79 lines
2.0 KiB
C
79 lines
2.0 KiB
C
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#include "malloc.h"
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#include <stdbool.h>
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#include <string.h>
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#include <sys/mman.h>
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// Fast allocator for sizes 16, 32, 48, 64 bytes
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malloc_header_t* free_blocks[5];
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void prepare_free_blocks(size_t size)
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{
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int block_id = size >> 4;
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const size_t alloc_size = MALLOC_DEFAULT_BLOCK_SIZE;
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intptr_t ret = (intptr_t)mmap(NULL, alloc_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
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if (ret < 0) {
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free_blocks[block_id] = NULL;
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return;
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}
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void* raw_area = (void*)ret;
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const size_t sizeof_block_with_header = size + sizeof(malloc_header_t);
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size_t passed = 0;
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free_blocks[block_id] = (malloc_header_t*)raw_area;
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malloc_header_t* prev_header = NULL;
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while (passed + sizeof_block_with_header <= alloc_size) {
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malloc_header_t* current = (malloc_header_t*)raw_area;
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current->flags = FLAG_SLAB | FLAG_ALLOCATED;
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current->next = NULL;
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current->prev = prev_header;
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current->size = size;
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prev_header = current;
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raw_area += sizeof_block_with_header;
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passed += sizeof_block_with_header;
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}
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malloc_header_t* next_header = NULL;
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while (prev_header) {
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prev_header->next = next_header;
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prev_header = prev_header->prev;
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}
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}
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void _slab_init()
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{
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prepare_free_blocks(16);
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prepare_free_blocks(32);
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prepare_free_blocks(48);
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prepare_free_blocks(64);
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}
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void* slab_alloc(size_t size)
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{
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if (size > 64) {
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return NULL;
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}
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int block_id = ((size + 15) >> 4);
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malloc_header_t* zone = free_blocks[block_id];
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if (!zone) {
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return NULL;
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}
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free_blocks[block_id] = zone->next;
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return (void*)&((malloc_header_t*)zone)[1];
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}
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void slab_free(malloc_header_t* mem_header)
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{
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malloc_header_t* next = free_blocks[((mem_header->size) >> 4)];
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free_blocks[((mem_header->size) >> 4)] = mem_header;
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mem_header->next = next;
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mem_header->prev = NULL;
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if (next) {
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next->prev = mem_header;
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}
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}
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