1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Class protected_stack_allocator</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. Coroutine"> 8<link rel="up" href="../stack.html" title="Stack allocation"> 9<link rel="prev" href="../stack.html" title="Stack allocation"> 10<link rel="next" href="standard_stack_allocator.html" title="Class standard_stack_allocator"> 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="../stack.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="standard_stack_allocator.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="coroutine.stack.protected_stack_allocator"></a><a class="link" href="protected_stack_allocator.html" title="Class protected_stack_allocator">Class <span class="emphasis"><em>protected_stack_allocator</em></span></a> 28</h3></div></div></div> 29<p> 30 <span class="bold"><strong>Boost.Coroutine</strong></span> provides the class <span class="emphasis"><em>protected_stack_allocator</em></span> 31 which models the <span class="emphasis"><em>stack-allocator concept</em></span>. It appends 32 a guard page at the end of each stack to protect against exceeding the stack. 33 If the guard page is accessed (read or write operation) a segmentation fault/access 34 violation is generated by the operating system. 35 </p> 36<div class="important"><table border="0" summary="Important"> 37<tr> 38<td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> 39<th align="left">Important</th> 40</tr> 41<tr><td align="left" valign="top"><p> 42 Using <span class="emphasis"><em>protected_stack_allocator</em></span> is expensive. That 43 is, launching a new coroutine with a new stack is expensive; the allocated 44 stack is just as efficient to use as any other stack. 45 </p></td></tr> 46</table></div> 47<div class="note"><table border="0" summary="Note"> 48<tr> 49<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td> 50<th align="left">Note</th> 51</tr> 52<tr><td align="left" valign="top"><p> 53 The appended <code class="computeroutput"><span class="identifier">guard</span> <span class="identifier">page</span></code> 54 is <span class="bold"><strong>not</strong></span> mapped to physical memory, only 55 virtual addresses are used. 56 </p></td></tr> 57</table></div> 58<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">coroutine</span><span class="special">/</span><span class="identifier">protected_stack_allocator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 59 60<span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">traitsT</span> <span class="special">></span> 61<span class="keyword">struct</span> <span class="identifier">basic_protected_stack_allocator</span> 62<span class="special">{</span> 63 <span class="keyword">typedef</span> <span class="identifier">traitT</span> <span class="identifier">traits_type</span><span class="special">;</span> 64 65 <span class="keyword">void</span> <span class="identifier">allocate</span><span class="special">(</span> <span class="identifier">stack_context</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> 66 67 <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&);</span> 68<span class="special">}</span> 69 70<span class="keyword">typedef</span> <span class="identifier">basic_protected_stack_allocator</span><span class="special"><</span> <span class="identifier">stack_traits</span> <span class="special">></span> <span class="identifier">protected_stack_allocator</span> 71</pre> 72<h5> 73<a name="coroutine.stack.protected_stack_allocator.h0"></a> 74 <span class="phrase"><a name="coroutine.stack.protected_stack_allocator._code__phrase_role__keyword__void__phrase___phrase_role__identifier__allocate__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___phrase_role__identifier__std__phrase__phrase_role__special______phrase__phrase_role__identifier__size_t__phrase___phrase_role__identifier__size__phrase__phrase_role__special_____phrase___code_"></a></span><a class="link" href="protected_stack_allocator.html#coroutine.stack.protected_stack_allocator._code__phrase_role__keyword__void__phrase___phrase_role__identifier__allocate__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___phrase_role__identifier__std__phrase__phrase_role__special______phrase__phrase_role__identifier__size_t__phrase___phrase_role__identifier__size__phrase__phrase_role__special_____phrase___code_"><code class="computeroutput"><span class="keyword">void</span> <span class="identifier">allocate</span><span class="special">(</span> <span class="identifier">stack_context</span> 75 <span class="special">&</span> <span class="identifier">sctx</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></code></a> 76 </h5> 77<div class="variablelist"> 78<p class="title"><b></b></p> 79<dl class="variablelist"> 80<dt><span class="term">Preconditions:</span></dt> 81<dd><p> 82 <code class="computeroutput"><span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">minimum_size</span><span class="special">()</span> 83 <span class="special"><=</span> <span class="identifier">size</span></code> 84 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> 85 <span class="special">(</span> <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum_size</span><span class="special">()</span> <span class="special">>=</span> <span class="identifier">size</span><span class="special">)</span></code>. 86 </p></dd> 87<dt><span class="term">Effects:</span></dt> 88<dd><p> 89 Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code> 90 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 91 (the stack grows downwards/upwards) the stored address is the highest/lowest 92 address of the stack. 93 </p></dd> 94</dl> 95</div> 96<h5> 97<a name="coroutine.stack.protected_stack_allocator.h1"></a> 98 <span class="phrase"><a name="coroutine.stack.protected_stack_allocator._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="protected_stack_allocator.html#coroutine.stack.protected_stack_allocator._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> 99 <span class="special">&</span> <span class="identifier">sctx</span><span class="special">)</span></code></a> 100 </h5> 101<div class="variablelist"> 102<p class="title"><b></b></p> 103<dl class="variablelist"> 104<dt><span class="term">Preconditions:</span></dt> 105<dd><p> 106 <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_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> 107 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> 108 <span class="special">&&</span> <span class="special">(</span> 109 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">maximum_size</span><span class="special">()</span> 110 <span class="special">>=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>. 111 </p></dd> 112<dt><span class="term">Effects:</span></dt> 113<dd><p> 114 Deallocates the stack space. 115 </p></dd> 116</dl> 117</div> 118</div> 119<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 120<td align="left"></td> 121<td align="right"><div class="copyright-footer">Copyright © 2009 Oliver Kowalke<p> 122 Distributed under the Boost Software License, Version 1.0. (See accompanying 123 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>) 124 </p> 125</div></td> 126</tr></table> 127<hr> 128<div class="spirit-nav"> 129<a accesskey="p" href="../stack.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="standard_stack_allocator.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 130</div> 131</body> 132</html> 133
