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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 The Apache Software Foundation.  All rights 
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00008  * Redistribution and use in source and binary forms, with or without
00009  * modification, are permitted provided that the following conditions
00010  * are met:
00011  *
00012  * 1. Redistributions of source code must retain the above copyright
00013  *    notice, this list of conditions and the following disclaimer. 
00014  *
00015  * 2. Redistributions in binary form must reproduce the above copyright
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00019  *
00020  * 3. The end-user documentation included with the redistribution,
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00022  *       "This product includes software developed by the
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00050  * This software consists of voluntary contributions made by many
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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 template<class ObjectType>
00074 class ReusableArenaAllocator : public ArenaAllocator<ObjectType,
00075                                                      ReusableArenaBlock<ObjectType> >
00076 {
00077 public:
00078 
00079     typedef ReusableArenaBlock<ObjectType>              ReusableArenaBlockType;
00080 
00081     typedef ReusableArenaBlockType::size_type           size_type;
00082 
00083     typedef ArenaAllocator<ObjectType,
00084                            ReusableArenaBlockType>      BaseClassType;
00085 
00086     // $$$ ToDo: This typedef is here because of a bug in gcc.
00087 #if defined (XALAN_NO_NAMESPACES)
00088     typedef vector<ReusableArenaBlockType*>             ArenaBlockListType;
00089 #else
00090     typedef std::vector<ReusableArenaBlockType*>        ArenaBlockListType;
00091 #endif
00092 
00093     /*
00094      * Construct an instance that will allocate blocks of the specified size.
00095      *
00096      * @param theBlockSize The block size.
00097      */
00098     ReusableArenaAllocator(size_type    theBlockSize) :
00099         BaseClassType(theBlockSize),
00100         m_lastBlockReferenced(0)
00101     {
00102     }
00103 
00104     virtual
00105     ~ReusableArenaAllocator()
00106     {
00107     }
00108 
00109     /*
00110      * Destroy the object, and free the block for re-use.
00111      *
00112      * @param theObject the address of the object.
00113      * @return true if the object was deleted, false if not.
00114      */
00115     bool
00116     destroyObject(ObjectType*   theObject)
00117     {
00118         bool    fSucess = false;
00119 
00120         // Check this, just in case...
00121         if (m_lastBlockReferenced != 0 && m_lastBlockReferenced->ownsObject(theObject) == true)
00122         {
00123             m_lastBlockReferenced->destroyObject(theObject);
00124 
00125             fSucess = true;
00126         }
00127         else
00128         {
00129             const ArenaBlockListType::reverse_iterator  theEnd = m_blocks.rend();
00130 
00131             ArenaBlockListType::reverse_iterator    i = m_blocks.rbegin();
00132 
00133             while(i != theEnd)
00134             {
00135                 if ((*i)->ownsObject(theObject) == true)
00136                 {
00137                     m_lastBlockReferenced = *i;
00138 
00139                     m_lastBlockReferenced->destroyObject(theObject);
00140 
00141                     fSucess = true;
00142 
00143                     break;
00144                 }
00145                 else
00146                 {
00147                     ++i;
00148                 }
00149             }
00150         }
00151 
00152         return fSucess;
00153     }
00154 
00155     /*
00156      * Allocate a block of the appropriate size for an
00157      * object.  Call commitAllocation() when after
00158      * the object is successfully constructed.  You _must_
00159      * commit an allocation before performing any other
00160      * operation on the allocator.
00161      *
00162      * @return A pointer to a block of memory
00163      */
00164     virtual ObjectType*
00165     allocateBlock()
00166     {
00167         if (m_lastBlockReferenced == 0 ||
00168             m_lastBlockReferenced->blockAvailable() == false)
00169         {
00170             // Search back for a block with some space available...
00171             const ArenaBlockListType::reverse_iterator  theEnd = m_blocks.rend();
00172 
00173             ArenaBlockListType::reverse_iterator    i = m_blocks.rbegin();
00174 
00175             while(i != theEnd)
00176             {
00177                 assert(*i != 0);
00178 
00179                 if (*i != m_lastBlockReferenced && (*i)->blockAvailable() == true)
00180                 {
00181                     // Ahh, found one with free space.
00182                     m_lastBlockReferenced = *i;
00183 
00184                     break;
00185                 }
00186                 else
00187                 {
00188                     ++i;
00189                 }
00190             }
00191 
00192             if (i == theEnd)
00193             {
00194                 // No blocks have free space available, so create a new block, and
00195                 // push it on the list.
00196                 m_lastBlockReferenced = new ReusableArenaBlockType(m_blockSize);
00197 
00198                 m_blocks.push_back(m_lastBlockReferenced);
00199             }
00200         }
00201         assert(m_lastBlockReferenced != 0 && m_lastBlockReferenced->blockAvailable() == true);
00202 
00203         return m_lastBlockReferenced->allocateBlock();
00204     }
00205 
00206     /*
00207      * Commits the allocation of the previous
00208      * allocateBlock() call.
00209      *
00210      * @param theObject A pointer to a block of memory
00211      */
00212     virtual void
00213     commitAllocation(ObjectType*    theObject)
00214     {
00215         assert(m_blocks.size() != 0 && m_lastBlockReferenced != 0 && m_lastBlockReferenced->ownsBlock(theObject) == true);
00216 
00217         m_lastBlockReferenced->commitAllocation(theObject);
00218         assert(m_lastBlockReferenced->ownsObject(theObject) == true);
00219     }
00220 
00221     virtual bool
00222     ownsObject(const ObjectType*    theObject) const
00223     {
00224         bool    fResult = false;
00225 
00226         // If no block has ever been referenced, then we haven't allocated
00227         // any objects.
00228         if (m_lastBlockReferenced != 0)
00229         {
00230             // Check the last referenced block first.
00231             fResult = m_lastBlockReferenced->ownsObject(theObject);
00232 
00233             if (fResult == false)
00234             {
00235                 // Search back for a block with some space available...
00236                 const ArenaBlockListType::const_reverse_iterator    theEnd = m_blocks.rend();
00237 
00238                 ArenaBlockListType::const_reverse_iterator  i = m_blocks.rbegin();
00239 
00240                 while(i != theEnd)
00241                 {
00242                     assert(*i != 0);
00243 
00244                     if ((*i)->ownsObject(theObject) == true)
00245                     {
00246                         fResult = true;
00247 
00248                         break;
00249                     }
00250                     else
00251                     {
00252                         ++i;
00253                     }
00254                 }
00255             }
00256         }
00257 
00258         return fResult;
00259     }
00260 
00261 private:
00262 
00263     // Not defined...
00264     ReusableArenaAllocator(const ReusableArenaAllocator<ObjectType>&);
00265 
00266     ReusableArenaAllocator<ObjectType>&
00267     operator=(const ReusableArenaAllocator<ObjectType>&);
00268 
00269     // Data members...
00270     ReusableArenaBlockType*     m_lastBlockReferenced;
00271 };
00272 
00273 
00274 
00275 #endif  // !defined(REUSABLEARENAALLOCATOR_INCLUDE_GUARD_1357924680)

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