AsyncRandomAccessReadDevice.html
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<title>Buffer-oriented asynchronous random-access read device requirements</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.AsyncRandomAccessReadDevice"></a><a class="link" href="AsyncRandomAccessReadDevice.html" title="Buffer-oriented asynchronous random-access read device requirements">Buffer-oriented
asynchronous random-access read device requirements</a>
</h3></div></div></div>
<p>
In the table below, <code class="computeroutput">a</code> denotes an asynchronous 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">h</code> denotes an object
satisfying <a class="link" href="ReadHandler.html" title="Read handler requirements">read handler</a>
requirements.
</p>
<div class="table">
<a name="asio.reference.AsyncRandomAccessReadDevice.t0"></a><p class="title"><b>Table 2. Buffer-oriented asynchronous random-access read device requirements</b></p>
<div class="table-contents"><table class="table" summary="Buffer-oriented asynchronous 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.get_executor()</code>
</p>
</td>
<td>
<p>
A type satisfying the <a class="link" href="Executor1.html" title="Executor requirements">Executor
requirements</a>.
</p>
</td>
<td>
<p>
Returns the associated I/O executor.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput">a.async_read_some_at(o, mb, h);</code>
</p>
</td>
<td>
<p>
<code class="computeroutput">void</code>
</p>
</td>
<td>
<p>
Initiates an asynchronous operation to read one or more bytes of
data from the device <code class="computeroutput">a</code> at the offset <code class="computeroutput">o</code>.
The operation is performed via the <code class="computeroutput">io_service</code> object
<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 operation</a>
requirements.<br> <br> The mutable buffer sequence <code class="computeroutput">mb</code>
specifies memory where the data should be placed. The <code class="computeroutput">async_read_some_at</code>
operation shall always fill a buffer in the sequence completely
before proceeding to the next.<br> <br> The implementation
shall maintain one or more copies of <code class="computeroutput">mb</code> until such
time as the read operation no longer requires access to the memory
specified by the buffers in the sequence. The program must ensure
the memory is valid until:<br> <br> — the last copy of <code class="computeroutput">mb</code>
is destroyed, or<br> <br> — the handler for the asynchronous
read operation is invoked,<br> <br> whichever comes first.<br>
<br> If the total size of all buffers in the sequence <code class="computeroutput">mb</code>
is <code class="computeroutput">0</code>, the asynchronous read operation shall complete
immediately and pass <code class="computeroutput">0</code> as the argument to the handler
that specifies the number of bytes read.
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 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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