturating">Saturating</a> +</h5></div></div></div> +<p> + A "saturating" signed integral type is developed. This type + has +/- infinity and a NaN (like IEEE floating-point) but otherwise obeys + signed integral arithmetic. This class is subsequently used as the template + parameter Rep in boost::chrono::<a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to demonstrate a duration + class that does not silently ignore overflow. + </p> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/saturating.cpp" target="_top">example/saturating.cpp</a></em></span> + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.duration.xtime_conversions"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration.xtime_conversions" title="xtime Conversions">xtime + Conversions</a> +</h5></div></div></div> +<p> + Example round_up utility: converts d to To, rounding up for inexact conversions + Being able to <span class="bold"><strong>easily</strong></span> write this function + is a major feature! + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> + +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">To</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">To</span> +<span class="identifier">round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="identifier">To</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">result</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> + <span class="special">++</span><span class="identifier">result</span><span class="special">;</span> + <span class="keyword">return</span> <span class="identifier">result</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + To demonstrate interaction with an xtime-like facility: + </p> +<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">xtime</span> +<span class="special">{</span> + <span class="keyword">long</span> <span class="identifier">sec</span><span class="special">;</span> + <span class="keyword">unsigned</span> <span class="keyword">long</span> <span class="identifier">usec</span><span class="special">;</span> +<span class="special">};</span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">xtime</span> +<span class="identifier">to_xtime_truncate</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">;</span> + <span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">).</span><span class="identifier">count</span><span class="special">());</span> + <span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span><span class="special">)).</span><span class="identifier">count</span><span class="special">());</span> + <span class="keyword">return</span> <span class="identifier">xt</span><span class="special">;</span> +<span class="special">}</span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">xtime</span> +<span class="identifier">to_xtime_round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">;</span> + <span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">).</span><span class="identifier">count</span><span class="special">());</span> + <span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">unsigned</span> <span class="keyword">long</span><span class="special">>(</span><span class="identifier">round_up</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span> <span class="special">-</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span><span class="special">)).</span><span class="identifier">count</span><span class="special">());</span> + <span class="keyword">return</span> <span class="identifier">xt</span><span class="special">;</span> +<span class="special">}</span> + +<span class="identifier">microseconds</span> +<span class="identifier">from_xtime</span><span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">)</span> +<span class="special">{</span> + <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span><span class="special">);</span> +<span class="special">}</span> + +<span class="keyword">void</span> <span class="identifier">print</span><span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">)</span> +<span class="special">{</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="char">'{'</span> <span class="special"><<</span> <span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span> <span class="special"><<</span> <span class="char">','</span> <span class="special"><<</span> <span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span> <span class="special"><<</span> <span class="string">"}\n"</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Usage + </p> +<pre class="programlisting"><span class="identifier">xtime</span> <span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_truncate</span><span class="special">(</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">(</span><span class="number">251</span><span class="special">));</span> +<span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> +<span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span> <span class="identifier">ms</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">>(</span><span class="identifier">from_xtime</span><span class="special">(</span><span class="identifier">xt</span><span class="special">));</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" milliseconds\n"</span><span class="special">;</span> +<span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_round_up</span><span class="special">(</span><span class="identifier">ms</span><span class="special">);</span> +<span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> +<span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_truncate</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a><span class="special">(</span><span class="number">999</span><span class="special">));</span> +<span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> +<span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a><span class="special">(</span><span class="number">999</span><span class="special">));</span> +<span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/xtime.cpp" target="_top">xtime.cpp</a></em></span> + </p> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.examples.clocks"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.clocks" title="Clocks">Clocks</a> +</h4></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.clocks.cycle_count">Cycle + count</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.clocks.xtime_clock">xtime_clock</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.clocks.cycle_count"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.clocks.cycle_count" title="Cycle count">Cycle + count</a> +</h5></div></div></div> +<p> + Users can easily create their own clocks, with both points in time and + time durations which have a representation and precision of their own + choosing. For example if there is a hardware counter which simply increments + a count with each cycle of the cpu, one can very easily build clocks, + time points and durations on top of that, using only a few tens of lines + of code. Such systems can be used to call the time-sensitive threading + API's such as sleep, wait on a condition variable, or wait for a mutex + lock. The API proposed herein is not sensitive as to whether this is + a 300MHz clock (with a 3 1/3 nanosecond tick period) or a 3GHz clock + (with a tick period of 1/3 of a nanosecond). And the resulting code will + be just as efficient as if the user wrote a special purpose clock cycle + counter. + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">speed</span><span class="special">></span> +<span class="keyword">struct</span> <span class="identifier">cycle_count</span> +<span class="special">{</span> + <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">__ratio_multiply__</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="identifier">speed</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">mega</span></code><span class="special">>::</span><span class="identifier">type</span> + <span class="identifier">frequency</span><span class="special">;</span> <span class="comment">// Mhz</span> + <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">__ratio_divide__</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="number">1</span><span