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that use it are valid. Merged revisions 53047-53048 via svnmerge from https://svn.boost.org/svn/boost/trunk ........ r53047 | danieljames | 2009-05-16 15:17:20 +0100 (Sat, 16 May 2009) | 1 line Fix some validation errors. ........ r53048 | danieljames | 2009-05-16 15:23:59 +0100 (Sat, 16 May 2009) | 1 line Use a local copy of the valid HTML 4.01 icon. ........ [SVN r53258]
168 lines
4.3 KiB
HTML
168 lines
4.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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"http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Language" content="en-us">
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<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
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<link href="../pool.css" rel="stylesheet" type="text/css">
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<title>Pool</title>
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</head>
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<body>
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<img src="../../../../boost.png" width="276" height="86" alt="C++ Boost">
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<h1 align="center">User Allocators</h1>
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<h2>Introduction</h2>
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<p>Pool objects need to request memory blocks from the system, which the
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Pool then splits into chunks to allocate to the user. By specifying a
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<span class="code">UserAllocator</span> template parameter to various Pool
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interfaces, users can control how those system memory blocks are
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allocated.</p>
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<h2>Semantics</h2>
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<table border align="center" summary="">
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<caption>
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<em>Symbol Table</em>
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</caption>
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<tr>
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<th>Symbol</th>
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<th>Meaning</th>
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</tr>
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<tr>
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<td class="code">UserAllocator</td>
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<td>A User Allocator type</td>
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</tr>
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<tr>
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<td class="code">block</td>
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<td>value of type <span class="code">char *</span></td>
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</tr>
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<tr>
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<td class="code">n</td>
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<td>value of type <span class=
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"code">UserAllocator::size_type</span></td>
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</tr>
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</table><br>
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<table border align="center" summary="">
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<caption>
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<em>Typedefs</em>
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</caption>
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<tr>
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<th>Expression</th>
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<th>Type</th>
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</tr>
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<tr>
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<td class="code">UserAllocator::size_type</td>
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<td>An unsigned integral type that can represent the size of the
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largest object to be allocated</td>
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</tr>
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<tr>
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<td class="code">UserAllocator::difference_type</td>
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<td>A signed integral type that can represent the difference of any two
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pointers</td>
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</tr>
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</table><br>
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<table border align="center" summary="">
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<caption>
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<em>Allocation and Deallocation</em>
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</caption>
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<tr>
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<th>Expression</th>
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<th>Return Type</th>
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<th>Pre-Condition/Notes</th>
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</tr>
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<tr>
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<td class="code">UserAllocator::malloc(n)</td>
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<td class="code">char *</td>
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<td>Attempts to allocate <span class="code">n</span> bytes from the
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system. Returns 0 if out-of-memory.</td>
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</tr>
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<tr>
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<td class="code">UserAllocator::free(block)</td>
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<td class="code">void</td>
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<td><span class="code">block</span> must have been previously returned
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from a call to <span class="code">UserAllocator::malloc</span>.</td>
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</tr>
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</table>
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<h2>Provided Implementations</h2>
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<p>There are two <span class="code">UserAllocator</span> classes provided.
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Both of them are in pool.hpp (see <a href="pool.html">pool</a>). The
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default value for the template parameter <span class=
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"code">UserAllocator</span> is always <span class=
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"code">default_user_allocator_new_delete</span>.</p>
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<h3>Synopsis</h3>
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<pre class="code">
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struct default_user_allocator_new_delete
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{
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typedef std::size_t size_type;
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typedef std::ptrdiff_t difference_type;
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static char * malloc(const size_type bytes)
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{ return new (std::nothrow) char[bytes]; }
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static void free(char * const block)
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{ delete [] block; }
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};
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struct default_user_allocator_malloc_free
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{
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typedef std::size_t size_type;
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typedef std::ptrdiff_t difference_type;
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static char * malloc(const size_type bytes)
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{ return reinterpret_cast<char *>(std::malloc(bytes)); }
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static void free(char * const block)
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{ std::free(block); }
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};
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</pre>
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<hr>
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<p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src=
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"../../../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional"
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height="31" width="88"></a></p>
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<p>Revised
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<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->05
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December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38516" --></p>
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<p><i>Copyright © 2000, 2001 Stephen Cleary (scleary AT jerviswebb DOT
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com)</i></p>
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<p><i>Distributed under the Boost Software License, Version 1.0. (See
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accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a>
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or copy at <a href=
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"http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p>
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</body>
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</html>
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