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<title>Buffer-oriented synchronous random-access read device requirements</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.reference.SyncRandomAccessReadDevice"></a><a class="link" href="SyncRandomAccessReadDevice.html" title="Buffer-oriented synchronous random-access read device requirements">Buffer-oriented
synchronous random-access read device requirements</a>
</h3></div></div></div>
<p>
In the table below, <code class="computeroutput">a</code> denotes a synchronous random-access read
device object, <code class="computeroutput">o</code> denotes an offset of type <code class="computeroutput">boost::uint64_t</code>,
<code class="computeroutput">mb</code> denotes an object satisfying <a class="link" href="MutableBufferSequence.html" title="Mutable buffer sequence requirements">mutable
buffer sequence</a> requirements, and <code class="computeroutput">ec</code> denotes an object
of type <code class="computeroutput">error_code</code>.
</p>
<div class="table">
<a name="boost_asio.reference.SyncRandomAccessReadDevice.t0"></a><p class="title"><b>Table 27. Buffer-oriented synchronous random-access read device requirements</b></p>
<div class="table-contents"><table class="table" summary="Buffer-oriented synchronous random-access read device requirements">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
operation
</p>
</th>
<th>
<p>
type
</p>
</th>
<th>
<p>
semantics, pre/post-conditions
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput">a.read_some_at(o, mb);</code>
</p>
</td>
<td>
<p>
<code class="computeroutput">size_t</code>
</p>
</td>
<td>
<p>
Equivalent to:
</p>
<pre class="programlisting">error_code ec;
size_t s = a.read_some_at(o, mb, ec);
if (ec) throw system_error(ec);
return s;
</pre>
<p>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput">a.read_some_at(o, mb, ec);</code>
</p>
</td>
<td>
<p>
<code class="computeroutput">size_t</code>
</p>
</td>
<td>
<p>
Reads one or more bytes of data from the device <code class="computeroutput">a</code>
at offset <code class="computeroutput">o</code>.<br> <br> The mutable buffer sequence
<code class="computeroutput">mb</code> specifies memory where the data should be placed.
The <code class="computeroutput">read_some_at</code> operation shall always fill a buffer
in the sequence completely before proceeding to the next.<br>
<br> If successful, returns the number of bytes read and sets
<code class="computeroutput">ec</code> such that <code class="computeroutput">!ec</code> is true. If an error
occurred, returns <code class="computeroutput">0</code> and sets <code class="computeroutput">ec</code> such
that <code class="computeroutput">!!ec</code> is true.<br> <br> If the total size
of all buffers in the sequence <code class="computeroutput">mb</code> is <code class="computeroutput">0</code>,
the function shall return <code class="computeroutput">0</code> immediately.
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<td align="right"><div class="copyright-footer">Copyright © 2003-2019 Christopher M. Kohlhoff<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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