class="special">>,</span> <span class="identifier">frequency</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">period</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">rep</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">rep</span><span class="special">,</span> <span class="identifier">period</span><span class="special">></span> <span class="identifier">duration</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><span class="identifier">cycle_count</span><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> + + <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">()</span> + <span class="special">{</span> + <span class="keyword">static</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">tick</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> + <span class="comment">// return exact cycle count</span> + <span class="keyword">return</span> <span class="identifier">time_point</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(++</span><span class="identifier">tick</span><span class="special">));</span> <span class="comment">// fake access to clock cycle count</span> + <span class="special">}</span> +<span class="special">};</span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">speed</span><span class="special">></span> +<span class="keyword">struct</span> <span class="identifier">approx_cycle_count</span> +<span class="special">{</span> + <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">frequency</span> <span class="special">=</span> <span class="identifier">speed</span> <span class="special">*</span> <span class="number">1000000</span><span class="special">;</span> <span class="comment">// MHz</span> + <span class="keyword">typedef</span> <span class="identifier">nanoseconds</span> <span class="identifier">duration</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">duration</span><span class="special">::</span><span class="identifier">rep</span> <span class="identifier">rep</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">duration</span><span class="special">::</span><span class="identifier">period</span> <span class="identifier">period</span><span class="special">;</span> + <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">nanosec_per_sec</span> <span class="special">=</span> <span class="identifier">period</span><span class="special">::</span><span class="identifier">den</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><span class="identifier">approx_cycle_count</span><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> + + <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">()</span> + <span class="special">{</span> + <span class="keyword">static</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">tick</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> + <span class="comment">// return cycle count as an approximate number of nanoseconds</span> + <span class="comment">// compute as if nanoseconds is only duration in the std::lib</span> + <span class="keyword">return</span> <span class="identifier">time_point</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(++</span><span class="identifier">tick</span> <span class="special">*</span> <span class="identifier">nanosec_per_sec</span> <span class="special">/</span> <span class="identifier">frequency</span><span class="special">));</span> + <span class="special">}</span> +<span class="special">};</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/cycle_count.cpp" target="_top">cycle_count.cpp</a></em></span> + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.clocks.xtime_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.clocks.xtime_clock" title="xtime_clock">xtime_clock</a> +</h5></div></div></div> +<p> + This example demonstrates the use of a timeval-like struct to be used + as the representation type for both <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>. + </p> +<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">xtime</span> <span class="special">{</span> +<span class="keyword">private</span><span class="special">:</span> + <span class="keyword">long</span> <span class="identifier">tv_sec</span><span class="special">;</span> + <span class="keyword">long</span> <span class="identifier">tv_usec</span><span class="special">;</span> + + <span class="keyword">void</span> <span class="identifier">fixup</span><span class="special">()</span> <span class="special">{</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">tv_usec</span> <span class="special"><</span> <span class="number">0</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_usec</span> <span class="special">+=</span> <span class="number">1000000</span><span class="special">;</span> + <span class="special">--</span><span class="identifier">tv_sec</span><span class="special">;</span> + <span class="special">}</span> + <span class="special">}</span> + +<span class="keyword">public</span><span class="special">:</span> + <span class="keyword">explicit</span> <span class="identifier">xtime</span><span class="special">(</span><span class="keyword">long</span> <span class="identifier">sec</span><span class="special">,</span> <span class="keyword">long</span> <span class="identifier">usec</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_sec</span> <span class="special">=</span> <span class="identifier">sec</span><span class="special">;</span> + <span class="identifier">tv_usec</span> <span class="special">=</span> <span class="identifier">usec</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">tv_usec</span> <span class="special"><</span> <span class="number">0</span> <span class="special">||</span> <span class="identifier">tv_usec</span> <span class="special">>=</span> <span class="number">1000000</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_sec</span> <span class="special">+=</span> <span class="identifier">tv_usec</span> <span class="special">/</span> <span class="number">1000000</span><span class="special">;</span> + <span class="identifier">tv_usec</span> <span class="special">%=</span> <span class="number">1000000</span><span class="special">;</span> + <span class="identifier">fixup</span><span class="special">();</span> + <span class="special">}</span> + <span class="special">}</span> + + <span class="keyword">explicit</span> <span class="identifier">xtime</span><span class="special">(</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">usec</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">usec</span> <span class="special">%</span> <span class="number">1000000</span><span class="special">);</span> + <span class="identifier">tv_sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">usec</span> <span class="special">/</span> <span class="number">1000000</span><span class="special">);</span> + <span class="identifier">fixup</span><span class="special">();</span> + <span class="special">}</span> + + <span class="comment">// explicit</span> + <span class="keyword">operator</span> <span class="keyword">long</span> <span class="keyword">long</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>(</span><span class="identifier">tv_sec</span><span class="special">)</span> <span class="special">*</span> <span class="number">1000000</span> <span class="special">+</span> <span class="identifier">tv_usec</span><span class="special">;}</span> + + <span class="identifier">xtime</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">+=</span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_sec</span> <span class="special">+=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">;</span> + <span class="identifier">tv_usec</span> <span class="special">+=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">tv_usec</span> <span class="special">>=</span> <span class="number">1000000</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_usec</span> <span class="special">-=</span> <span class="number">1000000</span><span class="special">;</span> + <span class="special">++</span><span class="identifier">tv_sec</span><span class="special">;</span> + <span class="special">}</span> + <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> + <span