1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Streams</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. Boost.Beast"> 8<link rel="up" href="../using_io.html" title="Networking"> 9<link rel="prev" href="asio_refresher.html" title="Refresher"> 10<link rel="next" href="timeouts.html" title="Timeouts ��"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="asio_refresher.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../using_io.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="timeouts.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="beast.using_io.stream_types"></a><a class="link" href="stream_types.html" title="Streams">Streams</a> 28</h3></div></div></div> 29<p> 30 A <a class="link" href="../concepts/streams.html" title="Streams"><span class="emphasis"><em>Stream</em></span></a> 31 is a communication channel where data is reliably transferred as an ordered 32 sequence of bytes. Streams are either synchronous or asynchronous, and may 33 allow reading, writing, or both. Note that a particular type may model more 34 than one concept. For example, the networking types <a href="../../../../../../doc/html/boost_asio/reference/ip__tcp/socket.html" target="_top"><code class="computeroutput"><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span></code></a> 35 and <a href="../../../../../../doc/html/boost_asio/reference/ssl__stream.html" target="_top"><code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">ssl</span><span class="special">::</span><span class="identifier">stream</span></code></a> 36 support both <a class="link" href="../concepts/streams.html#beast.concepts.streams.SyncStream"><span class="emphasis"><em>SyncStream</em></span></a> 37 and <a class="link" href="../concepts/streams.html#beast.concepts.streams.AsyncStream"><span class="emphasis"><em>AsyncStream</em></span></a>. 38 All stream algorithms in Beast are declared as template functions using these 39 concepts: 40 </p> 41<div class="table"> 42<a name="beast.using_io.stream_types.stream_concepts"></a><p class="title"><b>Table 1.4. Stream Concepts</b></p> 43<div class="table-contents"><table class="table" summary="Stream Concepts"> 44<colgroup> 45<col> 46<col> 47</colgroup> 48<thead><tr> 49<th> 50 <p> 51 Concept 52 </p> 53 </th> 54<th> 55 <p> 56 Description 57 </p> 58 </th> 59</tr></thead> 60<tbody> 61<tr> 62<td> 63 <p> 64 <a href="../../../../../../doc/html/boost_asio/reference/SyncReadStream.html" target="_top"><span class="emphasis"><em>SyncReadStream</em></span></a> 65 </p> 66 </td> 67<td> 68 <p> 69 Supports buffer-oriented blocking reads. 70 </p> 71 </td> 72</tr> 73<tr> 74<td> 75 <p> 76 <a href="../../../../../../doc/html/boost_asio/reference/SyncWriteStream.html" target="_top"><span class="emphasis"><em>SyncWriteStream</em></span></a> 77 </p> 78 </td> 79<td> 80 <p> 81 Supports buffer-oriented blocking writes. 82 </p> 83 </td> 84</tr> 85<tr> 86<td> 87 <p> 88 <a class="link" href="../concepts/streams.html#beast.concepts.streams.SyncStream"><span class="emphasis"><em>SyncStream</em></span></a> 89 </p> 90 </td> 91<td> 92 <p> 93 A stream supporting buffer-oriented blocking reads and writes. 94 </p> 95 </td> 96</tr> 97<tr> 98<td> 99 <p> 100 <a href="../../../../../../doc/html/boost_asio/reference/AsyncReadStream.html" target="_top"><span class="emphasis"><em>AsyncReadStream</em></span></a> 101 </p> 102 </td> 103<td> 104 <p> 105 Supports buffer-oriented asynchronous reads. 106 </p> 107 </td> 108</tr> 109<tr> 110<td> 111 <p> 112 <a href="../../../../../../doc/html/boost_asio/reference/AsyncWriteStream.html" target="_top"><span class="emphasis"><em>AsyncWriteStream</em></span></a> 113 </p> 114 </td> 115<td> 116 <p> 117 Supports buffer-oriented asynchronous writes. 118 </p> 119 </td> 120</tr> 121<tr> 122<td> 123 <p> 124 <a class="link" href="../concepts/streams.html#beast.concepts.streams.AsyncStream"><span class="emphasis"><em>AsyncStream</em></span></a> 125 </p> 126 </td> 127<td> 128 <p> 129 A stream supporting buffer-oriented asynchronous reads and writes. 130 </p> 131 </td> 132</tr> 133</tbody> 134</table></div> 135</div> 136<br class="table-break"><p> 137 These template metafunctions check whether a given type meets the requirements 138 for the various stream concepts, and some additional useful utilities. The 139 library uses these type checks internally and also provides them as public 140 interfaces so users may use the same techniques to augment their own code. 141 The use of these type checks helps provide more concise errors during compilation: 142 </p> 143<div class="table"> 144<a name="beast.using_io.stream_types.type_traits_and_metafunctions"></a><p class="title"><b>Table 1.5. Type Traits and Metafunctions</b></p> 145<div class="table-contents"><table class="table" summary="Type Traits and Metafunctions"> 146<colgroup> 147<col> 148<col> 149</colgroup> 150<thead><tr> 151<th> 152 <p> 153 Name 154 </p> 155 </th> 156<th> 157 <p> 158 Description 159 </p> 160 </th> 161</tr></thead> 162<tbody> 163<tr> 164<td> 165 <p> 166 <a class="link" href="../ref/boost__beast__executor_type.html" title="executor_type"><code class="computeroutput"><span class="identifier">executor_type</span></code></a> 167 </p> 168 </td> 169<td> 170 <p> 171 An alias for the type of object returned by <code class="computeroutput"><span class="identifier">get_executor</span></code>. 172 </p> 173 </td> 174</tr> 175<tr> 176<td> 177 <p> 178 <a class="link" href="../ref/boost__beast__has_get_executor.html" title="has_get_executor"><code class="computeroutput"><span class="identifier">has_get_executor</span></code></a> 179 </p> 180 </td> 181<td> 182 <p> 183 Determine if the <code class="computeroutput"><span class="identifier">get_executor</span></code> 184 member function is present. 