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| <div class="titlepage"><div><div><h3 class="title"> |
| <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> |
| </h3></div></div></div> |
| <p> |
| <span class="bold"><strong>Boost.Coroutine</strong></span> provides the class <span class="emphasis"><em>protected_stack_allocator</em></span> |
| which models the <span class="emphasis"><em>stack-allocator concept</em></span>. It appends |
| a guard page at the end of each stack to protect against exceeding the stack. |
| If the guard page is accessed (read or write operation) a segmentation fault/access |
| violation is generated by the operating system. |
| </p> |
| <div class="important"><table border="0" summary="Important"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td> |
| <th align="left">Important</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| Using <span class="emphasis"><em>protected_stack_allocator</em></span> is expensive. That |
| is, launching a new coroutine with a new stack is expensive; the allocated |
| stack is just as efficient to use as any other stack. |
| </p></td></tr> |
| </table></div> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| The appended <code class="computeroutput"><span class="identifier">guard</span> <span class="identifier">page</span></code> |
| is <span class="bold"><strong>not</strong></span> mapped to physical memory, only |
| virtual addresses are used. |
| </p></td></tr> |
| </table></div> |
| <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> |
| |
| <span class="keyword">template</span><span class="special"><</span> <span class="keyword">typename</span> <span class="identifier">traitsT</span> <span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">basic_protected_stack_allocator</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="identifier">traitT</span> <span class="identifier">traits_type</span><span class="special">;</span> |
| |
| <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> |
| |
| <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">(</span> <span class="identifier">stack_context</span> <span class="special">&);</span> |
| <span class="special">}</span> |
| |
| <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> |
| </pre> |
| <h5> |
| <a name="coroutine.stack.protected_stack_allocator.h0"></a> |
| <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> |
| <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> |
| </h5> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term">Preconditions:</span></dt> |
| <dd><p> |
| <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> <span class="identifier">size</span></code> |
| 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> |
| <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> <span class="identifier">size</span><span class="special">)</span></code>. |
| </p></dd> |
| <dt><span class="term">Effects:</span></dt> |
| <dd><p> |
| Allocates memory of at least <code class="computeroutput"><span class="identifier">size</span></code> |
| 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 |
| (the stack grows downwards/upwards) the stored address is the highest/lowest |
| address of the stack. |
| </p></dd> |
| </dl> |
| </div> |
| <h5> |
| <a name="coroutine.stack.protected_stack_allocator.h1"></a> |
| <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> |
| <span class="special">&</span> <span class="identifier">sctx</span><span class="special">)</span></code></a> |
| </h5> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term">Preconditions:</span></dt> |
| <dd><p> |
| <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> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span></code> 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> <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> <span class="identifier">sctx</span><span class="special">.</span><span class="identifier">size</span><span class="special">)</span></code>. |
| </p></dd> |
| <dt><span class="term">Effects:</span></dt> |
| <dd><p> |
| Deallocates the stack space. |
| </p></dd> |
| </dl> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2009 Oliver Kowalke<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
| </tr></table> |
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