1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Buffer-Oriented Serializing</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_http.html" title="HTTP"> 9<link rel="prev" href="parser_stream_operations/incremental_read.html" title="Incremental Read ��"> 10<link rel="next" href="buffer_oriented_parsing.html" title="Buffer-Oriented Parsing"> 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="parser_stream_operations/incremental_read.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../using_http.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="buffer_oriented_parsing.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_http.buffer_oriented_serializing"></a><a class="link" href="buffer_oriented_serializing.html" title="Buffer-Oriented Serializing">Buffer-Oriented 28 Serializing</a> 29</h3></div></div></div> 30<p> 31 An instance of <a class="link" href="../ref/boost__beast__http__serializer.html" title="http::serializer"><code class="computeroutput"><span class="identifier">serializer</span></code></a> can be invoked directly, 32 without using the provided stream operations. This could be useful for implementing 33 algorithms on objects whose interface does not conform to <a class="link" href="../concepts/streams.html" title="Streams"><span class="emphasis"><em>Stream</em></span></a>. 34 For example, a <a href="https://github.com/libuv/libuv" target="_top"><span class="bold"><strong>libuv</strong></span> 35 socket</a>. The serializer interface is interactive; the caller invokes 36 it repeatedly to produce buffers until all of the serialized octets have 37 been generated. Then the serializer is destroyed. 38 </p> 39<p> 40 To obtain the serialized next buffer sequence, call <a class="link" href="../ref/boost__beast__http__serializer/next.html" title="http::serializer::next"><code class="computeroutput"><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">next</span></code></a>. Then, call <a class="link" href="../ref/boost__beast__http__serializer/consume.html" title="http::serializer::consume"><code class="computeroutput"><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">consume</span></code></a> to indicate the number of 41 bytes consumed. This updates the next set of buffers to be returned, if any. 42 <code class="computeroutput"><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">next</span></code> takes an error code parameter and 43 invokes a visitor argument with the error code and buffer of unspecified 44 type. In C++14 this is easily expressed with a generic lambda. The function 45 <a class="link" href="../ref/boost__beast__http__serializer/is_done.html" title="http::serializer::is_done"><code class="computeroutput"><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">is_done</span></code></a> will return <code class="computeroutput"><span class="keyword">true</span></code> when all the buffers have been produced. 46 This C++14 example prints the buffers to standard output: 47 </p> 48<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Body</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Fields</span><span class="special">></span> 49<span class="keyword">void</span> 50<span class="identifier">print_cxx14</span><span class="special">(</span><span class="identifier">message</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">m</span><span class="special">)</span> 51<span class="special">{</span> 52 <span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">;</span> 53 <span class="identifier">serializer</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="identifier">sr</span><span class="special">{</span><span class="identifier">m</span><span class="special">};</span> 54 <span class="keyword">do</span> 55 <span class="special">{</span> 56 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">next</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span> 57 <span class="special">[&</span><span class="identifier">sr</span><span class="special">](</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span> <span class="keyword">auto</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">)</span> 58 <span class="special">{</span> 59 <span class="identifier">ec</span> <span class="special">=</span> <span class="special">{};</span> 60 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">make_printable</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">);</span> 61 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">consume</span><span class="special">(</span><span class="identifier">buffer_bytes</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">));</span> 62 <span class="special">});</span> 63 <span class="special">}</span> 64 <span class="keyword">while</span><span class="special">(!</span> <span class="identifier">ec</span> <span class="special">&&</span> <span class="special">!</span> <span class="identifier">sr</span><span class="special">.</span><span class="identifier">is_done</span><span class="special">());</span> 65 <span class="keyword">if</span><span class="special">(!</span> <span class="identifier">ec</span><span class="special">)</span> 66 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 67 <span class="keyword">else</span> 68 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> <span class="identifier">ec</span><span class="special">.</span><span class="identifier">message</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 69<span class="special">}</span> 70</pre> 71<p> 72 Generic lambda expressions are only available in C++14 or later. A functor 73 with a templated function call operator is necessary to use C++11 as shown: 74 </p> 75<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Serializer</span><span class="special">></span> 76<span class="keyword">struct</span> <span class="identifier">lambda</span> 77<span class="special">{</span> 78 <span class="identifier">Serializer</span><span class="special">&</span> <span class="identifier">sr</span><span class="special">;</span> 79 80 <span class="identifier">lambda</span><span class="special">(</span><span class="identifier">Serializer</span><span class="special">&</span> <span class="identifier">sr_</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">sr</span><span class="special">(</span><span class="identifier">sr_</span><span class="special">)</span> <span class="special">{}</span> 81 82 <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">ConstBufferSequence</span><span class="special">></span> 83 <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span> <span class="identifier">ConstBufferSequence</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">)</span> <span