class="special">}</span> + + <span class="identifier">xtime</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">-=</span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">tv_sec</span> <span class="special">-=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">;</span> + <span class="identifier">tv_usec</span> <span class="special">-=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">;</span> + <span class="identifier">fixup</span><span class="special">();</span> + <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> + <span class="special">}</span> + + <span class="identifier">xtime</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">%=</span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="special">{</span> + <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">tv_sec</span> <span class="special">*</span> <span class="number">1000000</span> <span class="special">+</span> <span class="identifier">tv_usec</span><span class="special">;</span> + <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">*</span> <span class="number">1000000</span> <span class="special">+</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">;</span> + <span class="identifier">t</span> <span class="special">%=</span> <span class="identifier">r</span><span class="special">;</span> + <span class="identifier">tv_sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">t</span> <span class="special">/</span> <span class="number">1000000</span><span class="special">);</span> + <span class="identifier">tv_usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">t</span> <span class="special">%</span> <span class="number">1000000</span><span class="special">);</span> + <span class="identifier">fixup</span><span class="special">();</span> + <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> + <span class="special">}</span> + + <span class="keyword">friend</span> <span class="identifier">xtime</span> <span class="keyword">operator</span><span class="special">+(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">+=</span> <span class="identifier">y</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="identifier">xtime</span> <span class="keyword">operator</span><span class="special">-(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">-=</span> <span class="identifier">y</span><span class="special">;}</span> + <span class="keyword">friend</span> <span class="identifier">xtime</span> <span class="keyword">operator</span><span class="special">%(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">%=</span> <span class="identifier">y</span><span class="special">;}</span> + + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> + <span class="special">{</span> <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">&&</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_usec</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">);</span> <span class="special">}</span> + + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">)</span> + <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_usec</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">);</span> + <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">);</span> + <span class="special">}</span> + + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">);</span> <span class="special">}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">></span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">;</span> <span class="special">}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><=(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">!(</span><span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">);</span> <span class="special">}</span> + <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">>=(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">);</span> <span class="special">}</span> + + <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">)</span> + <span class="special">{</span><span class="keyword">return</span> <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'{'</span> <span class="special"><<</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special"><<</span> <span class="char">','</span> <span class="special"><<</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_usec</span> <span class="special"><<</span> <span class="char">'}'</span><span class="special">;}</span> +<span class="special">};</span> +</pre> +<p> + Clock based on timeval-like struct. + </p> +<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">xtime_clock</span> +<span class="special">{</span> +<span class="keyword">public</span><span class="special">:</span> + <span class="keyword">typedef</span> <span class="identifier">xtime</span> <span class="identifier">rep</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">micro</span> <span class="identifier">period</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">rep</span><span class="special">,</span> <span class="identifier">period</span><span class="special">></span> <span class="identifier">duration</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span><span class="identifier">xtime_clock</span><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> + + <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">()</span> + <span class="special">{</span> + <span class="preprocessor">#if</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_CHRONO_WINDOWS_API</span><span class="special">)</span> + <span class="identifier">time_point</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(</span><span class="identifier">xtime</span><span class="special">(</span><span class="number">0</span><span class="special">)));</span> + <span class="identifier">gettimeofday</span><span class="special">((</span><span class="identifier">timeval</span><span class="special">*)&</span><span class="identifier">t</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span> + <span class="keyword">return</span> <span class="identifier">t</span><span class="special">;</span> + + <span class="preprocessor">#elif</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_CHRONO_MAC_API</span><span class="special">)</span> + + <span class="identifier">time_point</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(</span><span class="identifier">xtime</span><span class="special">(</span><span class="number">0</span><span class="special">)));</span> + <span class="identifier">gettimeofday</span><span class="special">((</span><span class="identifier">timeval</span><span class="special">*)&</span><span class="identifier">t</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span> + <span class="keyword">return</span> <span class="identifier">t</span><span class="special">;</span> + + <span class="preprocessor">#elif</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_CHRONO_POSIX_API</span><span class="special">)</span> + <span class="comment">//time_point t(0,0);</span> + + <span class="identifier">timespec</span> <span class="identifier">ts</span><span class="special">;</span> + <span class="special">::</span><span class="identifier">clock_gettime</span><span class="special">(</span> <span class="identifier">CLOCK_REALTIME</span><span class="special">,</span> <span class="special">&</span><span class="identifier">ts</span> <span class="special">);</span> + + <span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">(</span> <span class="identifier">ts</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">,</span> <span class="identifier">ts</span><span class="special">.