Nils O. Selåsdal
53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
#ifndef LALLOC_H_
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#define LALLOC_H_
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#include <stdint.h>
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#include <stddef.h>
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#ifdef __ccplusplus
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extern "C" {
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#endif
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// Internal header added in front of each allocation
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typedef struct LBlockHeader LBlockHeader;
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struct LBlockHeader {
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uint32_t next; // offset from base
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uint32_t prev; // offset from base
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uint32_t size_and_flags; // size | free_bit
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// Padding to ensure we always return 16 byte aligned pointers.
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uint8_t pad[4];
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};
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_Static_assert(sizeof(LBlockHeader) == 16, "sizeof(BlockHeader) is not 16");
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/**
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* General purpose allocator.
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* - Allocated pointers are aligned to 16 bytes.
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* - Backing buffer must be aligned to 16 bytes start
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* - 4Gb - 16 is max for the allocator backing buffer.
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* - Allocation of > 0 bytes returns a size aligned up to 16 bytes
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* - Allocation of 0 bytes returns a valid pointer with 0 usable space
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* The allocator maintains a doubly linked list of blocks,
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* when blocks are free'd, adjacent blocks are merged to keep
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* fragmentation to a minimum
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*/
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typedef struct LAlloc LAlloc;
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struct LAlloc {
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uint8_t *base; // backing store
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uint32_t size; // total size
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LBlockHeader *next_alloc; // start of free block search
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};
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void lalloc_init(LAlloc *allocator, void *backing_store, uint32_t size);
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void *lalloc(LAlloc *allocator, uint32_t size);
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void lfree(LAlloc *allocator, void *ptr);
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LBlockHeader *lblock_from_offset(const LAlloc *allocator, uint32_t offset);
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uint32_t lblock_size(const LBlockHeader *block);
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int lblock_is_free(const LBlockHeader *block);
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#ifdef __ccplusplus
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} // extern "C"
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#endif
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#endif
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