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/*
* malloc.c
*
* Very simple linked-list based malloc()/free().
*/
#include <stdlib.h>
#include <string.h>
#include "malloc.h"
struct free_arena_header __malloc_head = {
{
ARENA_TYPE_HEAD,
0,
&__malloc_head,
&__malloc_head,
},
&__malloc_head,
&__malloc_head
};
extern void *__mem_end; /* In argv.c */
void __init_memory_arena(void)
{
extern char __heap_end[];
struct free_arena_header *fp;
fp = (struct free_arena_header *)__mem_end;
fp->a.type = ARENA_TYPE_FREE;
fp->a.size = __heap_end - (char *)__mem_end;
/* Insert into chains */
fp->a.next = fp->a.prev = &__malloc_head;
fp->next_free = fp->prev_free = &__malloc_head;
__malloc_head.a.next = __malloc_head.a.prev = fp;
__malloc_head.next_free = __malloc_head.prev_free = fp;
}
static void *__malloc_from_block(struct free_arena_header *fp, size_t size)
{
size_t fsize;
struct free_arena_header *nfp, *na;
fsize = fp->a.size;
/* We need the 2* to account for the larger requirements of a free block */
if (fsize >= size + 2 * sizeof(struct arena_header)) {
/* Bigger block than required -- split block */
nfp = (struct free_arena_header *)((char *)fp + size);
na = fp->a.next;
nfp->a.type = ARENA_TYPE_FREE;
nfp->a.size = fsize - size;
fp->a.type = ARENA_TYPE_USED;
fp->a.size = size;
/* Insert into all-block chain */
nfp->a.prev = fp;
nfp->a.next = na;
na->a.prev = nfp;
fp->a.next = nfp;
/* Replace current block on free chain */
nfp->next_free = fp->next_free;
nfp->prev_free = fp->prev_free;
fp->next_free->prev_free = nfp;
fp->prev_free->next_free = nfp;
} else {
/* Allocate the whole block */
fp->a.type = ARENA_TYPE_USED;
/* Remove from free chain */
fp->next_free->prev_free = fp->prev_free;
fp->prev_free->next_free = fp->next_free;
}
return (void *)(&fp->a + 1);
}
void *malloc(size_t size)
{
struct free_arena_header *fp;
if (size == 0)
return NULL;
/* Add the obligatory arena header, and round up */
size = (size + 2 * sizeof(struct arena_header) - 1) & ~ARENA_SIZE_MASK;
for (fp = __malloc_head.next_free; fp->a.type != ARENA_TYPE_HEAD;
fp = fp->next_free) {
if (fp->a.size >= size) {
/* Found fit -- allocate out of this block */
return __malloc_from_block(fp, size);
}
}
/* Nothing found... need to request a block from the kernel */
return NULL; /* No kernel to get stuff from */
}
void *calloc(size_t nmemb, size_t size)
{
void *p;
size *= nmemb;
p = malloc(size);
if (p)
memset(p, 0, size);
return p;
}
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