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<div class="section" title="Buffer-oriented synchronous random-access read device requirements">
<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"><span class="identifier">a</span></code> denotes
a synchronous random-access read device object, <code class="computeroutput"><span class="identifier">o</span></code>
denotes an offset of type <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">uint64_t</span></code>,
<code class="computeroutput"><span class="identifier">mb</span></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"><span class="identifier">ec</span></code>
denotes an object of type <code class="computeroutput"><span class="identifier">error_code</span></code>.
</p>
<div class="table">
<a name="id655782"></a><p class="title"><b>Table 31. 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"><span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some_at</span><span class="special">(</span><span class="identifier">o</span><span class="special">,</span> <span class="identifier">mb</span><span class="special">);</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">size_t</span></code>
</p>
</td>
<td>
<p>
Equivalent to:
</p>
<pre class="programlisting"><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">;</span>
<span class="identifier">size_t</span> <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some_at</span><span class="special">(</span><span class="identifier">o</span><span class="special">,</span> <span class="identifier">mb</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span>
<span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span><span class="special">)</span> <span class="keyword">throw</span> <span class="identifier">system_error</span><span class="special">(</span><span class="identifier">ec</span><span class="special">);</span>
<span class="keyword">return</span> <span class="identifier">s</span><span class="special">;</span>
</pre>
<p>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">read_some_at</span><span class="special">(</span><span class="identifier">o</span><span class="special">,</span> <span class="identifier">mb</span><span class="special">,</span> <span class="identifier">ec</span><span class="special">);</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">size_t</span></code>
</p>
</td>
<td>
<p>
Reads one or more bytes of data from the device <code class="computeroutput"><span class="identifier">a</span></code>
at offset <code class="computeroutput"><span class="identifier">o</span></code>.<br>
<br> The mutable buffer sequence <code class="computeroutput"><span class="identifier">mb</span></code>
specifies memory where the data should be placed. The <code class="computeroutput"><span class="identifier">read_some_at</span></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"><span class="identifier">ec</span></code> such that <code class="computeroutput"><span class="special">!</span><span class="identifier">ec</span></code> is true. If an error occurred,
returns <code class="computeroutput"><span class="number">0</span></code> and sets <code class="computeroutput"><span class="identifier">ec</span></code> such that <code class="computeroutput"><span class="special">!!</span><span class="identifier">ec</span></code> is true.<br> <br> If the total
size of all buffers in the sequence <code class="computeroutput"><span class="identifier">mb</span></code>
is <code class="computeroutput"><span class="number">0</span></code>, the function shall
return <code class="computeroutput"><span class="number">0</span></code> immediately.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003 - 2010 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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