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  • Committer: Package Import Robot
  • Author(s): Steve M. Robbins
  • Date: 2012-02-26 00:31:44 UTC
  • Revision ID: package-import@ubuntu.com-20120226003144-eaytp12cbf6ubpms
Tags: upstream-1.49.0
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doc/html/boost_asio/reference/read_at/overload1.html
 
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<html>
 
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<head>
 
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<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
 
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<title>read_at (1 of 8 overloads)</title>
 
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<meta name="generator" content="DocBook XSL Stylesheets V1.76.1">
 
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<link rel="home" href="../../../boost_asio.html" title="Boost.Asio">
 
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<link rel="up" href="../read_at.html" title="read_at">
 
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<link rel="prev" href="../read_at.html" title="read_at">
 
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<link rel="next" href="overload2.html" title="read_at (2 of 8 overloads)">
 
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</head>
 
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
 
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<table cellpadding="2" width="100%"><tr>
 
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<td align="center"><a href="../../../../../index.html">Home</a></td>
 
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<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
 
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<td align="center"><a href="../../../../../more/index.htm">More</a></td>
 
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</tr></table>
 
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<hr>
 
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<div class="spirit-nav">
 
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<a accesskey="p" href="../read_at.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../read_at.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload2.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
 
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</div>
 
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<div class="section">
 
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<div class="titlepage"><div><div><h4 class="title">
 
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<a name="boost_asio.reference.read_at.overload1"></a><a class="link" href="overload1.html" title="read_at (1 of 8 overloads)">read_at (1
 
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        of 8 overloads)</a>
 
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</h4></div></div></div>
 
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<p>
 
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          Attempt to read a certain amount of data at the specified offset before
 
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          returning.
 
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        </p>
 
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<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
 
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    <span class="keyword">typename</span> <a class="link" href="../SyncRandomAccessReadDevice.html" title="Buffer-oriented synchronous random-access read device requirements">SyncRandomAccessReadDevice</a><span class="special">,</span>
 
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    <span class="keyword">typename</span> <a class="link" href="../MutableBufferSequence.html" title="Mutable buffer sequence requirements">MutableBufferSequence</a><span class="special">&gt;</span>
 
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">read_at</span><span class="special">(</span>
 
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    <span class="identifier">SyncRandomAccessReadDevice</span> <span class="special">&amp;</span> <span class="identifier">d</span><span class="special">,</span>
 
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    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">uint64_t</span> <span class="identifier">offset</span><span class="special">,</span>
 
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    <span class="keyword">const</span> <span class="identifier">MutableBufferSequence</span> <span class="special">&amp;</span> <span class="identifier">buffers</span><span class="special">);</span>
 
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</pre>
 
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<p>
 
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          This function is used to read a certain number of bytes of data from a
 
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          random access device at the specified offset. The call will block until
 
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          one of the following conditions is true:
 
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        </p>
 
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<div class="itemizedlist"><ul class="itemizedlist" type="disc">
 
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<li class="listitem">
 
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              The supplied buffers are full. That is, the bytes transferred is equal
 
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              to the sum of the buffer sizes.
 
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            </li>
 
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<li class="listitem">
 
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              An error occurred.
 
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            </li>
 
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</ul></div>
 
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<p>
 
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          This operation is implemented in terms of zero or more calls to the device's
 
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          read_some_at function.
 
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        </p>
 
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<h6>
 
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<a name="boost_asio.reference.read_at.overload1.h0"></a>
 
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          <span><a name="boost_asio.reference.read_at.overload1.parameters"></a></span><a class="link" href="overload1.html#boost_asio.reference.read_at.overload1.parameters">Parameters</a>
 
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        </h6>
 
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<div class="variablelist">
 
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<p class="title"><b></b></p>
 
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<dl>
 
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<dt><span class="term">d</span></dt>
 
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<dd><p>
 
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                The device from which the data is to be read. The type must support
 
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                the SyncRandomAccessReadDevice concept.
 
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              </p></dd>
 
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<dt><span class="term">offset</span></dt>
 
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<dd><p>
 
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                The offset at which the data will be read.
 
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              </p></dd>
 
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<dt><span class="term">buffers</span></dt>
 
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<dd><p>
 
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                One or more buffers into which the data will be read. The sum of
 
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                the buffer sizes indicates the maximum number of bytes to read from
 
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                the device.
 
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              </p></dd>
 
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</dl>
 
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</div>
 
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<h6>
 
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<a name="boost_asio.reference.read_at.overload1.h1"></a>
 
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          <span><a name="boost_asio.reference.read_at.overload1.return_value"></a></span><a class="link" href="overload1.html#boost_asio.reference.read_at.overload1.return_value">Return Value</a>
 
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        </h6>
 
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<p>
 
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          The number of bytes transferred.
 
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        </p>
 
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<h6>
 
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<a name="boost_asio.reference.read_at.overload1.h2"></a>
 
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          <span><a name="boost_asio.reference.read_at.overload1.exceptions"></a></span><a class="link" href="overload1.html#boost_asio.reference.read_at.overload1.exceptions">Exceptions</a>
 
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        </h6>
 
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<div class="variablelist">
 
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<p class="title"><b></b></p>
 
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<dl>
 
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<dt><span class="term">boost::system::system_error</span></dt>
 
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<dd><p>
 
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                Thrown on failure.
 
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              </p></dd>
 
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</dl>
 
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</div>
 
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<h6>
 
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<a name="boost_asio.reference.read_at.overload1.h3"></a>
 
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          <span><a name="boost_asio.reference.read_at.overload1.example"></a></span><a class="link" href="overload1.html#boost_asio.reference.read_at.overload1.example">Example</a>
 
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        </h6>
 
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<p>
 
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          To read into a single data buffer use the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput"><span class="identifier">buffer</span></code></a> function as follows:
 
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        </p>
 
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<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">read_at</span><span class="special">(</span><span class="identifier">d</span><span class="special">,</span> <span class="number">42</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">buffer</span><span class="special">(</span><span class="identifier">data</span><span class="special">,</span> <span class="identifier">size</span><span class="special">));</span>
 
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</pre>
 
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<p>
 
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          See the <a class="link" href="../buffer.html" title="buffer"><code class="computeroutput"><span class="identifier">buffer</span></code></a>
 
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          documentation for information on reading into multiple buffers in one go,
 
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          and how to use it with arrays, boost::array or std::vector.
 
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        </p>
 
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<h6>
 
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<a name="boost_asio.reference.read_at.overload1.h4"></a>
 
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          <span><a name="boost_asio.reference.read_at.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.read_at.overload1.remarks">Remarks</a>
 
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        </h6>
 
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<p>
 
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          This overload is equivalent to calling:
 
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        </p>
 
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<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">read_at</span><span class="special">(</span>
 
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    <span class="identifier">d</span><span class="special">,</span> <span class="number">42</span><span class="special">,</span> <span class="identifier">buffers</span><span class="special">,</span>
 
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    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">transfer_all</span><span class="special">());</span>
 
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</pre>
 
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</div>
 
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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 &#169; 2003-2012 Christopher 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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      </p>
 
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</div></td>
 
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</tr></table>
 
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<hr>
 
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<div class="spirit-nav">
 
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<a accesskey="p" href="../read_at.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../read_at.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../boost_asio.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload2.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a>
 
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</div>
 
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