</span><span class="identifier">tv_nsec</span><span class="special">/</span><span class="number">1000</span><span class="special">);</span> + <span class="keyword">return</span> <span class="identifier">time_point</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(</span><span class="identifier">xt</span><span class="special">));</span> + + <span class="preprocessor">#endif</span> <span class="comment">// POSIX</span> + <span class="special">}</span> +<span class="special">};</span> +</pre> +<p> + Usage of xtime_clock + </p> +<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sizeof xtime_clock::time_point = "</span> <span class="special"><<</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">time_point</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sizeof xtime_clock::duration = "</span> <span class="special"><<</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">duration</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sizeof xtime_clock::rep = "</span> <span class="special"><<</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">rep</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">delay</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span> +<span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span> <span class="special">=</span> <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> +<span class="keyword">while</span> <span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span> <span class="special"><=</span> <span class="identifier">delay</span><span class="special">)</span> <span class="special">{}</span> +<span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">stop</span> <span class="special">=</span> <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> +<span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">elapsed</span> <span class="special">=</span> <span class="identifier">stop</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"paused "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="identifier">elapsed</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" nanoseconds\n"</span><span class="special">;</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/timeval_demo.cpp" target="_top">example/timeval_demo.cpp</a></em></span> + </p> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.examples.time_point"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point" title="Time Point">Time Point</a> +</h4></div></div></div> +<div class="toc"><dl> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.min_utility">min + Utility</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.a_tiny_program_that_times_how_long_until_a_key_is_struck">A + Tiny Program that Times How Long Until a Key is Struck</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.24_hours_display">24 + Hours Display</a></span></dt> +<dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.simulated_thread_interface_demonstration_program">Simulated + Thread Interface Demonstration Program</a></span></dt> +</dl></div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.time_point.min_utility"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.min_utility" title="min Utility">min + Utility</a> +</h5></div></div></div> +<p> + The user can define a function returning the earliest <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> as follows: + </p> +<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration1</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration2</span></code></a><span class="special">></span> +<span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration1</span></code></a><span class="special">>,</span> + <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration2</span></code></a><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> +<span class="identifier">min</span><span class="special">(</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration1</span></code></a><span class="special">></span> <span class="identifier">t1</span><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration2</span></code></a><span class="special">></span> <span class="identifier">t2</span><span class="special">)</span> +<span class="special">{</span> + <span class="keyword">return</span> <span class="identifier">t2</span> <span class="special"><</span> <span class="identifier">t1</span> <span class="special">?</span> <span class="identifier">t2</span> <span class="special">:</span> <span class="identifier">t1</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Being able to <span class="bold"><strong>easily</strong></span> write this function + is a major feature! + </p> +<pre class="programlisting"><span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> +<span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">t2</span><span class="special">,</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> +<span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">t3</span><span class="special">,</span> <span class="identifier">min</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span> <span class="identifier">t2</span><span class="special">));</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/min_time_point.cpp" target="_top">example/min_time_point.cpp</a></em></span> + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.time_point.a_tiny_program_that_times_how_long_until_a_key_is_struck"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.a_tiny_program_that_times_how_long_until_a_key_is_struck" title="A Tiny Program that Times How Long Until a Key is Struck">A + Tiny Program that Times How Long Until a Key is Struck</a> +</h5></div></div></div> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iomanip</span><span class="special">></span> + +<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> + +<span class="keyword">template</span><span class="special"><</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a> <span class="special">></span> +<span class="keyword">class</span> <span class="identifier">timer</span> +<span class="special">{</span> + <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span><span class="special">;</span> +<span class="keyword">public</span><span class="special">:</span> + <span class="identifier">timer</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">start</span><span class="special">(</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">)</span> <span class="special">{}</span> + <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">elapsed</span><span class="special">()</span> <span class="keyword">const</span> + <span class="special">{</span> + <span class="keyword">return</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> + <span class="special">}</span> + <span class="keyword">double</span> <span class="identifier">seconds</span><span class="special">()</span> <span class="keyword">const</span> + <span class="special">{</span> + <span class="keyword">return</span> <span class="identifier">elapsed</span><span class="special">().</span><span class="identifier">count</span><span class="special">()</span> <span class="special">*</span> <span class="special">((</span><span class="keyword">double</span><span class="special">)</span><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">num</span><span class="special">/</span><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">den</span><span class="special">);</span> + <span class="special">}</span> +<span class="special">};</span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="identifier">timer</span><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">></span> <span class="identifier">t1</span><span class="special">;</span> + <span class="identifier">timer</span><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">></span> <span class="identifier">t2</span><span class="special">;</span> + <span class="identifier">timer</span><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">></span> <span class="identifier">t3</span><span class="special">;</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Type the Enter key: "</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span><span class="special">.</span><span class="identifier">get</span><span class="special">();</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">fixed</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">setprecision</span><span class="special">(</span><span class="number">9</span><span class="special">);</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"system_clock-----------: "</span> + <span class="special"><<</span> <span class="identifier">t1</span><span class="special">.