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

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  25 <div class="section">
  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="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 </h3></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 property <code class="computeroutput"><span class="identifier">segmented</span><span class="special">-</span><span class="identifier">stacks</span></code>,
  48           e.g. <span class="bold"><strong>toolset=gcc segmented-stacks=on</strong></span> at
  49           b2/bjam command line.
  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> <span class="special">{</span>
  56     <span class="keyword">typedef</span> <span class="identifier">traitT</span>  <span class="identifier">traits_type</span><span class="special">;</span>
  57
  58     <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>
  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">&amp;);</span>
  63 <span class="special">}</span>
  64
  65 <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>
  66 </pre>
  67 <h5>
  68 <a name="context.stack.segmented.h0"></a>
  69         <span><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>
  70       </h5>
  71 <div class="variablelist">
  72 <p class="title"><b></b></p>
  73 <dl>
  74 <dt><span class="term">Preconditions:</span></dt>
  75 <dd><p>
  76               <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>
  77               <span class="special">&lt;=</span> <span class="identifier">size</span></code>
  78               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>
  79               <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>.
  80             </p></dd>
  81 <dt><span class="term">Effects:</span></dt>
  82 <dd><p>
  83               Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code>
  84               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
  85               (the stack grows downwards/upwards) the stored address is the highest/lowest
  86               address of the stack.
  87             </p></dd>
  88 </dl>
  89 </div>
  90 <h5>
  91 <a name="context.stack.segmented.h1"></a>
  92         <span><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>
  93         <span class="special">&amp;</span> <span class="identifier">sctx</span><span class="special">)</span></code></a>
  94       </h5>
  95 <div class="variablelist">
  96 <p class="title"><b></b></p>
  97 <dl>
  98 <dt><span class="term">Preconditions:</span></dt>
  99 <dd><p>
 100               <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>
 101               <span class="identifier">traits_type</span><span class="special">::</span><span class="identifier">is_unbounded</span><span class="special">()</span>
 102               <span class="special">&amp;&amp;</span> <span class="special">(</span>
 103               <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>
 104               <span class="special">&gt;=</span> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>.
 105             </p></dd>
 106 <dt><span class="term">Effects:</span></dt>
 107 <dd><p>
 108               Deallocates the stack space.
 109             </p></dd>
 110 </dl>
 111 </div>
 112 <div class="note"><table border="0" summary="Note">
 113 <tr>
 114 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
 115 <th align="left">Note</th>
 116 </tr>
 117 <tr><td align="left" valign="top"><p>
 118           If the library is compiled for segmented stacks, __segmented_stack__ is
 119           the only available stack allocator.
 120         </p></td></tr>
 121 </table></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 &#169; 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>
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