1 /*
2 * libc/stdlib/malloc/heap.h -- heap allocator used for malloc
3 *
4 * Copyright (C) 2002,03 NEC Electronics Corporation
5 * Copyright (C) 2002,03 Miles Bader <miles@gnu.org>
6 *
7 * This file is subject to the terms and conditions of the GNU Lesser
8 * General Public License. See the file COPYING.LIB in the main
9 * directory of this archive for more details.
10 *
11 * Written by Miles Bader <miles@gnu.org>
12 */
13
14 #include <features.h>
15
16 #include <bits/uClibc_mutex.h>
17 #ifdef __UCLIBC_HAS_THREADS__
18 # define HEAP_USE_LOCKING
19 #endif
20
21 #define __heap_lock(heap_lock) __UCLIBC_MUTEX_LOCK_CANCEL_UNSAFE(*(heap_lock))
22 #define __heap_unlock(heap_lock) __UCLIBC_MUTEX_UNLOCK_CANCEL_UNSAFE(*(heap_lock))
23
24 /* The heap allocates in multiples of, and aligned to, HEAP_GRANULARITY.
25 HEAP_GRANULARITY must be a power of 2. Malloc depends on this being the
26 same as MALLOC_ALIGNMENT. */
27 #define HEAP_GRANULARITY_TYPE double __attribute_aligned__ (HEAP_GRANULARITY)
28 #define HEAP_GRANULARITY \
29 (__alignof__ (double) > sizeof (size_t) ? __alignof__ (double) : sizeof (size_t))
30
31
32
33 /* The HEAP_INIT_WITH_FA variant is used to initialize a heap
34 with an initial static free-area; its argument FA should be declared
35 using HEAP_DECLARE_STATIC_FREE_AREA. */
36 # define HEAP_INIT_WITH_FA(fa) &fa._fa
37
38 /* A free-list area `header'. These are actually stored at the _ends_ of
39 free areas (to make allocating from the beginning of the area simpler),
40 so one might call it a `footer'. */
41 struct heap_free_area
42 {
43 size_t size;
44 struct heap_free_area *next, *prev;
45 };
46
47 /* Return the address of the end of the frea area FA. */
48 #define HEAP_FREE_AREA_END(fa) ((void *)(fa + 1))
49 /* Return the address of the beginning of the frea area FA. FA is
50 evaulated multiple times. */
51 #define HEAP_FREE_AREA_START(fa) ((void *)((char *)(fa + 1) - (fa)->size))
52 /* Return the size of the frea area FA. */
53 #define HEAP_FREE_AREA_SIZE(fa) ((fa)->size)
54
55 /* This rather clumsy macro allows one to declare a static free-area for
56 passing to HEAP_INIT_WITH_FA initializer macro. This is only use for
57 which NAME is allowed. */
58 #define HEAP_DECLARE_STATIC_FREE_AREA(name, size) \
59 static struct \
60 { \
61 HEAP_GRANULARITY_TYPE aligned_space; \
62 char space[HEAP_ADJUST_SIZE(size) \
63 - sizeof (struct heap_free_area) \
64 - HEAP_GRANULARITY]; \
65 struct heap_free_area _fa; \
66 } name = { (HEAP_GRANULARITY_TYPE)0, "", { HEAP_ADJUST_SIZE(size), 0, 0 } }
67
68
69 /* Rounds SZ up to be a multiple of HEAP_GRANULARITY. */
70 #define HEAP_ADJUST_SIZE(sz) \
71 (((sz) + HEAP_GRANULARITY - 1) & ~(HEAP_GRANULARITY - 1))
72
73
74 /* The minimum allocatable size. */
75 #define HEAP_MIN_SIZE HEAP_ADJUST_SIZE (sizeof (struct heap_free_area))
76
77 /* The minimum size of a free area; if allocating memory from a free-area
78 would make the free-area smaller than this, the allocation is simply
79 given the whole free-area instead. It must include at least enough room
80 to hold a struct heap_free_area, plus some extra to avoid excessive heap
81 fragmentation (thus increasing speed). This is only a heuristic -- it's
82 possible for smaller free-areas than this to exist (say, by realloc
83 returning the tail-end of a previous allocation), but __heap_alloc will
84 try to get rid of them when possible. */
85 #define HEAP_MIN_FREE_AREA_SIZE \
86 HEAP_ADJUST_SIZE (sizeof (struct heap_free_area) + 32)
87
88 /* Define HEAP_DEBUGGING to cause the heap routines to emit debugging info
89 to stderr when the variable __heap_debug is set to true. */
90 #ifdef HEAP_DEBUGGING
91 extern int __heap_debug attribute_hidden;
92 #define HEAP_DEBUG(heap, str) (__heap_debug ? __heap_dump (heap, str) : 0)
93 #else
94 #define HEAP_DEBUG(heap, str) (void)0
95 #endif
96
97 /* Output a text representation of HEAP to stderr, labelling it with STR. */
98 extern void __heap_dump (struct heap_free_area *heap, const char *str) attribute_hidden;
99
100 /* Do some consistency checks on HEAP. If they fail, output an error
101 message to stderr, and exit. STR is printed with the failure message. */