class="keyword">const</span> 84 <span class="special">{</span> 85 <span class="identifier">ec</span> <span class="special">=</span> <span class="special">{};</span> 86 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">make_printable</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">);</span> 87 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">consume</span><span class="special">(</span><span class="identifier">buffer_bytes</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">));</span> 88 <span class="special">}</span> 89<span class="special">};</span> 90 91<span class="keyword">template</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Body</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Fields</span><span class="special">></span> 92<span class="keyword">void</span> 93<span class="identifier">print</span><span class="special">(</span><span class="identifier">message</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">m</span><span class="special">)</span> 94<span class="special">{</span> 95 <span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">;</span> 96 <span class="identifier">serializer</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="identifier">sr</span><span class="special">{</span><span class="identifier">m</span><span class="special">};</span> 97 <span class="keyword">do</span> 98 <span class="special">{</span> 99 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">next</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span> <span class="identifier">lambda</span><span class="special"><</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">sr</span><span class="special">)>{</span><span class="identifier">sr</span><span class="special">});</span> 100 <span class="special">}</span> 101 <span class="keyword">while</span><span class="special">(!</span> <span class="identifier">ec</span> <span class="special">&&</span> <span class="special">!</span> <span class="identifier">sr</span><span class="special">.</span><span class="identifier">is_done</span><span class="special">());</span> 102 <span class="keyword">if</span><span class="special">(!</span> <span class="identifier">ec</span><span class="special">)</span> 103 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 104 <span class="keyword">else</span> 105 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> <span class="identifier">ec</span><span class="special">.</span><span class="identifier">message</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 106<span class="special">}</span> 107</pre> 108<h5> 109<a name="beast.using_http.buffer_oriented_serializing.h0"></a> 110 <span class="phrase"><a name="beast.using_http.buffer_oriented_serializing.split_serialization"></a></span><a class="link" href="buffer_oriented_serializing.html#beast.using_http.buffer_oriented_serializing.split_serialization">Split 111 Serialization</a> 112 </h5> 113<p> 114 In some cases, such as the handling of the <a href="https://tools.ietf.org/html/rfc7231#section-5.1.1" target="_top">Expect: 115 100-continue</a> field, it may be desired to first serialize the header, 116 perform some other action, and then continue with serialization of the body. 117 This is accomplished by calling <a class="link" href="../ref/boost__beast__http__serializer/split.html" title="http::serializer::split"><code class="computeroutput"><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">split</span></code></a> with a boolean indicating 118 that when buffers are produced, the last buffer containing serialized header 119 octets will not contain any octets corresponding to the body. The function 120 <a class="link" href="../ref/boost__beast__http__serializer/is_header_done.html" title="http::serializer::is_header_done"><code class="computeroutput"><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">is_header_done</span></code></a> informs the caller 121 whether the header been serialized fully. In this C++14 example we print 122 the header first, followed by the body: 123 </p> 124<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Body</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Fields</span><span class="special">></span> 125<span class="keyword">void</span> 126<span class="identifier">split_print_cxx14</span><span class="special">(</span><span class="identifier">message</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">m</span><span class="special">)</span> 127<span class="special">{</span> 128 <span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">;</span> 129 <span class="identifier">serializer</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="identifier">sr</span><span class="special">{</span><span class="identifier">m</span><span class="special">};</span> 130 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">split</span><span class="special">(</span><span class="keyword">true</span><span class="special">);</span> 131 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Header:"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 132 <span class="keyword">do</span> 133 <span class="special">{</span> 134 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">next</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span> 135 <span class="special">[&</span><span class="identifier">sr</span><span class="special">](</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span> <span class="keyword">auto</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">)</span> 136 <span class="special">{</span> 137 <span class="identifier">ec</span> <span class="special">=</span> <span class="special">{};</span> 138 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">make_printable</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">);</span> 139 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">consume</span><span class="special">(</span><span class="identifier">buffer_bytes</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">));</span> 140 <span class="special">});</span> 141 <span class="special">}</span> 142 <span class="keyword">while</span><span class="special">(!</span> <span class="identifier">sr</span><span class="special">.</span><span class="identifier">is_header_done</span><span class="special">());</span> 143 <span class="keyword">if</span><span class="special">(!</span> <span class="identifier">ec</span> <span class="special">&&</span> <span class="special">!</span> <span class="identifier">sr</span><span class="special">.