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<a name="boost.intrusive.pointer_traits"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Struct template pointer_traits</span></h2>
<p>boost::intrusive::pointer_traits</p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../intrusive/reference.html#header.boost.intrusive.pointer_traits_hpp" title="Header <boost/intrusive/pointer_traits.hpp>">boost/intrusive/pointer_traits.hpp</a>>
</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Ptr<span class="special">></span>
<span class="keyword">struct</span> <a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> <span class="special">{</span>
<span class="comment">// <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traitstypes">types</a></span>
<span class="keyword">typedef</span> <span class="identifier">Ptr</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.pointer"><span class="identifier">pointer</span></a><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.element_type"><span class="identifier">element_type</span></a><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.difference_type"><span class="identifier">difference_type</span></a><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">unspecified</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.rebind"><span class="identifier">rebind</span></a><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.reference"><span class="identifier">reference</span></a><span class="special">;</span>
<span class="comment">// <a class="link" href="pointer_traits.html#idp49005200-bb">public static functions</a></span>
<span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idp49005760-bb"><span class="identifier">pointer_to</span></a><span class="special">(</span><span class="identifier">reference</span><span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> UPtr<span class="special">></span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idp49011008-bb"><span class="identifier">static_cast_from</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> UPtr<span class="special">></span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idp49017056-bb"><span class="identifier">const_cast_from</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> UPtr<span class="special">></span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idp49023104-bb"><span class="identifier">dynamic_cast_from</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idp286538784"></a><h2>Description</h2>
<p><a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> is the implementation of C++11 std::pointer_traits class with some extensions like castings.</p>
<p><a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> supplies a uniform interface to certain attributes of pointer-like types.</p>
<p><span class="bold"><strong>Note</strong></span>: When defining a custom family of pointers or references to be used with BI library, make sure the public static conversion functions accessed through the <code class="computeroutput"><a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a></code> interface (<code class="computeroutput">*_cast_from</code> and <code class="computeroutput">pointer_to</code>) can properly convert between const and nonconst referred member types <span class="bold"><strong>without the use of implicit constructor calls</strong></span>. It is suggested these conversions be implemented as function templates, where the template argument is the type of the object being converted from. </p>
<div class="refsect2">
<a name="idp286546016"></a><h3>
<a name="boost.intrusive.pointer_traitstypes"></a><code class="computeroutput">pointer_traits</code>
public
types</h3>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
<p>
<span class="keyword">typedef</span> <span class="identifier">Ptr</span> <a name="boost.intrusive.pointer_traits.pointer"></a><span class="identifier">pointer</span><span class="special">;</span></p>
<p>The pointer type queried by this <a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> instantiation </p>
</li>
<li class="listitem">
<p>
<span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a name="boost.intrusive.pointer_traits.element_type"></a><span class="identifier">element_type</span><span class="special">;</span></p>
<p>Ptr::element_type if such a type exists; otherwise, T if Ptr is a class template instantiation of the form SomePointer<T, Args>, where Args is zero or more type arguments ; otherwise , the specialization is ill-formed. </p>
</li>
<li class="listitem">
<p>
<span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a name="boost.intrusive.pointer_traits.difference_type"></a><span class="identifier">difference_type</span><span class="special">;</span></p>
<p>Ptr::difference_type if such a type exists; otherwise, std::ptrdiff_t. </p>
</li>
<li class="listitem">
<p>
<span class="keyword">typedef</span> <span class="identifier">unspecified</span> <a name="boost.intrusive.pointer_traits.rebind"></a><span class="identifier">rebind</span><span class="special">;</span></p>
<p>Ptr::rebind<U> if such a type exists; otherwise, SomePointer<U, Args> if Ptr is a class template instantiation of the form SomePointer<T, Args>, where Args is zero or more type arguments ; otherwise, the instantiation of rebind is ill-formed.</p>
<p>For portable code for C++03 and C++11, <span style="color: red"><preformatted>typename rebind_pointer<U>::type</preformatted></span> shall be used instead of rebind<U> to obtain a pointer to U. </p>
</li>
<li class="listitem">
<p>
<span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a name="boost.intrusive.pointer_traits.reference"></a><span class="identifier">reference</span><span class="special">;</span></p>
<p>Ptr::reference if such a type exists (non-standard extension); otherwise, element_type & </p>
</li>
</ol></div>
</div>
<div class="refsect2">
<a name="idp286569584"></a><h3>
<a name="idp49005200-bb"></a><code class="computeroutput">pointer_traits</code> public static functions</h3>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
<pre class="literallayout"><span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idp49005760-bb"></a><span class="identifier">pointer_to</span><span class="special">(</span><span class="identifier">reference</span> r<span class="special">)</span><span class="special">;</span></pre>
<p><span class="bold"><strong>Remark</strong></span>: If element_type is (possibly cv-qualified) void, r type is unspecified; otherwise, it is element_type &.</p>
<p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling Ptr::pointer_to(reference). Non-standard extension: If such function does not exist, returns pointer(addressof(r));</p>
<p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">pointer_to</code> is checked. </p>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> UPtr<span class="special">></span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idp49011008-bb"></a><span class="identifier">static_cast_from</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&</span> uptr<span class="special">)</span><span class="special">;</span></pre>
<p><span class="bold"><strong>Remark</strong></span>: Non-standard extension.</p>
<p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling the static template function Ptr::static_cast_from(UPpr/const UPpr &). If such function does not exist, returns pointer_to(static_cast<element_type&>(*uptr))</p>
<p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">static_cast_from</code> is checked. </p>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> UPtr<span class="special">></span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idp49017056-bb"></a><span class="identifier">const_cast_from</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&</span> uptr<span class="special">)</span><span class="special">;</span></pre>
<p><span class="bold"><strong>Remark</strong></span>: Non-standard extension.</p>
<p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling the static template function Ptr::const_cast_from<UPtr>(UPpr/const UPpr &). If such function does not exist, returns pointer_to(const_cast<element_type&>(*uptr))</p>
<p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">const_cast_from</code> is checked. </p>
</li>
<li class="listitem">
<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> UPtr<span class="special">></span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idp49023104-bb"></a><span class="identifier">dynamic_cast_from</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&</span> uptr<span class="special">)</span><span class="special">;</span></pre>
<p><span class="bold"><strong>Remark</strong></span>: Non-standard extension.</p>
<p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling the static template function Ptr::dynamic_cast_from<UPtr>(UPpr/const UPpr &). If such function does not exist, returns pointer_to(<span class="emphasis"><em>dynamic_cast<element_type</em></span>>(&*uptr))</p>
<p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">dynamic_cast_from</code> is checked. </p>
</li>
</ol></div>
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<td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla<br>Copyright © 2006-2015 Ion Gaztanaga<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>)
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