blob: 437a8fc019be0a36ab605b3c506d87f17b8d9758 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
|
/*
* free.c
*
* Very simple linked-list based malloc()/free().
*/
#include <stdlib.h>
#include "malloc.h"
static struct free_arena_header *
__free_block(struct free_arena_header *ah)
{
struct free_arena_header *pah, *nah;
pah = ah->a.prev;
nah = ah->a.next;
if ( ARENA_TYPE_GET(pah->a.attrs) == ARENA_TYPE_FREE &&
(char *)pah+ARENA_SIZE_GET(pah->a.attrs) == (char *)ah ) {
/* Coalesce into the previous block */
ARENA_SIZE_SET(pah->a.attrs, ARENA_SIZE_GET(pah->a.attrs) +
ARENA_SIZE_GET(ah->a.attrs));
pah->a.next = nah;
nah->a.prev = pah;
#ifdef DEBUG_MALLOC
ARENA_TYPE_SET(ah->a.attrs, ARENA_TYPE_DEAD);
#endif
ah = pah;
pah = ah->a.prev;
} else {
/* Need to add this block to the free chain */
ARENA_TYPE_SET(ah->a.attrs, ARENA_TYPE_FREE);
ah->a.tag = NULL;
ah->next_free = __malloc_head.next_free;
ah->prev_free = &__malloc_head;
__malloc_head.next_free = ah;
ah->next_free->prev_free = ah;
}
/* In either of the previous cases, we might be able to merge
with the subsequent block... */
if ( ARENA_TYPE_GET(nah->a.attrs) == ARENA_TYPE_FREE &&
(char *)ah+ARENA_SIZE_GET(ah->a.attrs) == (char *)nah ) {
ARENA_SIZE_SET(ah->a.attrs, ARENA_SIZE_GET(ah->a.attrs) +
ARENA_SIZE_GET(nah->a.attrs));
/* Remove the old block from the chains */
nah->next_free->prev_free = nah->prev_free;
nah->prev_free->next_free = nah->next_free;
ah->a.next = nah->a.next;
nah->a.next->a.prev = ah;
#ifdef DEBUG_MALLOC
ARENA_TYPE_SET(nah->a.attrs, ARENA_TYPE_DEAD);
#endif
}
/* Return the block that contains the called block */
return ah;
}
void free(void *ptr)
{
struct free_arena_header *ah;
if ( !ptr )
return;
ah = (struct free_arena_header *)
((struct arena_header *)ptr - 1);
#ifdef DEBUG_MALLOC
assert( ARENA_TYPE_GET(ah->a.attrs) == ARENA_TYPE_USED );
#endif
__free_block(ah);
/* Here we could insert code to return memory to the system. */
}
|
