libs/context/doc/html/context/stack/segmented.html

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="context.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.Context</strong></span> supports usage of a <a class="link" href="segmented.html#segmented"><span class="emphasis"><em>segmented_stack</em></span></a>, e. g. the
  32         size of the stack grows on demand. The coroutine is created with a minimal
  33         stack size and will be increased as required. Class <a class="link" href="segmented.html#segmented"><span class="emphasis"><em>segmented_stack</em></span></a>
  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           at b2/bjam command line.
  52         </p></td></tr>
  53 </table></div>
  54 <div class="note"><table border="0" summary="Note">
  55 <tr>
  56 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
  57 <th align="left">Note</th>
  58 </tr>
  59 <tr><td align="left" valign="top"><p>
  60           Segmented stacks can only be used with <a class="link" href="../cc.html#cc"><span class="emphasis"><em>callcc()</em></span></a>
  61           (using <a class="link" href="../ff/implementations__fcontext_t__ucontext_t_and_winfiber.html#implementation"><span class="emphasis"><em>ucontext_t</em></span></a>)
  62         </p></td></tr>
  63 </table></div>
  64 <p>
  65         .
  66       </p>
  67 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">context</span><span class="special">/</span><span class="identifier">segmented_stack</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  68
  69 <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">traitsT</span> <span class="special">&gt;</span>
  70 <span class="keyword">struct</span> <span class="identifier">basic_segmented_stack</span> <span class="special">{</span>
  71     <span class="keyword">typedef</span> <span class="identifier">traitT</span>  <span class="identifier">traits_type</span><span class="special">;</span>
  72
  73     <span class="identifier">basic_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>
  74
  75     <span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">();</span>
  76
  77     <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&amp;);</span>
  78 <span class="special">}</span>
  79
  80 <span class="keyword">typedef</span> <span class="identifier">basic_segmented_stack</span><span class="special">&lt;</span> <span class="identifier">stack_traits</span> <span class="special">&gt;</span> <span class="identifier">segmented_stack</span><span class="special">;</span>
  81 </pre>
  82 <h5>
  83 <a name="context.stack.segmented.h0"></a>
  84         <span class="phrase"><a name="context.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#context.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>
  85       </h5>
  86 <div class="variablelist">
  87 <p class="title"><b></b></p>
  88 <dl class="variablelist">
  89 <dt><span class="term">Preconditions:</span></dt>
  90 <dd><p>
  91               <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>
  92               <span class="special">&lt;=</span> <span class="identifier">size</span></code>
  93               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">&amp;&amp;</span>
  94               <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">&gt;=</span> <span class="identifier">size</span><span class="special">)</span></code>.
  95             </p></dd>
  96 <dt><span class="term">Effects:</span></dt>
  97 <dd><p>
  98               Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code>
  99               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
 100               (the stack grows downwards/upwards) the stored address is the highest/lowest
 101               address of the stack.
 102             </p></dd>
 103 </dl>
 104 </div>
 105 <h5>
 106 <a name="context.stack.segmented.h1"></a>
 107         <span class="phrase"><a name="context.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#context.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>
 108         <span class="special">&amp;</span> <span class="identifier">sctx</span><span class="special">)</span></code></a>
 109       </h5>
 110 <div class="variablelist">
 111 <p class="title"><b></b></p>
 112 <dl class="variablelist">
 113 <dt><span class="term">Preconditions:</span></dt>
 114 <dd><p>
 115               <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">&lt;=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> and <code class="computeroutput"><span class="special">!</span>
 116               <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span>
 117               <span class="special">&amp;&amp;</span> <span class="special">(</span>
 118               <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>
 119               <span class="special">&gt;=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>.
 120             </p></dd>
 121 <dt><span class="term">Effects:</span></dt>
 122 <dd><p>
 123               Deallocates the stack space.
 124             </p></dd>
 125 </dl>
 126 </div>
 127 <div class="note"><table border="0" summary="Note">
 128 <tr>
 129 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
 130 <th align="left">Note</th>
 131 </tr>
 132 <tr><td align="left" valign="top"><p>
 133           If the library is compiled for segmented stacks, <span class="emphasis"><em>segmented_stack</em></span>
 134           is the only available stack allocator.
 135         </p></td></tr>
 136 </table></div>
 137 </div>
 138 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 139 <td align="left"></td>
 140 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Oliver Kowalke<p>
 141         Distributed under the Boost Software License, Version 1.0. (See accompanying
 142         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>)
 143       </p>
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