1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Class segmented_stack</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. Coroutine2"> 8<link rel="up" href="../stack.html" title="Stack allocation"> 9<link rel="prev" href="fixedsize.html" title="Class fixedsize_stack"> 10<link rel="next" href="stack_traits.html" title="Class stack_traits"> 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="fixedsize.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../stack.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="stack_traits.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="coroutine2.stack.segmented"></a><a name="segmented"></a><a class="link" href="segmented.html" title="Class segmented_stack">Class 28 <span class="emphasis"><em>segmented_stack</em></span></a> 29</h3></div></div></div> 30<p> 31 <span class="bold"><strong>Boost.Coroutine2</strong></span> supports usage of a <span class="emphasis"><em>segmented_stack</em></span>, 32 e. g. the size of the stack grows on demand. The coroutine is created with 33 a minimal stack size and will be increased as required. Class <span class="emphasis"><em>segmented_stack</em></span> 34 models the <span class="emphasis"><em>stack-allocator concept</em></span>. In contrast to 35 <span class="emphasis"><em>protected_fixedsize_stack</em></span> and <span class="emphasis"><em>fixedsize_stack</em></span> 36 it creates a stack which grows on demand. 37 </p> 38<div class="note"><table border="0" summary="Note"> 39<tr> 40<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td> 41<th align="left">Note</th> 42</tr> 43<tr><td align="left" valign="top"><p> 44 Segmented stacks are currently only supported by <span class="bold"><strong>gcc</strong></span> 45 from version <span class="bold"><strong>4.7</strong></span> <span class="bold"><strong>clang</strong></span> 46 from version <span class="bold"><strong>3.4</strong></span> onwards. In order to 47 use a <span class="emphasis"><em>segmented-stack</em></span> <span class="bold"><strong>Boost.Context</strong></span> 48 must be built with property <code class="computeroutput"><span class="identifier">segmented</span><span class="special">-</span><span class="identifier">stacks</span></code>, 49 e.g. <span class="bold"><strong>toolset=gcc segmented-stacks=on</strong></span> and 50 applying <code class="computeroutput"><span class="identifier">BOOST_USE_SEGMENTED_STACKS</span></code> 51 and <code class="computeroutput"><span class="identifier">BOOST_USE_UCONTEXT</span></code> 52 at b2/bjam command line. 53 </p></td></tr> 54</table></div> 55<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">coroutine2</span><span class="special">/</span><span class="identifier">segmented_stack</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 56 57<span class="keyword">struct</span> <span class="identifier">segmented_stack</span> <span class="special">{</span> 58 <span class="identifier">segmented_stack</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span> <span class="special">=</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">default_size</span><span class="special">());</span> 59 60 <span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">();</span> 61 62 <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&);</span> 63<span class="special">}</span> 64</pre> 65<h5> 66<a name="coroutine2.stack.segmented.h0"></a> 67 <span class="phrase"><a name="coroutine2.stack.segmented._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"></a></span><a class="link" href="segmented.html#coroutine2.stack.segmented._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"><code class="computeroutput"><span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">()</span></code></a> 68 </h5> 69<div class="variablelist"> 70<p class="title"><b></b></p> 71<dl class="variablelist"> 72<dt><span class="term">Preconditions:</span></dt> 73<dd><p> 74 <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> 75 <span class="special"><=</span> <span class="identifier">size</span></code> 76 and <code class="computeroutput"><span class="special">!</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> <span class="special">&&</span> 77 <span class="special">(</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> <span class="special">>=</span> <span class="identifier">size</span><span class="special">)</span></code>. 78 </p></dd> 79<dt><span class="term">Effects:</span></dt> 80<dd><p> 81 Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code> 82 bytes and stores a pointer to the stack and its actual size in <code class="computeroutput"><span class="identifier">sctx</span></code>. Depending on the architecture 83 (the stack grows downwards/upwards) the stored address is the highest/lowest 84 address of the stack. 85 </p></dd> 86</dl> 87</div> 88<h5> 89<a name="coroutine2.stack.segmented.h1"></a> 90 <span class="phrase"><a name="coroutine2.stack.segmented._code__phrase_role__keyword__void__phrase___phrase_role__identifier__deallocate__phrase__phrase_role__special_____phrase___phrase_role__identifier__stack_context__phrase___phrase_role__special___amp___phrase___phrase_role__identifier__sctx__phrase__phrase_role__special_____phrase___code_"></a></span><a class="link" href="segmented.html#coroutine2.stack.segmented._code__phrase_role__keyword__void__phrase___phrase_role__identifier__deallocate__phrase__phrase_role__special_____phrase___phrase_role__identifier__stack_context__phrase___phrase_role__special___amp___phrase___phrase_role__identifier__sctx__phrase__phrase_role__special_____phrase___code_"><code class="computeroutput"><span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> 91 <span class="special">&</span> <span class="identifier">sctx</span><span class="special">)</span></code></a> 92 </h5> 93<div class="variablelist"> 94<p class="title"><b></b></p> 95<dl class="variablelist"> 96<dt><span class="term">Preconditions:</span></dt> 97<dd><p> 98 <code class="computeroutput"><span class="identifier">sctx</span><span class="special">.</span><span class="identifier">sp</span></code> is valid, <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> <span class="special"><=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> and <code class="computeroutput"><span class="special">!</span> 99 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> 100 <span class="special">&&</span> <span class="special">(</span> 101 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum</span><span class="special">:</span><span class="identifier">size</span><span class="special">()</span> 102 <span class="special">>=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>. 103 </p></dd> 104<dt><span class="term">Effects:</span></dt> 105<dd><p> 106 Deallocates the stack space. 107 </p></dd> 108</dl> 109</div> 110<div class="note"><table border="0" summary="Note"> 111<tr> 112<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td> 113<th align="left">Note</th> 114</tr> 115<tr><td align="left" valign="top"><p> 116 If the library is compiled for segmented stacks, <span class="emphasis"><em>segmented-stack</em></span> 117 is the only available stack allocator. 118 </p></td></tr> 119</table></div> 120</div> 121<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 122<td align="left"></td> 123<td align="right"><div class="copyright-footer">Copyright © 2014 Oliver Kowalke<p> 124 Distributed under the Boost Software License, Version 1.0. (See accompanying 125 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>) 126 </p> 127</div></td> 128</tr></table> 129<hr> 130<div class="spirit-nav"> 131<a accesskey="p" href="fixedsize.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../stack.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="stack_traits.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 132</div> 133</body> 134</html> 135
