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125 lines
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<title>write_at (4 of 8 overloads)</title>
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<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../../asio.png"></td></tr></table>
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<a accesskey="p" href="overload3.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../write_at.html"><img src="../../../up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../home.png" alt="Home"></a><a accesskey="n" href="overload5.html"><img src="../../../next.png" alt="Next"></a>
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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="asio.reference.write_at.overload4"></a><a class="link" href="overload4.html" title="write_at (4 of 8 overloads)">write_at (4 of 8
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overloads)</a>
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</h4></div></div></div>
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<p>
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Write a certain amount of data at a specified offset before returning.
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</p>
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<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
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<span class="keyword">typename</span> <a class="link" href="../SyncRandomAccessWriteDevice.html" title="Buffer-oriented synchronous random-access write device requirements">SyncRandomAccessWriteDevice</a><span class="special">,</span>
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<span class="keyword">typename</span> <a class="link" href="../ConstBufferSequence.html" title="Constant buffer sequence requirements">ConstBufferSequence</a><span class="special">,</span>
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<span class="keyword">typename</span> <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a><span class="special">></span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">write_at</span><span class="special">(</span>
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<span class="identifier">SyncRandomAccessWriteDevice</span> <span class="special">&</span> <span class="identifier">d</span><span class="special">,</span>
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<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">ConstBufferSequence</span> <span class="special">&</span> <span class="identifier">buffers</span><span class="special">,</span>
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<span class="identifier">CompletionCondition</span> <span class="identifier">completion_condition</span><span class="special">,</span>
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<span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&</span> <span class="identifier">ec</span><span class="special">);</span>
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</pre>
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<p>
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This function is used to write a certain number of bytes of data to a random
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access device at a specified offset. The call will block until one of the
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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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All of the data in the supplied buffers has been written. That is,
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the bytes transferred is equal to the sum of the buffer sizes.
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</li>
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<li class="listitem">
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The completion_condition function object returns 0.
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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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write_some_at function.
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</p>
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<h6>
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<a name="asio.reference.write_at.overload4.h0"></a>
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<span><a name="asio.reference.write_at.overload4.parameters"></a></span><a class="link" href="overload4.html#asio.reference.write_at.overload4.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 to which the data is to be written. The type must support
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the SyncRandomAccessWriteDevice 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 written.
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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 containing the data to be written. The sum of
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the buffer sizes indicates the maximum number of bytes to write to
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the device.
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</p></dd>
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<dt><span class="term">completion_condition</span></dt>
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<dd>
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<p>
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The function object to be called to determine whether the write operation
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is complete. The signature of the function object must be:
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</p>
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<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">completion_condition</span><span class="special">(</span>
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<span class="comment">// Result of latest write_some_at operation.</span>
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<span class="keyword">const</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">error</span><span class="special">,</span>
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<span class="comment">// Number of bytes transferred so far.</span>
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<span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span>
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<span class="special">);</span>
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</pre>
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<p>
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A return value of 0 indicates that the write operation is complete.
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A non-zero return value indicates the maximum number of bytes to
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be written on the next call to the device's write_some_at function.
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</p>
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</dd>
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<dt><span class="term">ec</span></dt>
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<dd><p>
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Set to indicate what error occurred, if any.
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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="asio.reference.write_at.overload4.h1"></a>
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<span><a name="asio.reference.write_at.overload4.return_value"></a></span><a class="link" href="overload4.html#asio.reference.write_at.overload4.return_value">Return
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Value</a>
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</h6>
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<p>
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The number of bytes written. If an error occurs, returns the total number
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of bytes successfully transferred prior to the error.
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</p>
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</div>
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<div class="copyright-footer">Copyright © 2003-2023 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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