</span><span class="identifier">seconds</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"steady_clock--------: "</span> + <span class="special"><<</span> <span class="identifier">t2</span><span class="special">.</span><span class="identifier">seconds</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"high_resolution_clock--: "</span> + <span class="special"><<</span> <span class="identifier">t3</span><span class="special">.</span><span class="identifier">seconds</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> + + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d4</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d5</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nsystem_clock latency-----------: "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">d5</span> <span class="special">-</span> <span class="identifier">d4</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> + + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d6</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d7</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"steady_clock latency--------: "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">d7</span> <span class="special">-</span> <span class="identifier">d6</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> + + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d8</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d9</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"high_resolution_clock latency--: "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">d9</span> <span class="special">-</span> <span class="identifier">d8</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">time_t</span> <span class="identifier">now</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">to_time_t</span><span class="special">(</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">());</span> + + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nsystem_clock::now() reports UTC is "</span> + <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">asctime</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">gmtime</span><span class="special">(&</span><span class="identifier">now</span><span class="special">))</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span> + + <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The output of this program run looks like this: + </p> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/await_keystroke.cpp" target="_top">example/await_keystroke.cpp</a></em></span> + </p> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.time_point.24_hours_display"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.24_hours_display" title="24 Hours Display">24 + Hours Display</a> +</h5></div></div></div> +<p> + In the example above we take advantage of the fact that <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s convert as long + as they have the same clock, and as long as their internal <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s convert. We also take + advantage of the fact that a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> with a floating-point + representation will convert from anything. Finally the I/O system discovers + the more readable "hours" unit for our <code class="computeroutput"><span class="identifier">duration</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">ratio</span><span class="special"><</span><span class="number">3600</span><span class="special">>></span></code>. + </p> +<p> + There are many other ways to format <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s. For example see + <a href="http://en.wikipedia.org/wiki/ISO_8601#Durations" target="_top">ISO 8601</a>. + Instead of coding every possibility into <code class="computeroutput"><span class="keyword">operator</span><span class="special"><<</span></code>, which would lead to significant + code bloat for even the most trivial uses, this document seeks to inform + the reader how to write custom I/O when desired. + </p> +<p> + As an example, the function below streams arbitrary <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s to arbitrary <code class="computeroutput"><span class="identifier">basic_ostreams</span></code> using the format: + </p> +<pre class="programlisting"><span class="special">[-]</span><span class="identifier">d</span><span class="special">/</span><span class="identifier">hh</span><span class="special">:</span><span class="identifier">mm</span><span class="special">:</span><span class="identifier">ss</span><span class="special">.</span><span class="identifier">cc</span> +</pre> +<p> + Where: + </p> +<div class="itemizedlist"><ul class="itemizedlist" type="disc"> +<li class="listitem"> + <code class="computeroutput"><span class="identifier">d</span></code> is the number of + <code class="computeroutput"><span class="identifier">days</span></code> + </li> +<li class="listitem"> + <code class="computeroutput"><span class="identifier">h</span></code> is the number of + <code class="computeroutput"><span class="identifier">hours</span></code> + </li> +<li class="listitem"> + <code class="computeroutput"><span class="identifier">m</span></code> is the number of + <code class="computeroutput"><span class="identifier">minutes</span></code> + </li> +<li class="listitem"> + <code class="computeroutput"><span class="identifier">ss</span><span class="special">.</span><span class="identifier">cc</span></code> is the number of <code class="computeroutput"><span class="identifier">seconds</span></code> rounded to the nearest + hundreth of a second + <div class="orderedlist"><ol class="orderedlist" type="1"> +<li class="listitem"> + include <boost/chrono/chrono_io.hpp> + </li> +<li class="listitem"> + include <ostream> + </li> +<li class="listitem"> + include <iostream> + </li> +</ol></div> + </li> +</ul></div> +<pre class="programlisting"><span class="comment">// format duration as [-]d/hh::mm::ss.cc</span> +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharT</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharT</span><span class="special">,</span> <span class="identifier">Traits</span><span class="special">>&</span> +<span class="identifier">display</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharT</span><span class="special">,</span> <span class="identifier">Traits</span><span class="special">>&</span> <span class="identifier">os</span><span class="special">,</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> + + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">86400</span><span class="special">></span> <span class="special">></span> <span class="identifier">days</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">:</span><span class="identifier">centi</span><span class="special">></span> <span class="identifier">centiseconds</span><span class="special">;</span> + + <span class="comment">// if negative, print negative sign and negate</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">d</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>(</span><span class="number">0</span><span class="special">))</span> + <span class="special">{</span> + <span class="identifier">d</span> <span class="special">=</span> <span class="special">-</span><span class="identifier">d</span><span class="special">;</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'-'</span><span class="special">;</span> + <span class="special">}</span> + <span class="comment">// round d to nearest centiseconds, to even on tie</span> + <span class="identifier">centiseconds</span> <span class="identifier">cs</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">centiseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">d</span> <span class="special">-</span> <span class="identifier">cs</span> <span class="special">></span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">5</span><span class="special">)</span> + <span class="special">||</span> <span class="special">(</span><span class="identifier">d</span> <span class="special">-</span> <span class="identifier">cs</span> <span class="special">==</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">5</span><span class="special">)</span> <span