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Aquaria/BBGE/MemoryAllocatorSmallBlock.h

100 lines
2.8 KiB
C++

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// Originally made for LV3proj_ng (https://github.com/fgenesis/lv3proj_ng)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