ceph/src/boost/libs/context/doc/html/context/abstract_context/stack/segmented.html

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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.segmented"></a><a class="link" href="segmented.html" title="Class segmented_stack">Class <span class="emphasis"><em>segmented_stack</em></span></a>
  28 </h4></div></div></div>
  29 <p>
  30           <span class="bold"><strong>Boost.Context</strong></span> supports usage of a <span class="emphasis"><em>segmented_stack</em></span>,
  31           e. g. the size of the stack grows on demand. The coroutine is created with
  32           a minimal stack size and will be increased as required. Class <span class="emphasis"><em>segmented_stack</em></span>
  33           models the <span class="emphasis"><em>stack-allocator concept</em></span>. In contrast to
  34           <span class="emphasis"><em>protected_fixedsize_stack</em></span> and <span class="emphasis"><em>fixedsize_stack</em></span>
  35           it creates a stack which grows on demand.
  36         </p>
  37 <div class="note"><table border="0" summary="Note">
  38 <tr>
  39 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
  40 <th align="left">Note</th>
  41 </tr>
  42 <tr><td align="left" valign="top"><p>
  43             Segmented stacks are currently only supported by <span class="bold"><strong>gcc</strong></span>
  44             from version <span class="bold"><strong>4.7</strong></span> <span class="bold"><strong>clang</strong></span>
  45             from version <span class="bold"><strong>3.4</strong></span> onwards. In order to
  46             use a __segmented_stack__ <span class="bold"><strong>Boost.Context</strong></span>
  47             must be built with <span class="bold"><strong>toolset=gcc segmented-stacks=on</strong></span>
  48             at b2/bjam command-line. Applications must be compiled with compiler-flags
  49             <span class="bold"><strong>-fsplit-stack -DBOOST_USE_SEGMENTED_STACKS</strong></span>.
  50           </p></td></tr>
  51 </table></div>
  52 <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>
  53
  54 <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>
  55 <span class="keyword">struct</span> <span class="identifier">basic_segmented_stack</span>
  56 <span class="special">{</span>
  57     <span class="keyword">typedef</span> <span class="identifier">traitT</span>  <span class="identifier">traits_type</span><span class="special">;</span>
  58
  59     <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>
  60
  61     <span class="identifier">stack_context</span> <span class="identifier">allocate</span><span class="special">();</span>
  62
  63     <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>
  64 <span class="special">}</span>
  65
  66 <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>
  67 </pre>
  68 <h6>
  69 <a name="context.abstract_context.stack.segmented.h0"></a>
  70           <span><a name="context.abstract_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.abstract_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>
  71         </h6>
  72 <div class="variablelist">
  73 <p class="title"><b></b></p>
  74 <dl>
  75 <dt><span class="term">Preconditions:</span></dt>
  76 <dd><p>
  77                 <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>
  78                 <span class="special">&lt;=</span> <span class="identifier">size</span></code>
  79                 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>
  80                 <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>
  81                 <span class="identifier">size</span><span class="special">)</span></code>.
  82               </p></dd>
  83 <dt><span class="term">Effects:</span></dt>
  84 <dd><p>
  85                 Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code>
  86                 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
  87                 (the stack grows downwards/upwards) the stored address is the highest/lowest
  88                 address of the stack.
  89               </p></dd>
  90 </dl>
  91 </div>
  92 <h6>
  93 <a name="context.abstract_context.stack.segmented.h1"></a>
  94           <span><a name="context.abstract_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.abstract_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>
  95           <span class="special">&amp;</span> <span class="identifier">sctx</span><span class="special">)</span></code></a>
  96         </h6>
  97 <div class="variablelist">
  98 <p class="title"><b></b></p>
  99 <dl>
 100 <dt><span class="term">Preconditions:</span></dt>
 101 <dd><p>
 102                 <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>
 103                 <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> and <code class="computeroutput"><span class="special">!</span>
 104                 <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span>
 105                 <span class="special">&amp;&amp;</span> <span class="special">(</span>
 106                 <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>
 107                 <span class="special">&gt;=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>.
 108               </p></dd>
 109 <dt><span class="term">Effects:</span></dt>
 110 <dd><p>
 111                 Deallocates the stack space.
 112               </p></dd>
 113 </dl>
 114 </div>
 115 <div class="note"><table border="0" summary="Note">
 116 <tr>
 117 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
 118 <th align="left">Note</th>
 119 </tr>
 120 <tr><td align="left" valign="top"><p>
 121             If the library is compiled for segmented stacks, __segmented_stack__
 122             is the only available stack allocator.
 123           </p></td></tr>
 124 </table></div>
 125 </div>
 126 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 127 <td align="left"></td>
 128 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Oliver Kowalke<p>
 129         Distributed under the Boost Software License, Version 1.0. (See accompanying
 130         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>)
 131       </p>
 132 </div></td>
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