class="special">&&</span> <span class="identifier">cs</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special">&</span> <span class="number">1</span><span class="special">))</span> + <span class="special">++</span><span class="identifier">cs</span><span class="special">;</span> + <span class="comment">// separate seconds from centiseconds</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span> <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">cs</span><span class="special">);</span> + <span class="identifier">cs</span> <span class="special">-=</span> <span class="identifier">s</span><span class="special">;</span> + <span class="comment">// separate minutes from seconds</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span> <span class="identifier">m</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">>(</span><span class="identifier">s</span><span class="special">);</span> + <span class="identifier">s</span> <span class="special">-=</span> <span class="identifier">m</span><span class="special">;</span> + <span class="comment">// separate hours from minutes</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span> <span class="identifier">h</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">>(</span><span class="identifier">m</span><span class="special">);</span> + <span class="identifier">m</span> <span class="special">-=</span> <span class="identifier">h</span><span class="special">;</span> + <span class="comment">// separate days from hours</span> + <span class="identifier">days</span> <span class="identifier">dy</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">days</span><span class="special">>(</span><span class="identifier">h</span><span class="special">);</span> + <span class="identifier">h</span> <span class="special">-=</span> <span class="identifier">dy</span><span class="special">;</span> + <span class="comment">// print d/hh:mm:ss.cc</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">dy</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'/'</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">h</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">h</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">':'</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">m</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">':'</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">s</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'.'</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">cs</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">centiseconds</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> + <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">cs</span><span class="special">.</span><span class="identifier">count</span><span class="special">();</span> + <span class="keyword">return</span> <span class="identifier">os</span><span class="special">;</span> +<span class="special">}</span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> + + <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">().</span><span class="identifier">time_since_epoch</span><span class="special">()</span> + <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mega</span><span class="special">>(</span><span class="number">1</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="special">-</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">6</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mega</span><span class="special">>(</span><span class="number">1</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> + <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="special">-</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mega</span><span class="special">>(</span><span class="number">1</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + The output could be: + </p> +<pre class="programlisting"><span class="number">12</span><span class="special">/</span><span class="number">06</span><span class="special">:</span><span class="number">03</span><span class="special">:</span><span class="number">22.95</span> +<span class="special">-</span><span class="number">0</span><span class="special">/</span><span class="number">00</span><span class="special">:</span><span class="number">00</span><span class="special">:</span><span class="number">00</span><span class="special">.</span><span class="number">01</span> +<span class="number">11</span><span class="special">/</span><span class="number">13</span><span class="special">:</span><span class="number">46</span><span class="special">:</span><span class="number">40.00</span> +<span class="special">-</span><span class="number">11</span><span class="special">/</span><span class="number">13</span><span class="special">:</span><span class="number">46</span><span class="special">:</span><span class="number">40.00</span> +</pre> +</div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.time_point.simulated_thread_interface_demonstration_program"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.simulated_thread_interface_demonstration_program" title="Simulated Thread Interface Demonstration Program">Simulated + Thread Interface Demonstration Program</a> +</h5></div></div></div> +<p> + The C++0x standard library's multi-threading library requires the ability + to deal with the representation of time in a manner consistent with modern + C++ practices. Next is a simulation of this interface. + </p> +<p> + The non-member sleep functions can be emulated as follows: + </p> +<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">this_thread</span> <span class="special">{</span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> +<span class="keyword">void</span> <span class="identifier">sleep_for</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> + <span class="special">++</span><span class="identifier">t</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special">></span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">(</span><span class="number">0</span><span class="special">))</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sleep_for "</span> <span class="special"><<</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds\n"</span><span class="special">;</span> +<span class="special">}</span> + +<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> +<span class="keyword">void</span> <span class="identifier">sleep_until</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> <span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">chrono</span><span class="special">;</span> + <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> <span class="identifier">Time</span><span class="special">;</span> + <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">SysTime</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special">></span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">())</span> <span class="special">{</span> + <span class="keyword">typedef</span> <span class="keyword">typename</span> <code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">::</span><span class="identifier">duration</span><span class="special">,</span> + <span class="keyword">typename</span> <span class="identifier">SysTime</span><span class="special">::</span><span class="identifier">duration</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">D</span><span class="special">;</span> + <span class="comment">/* auto */</span> <span class="identifier">D</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">t</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">microseconds</span> <span class="identifier">us</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">us</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> + <span class="special">++</span><span class="identifier">us</span><span class="special">;</span> + <span class="identifier">SysTime</span> <span class="identifier">st</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">us</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sleep_until "</span><span class="special">;</span> + <span class="identifier">detail</span><span class="special">::</span><span class="identifier">print_time</span><span class="special">(</span><span class="identifier">st</span><span class="special">);</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" which is "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">st</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds away\n"</span><span class="special">;</span> + <span class="special">}</span> +<span class="special">}</span> + +<span class="special">}}</span> +</pre> +<p> + Next is the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span><span class="special">::</span><span class="identifier">timed_mutex</span></code> modified fuctions + </p> +<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> +<span class="keyword">struct</span> <span class="identifier">timed_mutex</span> <span class="special">{</span> + <span class="comment">// ...