</span><span class="identifier">is_done</span><span class="special">())</span> 144 <span class="special">{</span> 145 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Body:"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 146 <span class="keyword">do</span> 147 <span class="special">{</span> 148 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">next</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span> 149 <span class="special">[&</span><span class="identifier">sr</span><span class="special">](</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span> <span class="keyword">auto</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">)</span> 150 <span class="special">{</span> 151 <span class="identifier">ec</span> <span class="special">=</span> <span class="special">{};</span> 152 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">make_printable</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">);</span> 153 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">consume</span><span class="special">(</span><span class="identifier">buffer_bytes</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">));</span> 154 <span class="special">});</span> 155 <span class="special">}</span> 156 <span class="keyword">while</span><span class="special">(!</span> <span class="identifier">ec</span> <span class="special">&&</span> <span class="special">!</span> <span class="identifier">sr</span><span class="special">.</span><span class="identifier">is_done</span><span class="special">());</span> 157 <span class="special">}</span> 158 <span class="keyword">if</span><span class="special">(</span><span class="identifier">ec</span><span class="special">)</span> 159 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cerr</span> <span class="special"><<</span> <span class="identifier">ec</span><span class="special">.</span><span class="identifier">message</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 160<span class="special">}</span> 161</pre> 162<div class="section"> 163<div class="titlepage"><div><div><h4 class="title"> 164<a name="beast.using_http.buffer_oriented_serializing.write_to_std_ostream"></a><a class="link" href="buffer_oriented_serializing.html#beast.using_http.buffer_oriented_serializing.write_to_std_ostream" title="Write To std::ostream ��">Write 165 To std::ostream ��</a> 166</h4></div></div></div> 167<p> 168 The standard library provides the type <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span></code> 169 for performing high level write operations on character streams. The variable 170 <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span></code> is based on this output stream. 171 This example uses the buffer oriented interface of <a class="link" href="../ref/boost__beast__http__serializer.html" title="http::serializer"><code class="computeroutput"><span class="identifier">serializer</span></code></a> to write an HTTP message 172 to a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span></code>: 173 </p> 174<pre class="programlisting"><span class="comment">// The detail namespace means "not public"</span> 175<span class="keyword">namespace</span> <span class="identifier">detail</span> <span class="special">{</span> 176 177<span class="comment">// This helper is needed for C++11.</span> 178<span class="comment">// When invoked with a buffer sequence, writes the buffers `to the std::ostream`.</span> 179<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">Serializer</span><span class="special">></span> 180<span class="keyword">class</span> <span class="identifier">write_ostream_helper</span> 181<span class="special">{</span> 182 <span class="identifier">Serializer</span><span class="special">&</span> <span class="identifier">sr_</span><span class="special">;</span> 183 <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os_</span><span class="special">;</span> 184 185<span class="keyword">public</span><span class="special">:</span> 186 <span class="identifier">write_ostream_helper</span><span class="special">(</span><span class="identifier">Serializer</span><span class="special">&</span> <span class="identifier">sr</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os</span><span class="special">)</span> 187 <span class="special">:</span> <span class="identifier">sr_</span><span class="special">(</span><span class="identifier">sr</span><span class="special">)</span> 188 <span class="special">,</span> <span class="identifier">os_</span><span class="special">(</span><span class="identifier">os</span><span class="special">)</span> 189 <span class="special">{</span> 190 <span class="special">}</span> 191 192 <span class="comment">// This function is called by the serializer</span> 193 <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">ConstBufferSequence</span><span class="special">></span> 194 <span class="keyword">void</span> 195 <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">,</span> <span class="identifier">ConstBufferSequence</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">buffers</span><span class="special">)</span> <span class="keyword">const</span> 196 <span class="special">{</span> 197 <span class="comment">// Error codes must be cleared on success</span> 198 <span class="identifier">ec</span> <span class="special">=</span> <span class="special">{};</span> 199 200 <span class="comment">// Keep a running total of how much we wrote</span> 201 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> 202 203 <span class="comment">// Loop over the buffer sequence</span> 204 <span class="keyword">for</span><span class="special">(</span><span class="keyword">auto</span> <span class="identifier">it</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_sequence_begin</span><span class="special">(</span><span class="identifier">buffers</span><span class="special">);</span> 205 <span class="identifier">it</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_sequence_end</span><span class="special">(</span><span class="identifier">buffers</span><span class="special">);</span> <span class="special">++</span><span class="identifier">it</span><span class="special">)</span> 206 <span class="special">{</span> 207 <span class="comment">// This is the next buffer in the sequence</span> 208 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">const_buffer</span> <span class="keyword">const</span> <span class="identifier">buffer</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">it</span><span class="special">;</span> 209 210 <span class="comment">// Write it to the std::ostream</span> 211 <span class="identifier">os_</span><span class="special">.