74 lines
1.6 KiB
C
74 lines
1.6 KiB
C
/*
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* free.c
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*
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* Very simple linked-list based malloc()/free().
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*/
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#include <stdlib.h>
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#include "malloc.h"
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static struct free_arena_header *__free_block(struct free_arena_header *ah)
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{
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struct free_arena_header *pah, *nah;
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pah = ah->a.prev;
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nah = ah->a.next;
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if (pah->a.type == ARENA_TYPE_FREE &&
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(char *)pah + pah->a.size == (char *)ah) {
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/* Coalesce into the previous block */
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pah->a.size += ah->a.size;
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pah->a.next = nah;
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nah->a.prev = pah;
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#ifdef DEBUG_MALLOC
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ah->a.type = ARENA_TYPE_DEAD;
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#endif
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ah = pah;
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pah = ah->a.prev;
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} else {
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/* Need to add this block to the free chain */
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ah->a.type = ARENA_TYPE_FREE;
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ah->next_free = __malloc_head.next_free;
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ah->prev_free = &__malloc_head;
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__malloc_head.next_free = ah;
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ah->next_free->prev_free = ah;
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}
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/* In either of the previous cases, we might be able to merge
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with the subsequent block... */
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if (nah->a.type == ARENA_TYPE_FREE &&
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(char *)ah + ah->a.size == (char *)nah) {
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ah->a.size += nah->a.size;
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/* Remove the old block from the chains */
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nah->next_free->prev_free = nah->prev_free;
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nah->prev_free->next_free = nah->next_free;
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ah->a.next = nah->a.next;
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nah->a.next->a.prev = ah;
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#ifdef DEBUG_MALLOC
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nah->a.type = ARENA_TYPE_DEAD;
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#endif
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}
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/* Return the block that contains the called block */
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return ah;
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}
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void free(void *ptr)
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{
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struct free_arena_header *ah;
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if (!ptr)
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return;
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ah = (struct free_arena_header *)
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((struct arena_header *)ptr - 1);
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__free_block(ah);
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/* Here we could insert code to return memory to the system. */
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}
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