</span> + + <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> + <span class="keyword">bool</span> <span class="identifier">try_lock_for</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">(</span><span class="number">0</span><span class="special">))</span> + <span class="keyword">return</span> <span class="identifier">try_lock</span><span class="special">();</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"try_lock_for "</span> <span class="special"><<</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds\n"</span><span class="special">;</span> + <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> + <span class="special">}</span> + + <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> + <span class="keyword">bool</span> <span class="identifier">try_lock_until</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> + <span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">chrono</span><span class="special">;</span> + <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> <span class="identifier">Time</span><span class="special">;</span> + <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">SysTime</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">())</span> + <span class="keyword">return</span> <span class="identifier">try_lock</span><span class="special">();</span> + <span class="keyword">typedef</span> <span class="keyword">typename</span> <code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">::</span><span class="identifier">duration</span><span class="special">,</span> + <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">duration</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">D</span><span class="special">;</span> + <span class="comment">/* auto */</span> <span class="identifier">D</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">t</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">microseconds</span> <span class="identifier">us</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="identifier">SysTime</span> <span class="identifier">st</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">us</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"try_lock_until "</span><span class="special">;</span> + <span class="identifier">detail</span><span class="special">::</span><span class="identifier">print_time</span><span class="special">(</span><span class="identifier">st</span><span class="special">);</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" which is "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">st</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()).</span><span class="identifier">count</span><span class="special">()</span> + <span class="special"><<</span> <span class="string">" microseconds away\n"</span><span class="special">;</span> + <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> + <span class="special">}</span> +<span class="special">};</span> +<span class="special">}</span> +</pre> +<p> + <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span><span class="special">::</span><span class="identifier">condition_variable</span></code> time related function + are modified as follows: + </p> +<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> +<span class="keyword">struct</span> <span class="identifier">condition_variable</span> +<span class="special">{</span> + <span class="comment">// ...</span> + + <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> + <span class="keyword">bool</span> <span class="identifier">wait_for</span><span class="special">(</span><span class="identifier">mutex</span><span class="special">&,</span> <span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">{</span> + <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"wait_for "</span> <span class="special"><<</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds\n"</span><span class="special">;</span> + <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> + <span class="special">}</span> + + <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> + <span class="keyword">bool</span> <span class="identifier">wait_until</span><span class="special">(</span><span class="identifier">mutex</span><span class="special">&,</span> <span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> <span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> + <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> <span class="identifier">Time</span><span class="special">;</span> + <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">SysTime</span><span class="special">;</span> + <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">())</span> + <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span> + <span class="keyword">typedef</span> <span class="keyword">typename</span> <code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">::</span><span class="identifier">duration</span><span class="special">,</span> + <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">duration</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">D</span><span class="special">;</span> + <span class="comment">/* auto */</span> <span class="identifier">D</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">t</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> + <span class="identifier">microseconds</span> <span class="identifier">us</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> + <span class="identifier">SysTime</span> <span class="identifier">st</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">us</span><span class="special">;</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"wait_until "</span><span class="special">;</span> + <span class="identifier">detail</span><span class="special">::</span><span class="identifier">print_time</span><span class="special">(</span><span class="identifier">st</span><span class="special">);</span> + <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" which is "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">st</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()).</span><span class="identifier">count</span><span class="special">()</span> + <span class="special"><<</span> <span class="string">" microseconds away\n"</span><span class="special">;</span> + <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> + <span class="special">}</span> +<span class="special">};</span> +<span class="special">}</span> +</pre> +<p> + Next follows how simple is the usage of this functions: + </p> +<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span> <span class="identifier">m</span><span class="special">;</span> +<span class="identifier">boost</span><span class="special">::</span><span class="identifier">timed_mutex</span> <span class="identifier">mut</span><span class="special">;</span> +<span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition_variable</span> <span class="identifier">cv</span><span class="special">;</span> + +<span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> + +<span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="number">3</span><span class="special">));</span> +<span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a><span class="special">(</span><span class="number">300</span><span class="special">));</span> +<span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">time_limit</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">__seconds_</span><span class="special">(</span><span class="number">4</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">(</span><span class="number">500</span><span class="special">);</span> +<span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_until</span><span class="special">(</span><span class="identifier">time_limit</span><span class="special">);</span> + +<span class="identifier">mut</span><span class="special">.