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# ReusableArenaAllocator.hpp

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    00001 /*
    00002  * The Apache Software License, Version 1.1
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    00004  *
    00005  * Copyright (c) 2000-2002 The Apache Software Foundation.  All rights
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    00009  * modification, are permitted provided that the following conditions
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    00019  *
    00020  * 3. The end-user documentation included with the redistribution,
    00021  *    if any, must include the following acknowledgment:
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    00023  *        Apache Software Foundation (http://www.apache.org/)."
    00024  *    Alternately, this acknowledgment may appear in the software itself,
    00025  *    if and wherever such third-party acknowledgments normally appear.
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    00027  * 4. The names "Xalan" and "Apache Software Foundation" must
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    00036  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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    00048  * ====================================================================
    00049  *
    00050  * This software consists of voluntary contributions made by many
    00051  * individuals on behalf of the Apache Software Foundation and was
    00052  * originally based on software copyright (c) 1999, International
    00053  * Business Machines, Inc., http://www.ibm.com.  For more
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    00055  * <http://www.apache.org/>.
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    00057
    00058 #if !defined(REUSABLEARENAALLOCATOR_INCLUDE_GUARD_1357924680)
    00059 #define REUSABLEARENAALLOCATOR_INCLUDE_GUARD_1357924680
    00060
    00061
    00062
    00063 #include <algorithm>
    00064 #include <vector>
    00065
    00066
    00067
    00068 #include "ReusableArenaBlock.hpp"
    00069 #include "ArenaAllocator.hpp"
    00070
    00071
    00072
    00073 XALAN_CPP_NAMESPACE_BEGIN
    00074
    00075
    00076
    00077 template<class ObjectType>
    00078 class ReusableArenaAllocator : public ArenaAllocator<ObjectType,
    00079                                                      ReusableArenaBlock<ObjectType> >
    00080 {
    00081 public:
    00082
    00083     typedef ReusableArenaBlock<ObjectType>              ReusableArenaBlockType;
    00084
    00085     typedef typename ReusableArenaBlockType::size_type  size_type;
    00086
    00087     typedef ArenaAllocator<ObjectType,
    00088                            ReusableArenaBlockType>      BaseClassType;
    00089
    00090 #if defined (XALAN_NO_STD_NAMESPACE)
    00091     typedef vector<ReusableArenaBlockType*>             ArenaBlockListType;
    00092 #else
    00093     typedef std::vector<ReusableArenaBlockType*>        ArenaBlockListType;
    00094 #endif
    00095
    00096     /*
    00097      * Construct an instance that will allocate blocks of the specified size.
    00098      *
    00099      * @param theBlockSize The block size.
    00100      */
    00101     ReusableArenaAllocator(size_type    theBlockSize) :
    00102         BaseClassType(theBlockSize),
    00103         m_lastBlockReferenced(0)
    00104     {
    00105     }
    00106
    00107     virtual
    00108     ~ReusableArenaAllocator()
    00109     {
    00110     }
    00111
    00112     /*
    00113      * Destroy the object, and free the block for re-use.
    00114      *
    00115      * @param theObject the address of the object.
    00116      * @return true if the object was deleted, false if not.
    00117      */
    00118     bool
    00119     destroyObject(ObjectType*   theObject)
    00120     {
    00121         bool    fSuccess = false;
    00122
    00123         // Check this, just in case...
    00124         if (m_lastBlockReferenced != 0 && m_lastBlockReferenced->ownsObject(theObject) == true)
    00125         {
    00126             m_lastBlockReferenced->destroyObject(theObject);
    00127
    00128             fSuccess = true;
    00129         }
    00130         else
    00131         {
    00132             // Note that this-> is required by template lookup rules.
    00133             const typename ArenaBlockListType::reverse_iterator theEnd = this->m_blocks.rend();
    00134
    00135             typename ArenaBlockListType::reverse_iterator   i = this->m_blocks.rbegin();
    00136
    00137             while(i != theEnd)
    00138             {
    00139                 if ((*i)->ownsObject(theObject) == true)
    00140                 {
    00141                     m_lastBlockReferenced = *i;
    00142
    00143                     m_lastBlockReferenced->destroyObject(theObject);
    00144
    00145                     fSuccess = true;
    00146
    00147                     break;
    00148                 }
    00149                 else
    00150                 {
    00151                     ++i;
    00152                 }
    00153             }
    00154         }
    00155
    00156         return fSuccess;
    00157     }
    00158
    00159     /*
    00160      * Allocate a block of the appropriate size for an
    00161      * object.  Call commitAllocation() when after
    00162      * the object is successfully constructed.  You _must_
    00163      * commit an allocation before performing any other
    00164      * operation on the allocator.
