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4 | <title>Class protected_fixedsize</title> | |
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7 | <link rel="home" href="../../../index.html" title="Chapter 1. Context"> | |
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24 | </div> | |
25 | <div class="section"> | |
26 | <div class="titlepage"><div><div><h4 class="title"> | |
27 | <a name="context.abstract_context.stack.protected_fixedsize"></a><a class="link" href="protected_fixedsize.html" title="Class protected_fixedsize">Class | |
28 | <span class="emphasis"><em>protected_fixedsize</em></span></a> | |
29 | </h4></div></div></div> | |
30 | <p> | |
31 | <span class="bold"><strong>Boost.Context</strong></span> provides the class <span class="emphasis"><em>protected_fixedsize_stack</em></span> | |
32 | which models the <span class="emphasis"><em>stack-allocator concept</em></span>. It appends | |
33 | a guard page at the end of each stack to protect against exceeding the | |
34 | stack. If the guard page is accessed (read or write operation) a segmentation | |
35 | fault/access violation is generated by the operating system. | |
36 | </p> | |
37 | <div class="important"><table border="0" summary="Important"> | |
38 | <tr> | |
39 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../../doc/src/images/important.png"></td> | |
40 | <th align="left">Important</th> | |
41 | </tr> | |
42 | <tr><td align="left" valign="top"><p> | |
43 | Using <span class="emphasis"><em>protected_fixedsize_stack</em></span> is expensive. That | |
44 | is, launching a new coroutine with a new stack is expensive; the allocated | |
45 | stack is just as efficient to use as any other stack. | |
46 | </p></td></tr> | |
47 | </table></div> | |
48 | <div class="note"><table border="0" summary="Note"> | |
49 | <tr> | |
50 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td> | |
51 | <th align="left">Note</th> | |
52 | </tr> | |
53 | <tr><td align="left" valign="top"><p> | |
54 | The appended <code class="computeroutput"><span class="identifier">guard</span> <span class="identifier">page</span></code> | |
55 | is <span class="bold"><strong>not</strong></span> mapped to physical memory, only | |
56 | virtual addresses are used. | |
57 | </p></td></tr> | |
58 | </table></div> | |
59 | <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">context</span><span class="special">/</span><span class="identifier">protected_fixedsize</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> | |
60 | ||
61 | <span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">traitsT</span> <span class="special">></span> | |
62 | <span class="keyword">struct</span> <span class="identifier">basic_protected_fixedsize</span> | |
63 | <span class="special">{</span> | |
64 | <span class="keyword">typedef</span> <span class="identifier">traitT</span> <span class="identifier">traits_type</span><span class="special">;</span> | |
65 | ||
66 | <span class="identifier">basic_protected_fixesize</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> | |
67 | ||
68 | <span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">();</span> | |
69 | ||
70 | <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&);</span> | |
71 | <span class="special">}</span> | |
72 | ||
73 | <span class="keyword">typedef</span> <span class="identifier">basic_protected_fixedsize</span><span class="special"><</span> <span class="identifier">stack_traits</span> <span class="special">></span> <span class="identifier">protected_fixedsize</span> | |
74 | </pre> | |
75 | <h6> | |
76 | <a name="context.abstract_context.stack.protected_fixedsize.h0"></a> | |
77 | <span><a name="context.abstract_context.stack.protected_fixedsize._code__phrase_role__identifier__stack_context__phrase___phrase_role__identifier__allocate__phrase__phrase_role__special______phrase___code_"></a></span><a class="link" href="protected_fixedsize.html#context.abstract_context.stack.protected_fixedsize._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> | |
78 | </h6> | |
79 | <div class="variablelist"> | |
80 | <p class="title"><b></b></p> | |
81 | <dl> | |
82 | <dt><span class="term">Preconditions:</span></dt> | |
83 | <dd><p> | |
84 | <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> | |
85 | <span class="special"><=</span> <span class="identifier">size</span></code> | |
86 | 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> | |
87 | <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> | |
88 | <span class="identifier">size</span><span class="special">)</span></code>. | |
89 | </p></dd> | |
90 | <dt><span class="term">Effects:</span></dt> | |
91 | <dd><p> | |
92 | Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code> | |
93 | 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 | |
94 | (the stack grows downwards/upwards) the stored address is the highest/lowest | |
95 | address of the stack. | |
96 | </p></dd> | |
97 | </dl> | |
98 | </div> | |
99 | <h6> | |
100 | <a name="context.abstract_context.stack.protected_fixedsize.h1"></a> | |
101 | <span><a name="context.abstract_context.stack.protected_fixedsize._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_fixedsize.html#context.abstract_context.stack.protected_fixedsize._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> | |
102 | <span class="special">&</span> <span class="identifier">sctx</span><span class="special">)</span></code></a> | |
103 | </h6> | |
104 | <div class="variablelist"> | |
105 | <p class="title"><b></b></p> | |
106 | <dl> | |
107 | <dt><span class="term">Preconditions:</span></dt> | |
108 | <dd><p> | |
109 | <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> | |
110 | <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> and <code class="computeroutput"><span class="special">!</span> | |
111 | <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span> | |
112 | <span class="special">&&</span> <span class="special">(</span> | |
113 | <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> | |
114 | <span class="special">>=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>. | |
115 | </p></dd> | |
116 | <dt><span class="term">Effects:</span></dt> | |
117 | <dd><p> | |
118 | Deallocates the stack space. | |
119 | </p></dd> | |
120 | </dl> | |
121 | </div> | |
122 | </div> | |
123 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
124 | <td align="left"></td> | |
125 | <td align="right"><div class="copyright-footer">Copyright © 2014 Oliver Kowalke<p> | |
126 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
127 | 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>) | |
128 | </p> | |
129 | </div></td> | |
130 | </tr></table> | |
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