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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_asio.overview.core.streams"></a><a class="link" href="streams.html" title="Streams, Short Reads and Short Writes">Streams, Short Reads |
| and Short Writes</a> |
| </h4></div></div></div> |
| <p> |
| Many I/O objects in Boost.Asio are stream-oriented. This means that: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| There are no message boundaries. The data being transferred is a continuous |
| sequence of bytes. |
| </li> |
| <li class="listitem"> |
| Read or write operations may transfer fewer bytes than requested. This |
| is referred to as a short read or short write. |
| </li> |
| </ul></div> |
| <p> |
| Objects that provide stream-oriented I/O model one or more of the following |
| type requirements: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">SyncReadStream</span></code>, where |
| synchronous read operations are performed using a member function called |
| <code class="computeroutput"><span class="identifier">read_some</span><span class="special">()</span></code>. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">AsyncReadStream</span></code>, where |
| asynchronous read operations are performed using a member function |
| called <code class="computeroutput"><span class="identifier">async_read_some</span><span class="special">()</span></code>. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">SyncWriteStream</span></code>, where |
| synchronous write operations are performed using a member function |
| called <code class="computeroutput"><span class="identifier">write_some</span><span class="special">()</span></code>. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">AsyncWriteStream</span></code>, where |
| synchronous write operations are performed using a member function |
| called <code class="computeroutput"><span class="identifier">async_write_some</span><span class="special">()</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| Examples of stream-oriented I/O objects include <code class="computeroutput"><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span></code>, |
| <code class="computeroutput"><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span><span class="special"><></span></code>, |
| <code class="computeroutput"><span class="identifier">posix</span><span class="special">::</span><span class="identifier">stream_descriptor</span></code>, <code class="computeroutput"><span class="identifier">windows</span><span class="special">::</span><span class="identifier">stream_handle</span></code>, |
| etc. |
| </p> |
| <p> |
| Programs typically want to transfer an exact number of bytes. When a short |
| read or short write occurs the program must restart the operation, and |
| continue to do so until the required number of bytes has been transferred. |
| Boost.Asio provides generic functions that do this automatically: <code class="computeroutput"><span class="identifier">read</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">async_read</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">write</span><span class="special">()</span></code> |
| and <code class="computeroutput"><span class="identifier">async_write</span><span class="special">()</span></code>. |
| </p> |
| <a name="boost_asio.overview.core.streams.why_eof_is_an_error"></a><h6> |
| <a name="id764383"></a> |
| <a class="link" href="streams.html#boost_asio.overview.core.streams.why_eof_is_an_error">Why |
| EOF is an Error</a> |
| </h6> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| The end of a stream can cause <code class="computeroutput"><span class="identifier">read</span></code>, |
| <code class="computeroutput"><span class="identifier">async_read</span></code>, <code class="computeroutput"><span class="identifier">read_until</span></code> or <code class="computeroutput"><span class="identifier">async_read_until</span></code> |
| functions to violate their contract. E.g. a read of N bytes may finish |
| early due to EOF. |
| </li> |
| <li class="listitem"> |
| An EOF error may be used to distinguish the end of a stream from a |
| successful read of size 0. |
| </li> |
| </ul></div> |
| <a name="boost_asio.overview.core.streams.see_also"></a><h6> |
| <a name="id764455"></a> |
| <a class="link" href="streams.html#boost_asio.overview.core.streams.see_also">See Also</a> |
| </h6> |
| <p> |
| <a class="link" href="../../reference/async_read.html" title="async_read">async_read()</a>, <a class="link" href="../../reference/async_write.html" title="async_write">async_write()</a>, <a class="link" href="../../reference/read.html" title="read">read()</a>, <a class="link" href="../../reference/write.html" title="write">write()</a>, |
| <a class="link" href="../../reference/AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>, |
| <a class="link" href="../../reference/AsyncWriteStream.html" title="Buffer-oriented asynchronous write stream requirements">AsyncWriteStream</a>, |
| <a class="link" href="../../reference/SyncReadStream.html" title="Buffer-oriented synchronous read stream requirements">SyncReadStream</a>, |
| <a class="link" href="../../reference/SyncWriteStream.html" title="Buffer-oriented synchronous write stream requirements">SyncWriteStream</a>. |
| </p> |
| </div> |
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| <td align="left"></td> |
| <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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