lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 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 | |
| 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)) |
| 23 | #else |
| 24 | # define __heap_lock(heap_lock) |
| 25 | # define __heap_unlock(heap_lock) |
| 26 | #endif |
| 27 | |
| 28 | |
| 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)) |
| 35 | |
| 36 | |
| 37 | |
| 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. */ |
| 42 | # define HEAP_INIT 0 |
| 43 | # define HEAP_INIT_WITH_FA(fa) &fa._fa |
| 44 | |
| 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'. */ |
| 48 | struct heap_free_area |
| 49 | { |
| 50 | size_t size; |
| 51 | struct heap_free_area *next, *prev; |
| 52 | }; |
| 53 | |
| 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) |
| 61 | |
| 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) \ |
| 66 | static struct \ |
| 67 | { \ |
| 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 } } |
| 74 | |
| 75 | |
| 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)) |
| 79 | |
| 80 | |
| 81 | /* The minimum allocatable size. */ |
| 82 | #define HEAP_MIN_SIZE HEAP_ADJUST_SIZE (sizeof (struct heap_free_area)) |
| 83 | |
| 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) |
| 94 | |
| 95 | |
| 96 | /* branch-prediction macros; they may already be defined by libc. */ |
| 97 | #ifndef likely |
| 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) |
| 101 | #else |
| 102 | #define likely(cond) (cond) |
| 103 | #define unlikely(cond) (cond) |
| 104 | #endif |
| 105 | #endif /* !likely */ |
| 106 | |
| 107 | |
| 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) |
| 113 | #else |
| 114 | #define HEAP_DEBUG(heap, str) (void)0 |
| 115 | #endif |
| 116 | |
| 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); |
| 119 | |
| 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); |
| 123 | |
| 124 | |
| 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) |
| 128 | { |
| 129 | if (fa->next) |
| 130 | fa->next->prev = fa->prev; |
| 131 | if (fa->prev) |
| 132 | fa->prev->next = fa->next; |
| 133 | else |
| 134 | *heap = fa->next; |
| 135 | } |
| 136 | |
| 137 | |
| 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 |
| 140 | first free-area. */ |
| 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) |
| 145 | { |
| 146 | fa->next = next; |
| 147 | fa->prev = prev; |
| 148 | |
| 149 | if (prev) |
| 150 | prev->next = fa; |
| 151 | else |
| 152 | *heap = fa; |
| 153 | if (next) |
| 154 | next->prev = fa; |
| 155 | } |
| 156 | |
| 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 |
| 159 | FA may not be 0). */ |
| 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) |
| 164 | { |
| 165 | if (prev) |
| 166 | prev->next = fa; |
| 167 | else |
| 168 | *heap = fa; |
| 169 | fa->prev = prev; |
| 170 | } |
| 171 | |
| 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 |
| 175 | free-area. */ |
| 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) |
| 180 | { |
| 181 | struct heap_free_area *fa = (struct heap_free_area *) |
| 182 | ((char *)mem + size - sizeof (struct heap_free_area)); |
| 183 | |
| 184 | fa->size = size; |
| 185 | |
| 186 | __heap_link_free_area (heap, fa, prev, next); |
| 187 | |
| 188 | return fa; |
| 189 | } |
| 190 | |
| 191 | |
| 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) |
| 197 | { |
| 198 | size_t fa_size = fa->size; |
| 199 | |
| 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. */ |
| 203 | { |
| 204 | __heap_delete (heap, fa); |
| 205 | /* Remember that we've alloced the whole area. */ |
| 206 | size = fa_size; |
| 207 | } |
| 208 | else |
| 209 | /* Reduce size of FA to account for this allocation. */ |
| 210 | fa->size = fa_size - size; |
| 211 | |
| 212 | return size; |
| 213 | } |
| 214 | |
| 215 | |
| 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); |
| 220 | |
| 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); |
| 224 | |
| 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); |
| 229 | |
| 230 | /* Return true if HEAP contains absolutely no memory. */ |
| 231 | #define __heap_is_empty(heap) (! (heap)) |