2 * libc/stdlib/malloc/heap.h -- heap allocator used for malloc
4 * Copyright (C) 2002,03 NEC Electronics Corporation
5 * Copyright (C) 2002,03 Miles Bader <miles@gnu.org>
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.
11 * Written by Miles Bader <miles@gnu.org>
17 /* On multi-threaded systems, the heap includes a lock. */
18 #ifdef __UCLIBC_HAS_THREADS__
19 # include <bits/uClibc_mutex.h>
20 # define HEAP_USE_LOCKING
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))
24 # define __heap_lock(heap_lock)
25 # define __heap_unlock(heap_lock)
29 /* The heap allocates in multiples of, and aligned to, HEAP_GRANULARITY.
30 HEAP_GRANULARITY must be a power of 2. Malloc depends on this being the
31 same as MALLOC_ALIGNMENT. */
32 #define HEAP_GRANULARITY_TYPE double __attribute_aligned__ (HEAP_GRANULARITY)
33 #define HEAP_GRANULARITY \
34 (__alignof__ (double) > sizeof (size_t) ? __alignof__ (double) : sizeof (size_t))
38 /* The HEAP_INIT macro can be used as a static initializer for a heap
39 variable. The HEAP_INIT_WITH_FA variant is used to initialize a heap
40 with an initial static free-area; its argument FA should be declared
41 using HEAP_DECLARE_STATIC_FREE_AREA. */
43 # define HEAP_INIT_WITH_FA(fa) &fa._fa
45 /* A free-list area `header'. These are actually stored at the _ends_ of
46 free areas (to make allocating from the beginning of the area simpler),
47 so one might call it a `footer'. */
51 struct heap_free_area *next, *prev;
54 /* Return the address of the end of the frea area FA. */
55 #define HEAP_FREE_AREA_END(fa) ((void *)(fa + 1))
56 /* Return the address of the beginning of the frea area FA. FA is
57 evaulated multiple times. */
58 #define HEAP_FREE_AREA_START(fa) ((void *)((char *)(fa + 1) - (fa)->size))
59 /* Return the size of the frea area FA. */
60 #define HEAP_FREE_AREA_SIZE(fa) ((fa)->size)
62 /* This rather clumsy macro allows one to declare a static free-area for
63 passing to HEAP_INIT_WITH_FA initializer macro. This is only use for
64 which NAME is allowed. */
65 #define HEAP_DECLARE_STATIC_FREE_AREA(name, size) \
68 HEAP_GRANULARITY_TYPE aligned_space; \
69 char space[HEAP_ADJUST_SIZE(size) \
70 - sizeof (struct heap_free_area) \
71 - HEAP_GRANULARITY]; \
72 struct heap_free_area _fa; \
73 } name = { (HEAP_GRANULARITY_TYPE)0, "", { HEAP_ADJUST_SIZE(size), 0, 0 } }
76 /* Rounds SZ up to be a multiple of HEAP_GRANULARITY. */
77 #define HEAP_ADJUST_SIZE(sz) \
78 (((sz) + HEAP_GRANULARITY - 1) & ~(HEAP_GRANULARITY - 1))
81 /* The minimum allocatable size. */
82 #define HEAP_MIN_SIZE HEAP_ADJUST_SIZE (sizeof (struct heap_free_area))
84 /* The minimum size of a free area; if allocating memory from a free-area
85 would make the free-area smaller than this, the allocation is simply
86 given the whole free-area instead. It must include at least enough room
87 to hold a struct heap_free_area, plus some extra to avoid excessive heap
88 fragmentation (thus increasing speed). This is only a heuristic -- it's
89 possible for smaller free-areas than this to exist (say, by realloc
90 returning the tail-end of a previous allocation), but __heap_alloc will
91 try to get rid of them when possible. */
92 #define HEAP_MIN_FREE_AREA_SIZE \
93 HEAP_ADJUST_SIZE (sizeof (struct heap_free_area) + 32)
96 /* branch-prediction macros; they may already be defined by libc. */
98 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
99 #define likely(cond) __builtin_expect(!!(int)(cond), 1)
100 #define unlikely(cond) __builtin_expect((int)(cond), 0)
102 #define likely(cond) (cond)
103 #define unlikely(cond) (cond)