</span><span class="identifier">try_lock_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">(</span><span class="number">30</span><span class="special">));</span> +<span class="identifier">mut</span><span class="special">.</span><span class="identifier">try_lock_until</span><span class="special">(</span><span class="identifier">time_limit</span><span class="special">);</span> + +<span class="identifier">cv</span><span class="special">.</span><span class="identifier">wait_for</span><span class="special">(</span><span class="identifier">m</span><span class="special">,</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">));</span> <span class="comment">// real code would put this in a loop</span> +<span class="identifier">cv</span><span class="special">.</span><span class="identifier">wait_until</span><span class="special">(</span><span class="identifier">m</span><span class="special">,</span> <span class="identifier">time_limit</span><span class="special">);</span> <span class="comment">// real code would put this in a loop</span> + +<span class="comment">// For those who prefer floating-point</span> +<span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">0.25</span><span class="special">));</span> +<span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_until</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">1.5</span><span class="special">));</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/simulated_thread_interface_demo.cpp" target="_top">example/simulated_thread_interface_demo.cpp</a></em></span> + </p> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h4 class="title"> +<a name="chrono.users_guide.examples.io"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.io" title="IO">IO</a> +</h4></div></div></div> +<div class="toc"><dl><dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.io.french">French Output</a></span></dt></dl></div> +<div class="section"> +<div class="titlepage"><div><div><h5 class="title"> +<a name="chrono.users_guide.examples.io.french"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.io.french" title="French Output">French Output</a> +</h5></div></div></div> +<p> + Example use of output in French + </p> +<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> +<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">locale</span><span class="special">></span> + +<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> +<span class="special">{</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> + <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> + + <span class="identifier">cout</span><span class="special">.</span><span class="identifier">imbue</span><span class="special">(</span><span class="identifier">locale</span><span class="special">(</span><span class="identifier">locale</span><span class="special">(),</span> <span class="keyword">new</span> <span class="identifier">duration_punct</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> + <span class="special">(</span> + <span class="identifier">duration_punct</span><span class="special"><</span><span class="keyword">char</span><span class="special">>::</span><span class="identifier">use_long</span><span class="special">,</span> + <span class="string">"secondes"</span><span class="special">,</span> <span class="string">"minutes"</span><span class="special">,</span> <span class="string">"heures"</span><span class="special">,</span> + <span class="string">"s"</span><span class="special">,</span> <span class="string">"m"</span><span class="special">,</span> <span class="string">"h"</span> + <span class="special">)));</span> + <span class="identifier">hours</span> <span class="identifier">h</span><span class="special">(</span><span class="number">5</span><span class="special">);</span> + <span class="identifier">minutes</span> <span class="identifier">m</span><span class="special">(</span><span class="number">45</span><span class="special">);</span> + <span class="identifier">seconds</span> <span class="identifier">s</span><span class="special">(</span><span class="number">15</span><span class="special">);</span> + <span class="identifier">milliseconds</span> <span class="identifier">ms</span><span class="special">(</span><span class="number">763</span><span class="special">);</span> + <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">h</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">m</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">s</span> <span class="special"><<</span> <span class="string">" et "</span> <span class="special"><<</span> <span class="identifier">ms</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> +<span class="special">}</span> +</pre> +<p> + Output is: + </p> +<pre class="programlisting"><span class="number">5</span> <span class="identifier">heures</span><span class="special">,</span> <span class="number">45</span> <span class="identifier">minutes</span><span class="special">,</span> <span class="number">15</span> <span class="identifier">secondes</span> <span class="identifier">et</span> <span class="number">763</span> <span class="identifier">millisecondes</span> +</pre> +<p> + <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/french.cpp" target="_top">example/french.cpp</a></em></span> + </p> +</div> +</div> +</div> +<div class="section"> +<div class="titlepage"><div><div><h3 class="title"> +<a name="chrono.users_guide.ext_references"></a><a class="link" href="users_guide.html#chrono.users_guide.ext_references" title="External Resources">External Resources</a> +</h3></div></div></div> +<div class="variablelist"> +<p class="title"><b></b></p> +<dl> +<dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21" target="_top"><span class="bold"><strong>C++ + Standards Committee's current Working Paper</strong></span></a></span></dt> +<dd><p> + The most authoritative reference material for the library is the C++ + Standards Committee's current Working Paper (WP). 20.11 Time utilities + "time" + </p></dd> +<dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2661.htm" target="_top"><span class="bold"><strong>N2661 - A Foundation to Sleep On</strong></span></a></span></dt> +<dd><p> + From Howard E. Hinnant, Walter E. Brown, Jeff Garland and Marc Paterno. + Is very informative and provides motivation for key design decisions + </p></dd> +<dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3134.html#934" target="_top"><span class="bold"><strong>LGW 934. duration is missing operator%</strong></span></a></span></dt> +<dd><p> + From Terry Golubiewski. Is very informative and provides motivation + for key design decisions + </p></dd> +<dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3135.html#935" target="_top"><span class="bold"><strong>LGW 935. clock error handling needs to be specified</strong></span></a></span></dt> +<dd><p> + From Beman Dawes. This issue has been stated as NAD Future. + </p></dd> +</dl> +</div> +</div> +</div> +<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> +<td align="left"></td> +<td align="right"><div class="copyright-footer">Copyright © 2008 Howard Hinnant<br>Copyright © 2006, 2008 Beman Dawes<br>Copyright © 2009-2011 Vicente J. Botet + Escriba<p> + Distributed under the Boost Software License, Version 1.0. (See accompanying + file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) + </p> +</div></td> +</tr></table> +<hr> +<div class="spirit-nav"> +<a accesskey="p" href="../chrono.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../chrono.html"><img src="../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="reference.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> +</div> +</body> +</html> |