</span><span class="identifier">write</span><span class="special">(</span> 212 <span class="keyword">reinterpret_cast</span><span class="special"><</span><span class="keyword">char</span> <span class="keyword">const</span><span class="special">*>(</span><span class="identifier">buffer</span><span class="special">.</span><span class="identifier">data</span><span class="special">()),</span> 213 <span class="identifier">buffer</span><span class="special">.</span><span class="identifier">size</span><span class="special">());</span> 214 215 <span class="comment">// If the std::ostream fails, convert it to an error code</span> 216 <span class="keyword">if</span><span class="special">(</span><span class="identifier">os_</span><span class="special">.</span><span class="identifier">fail</span><span class="special">())</span> 217 <span class="special">{</span> 218 <span class="identifier">ec</span> <span class="special">=</span> <span class="identifier">make_error_code</span><span class="special">(</span><span class="identifier">errc</span><span class="special">::</span><span class="identifier">io_error</span><span class="special">);</span> 219 <span class="keyword">return</span><span class="special">;</span> 220 <span class="special">}</span> 221 222 <span class="comment">// Adjust our running total</span> 223 <span class="identifier">bytes_transferred</span> <span class="special">+=</span> <span class="identifier">buffer_size</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">);</span> 224 <span class="special">}</span> 225 226 <span class="comment">// Inform the serializer of the amount we consumed</span> 227 <span class="identifier">sr_</span><span class="special">.</span><span class="identifier">consume</span><span class="special">(</span><span class="identifier">bytes_transferred</span><span class="special">);</span> 228 <span class="special">}</span> 229<span class="special">};</span> 230 231<span class="special">}</span> <span class="comment">// detail</span> 232 233<span class="comment">/** Write a message to a `std::ostream`. 234 235 This function writes the serialized representation of the 236 HTTP/1 message to the sream. 237 238 @param os The `std::ostream` to write to. 239 240 @param msg The message to serialize. 241 242 @param ec Set to the error, if any occurred. 243*/</span> 244<span class="keyword">template</span><span class="special"><</span> 245 <span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span> 246 <span class="keyword">class</span> <span class="identifier">Body</span><span class="special">,</span> 247 <span class="keyword">class</span> <span class="identifier">Fields</span><span class="special">></span> 248<span class="keyword">void</span> 249<span class="identifier">write_ostream</span><span class="special">(</span> 250 <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os</span><span class="special">,</span> 251 <span class="identifier">message</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">>&</span> <span class="identifier">msg</span><span class="special">,</span> 252 <span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">ec</span><span class="special">)</span> 253<span class="special">{</span> 254 <span class="comment">// Create the serializer instance</span> 255 <span class="identifier">serializer</span><span class="special"><</span><span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span><span class="special">></span> <span class="identifier">sr</span><span class="special">{</span><span class="identifier">msg</span><span class="special">};</span> 256 257 <span class="comment">// This lambda is used as the "visit" function</span> 258 <span class="identifier">detail</span><span class="special">::</span><span class="identifier">write_ostream_helper</span><span class="special"><</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">sr</span><span class="special">)></span> <span class="identifier">lambda</span><span class="special">{</span><span class="identifier">sr</span><span class="special">,</span> <span class="identifier">os</span><span class="special">};</span> 259 <span class="keyword">do</span> 260 <span class="special">{</span> 261 <span class="comment">// In C++14 we could use a generic lambda but since we want</span> 262 <span class="comment">// to require only C++11, the lambda is written out by hand.</span> 263 <span class="comment">// This function call retrieves the next serialized buffers.</span> 264 <span class="identifier">sr</span><span class="special">.</span><span class="identifier">next</span><span class="special">(</span><span class="identifier">ec</span><span class="special">,</span> <span class="identifier">lambda</span><span class="special">);</span> 265 <span class="keyword">if</span><span class="special">(</span><span class="identifier">ec</span><span class="special">)</span> 266 <span class="keyword">return</span><span class="special">;</span> 267 <span class="special">}</span> 268 <span class="keyword">while</span><span class="special">(!</span> <span class="identifier">sr</span><span class="special">.</span><span class="identifier">is_done</span><span class="special">());</span> 269<span class="special">}</span> 270</pre> 271<div class="tip"><table border="0" summary="Tip"> 272<tr> 273<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../../doc/src/images/tip.png"></td> 274<th align="left">Tip</th> 275</tr> 276<tr><td align="left" valign="top"><p> 277 Serializing to a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span></code> 278 could be implemented using an alternate strategy: adapt the <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span></code> interface to a <a href="../../../../../../doc/html/boost_asio/reference/SyncWriteStream.html" target="_top"><span class="emphasis"><em>SyncWriteStream</em></span></a>, 279 enabling use with the library's existing stream algorithms. This is left 280 as an exercise for the reader. 281 </p></td></tr> 282</table></div> 283</div> 284</div> 285<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 286<td align="left"></td> 287<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 288 Falco<p> 289 Distributed under the Boost Software License, Version 1.0. (See accompanying 290 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>) 291 </p> 292</div></td> 293</tr></table> 294<hr> 295<div class="spirit-nav"> 296<a accesskey="p" href="parser_stream_operations/incremental_read.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../using_http.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="buffer_oriented_parsing.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 297</div> 298</body> 299</html> 300
