summaryrefslogtreecommitdiff
path: root/libc/stdlib/malloc/heap.h
blob: 74b56603bf691b8f2d7aae552da43934f510a8a6 (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
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
/*
 * libc/stdlib/malloc-zarg/heap.h -- heap allocator used for malloc
 *
 *  Copyright (C) 2002  NEC Corporation
 *  Copyright (C) 2002  Miles Bader <miles@gnu.org>
 *
 * This file is subject to the terms and conditions of the GNU Lesser
 * General Public License.  See the file COPYING.LIB in the main
 * directory of this archive for more details.
 * 
 * Written by Miles Bader <miles@gnu.org>
 */

#include <features.h>


#ifdef __UCLIBC_HAS_THREADS__
#include <pthread.h>
typedef pthread_mutex_t mutex_t;
# define MUTEX_INITIALIZER  PTHREAD_MUTEX_INITIALIZER
# define mutex_lock(x)	    pthread_mutex_lock(&(x))
# define mutex_unlock(x)    pthread_mutex_unlock(&(x));
#else
/* Mutex operations are currently a nop.  */
typedef int mutex_t;
# define MUTEX_INITIALIZER 0
# define mutex_lock(x)
# define mutex_unlock(x)
#endif



/* The unit in which allocation is done, due to alignment constraints, etc.
   All allocation requests are rounded up to a multiple of this size.
   Must be a power of 2.  */
#define HEAP_GRANULARITY	(sizeof (double))


struct heap
{
  struct heap_free_area *free_areas;
  mutex_t lock;
};

#define HEAP_INIT 	{ 0, MUTEX_INITIALIZER }


/* A free-list area `header'.  These are actually stored at the _ends_ of
   free areas (to make allocating from the beginning of the area simpler),
   so one might call it a `footer'.  */
struct heap_free_area
{
	size_t size;
	struct heap_free_area *next, *prev;
};

/* Return the address of the end of the frea area FA.  */
#define HEAP_FREE_AREA_END(fa) ((void *)(fa + 1))
/* Return the address of the beginning of the frea area FA.  FA is
   evaulated multiple times.  */
#define HEAP_FREE_AREA_START(fa) ((void *)((char *)(fa + 1) - (fa)->size))


/* Rounds SZ up to be a multiple of HEAP_GRANULARITY.  */
#define HEAP_ADJUST_SIZE(sz)  \
   (((sz) + HEAP_GRANULARITY - 1) & ~(HEAP_GRANULARITY - 1))

/* The minimum size of a free area.  It must include at least enough room
   to hold a struct heap_free_area, plus enough extra to be usefully
   allocated.  */
#define HEAP_MIN_FREE_AREA_SIZE  \
  (sizeof (struct heap_free_area) + HEAP_ADJUST_SIZE (1))


#if 0
#include <stdio.h>
static void HEAP_DEBUG (struct heap *heap, const char *str)
{
  static int recursed = 0;
  if (! recursed)
    {
      struct heap_free_area *fa;
      recursed = 1;
      fprintf (stderr, "  %s: heap @0x%lx:\n", str, (long)heap);
      for (fa = heap->free_areas; fa; fa = fa->next)
	fprintf (stderr,
		 "    0x%lx:  0x%lx - 0x%lx  (%d)\tN=0x%lx, P=0x%lx\n",
		 (long)fa,
		 (long)HEAP_FREE_AREA_START (fa),
		 (long)HEAP_FREE_AREA_END (fa),
		 fa->size,
		 (long)fa->prev,
		 (long)fa->next);
      recursed = 0;
    }
}
#else
#define HEAP_DEBUG(heap, str) (void)0
#endif


/* Allocate SIZE bytes from the front of the free-area FA in HEAP, and
   return the amount actually allocated (which may be more than SIZE).  */
extern inline size_t
__heap_free_area_alloc (struct heap *heap,
			struct heap_free_area *fa, size_t size)
{
  size_t fa_size = fa->size;

  if (fa_size < size + HEAP_MIN_FREE_AREA_SIZE)
    /* There's not enough room left over in FA after allocating the block, so
       just use the whole thing, removing it from the list of free areas.  */
    {
      if (fa->next)
	fa->next->prev = fa->prev;
      if (fa->prev)
	fa->prev->next = fa->next;
      else
	heap->free_areas = fa->next;
      /* Remember that we've alloced the whole area.  */
      size = fa_size;
    }
  else
    /* Reduce size of FA to account for this allocation.  */
    fa->size = fa_size - size;

  return size;
}


/* Allocate and return a block at least *SIZE bytes long from HEAP.
   *SIZE is adjusted to reflect the actual amount allocated (which may be
   greater than requested).  */
extern void *__heap_alloc (struct heap *heap, size_t *size);

/* Allocate SIZE bytes at address MEM in HEAP.  Return the actual size
   allocated, or 0 if we failed.  */
extern size_t __heap_alloc_at (struct heap *heap, void *mem, size_t size);

/* Return the memory area MEM of size SIZE to HEAP.  */
extern void __heap_free (struct heap *heap, void *mem, size_t size);

/* If the memory area MEM, of size SIZE, immediately follows an existing
   free-area in HEAP, use it to extend that free-area, and return true;
   otherwise return false.  */
extern int __heap_append_free (struct heap *heap, void *mem, size_t size);