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# XalanArrayAllocator.hpp

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    00001 /*
    00002  * The Apache Software License, Version 1.1
    00003  *
    00004  *
    00005  * Copyright (c) 1999-2002 The Apache Software Foundation.  All rights
    00006  * reserved.
    00007  *
    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
    00016  *    notice, this list of conditions and the following disclaimer in
    00017  *    the documentation and/or other materials provided with the
    00018  *    distribution.
    00019  *
    00020  * 3. The end-user documentation included with the redistribution,
    00021  *    if any, must include the following acknowledgment:
    00022  *       "This product includes software developed by the
    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.
    00026  *
    00027  * 4. The names "Xalan" and "Apache Software Foundation" must
    00028  *    not be used to endorse or promote products derived from this
    00029  *    software without prior written permission. For written
    00030  *    permission, please contact apache@apache.org.
    00031  *
    00032  * 5. Products derived from this software may not be called "Apache",
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    00034  *    permission of the Apache Software Foundation.
    00035  *
    00036  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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    00038  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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    00046  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    00047  * SUCH DAMAGE.
    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
    00054  * information on the Apache Software Foundation, please see
    00055  * <http://www.apache.org/>.
    00056  */
    00057 #if !defined(XALANARRAYALLOCATOR_HEADER_GUARD_1357924680)
    00058 #define XALANARRAYALLOCATOR_HEADER_GUARD_1357924680
    00059
    00060
    00061
    00062 #include <xalanc/PlatformSupport/PlatformSupportDefinitions.hpp>
    00063
    00064
    00065
    00066 #include <cassert>
    00067 #include <list>
    00068 #include <utility>
    00069 #include <vector>
    00070
    00071
    00072
    00073 XALAN_CPP_NAMESPACE_BEGIN
    00074
    00075
    00076
    00077 template<class Type>
    00078 class XALAN_PLATFORMSUPPORT_EXPORT XalanArrayAllocator
    00079 {
    00080 public:
    00081
    00082 #if defined(XALAN_NO_STD_NAMESPACE)
    00083     typedef vector<Type>                    VectorType;
    00084     typedef typename VectorType::size_type  size_type;
    00085     typedef pair<size_type, VectorType>     ListEntryType;
    00086     typedef list<ListEntryType>             ListType;
    00087 #else
    00088     typedef std::vector<Type>                   VectorType;
    00089     typedef typename VectorType::size_type      size_type;
    00090     typedef std::pair<size_type, VectorType>    ListEntryType;
    00091     typedef std::list<ListEntryType>            ListType;
    00092 #endif
    00093
    00094     typedef Type                            value_type;
    00095
    00096     typedef typename ListType::iterator     ListIteratorType;
    00097
    00098     // Default size for vector allocation.
    00099     enum { eDefaultBlockSize = 500 };
    00100
    00106     XalanArrayAllocator(size_type   theBlockSize = eDefaultBlockSize) :
    00107         m_list(),
    00108         m_blockSize(theBlockSize),
    00109         m_lastEntryFound(0)
    00110     {
    00111     }
    00112
    00113     ~XalanArrayAllocator()
    00114     {
    00115     }
    00116
    00120     void
    00121     clear()
    00122     {
    00123         m_list.clear();
    00124
    00125         m_lastEntryFound = 0;
    00126     }
    00127
    00133     void
    00134     reset()
    00135     {
    00136         if (m_list.empty() == true)
    00137         {
    00138             m_lastEntryFound = 0;
    00139         }
    00140         else
    00141         {
    00142             const ListIteratorType  theEnd = m_list.end();
    00143             ListIteratorType        theCurrent = m_list.begin();
    00144
    00145             do
    00146             {
    00147                 (*theCurrent).first = (*theCurrent).second.size();
    00148
    00149                 ++theCurrent;
    00150             } while(theCurrent != theEnd);
    00151
    00152             m_lastEntryFound = &*m_list.begin();
    00153         }
    00154     }
    00155
    00162     Type*
    00163     allocate(size_type  theCount)
    00164     {
    00165         // Handle the case of theCount being greater than the block size first...
    00166         if (theCount >= m_blockSize)
    00167         {
    00168             return createEntry(theCount, theCount);
    00169         }
    00170         else
    00171         {
    00172             ListEntryType*  theEntry =
    00173                 findEntry(theCount);
    00174
    00175             // Did we find a slot?