185 </p> 186 </td> 187</tr> 188<tr> 189<td> 190 <p> 191 <a class="link" href="../ref/boost__beast__is_async_read_stream.html" title="is_async_read_stream"><code class="computeroutput"><span class="identifier">is_async_read_stream</span></code></a> 192 </p> 193 </td> 194<td> 195 <p> 196 Determine if a type meets the requirements of <a href="../../../../../../doc/html/boost_asio/reference/AsyncReadStream.html" target="_top"><span class="emphasis"><em>AsyncReadStream</em></span></a>. 197 </p> 198 </td> 199</tr> 200<tr> 201<td> 202 <p> 203 <a class="link" href="../ref/boost__beast__is_async_stream.html" title="is_async_stream"><code class="computeroutput"><span class="identifier">is_async_stream</span></code></a> 204 </p> 205 </td> 206<td> 207 <p> 208 Determine if a type meets the requirements of both <a href="../../../../../../doc/html/boost_asio/reference/AsyncReadStream.html" target="_top"><span class="emphasis"><em>AsyncReadStream</em></span></a> 209 and <a href="../../../../../../doc/html/boost_asio/reference/AsyncWriteStream.html" target="_top"><span class="emphasis"><em>AsyncWriteStream</em></span></a>. 210 </p> 211 </td> 212</tr> 213<tr> 214<td> 215 <p> 216 <a class="link" href="../ref/boost__beast__is_async_write_stream.html" title="is_async_write_stream"><code class="computeroutput"><span class="identifier">is_async_write_stream</span></code></a> 217 </p> 218 </td> 219<td> 220 <p> 221 Determine if a type meets the requirements of <a href="../../../../../../doc/html/boost_asio/reference/AsyncWriteStream.html" target="_top"><span class="emphasis"><em>AsyncWriteStream</em></span></a>. 222 </p> 223 </td> 224</tr> 225<tr> 226<td> 227 <p> 228 <a class="link" href="../ref/boost__beast__is_sync_read_stream.html" title="is_sync_read_stream"><code class="computeroutput"><span class="identifier">is_sync_read_stream</span></code></a> 229 </p> 230 </td> 231<td> 232 <p> 233 Determine if a type meets the requirements of <a href="../../../../../../doc/html/boost_asio/reference/SyncReadStream.html" target="_top"><span class="emphasis"><em>SyncReadStream</em></span></a>. 234 </p> 235 </td> 236</tr> 237<tr> 238<td> 239 <p> 240 <a class="link" href="../ref/boost__beast__is_sync_stream.html" title="is_sync_stream"><code class="computeroutput"><span class="identifier">is_sync_stream</span></code></a> 241 </p> 242 </td> 243<td> 244 <p> 245 Determine if a type meets the requirements of both <a href="../../../../../../doc/html/boost_asio/reference/SyncReadStream.html" target="_top"><span class="emphasis"><em>SyncReadStream</em></span></a> 246 and <a href="../../../../../../doc/html/boost_asio/reference/SyncWriteStream.html" target="_top"><span class="emphasis"><em>SyncWriteStream</em></span></a>. 247 </p> 248 </td> 249</tr> 250<tr> 251<td> 252 <p> 253 <a class="link" href="../ref/boost__beast__is_sync_write_stream.html" title="is_sync_write_stream"><code class="computeroutput"><span class="identifier">is_sync_write_stream</span></code></a> 254 </p> 255 </td> 256<td> 257 <p> 258 Determine if a type meets the requirements of <a href="../../../../../../doc/html/boost_asio/reference/SyncWriteStream.html" target="_top"><span class="emphasis"><em>SyncWriteStream</em></span></a>. 259 </p> 260 </td> 261</tr> 262</tbody> 263</table></div> 264</div> 265<br class="table-break"><p> 266 Using the type checks with <code class="computeroutput"><span class="keyword">static_assert</span></code> 267 on function or class template types will provide users with helpful error 268 messages and prevent undefined behaviors. This example shows how a template 269 function which writes to a synchronous stream may check its argument: 270 </p> 271<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">SyncWriteStream</span><span class="special">></span> 272<span class="keyword">void</span> <span class="identifier">write_string</span><span class="special">(</span><span class="identifier">SyncWriteStream</span><span class="special">&</span> <span class="identifier">stream</span><span class="special">,</span> <span class="identifier">string_view</span> <span class="identifier">s</span><span class="special">)</span> 273<span class="special">{</span> 274 <span class="keyword">static_assert</span><span class="special">(</span><span class="identifier">is_sync_write_stream</span><span class="special"><</span><span class="identifier">SyncWriteStream</span><span class="special">>::</span><span class="identifier">value</span><span class="special">,</span> 275 <span class="string">"SyncWriteStream type requirements not met"</span><span class="special">);</span> 276 <span class="identifier">net</span><span class="special">::</span><span class="identifier">write</span><span class="special">(</span><span class="identifier">stream</span><span class="special">,</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">const_buffer</span><span class="special">(</span><span class="identifier">s</span><span class="special">.</span><span class="identifier">data</span><span class="special">(),</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">size</span><span class="special">()));</span> 277<span class="special">}</span> 278</pre> 279</div> 280<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 281<td align="left"></td> 282<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 283 Falco<p> 284 Distributed under the Boost Software License, Version 1.0. (See accompanying 285 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>) 286 </p> 287</div></td> 288</tr></table> 289<hr> 290<div class="spirit-nav"> 291<a accesskey="p" href="asio_refresher.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../using_io.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="timeouts.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 292</div> 293</body> 294</html> 295
