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  ** Copyright (C) 2016 The Qt Company Ltd.
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  ** This file is part of the QtQml module of the Qt Toolkit.
  **
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  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
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  #ifndef QV4EXECUTABLEALLOCATOR_H
  #define QV4EXECUTABLEALLOCATOR_H
  
  //
  //  W A R N I N G
  //  -------------
  //
  // This file is not part of the Qt API.  It exists purely as an
  // implementation detail.  This header file may change from version to
  // version without notice, or even be removed.
  //
  // We mean it.
  //
  
  #include "qv4global_p.h"
  
  #include <QMultiMap>
  #include <QHash>
  #include <QVector>
  #include <QByteArray>
  #include <QMutex>
  
  namespace WTF {
  class PageAllocation;
  }
  
  QT_BEGIN_NAMESPACE
  
  namespace QV4 {
  
  class Q_QML_AUTOTEST_EXPORT ExecutableAllocator
  {
  public:
      struct ChunkOfPages;
      struct Allocation;
  
      ExecutableAllocator();
      ~ExecutableAllocator();
  
      Allocation *allocate(size_t size);
      void free(Allocation *allocation);
  
      struct Allocation
      {
          Allocation()
              : addr(0)
              , size(0)
              , free(true)
              , next(0)
              , prev(0)
          {}
  
          void *start() const;
          void invalidate() { addr = 0; }
          bool isValid() const { return addr != 0; }
          void deallocate(ExecutableAllocator *allocator);
  
      private:
          ~Allocation() {}
  
          friend class ExecutableAllocator;
  
          Allocation *split(size_t dividingSize);
          bool mergeNext(ExecutableAllocator *allocator);
          bool mergePrevious(ExecutableAllocator *allocator);
  
          quintptr addr;
          uint size : 31; // More than 2GB of function code? nah :)
          uint free : 1;
          Allocation *next;
          Allocation *prev;
      };
  
      // for debugging / unit-testing
      int freeAllocationCount() const { return freeAllocations.count(); }
      int chunkCount() const { return chunks.count(); }
  
      struct ChunkOfPages
      {
          ChunkOfPages()
              : pages(0)
              , firstAllocation(0)
          {}
          ~ChunkOfPages();
  
          WTF::PageAllocation *pages;
          Allocation *firstAllocation;
  
          bool contains(Allocation *alloc) const;
      };
  
      ChunkOfPages *chunkForAllocation(Allocation *allocation) const;
  
  private:
      QMultiMap<size_t, Allocation*> freeAllocations;
      QMap<quintptr, ChunkOfPages*> chunks;
      mutable QMutex mutex;
  };
  
  }
  
  QT_END_NAMESPACE
  
  #endif // QV4EXECUTABLEALLOCATOR_H
  