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| 3 | <HEAD> |
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| 4 | <TITLE>pool_alloc - Boost Pool Standard Allocators Implementation</TITLE> |
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| 5 | <LINK HREF="../pool.css" REL="stylesheet" TYPE="text/css"> |
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| 6 | </HEAD> |
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| 7 | <BODY> |
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| 8 | |
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| 9 | <IMG SRC="../../../../boost.png" WIDTH=276 HEIGHT=86 ALT="C++ Boost"> |
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| 10 | |
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| 11 | <H1 ALIGN=CENTER>pool_alloc - Boost Pool Standard Allocators Implementation</H1> |
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| 12 | |
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| 13 | <P> |
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| 14 | <H2>Dependencies</H2> |
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| 15 | |
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| 16 | <P> |
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| 17 | Includes the system headers <SPAN CLASS="code"><new></SPAN> and <SPAN CLASS="code"><limits></SPAN>. |
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| 18 | |
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| 19 | <P> |
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| 20 | Includes the Boost headers <SPAN CLASS="code">"singleton_pool.hpp"</SPAN> (see <A HREF="singleton_pool.html">singleton_pool.html</A>) and <SPAN CLASS="code">"detail/mutex.hpp"</SPAN> (see <A HREF="mutex.html">mutex.html</A>). |
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| 21 | |
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| 22 | <P> |
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| 23 | <H2>Synopsis</H2> |
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| 24 | |
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| 25 | <PRE CLASS="code">template <typename T, |
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| 26 | typename UserAllocator = default_user_allocator_new_delete, |
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| 27 | typename Mutex = details::pool::default_mutex, |
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| 28 | unsigned NextSize = 32> |
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| 29 | class pool_allocator |
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| 30 | { |
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| 31 | public: |
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| 32 | ... // public interface |
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| 33 | |
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| 34 | public: // extensions to public interface |
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| 35 | typedef Mutex mutex; |
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| 36 | static const unsigned next_size = NextSize; |
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| 37 | |
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| 38 | template <typename U> |
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| 39 | struct rebind |
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| 40 | { |
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| 41 | typedef pool_allocator<U, UserAllocator, Mutex, NextSize> other; |
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| 42 | }; |
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| 43 | }; |
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| 44 | |
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| 45 | template <typename T, |
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| 46 | typename UserAllocator = default_user_allocator_new_delete, |
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| 47 | typename Mutex = details::pool::default_mutex, |
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| 48 | unsigned NextSize = 32> |
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| 49 | class fast_pool_allocator |
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| 50 | { |
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| 51 | public: |
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| 52 | ... // public interface |
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| 53 | |
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| 54 | public: // extensions to public interface |
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| 55 | typedef Mutex mutex; |
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| 56 | static const unsigned next_size = NextSize; |
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| 57 | |
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| 58 | template <typename U> |
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| 59 | struct rebind |
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| 60 | { |
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| 61 | typedef fast_pool_allocator<U, UserAllocator, Mutex, NextSize> other; |
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| 62 | }; |
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| 63 | };</PRE> |
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| 64 | |
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| 65 | <P> |
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| 66 | <H2>Extensions to Public Interface</H2> |
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| 67 | |
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| 68 | <P> |
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| 69 | <H3>Additional template parameters</H3> |
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| 70 | |
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| 71 | <P> |
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| 72 | <H4 CLASS="code">Mutex</H4> |
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| 73 | |
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| 74 | <P> |
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| 75 | This parameter allows the user to determine the type of synchronization to be used on the underlying singleton pool. See the extensions to the public interface of <A HREF="singleton_pool.html">singleton pool</A> for more information. |
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| 76 | |
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| 77 | <P> |
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| 78 | <H4 CLASS="code">NextSize</H4> |
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| 79 | |
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| 80 | <P> |
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| 81 | The value of this parameter is passed to the underlying Pool when it is created. See the extensions to the public interface of <A HREF="pool.html">pool</A> for more information. |
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| 82 | |
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| 83 | <P> |
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| 84 | <H3>Modification of <SPAN CLASS="code">rebind</SPAN></H3> |
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| 85 | |
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| 86 | <P> |
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| 87 | The struct <SPAN CLASS="code">rebind</SPAN> has been redefined to preserve the values of the additional template parameters. |
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| 88 | |
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| 89 | <P> |
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| 90 | <H3>Additional members</H3> |
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| 91 | |
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| 92 | <P> |
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| 93 | The typedef <SPAN CLASS="code">mutex</SPAN> and the static const value <SPAN CLASS="code">next_size</SPAN> publish the values of the template parameters <SPAN CLASS="code">Mutex</SPAN> and <SPAN CLASS="code">NextSize</SPAN>, respectively. |
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| 94 | |
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| 95 | <P> |
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| 96 | <H2>Notes</H2> |
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| 97 | |
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| 98 | <P> |
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| 99 | A number of common STL libraries contain bugs in their using of allocators. Specifically, they pass null pointers to the <SPAN CLASS="code">deallocate</SPAN> function, which is explicitly forbidden by the Standard [20.1.5 Table 32]. PoolAlloc will work around these libraries if it detects them; currently, workarounds are in place for: |
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| 100 | <UL> |
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| 101 | <LI>Borland C++ (Builder and command-line compiler) with default (RogueWave) library, ver. 5 and earlier</LI> |
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| 102 | <LI>STLport (with any compiler), ver. 4.0 and earlier</LI> |
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| 103 | </UL> |
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| 104 | |
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| 105 | <P> |
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| 106 | <H2>Future Directions</H2> |
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| 107 | |
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| 108 | <P> |
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| 109 | When the Boost multithreading library is completed, the <SPAN CLASS="code">Mutex</SPAN> parameter will be replaced by something from that library providing the same flexibility and will move from an implementation detail into the interface specification. |
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| 110 | |
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| 111 | <P> |
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| 112 | <H2><A HREF="../interfaces/pool_alloc.html">Interface Description</A></H2> |
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| 113 | |
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| 114 | <P> |
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| 115 | <HR> |
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| 116 | |
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| 117 | <P> |
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| 118 | Copyright © 2000, 2001 Stephen Cleary (scleary AT jerviswebb DOT com) |
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| 119 | |
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| 120 | <P> |
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| 121 | This file can be redistributed and/or modified under the terms found in <A HREF="../copyright.html">copyright.html</A> |
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| 122 | |
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| 123 | <P> |
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| 124 | This software and its documentation is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose. |
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| 125 | |
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| 126 | </BODY> |
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| 127 | </HTML> |
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