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<div class="titlepage"><div><div><h3 class="title">
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<a name="boost_asio.reference.AsyncRandomAccessReadDevice"></a><a class="link" href="AsyncRandomAccessReadDevice.html" title="Buffer-oriented asynchronous random-access read device requirements">Buffer-oriented
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asynchronous random-access read device requirements</a>
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</h3></div></div></div>
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<p>
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In the table below, <code class="computeroutput">a</code> denotes an asynchronous random access
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read device object, <code class="computeroutput">o</code> denotes an offset of type <code class="computeroutput">boost::uint64_t</code>,
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<code class="computeroutput">mb</code> denotes an object satisfying <a class="link" href="MutableBufferSequence.html" title="Mutable buffer sequence requirements">mutable
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buffer sequence</a> requirements, and <code class="computeroutput">h</code> denotes an object
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satisfying <a class="link" href="ReadHandler.html" title="Read handler requirements">read handler</a>
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requirements.
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</p>
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<div class="table">
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<a name="boost_asio.reference.AsyncRandomAccessReadDevice.t0"></a><p class="title"><b>Table 2. Buffer-oriented asynchronous random-access read device requirements</b></p>
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<div class="table-contents"><table class="table" summary="Buffer-oriented asynchronous random-access read device requirements">
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<colgroup>
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<col>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>
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<p>
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operation
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</p>
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</th>
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<th>
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<p>
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type
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</p>
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</th>
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<th>
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<p>
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semantics, pre/post-conditions
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</p>
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</th>
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</tr></thead>
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<tbody>
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<tr>
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<td>
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<p>
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<code class="computeroutput">a.get_executor()</code>
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</p>
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</td>
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<td>
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<p>
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A type satisfying the <a class="link" href="Executor1.html" title="Executor requirements">Executor
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requirements</a>.
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</p>
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</td>
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<td>
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<p>
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Returns the associated I/O executor.
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</p>
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</td>
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</tr>
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<tr>
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<td>
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<p>
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<code class="computeroutput">a.async_read_some_at(o, mb, h);</code>
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</p>
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</td>
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<td>
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<p>
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<code class="computeroutput">void</code>
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</p>
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</td>
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<td>
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<p>
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Initiates an asynchronous operation to read one or more bytes of
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data from the device <code class="computeroutput">a</code> at the offset <code class="computeroutput">o</code>.
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The operation is performed via the <code class="computeroutput">io_service</code> object
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<code class="computeroutput">a.get_io_service()</code> and behaves according to <a class="link" href="asynchronous_operations.html" title="Requirements on asynchronous operations">asynchronous
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operation</a> requirements.<br> <br> The mutable buffer
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sequence <code class="computeroutput">mb</code> specifies memory where the data should
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be placed. The <code class="computeroutput">async_read_some_at</code> operation shall
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always fill a buffer in the sequence completely before proceeding
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to the next.<br> <br> The implementation shall maintain one
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or more copies of <code class="computeroutput">mb</code> until such time as the read operation
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no longer requires access to the memory specified by the buffers
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in the sequence. The program must ensure the memory is valid until:<br>
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<br> — the last copy of <code class="computeroutput">mb</code> is destroyed, or<br>
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<br> — the handler for the asynchronous read operation is invoked,<br>
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<br> whichever comes first.<br> <br> If the total size of
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all buffers in the sequence <code class="computeroutput">mb</code> is <code class="computeroutput">0</code>,
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the asynchronous read operation shall complete immediately and
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pass <code class="computeroutput">0</code> as the argument to the handler that specifies
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the number of bytes read.
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</p>
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</td>
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</tr>
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</tbody>
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</table></div>
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</div>
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<br class="table-break">
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2021 Christopher
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M. Kohlhoff<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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