    00176             if (theEntry == 0)
    00177             {
    00178                 // Nope, create a new one...
    00179                 return createEntry(m_blockSize, theCount);
    00180             }
    00181             else
    00182             {
    00183                 // The address we want is that of the first free element in the
    00184                 // vector...
    00185                 Type* const     thePointer =
    00186                     &*theEntry->second.begin() + (theEntry->second.size() - theEntry->first);
    00187
    00188                 // Resize the vector to the appropriate size...
    00189                 theEntry->first -= theCount;
    00190
    00191                 return thePointer;
    00192             }
    00193         }
    00194     }
    00195
    00196 private:
    00197
    00198     // Utility functions...
    00199     Type*
    00200     createEntry(
    00201             size_type   theBlockSize,
    00202             size_type   theCount)
    00203     {
    00204         assert(theBlockSize >= theCount);
    00205
    00206         // Push on a new entry.  The entry has no open space,
    00207         // since it's greater than our block size...
    00208         m_list.push_back(ListEntryType(0, VectorType()));
    00209
    00210         // Get the new entry...
    00211         ListEntryType&  theNewEntry = m_list.back();
    00212
    00213         // Resize the vector to the appropriate size...
    00214         theNewEntry.second.resize(theBlockSize, VectorType::value_type(0));
    00215
    00216         // Set the number of free spaces accordingly...
    00217         theNewEntry.first = theBlockSize - theCount;
    00218
    00219         if (theNewEntry.first != 0)
    00220         {
    00221             m_lastEntryFound = &theNewEntry;
    00222         }
    00223
    00224         // Return a pointer to the beginning of the allocated memory...
    00225         return &*theNewEntry.second.begin();
    00226     }
    00227
    00228     ListEntryType*
    00229     findEntry(size_type     theCount)
    00230     {
    00231         // Search for an entry that has some free space.
    00232
    00233         if (m_lastEntryFound != 0 && m_lastEntryFound->first >= theCount)
    00234         {
    00235             return m_lastEntryFound;
    00236         }
    00237         else
    00238         {
    00239             const ListIteratorType  theEnd = m_list.end();
    00240             ListIteratorType        theCurrent = m_list.begin();
    00241
    00242             ListEntryType*  theEntry = 0;
    00243
    00244             while(theCurrent != theEnd)
    00245             {
    00246                 // We're looking for the best fit, so
    00247                 // if the free space and the count we're
    00248                 // looking for are equal, that's pretty
    00249                 // much the best we can do...
    00250                 if ((*theCurrent).first == theCount)
    00251                 {
    00252                     theEntry = &*theCurrent;
    00253
    00254                     break;
    00255                 }
    00256                 else if ((*theCurrent).first >= theCount)
    00257                 {
    00258                     // If we haven't found anything yet, the first
    00259                     // entry we find that's large enough becomes
    00260                     // our best fit.
    00261                     //
    00262                     // Otherwise, we'll assume that a smaller
    00263                     // slot is a better fit, though I may be
    00264                     // wrong about this...
    00265                     if (theEntry == 0 ||
    00266                         (*theCurrent).first < theEntry->first)
    00267                     {
    00268                         // Nope, so this becomes our best-fit so far.
    00269                         theEntry = &*theCurrent;
    00270                     }
    00271
    00272                     ++theCurrent;
    00273                 }
    00274                 else
    00275                 {
    00276                     // Won't fit, so just continue...
    00277                     ++theCurrent;
    00278                 }
    00279             }
    00280
    00281             m_lastEntryFound = theEntry;
    00282
    00283             return theEntry;
    00284         }
    00285     }
    00286
    00287     // Not implemented...
    00288     XalanArrayAllocator(const XalanArrayAllocator<Type>&    theSource);
    00289
    00290     XalanArrayAllocator<Type>&
    00291     operator=(const XalanArrayAllocator<Type>&  theSource);
    00292
    00293     bool
    00294     operator==(const XalanArrayAllocator<Type>& theRHS) const;
    00295
    00296
    00297     // Data members...
    00298     ListType            m_list;
    00299
    00300     const size_type     m_blockSize;
    00301
    00302     ListEntryType*      m_lastEntryFound;
    00303 };
    00304
    00305
    00306
    00307 XALAN_CPP_NAMESPACE_END
    00308
    00309
    00310
    00311 #endif  // !defined(XALANARRAYALLOCATOR_HEADER_GUARD_1357924680)

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