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 // Created on: 2005-03-15
 // Created by: Peter KURNEV
 // Copyright (c) 2005-2014 OPEN CASCADE SAS
 //
 // This file is part of Open CASCADE Technology software library.
 //
 // This library is free software; you can redistribute it and/or modify it under
 // the terms of the GNU Lesser General Public License version 2.1 as published
 // by the Free Software Foundation, with special exception defined in the file
 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
 // distribution for complete text of the license and disclaimer of any warranty.
 //
 // Alternatively, this file may be used under the terms of Open CASCADE
 // commercial license or contractual agreement.
 
 #ifndef _Standard_MMgrOpt_HeaderFile
 #define _Standard_MMgrOpt_HeaderFile
 
 #include <Standard_MMgrRoot.hxx>
 #include <Standard_Mutex.hxx>
 
 /**
 * @brief Open CASCADE memory manager optimized for speed.
 *
 * The behaviour is different for memory blocks of different sizes,
 * according to specified options provided to constructor:
 *
 * - Small blocks with size less than or equal to aCellSize are allocated 
 *   in big pools of memory. The parameter aNbPages specifies size of 
 *   these pools in pages (operating system-dependent). 
 *   When freed, small block is not returned to the system but added
 *   into free blocks list and reused when block of the same size is 
 *   requested.
 * 
 * - Medium size blocks with size less than aThreshold are allocated 
 *   using malloc() or calloc() function but not returned to the system
 *   when method Free() is called; instead they are put into free list
 *   and reused when block of the same size is requested.
 *   Blocks of medium size stored in free lists can be released to the 
 *   system (by free()) by calling method Purge().
 *
 * - Large blocks with size greater than or equal to aThreshold are allocated 
 *   and freed directly: either using malloc()/calloc() and free(), or using 
 *   memory mapped files (if option aMMap is True)
 *   
 * Thus the optimization of memory allocation/deallocation is reached 
 * for small and medium size blocks using free lists method; 
 * note that space allocated for small blocks cannot be (currently) released
 * to the system while space for medium size blocks can be released by method Purge().
 *
 * Note that destructor of that class frees all free lists and memory pools 
 * allocated for small blocks.
 * 
 * Note that size of memory blocks allocated by this memory manager is always 
 * rounded up to 16 bytes. In addition, 8 bytes are added at the beginning 
 * of the memory block to hold auxiliary information (size of the block when
 * in use, or pointer to the next free block when in free list).
 * This the expense of speed optimization. At the same time, allocating small 
 * blocks is usually less costly than directly by malloc since allocation is made
 * once (when allocating a pool) and overheads induced by malloc are minimized.
 */
 class Standard_MMgrOpt : public Standard_MMgrRoot
 {
  public:
   
   //! Constructor. If aClear is True, the allocated emmory will be 
   //! nullified. For description of other parameters, see description 
   //! of the class above.
   Standard_EXPORT Standard_MMgrOpt
                         (const Standard_Boolean aClear      = Standard_True,
                          const Standard_Boolean aMMap       = Standard_True,
                          const Standard_Size    aCellSize   = 200,
                          const Standard_Integer aNbPages    = 10000,
                          const Standard_Size    aThreshold  = 40000);
 
   //! Frees all free lists and pools allocated for small blocks 
   Standard_EXPORT virtual ~Standard_MMgrOpt();
   
   //! Allocate aSize bytes; see class description above
   Standard_EXPORT virtual Standard_Address Allocate(const Standard_Size aSize);
   
   //! Reallocate previously allocated aPtr to a new size; new address is returned.
   //! In case that aPtr is null, the function behaves exactly as Allocate.
   Standard_EXPORT virtual Standard_Address Reallocate (Standard_Address thePtr, 
                                                        const Standard_Size theSize);
   
   //! Free previously allocated block.
   //! Note that block can not all blocks are released to the OS by this 
   //! method (see class description)
   Standard_EXPORT virtual void Free (Standard_Address thePtr);
   
   //! Release medium-sized blocks of memory in free lists to the system.
   //! Returns number of actually freed blocks
   Standard_EXPORT virtual Standard_Integer Purge(Standard_Boolean isDestroyed);
 
   //! Declaration of a type pointer to the callback function that should accept the following arguments:
   //! @param theIsAlloc   true if the data is allocated, false if it is freed
   //! @param theStorage   address of the allocated/freed block
   //! @param theRoundSize the real rounded size of the block
   //! @param theSize      the size of the block that was requested by application (this value is correct only if theIsAlloc is true)
   typedef void (*TPCallBackFunc)(const Standard_Boolean theIsAlloc,
                                  const Standard_Address theStorage,
                                  const Standard_Size theRoundSize,
                                  const Standard_Size theSize);
 
   //! Set the callback function. You may pass 0 there to turn off the callback.
   //! The callback function, if set, will be automatically called from within
   //! Allocate and Free methods.
   Standard_EXPORT static void SetCallBackFunction(TPCallBackFunc pFunc);
 
 protected:
  
   //! Internal - initialization of buffers
   Standard_EXPORT void Initialize();
 
   //! Internal - allocation of memory using either malloc or memory mapped files.
   //! The size of the actually allocated block may be greater than requested one
   //! when memory mapping is used, since it is aligned to page size 
   Standard_Size* AllocMemory (Standard_Size &aSize);
   
   //! Internal - deallocation of memory taken by AllocMemory
   void FreeMemory (Standard_Address aPtr, const Standard_Size aSize);
   
   //! Internal - free memory pools allocated for small size blocks
   void FreePools();
 
  protected:
   Standard_Boolean myClear;         //!< option to clear allocated memory
   
   Standard_Size    myFreeListMax;   //!< last allocated index in the free blocks list
   Standard_Size ** myFreeList;      //!< free blocks list 
 
   Standard_Size    myCellSize;      //!< small blocks size
   Standard_Integer myNbPages;       //!< size (pages) for small block memory pools
   Standard_Size    myPageSize;      //!< system-dependent memory page size
   Standard_Size *  myAllocList;     //!< list of memory pools for small blocks
   Standard_Size *  myNextAddr;      //!< next free address in the active memory pool
   Standard_Size *  myEndBlock;      //!< end of the active memory pool
   
   Standard_Integer myMMap;          //!< non-null if using memory mapped files for allocation of large blocks
   Standard_Size    myThreshold;     //!< large block size  
   
   Standard_Mutex   myMutex;         //!< Mutex to protect free lists data
   Standard_Mutex   myMutexPools;    //!< Mutex to protect small block pools data
 };
 
 #endif

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