    00165      *
    00166      * @return A pointer to a block of memory
    00167      */
    00168     virtual ObjectType*
    00169     allocateBlock()
    00170     {
    00171         if (m_lastBlockReferenced == 0 ||
    00172             m_lastBlockReferenced->blockAvailable() == false)
    00173         {
    00174             // Search back for a block with some space available...
    00175             const typename ArenaBlockListType::reverse_iterator theEnd = this->m_blocks.rend();
    00176
    00177             // Note that this-> is required by template lookup rules.
    00178             typename ArenaBlockListType::reverse_iterator   i = this->m_blocks.rbegin();
    00179
    00180             while(i != theEnd)
    00181             {
    00182                 assert(*i != 0);
    00183
    00184                 if (*i != m_lastBlockReferenced && (*i)->blockAvailable() == true)
    00185                 {
    00186                     // Ahh, found one with free space.
    00187                     m_lastBlockReferenced = *i;
    00188
    00189                     break;
    00190                 }
    00191                 else
    00192                 {
    00193                     ++i;
    00194                 }
    00195             }
    00196
    00197             if (i == theEnd)
    00198             {
    00199                 // No blocks have free space available, so create a new block, and
    00200                 // push it on the list.
    00201                 // Note that this-> is required by template lookup rules.
    00202                 m_lastBlockReferenced = new ReusableArenaBlockType(this->m_blockSize);
    00203
    00204                 this->m_blocks.push_back(m_lastBlockReferenced);
    00205             }
    00206         }
    00207         assert(m_lastBlockReferenced != 0 && m_lastBlockReferenced->blockAvailable() == true);
    00208
    00209         return m_lastBlockReferenced->allocateBlock();
    00210     }
    00211
    00212     /*
    00213      * Commits the allocation of the previous
    00214      * allocateBlock() call.
    00215      *
    00216      * @param theObject A pointer to a block of memory
    00217      */
    00218     virtual void
    00219     commitAllocation(ObjectType*    theObject)
    00220     {
    00221         // Note that this-> is required by template lookup rules.
    00222         assert(this->m_blocks.empty() == false && m_lastBlockReferenced != 0 && m_lastBlockReferenced->ownsBlock(theObject) == true);
    00223
    00224         m_lastBlockReferenced->commitAllocation(theObject);
    00225         assert(m_lastBlockReferenced->ownsObject(theObject) == true);
    00226     }
    00227
    00228     virtual void
    00229     reset()
    00230     {
    00231         m_lastBlockReferenced = 0;
    00232
    00233         BaseClassType::reset();
    00234     }
    00235
    00236     virtual bool
    00237     ownsObject(const ObjectType*    theObject) const
    00238     {
    00239         bool    fResult = false;
    00240
    00241         // If no block has ever been referenced, then we haven't allocated
    00242         // any objects.
    00243         if (m_lastBlockReferenced != 0)
    00244         {
    00245             // Check the last referenced block first.
    00246             fResult = m_lastBlockReferenced->ownsObject(theObject);
    00247
    00248             if (fResult == false)
    00249             {
    00250                 fResult = BaseClassType::ownsObject(theObject);
    00251             }
    00252         }
    00253
    00254         return fResult;
    00255     }
    00256
    00257 private:
    00258
    00259     // Not defined...
    00260     ReusableArenaAllocator(const ReusableArenaAllocator<ObjectType>&);
    00261
    00262     ReusableArenaAllocator<ObjectType>&
    00263     operator=(const ReusableArenaAllocator<ObjectType>&);
    00264
    00265     // Data members...
    00266     ReusableArenaBlockType*     m_lastBlockReferenced;
    00267 };
    00268
    00269
    00270
    00271 XALAN_CPP_NAMESPACE_END
    00272
    00273
    00274
    00275 #endif  // !defined(REUSABLEARENAALLOCATOR_INCLUDE_GUARD_1357924680)

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