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https://github.com/AquariaOSE/Aquaria.git
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100 lines
2.7 KiB
C++
100 lines
2.7 KiB
C++
#ifndef MEMORY_ALLOCATOR_SMALL_BLOCK_H
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#define MEMORY_ALLOCATOR_SMALL_BLOCK_H
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/* Optimized memory allocator for small & frequent (de-)allocations.
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* Low memory overhead. Used for Lua.
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* Inspired by http://dns.achurch.org/cgi-bin/hg/aquaria-psp/file/tip/PSP/src/lalloc.c
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*/
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// Originally made for LV3proj_ng (https://github.com/fgenesis/lv3proj_ng)
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// Hacked in shape for use in Aquaria
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// Public domain
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#include <vector>
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class SmallBlockAllocator
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{
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public:
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SmallBlockAllocator(unsigned int blockSizeMin, unsigned int blockSizeMax, unsigned int blockSizeIncr = 8,
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unsigned int elemsPerBlockMin = 64, unsigned int elemsPerBlockMax = 2048);
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~SmallBlockAllocator();
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void *Alloc(void *ptr, size_t newsize, size_t oldsize);
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private:
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void *_Alloc(unsigned int size);
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void *_Realloc(void *ptr, unsigned int newsize, unsigned int oldsize);
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void _Free(void* ptr, unsigned int size);
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void *_FallbackAlloc(unsigned int size);
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void _FallbackFree(void *ptr);
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struct Block
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{
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// block header start
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Block *next;
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Block *prev;
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unsigned short maxElems;
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unsigned short freeElems;
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unsigned short elemSize;
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unsigned short bitmapInts;
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// block header end
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unsigned int bitmap[1]; // variable sized
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// actual storage memory starts after bitmap[bitmapInts]
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inline unsigned char *getPtr()
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{
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return (unsigned char*)&bitmap[bitmapInts];
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}
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inline const unsigned char *getPtr() const
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{
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return (unsigned char*)&bitmap[bitmapInts];
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}
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inline unsigned char *getEndPtr()
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{
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return getPtr() + (maxElems * elemSize);
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}
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inline const unsigned char *getEndPtr() const
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{
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return getPtr() + (maxElems * elemSize);
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}
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void *allocElem();
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void freeElem(unsigned char *ptr);
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bool contains(unsigned char *ptr) const;
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};
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Block *_AllocBlock(unsigned int elemCount, unsigned int elemSize);
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void _FreeBlock(Block *blk);
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Block *_AppendBlock(unsigned int elemSize);
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Block *_GetFreeBlock(unsigned int elemSize); // NULL if none free
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Block *_FindBlockContainingPtr(void *ptr);
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inline unsigned int GetIndexForElemSize(unsigned int elemSize)
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{
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return ((elemSize + (_blockSizeIncr - 1)) / _blockSizeIncr) - 1;
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}
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static bool Block_ptr_cmp(const Block *blk, const void *ptr);
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Block **_blocks;
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std::vector<Block*> _allblocks; // always sorted by pointer address
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unsigned int _blockSizeMin;
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unsigned int _blockSizeMax;
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unsigned int _blockSizeIncr;
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unsigned int _elemsPerBlockMin;
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unsigned int _elemsPerBlockMax;
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};
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#endif
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