102 extern void __heap_check (struct heap_free_area *heap, const char *str) attribute_hidden;
103
104
105 /* Delete the free-area FA from HEAP. */
106 static __inline__ void
__heap_delete(struct heap_free_area ** heap,struct heap_free_area * fa)107 __heap_delete (struct heap_free_area **heap, struct heap_free_area *fa)
108 {
109 if (fa->next)
110 fa->next->prev = fa->prev;
111 if (fa->prev)
112 fa->prev->next = fa->next;
113 else
114 *heap = fa->next;
115 }
116
117
118 /* Link the free-area FA between the existing free-area's PREV and NEXT in
119 HEAP. PREV and NEXT may be 0; if PREV is 0, FA is installed as the
120 first free-area. */
121 static __inline__ void
__heap_link_free_area(struct heap_free_area ** heap,struct heap_free_area * fa,struct heap_free_area * prev,struct heap_free_area * next)122 __heap_link_free_area (struct heap_free_area **heap, struct heap_free_area *fa,
123 struct heap_free_area *prev,
124 struct heap_free_area *next)
125 {
126 fa->next = next;
127 fa->prev = prev;
128
129 if (prev)
130 prev->next = fa;
131 else
132 *heap = fa;
133 if (next)
134 next->prev = fa;
135 }
136
137 /* Update the mutual links between the free-areas PREV and FA in HEAP.
138 PREV may be 0, in which case FA is installed as the first free-area (but
139 FA may not be 0). */
140 static __inline__ void
__heap_link_free_area_after(struct heap_free_area ** heap,struct heap_free_area * fa,struct heap_free_area * prev)141 __heap_link_free_area_after (struct heap_free_area **heap,
142 struct heap_free_area *fa,
143 struct heap_free_area *prev)
144 {
145 if (prev)
146 prev->next = fa;
147 else
148 *heap = fa;
149 fa->prev = prev;
150 }
151
152 /* Add a new free-area MEM, of length SIZE, in between the existing
153 free-area's PREV and NEXT in HEAP, and return a pointer to its header.
154 PREV and NEXT may be 0; if PREV is 0, MEM is installed as the first
155 free-area. */
156 static __inline__ struct heap_free_area *
__heap_add_free_area(struct heap_free_area ** heap,void * mem,size_t size,struct heap_free_area * prev,struct heap_free_area * next)157 __heap_add_free_area (struct heap_free_area **heap, void *mem, size_t size,
158 struct heap_free_area *prev,
159 struct heap_free_area *next)
160 {
161 struct heap_free_area *fa = (struct heap_free_area *)
162 ((char *)mem + size - sizeof (struct heap_free_area));
163
164 fa->size = size;
165
166 __heap_link_free_area (heap, fa, prev, next);
167
168 return fa;
169 }
170
171
172 /* Allocate SIZE bytes from the front of the free-area FA in HEAP, and
173 return the amount actually allocated (which may be more than SIZE). */
174 static __inline__ size_t
__heap_free_area_alloc(struct heap_free_area ** heap,struct heap_free_area * fa,size_t size)175 __heap_free_area_alloc (struct heap_free_area **heap,
176 struct heap_free_area *fa, size_t size)
177 {
178 size_t fa_size = fa->size;
179
180 if (fa_size < size + HEAP_MIN_FREE_AREA_SIZE)
181 /* There's not enough room left over in FA after allocating the block, so
182 just use the whole thing, removing it from the list of free areas. */
183 {
184 __heap_delete (heap, fa);
185 /* Remember that we've alloced the whole area. */
186 size = fa_size;
187 }
188 else
189 /* Reduce size of FA to account for this allocation. */
190 fa->size = fa_size - size;
191
192 return size;
193 }
194
195
196 /* Allocate and return a block at least *SIZE bytes long from HEAP.
197 *SIZE is adjusted to reflect the actual amount allocated (which may be
198 greater than requested). */
199 extern void *__heap_alloc (struct heap_free_area **heap, size_t *size) attribute_hidden;
200
201 /* Allocate SIZE bytes at address MEM in HEAP. Return the actual size
202 allocated, or 0 if we failed. */
203 extern size_t __heap_alloc_at (struct heap_free_area **heap, void *mem, size_t size) attribute_hidden;
204
205 /* Return the memory area MEM of size SIZE to HEAP.
206 Returns the heap free area into which the memory was placed. */
207 extern struct heap_free_area *__heap_free (struct heap_free_area **heap,
208 void *mem, size_t size) attribute_hidden;
209
210 /* Return true if HEAP contains absolutely no memory. */
211 #define __heap_is_empty(heap) (! (heap))
212