87 lines
3.2 KiB
C++
87 lines
3.2 KiB
C++
/** @file
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* @author Daniel Chappuis
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* @copyright 2010-2016 Daniel Chappuis
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* @license BSD 3 clauses (see license file)
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*/
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#pragma once
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// Libraries
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#include <ephysics/configuration.hpp>
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/// ReactPhysics3D namespace
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namespace ephysics {
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// Class MemoryAllocator
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/**
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* This class is used to efficiently allocate memory on the heap.
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* It allows us to allocate small blocks of memory (smaller or equal to 1024 bytes)
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* efficiently. This implementation is inspired by the small block allocator
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* described here : http://www.codeproject.com/useritems/Small_Block_Allocator.asp
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*/
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class MemoryAllocator {
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private :
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// Structure MemoryUnit
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/**
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* Represent a memory unit that is used for a single memory allocation
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* request.
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*/
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struct MemoryUnit {
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public :
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/// Pointer to the next memory unit inside a memory block
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MemoryUnit* nextUnit;
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};
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// Structure MemoryBlock
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/**
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* A memory block is a large piece of memory that is allocated once and that
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* will contain multiple memory unity.
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*/
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struct MemoryBlock {
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public :
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/// Pointer to the first element of a linked-list of memory unity.
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MemoryUnit* memoryUnits;
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};
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/// Number of heaps
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static const int32_t NB_HEAPS = 128;
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/// Maximum memory unit size. An allocation request of a size smaller or equal to
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/// this size will be handled using the small block allocator. However, for an
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/// allocation request larger than the maximum block size, the standard malloc()
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/// will be used.
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static const size_t MAX_UNIT_SIZE = 1024;
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/// Size a memory chunk
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static const size_t BLOCK_SIZE = 16 * MAX_UNIT_SIZE;
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// -------------------- Attributes -------------------- //
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/// Size of the memory units that each heap is responsible to allocate
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static size_t m_unitSizes[NB_HEAPS];
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/// Lookup table that mape size to allocate to the index of the
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/// corresponding heap we will use for the allocation.
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static int32_t m_mapSizeToHeapIndex[MAX_UNIT_SIZE + 1];
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/// True if the m_mapSizeToHeapIndex array has already been initialized
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static bool isMapSizeToHeadIndexInitialized;
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/// Pointers to the first free memory unit for each heap
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MemoryUnit* m_freeMemoryUnits[NB_HEAPS];
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/// All the allocated memory blocks
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MemoryBlock* m_memoryBlocks;
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/// Number of allocated memory blocks
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uint32_t m_numberAllocatedMemoryBlocks;
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/// Current number of used memory blocks
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uint32_t m_numberCurrentMemoryBlocks;
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#ifndef NDEBUG
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/// This variable is incremented by one when the allocate() method has been
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/// called and decreased by one when the release() method has been called.
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/// This variable is used in debug mode to check that the allocate() and release()
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/// methods are called the same number of times
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int32_t m_numberTimesAllocateMethodCalled;
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#endif
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public :
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// -------------------- Methods -------------------- //
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/// Constructor
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MemoryAllocator();
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/// Destructor
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~MemoryAllocator();
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/// Allocate memory of a given size (in bytes) and return a pointer to the
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/// allocated memory.
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void* allocate(size_t size);
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/// Release previously allocated memory.
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void release(void* pointer, size_t size);
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};
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}
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