108 /* Define HEAP_DEBUGGING to cause the heap routines to emit debugging info
109 to stderr when the variable __heap_debug is set to true. */
110 #ifdef HEAP_DEBUGGING
111 extern int __heap_debug;
112 #define HEAP_DEBUG(heap, str) (__heap_debug ? __heap_dump (heap, str) : 0)
114 #define HEAP_DEBUG(heap, str) (void)0
117 /* Output a text representation of HEAP to stderr, labelling it with STR. */
118 extern void __heap_dump (struct heap_free_area *heap, const char *str);
120 /* Do some consistency checks on HEAP. If they fail, output an error
121 message to stderr, and exit. STR is printed with the failure message. */
122 extern void __heap_check (struct heap_free_area *heap, const char *str);
125 /* Delete the free-area FA from HEAP. */
126 static __inline__ void
127 __heap_delete (struct heap_free_area **heap, struct heap_free_area *fa)
130 fa->next->prev = fa->prev;
132 fa->prev->next = fa->next;
138 /* Link the free-area FA between the existing free-area's PREV and NEXT in
139 HEAP. PREV and NEXT may be 0; if PREV is 0, FA is installed as the
141 static __inline__ void
142 __heap_link_free_area (struct heap_free_area **heap, struct heap_free_area *fa,
143 struct heap_free_area *prev,
144 struct heap_free_area *next)
157 /* Update the mutual links between the free-areas PREV and FA in HEAP.
158 PREV may be 0, in which case FA is installed as the first free-area (but
160 static __inline__ void
161 __heap_link_free_area_after (struct heap_free_area **heap,
162 struct heap_free_area *fa,
163 struct heap_free_area *prev)
172 /* Add a new free-area MEM, of length SIZE, in between the existing
173 free-area's PREV and NEXT in HEAP, and return a pointer to its header.
174 PREV and NEXT may be 0; if PREV is 0, MEM is installed as the first
176 static __inline__ struct heap_free_area *
177 __heap_add_free_area (struct heap_free_area **heap, void *mem, size_t size,
178 struct heap_free_area *prev,
179 struct heap_free_area *next)
181 struct heap_free_area *fa = (struct heap_free_area *)
182 ((char *)mem + size - sizeof (struct heap_free_area));
186 __heap_link_free_area (heap, fa, prev, next);
192 /* Allocate SIZE bytes from the front of the free-area FA in HEAP, and
193 return the amount actually allocated (which may be more than SIZE). */
194 static __inline__ size_t
195 __heap_free_area_alloc (struct heap_free_area **heap,
196 struct heap_free_area *fa, size_t size)
198 size_t fa_size = fa->size;
200 if (fa_size < size + HEAP_MIN_FREE_AREA_SIZE)
201 /* There's not enough room left over in FA after allocating the block, so
202 just use the whole thing, removing it from the list of free areas. */
204 __heap_delete (heap, fa);
205 /* Remember that we've alloced the whole area. */
209 /* Reduce size of FA to account for this allocation. */
210 fa->size = fa_size - size;
216 /* Allocate and return a block at least *SIZE bytes long from HEAP.
217 *SIZE is adjusted to reflect the actual amount allocated (which may be
218 greater than requested). */
219 extern void *__heap_alloc (struct heap_free_area **heap, size_t *size);
221 /* Allocate SIZE bytes at address MEM in HEAP. Return the actual size
222 allocated, or 0 if we failed. */
223 extern size_t __heap_alloc_at (struct heap_free_area **heap, void *mem, size_t size);
225 /* Return the memory area MEM of size SIZE to HEAP.
226 Returns the heap free area into which the memory was placed. */
227 extern struct heap_free_area *__heap_free (struct heap_free_area **heap,
228 void *mem, size_t size);
230 /* Return true if HEAP contains absolutely no memory. */
231 #define __heap_is_empty(heap) (! (heap))