| 1 | /* objalloc.c -- routines to allocate memory for objects |
| 2 | Copyright 1997 Free Software Foundation, Inc. |
| 3 | Written by Ian Lance Taylor, Cygnus Solutions. |
| 4 | |
| 5 | This program is free software; you can redistribute it and/or modify it |
| 6 | under the terms of the GNU General Public License as published by the |
| 7 | Free Software Foundation; either version 2, or (at your option) any |
| 8 | later version. |
| 9 | |
| 10 | This program is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | GNU General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU General Public License |
| 16 | along with this program; if not, write to the Free Software |
| 17 | Foundation, 51 Franklin Street - Fifth Floor, |
| 18 | Boston, MA 02110-1301, USA. */ |
| 19 | |
| 20 | #include "config.h" |
| 21 | #include "ansidecl.h" |
| 22 | |
| 23 | #include "objalloc.h" |
| 24 | |
| 25 | /* Get a definition for NULL. */ |
| 26 | #include <stdio.h> |
| 27 | |
| 28 | #if VMS |
| 29 | #include <stdlib.h> |
| 30 | #include <unixlib.h> |
| 31 | #else |
| 32 | |
| 33 | /* Get a definition for size_t. */ |
| 34 | #include <stddef.h> |
| 35 | |
| 36 | #ifdef HAVE_STDLIB_H |
| 37 | #include <stdlib.h> |
| 38 | #else |
| 39 | /* For systems with larger pointers than ints, this must be declared. */ |
| 40 | extern PTR malloc (size_t); |
| 41 | extern void free (PTR); |
| 42 | #endif |
| 43 | |
| 44 | #endif |
| 45 | |
| 46 | /* These routines allocate space for an object. Freeing allocated |
| 47 | space may or may not free all more recently allocated space. |
| 48 | |
| 49 | We handle large and small allocation requests differently. If we |
| 50 | don't have enough space in the current block, and the allocation |
| 51 | request is for more than 512 bytes, we simply pass it through to |
| 52 | malloc. */ |
| 53 | |
| 54 | /* The objalloc structure is defined in objalloc.h. */ |
| 55 | |
| 56 | /* This structure appears at the start of each chunk. */ |
| 57 | |
| 58 | struct objalloc_chunk |
| 59 | { |
| 60 | /* Next chunk. */ |
| 61 | struct objalloc_chunk *next; |
| 62 | /* If this chunk contains large objects, this is the value of |
| 63 | current_ptr when this chunk was allocated. If this chunk |
| 64 | contains small objects, this is NULL. */ |
| 65 | char *current_ptr; |
| 66 | }; |
| 67 | |
| 68 | /* The aligned size of objalloc_chunk. */ |
| 69 | |
| 70 | #define CHUNK_HEADER_SIZE \ |
| 71 | ((sizeof (struct objalloc_chunk) + OBJALLOC_ALIGN - 1) \ |
| 72 | &~ (OBJALLOC_ALIGN - 1)) |
| 73 | |
| 74 | /* We ask for this much memory each time we create a chunk which is to |
| 75 | hold small objects. */ |
| 76 | |
| 77 | #define CHUNK_SIZE (4096 - 32) |
| 78 | |
| 79 | /* A request for this amount or more is just passed through to malloc. */ |
| 80 | |
| 81 | #define BIG_REQUEST (512) |
| 82 | |
| 83 | /* Create an objalloc structure. */ |
| 84 | |
| 85 | struct objalloc * |
| 86 | objalloc_create (void) |
| 87 | { |
| 88 | struct objalloc *ret; |
| 89 | struct objalloc_chunk *chunk; |
| 90 | |
| 91 | ret = (struct objalloc *) malloc (sizeof *ret); |
| 92 | if (ret == NULL) |
| 93 | return NULL; |
| 94 | |
| 95 | ret->chunks = (PTR) malloc (CHUNK_SIZE); |
| 96 | if (ret->chunks == NULL) |
| 97 | { |
| 98 | free (ret); |
| 99 | return NULL; |
| 100 | } |
| 101 | |
| 102 | chunk = (struct objalloc_chunk *) ret->chunks; |
| 103 | chunk->next = NULL; |
| 104 | chunk->current_ptr = NULL; |
| 105 | |
| 106 | ret->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE; |
| 107 | ret->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE; |
| 108 | |
| 109 | return ret; |
| 110 | } |
| 111 | |
| 112 | /* Allocate space from an objalloc structure. */ |
| 113 | |
| 114 | PTR |
| 115 | _objalloc_alloc (struct objalloc *o, unsigned long len) |
| 116 | { |
| 117 | /* We avoid confusion from zero sized objects by always allocating |
| 118 | at least 1 byte. */ |
| 119 | if (len == 0) |
| 120 | len = 1; |
| 121 | |
| 122 | len = (len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1); |
| 123 | |
| 124 | if (len <= o->current_space) |
| 125 | { |
| 126 | o->current_ptr += len; |
| 127 | o->current_space -= len; |
| 128 | return (PTR) (o->current_ptr - len); |
| 129 | } |
| 130 | |
| 131 | if (len >= BIG_REQUEST) |
| 132 | { |
| 133 | char *ret; |
| 134 | struct objalloc_chunk *chunk; |
| 135 | |
| 136 | ret = (char *) malloc (CHUNK_HEADER_SIZE + len); |
| 137 | if (ret == NULL) |
| 138 | return NULL; |
| 139 | |
| 140 | chunk = (struct objalloc_chunk *) ret; |
| 141 | chunk->next = (struct objalloc_chunk *) o->chunks; |
| 142 | chunk->current_ptr = o->current_ptr; |
| 143 | |
| 144 | o->chunks = (PTR) chunk; |
| 145 | |
| 146 | return (PTR) (ret + CHUNK_HEADER_SIZE); |
| 147 | } |
| 148 | else |
| 149 | { |
| 150 | struct objalloc_chunk *chunk; |
| 151 | |
| 152 | chunk = (struct objalloc_chunk *) malloc (CHUNK_SIZE); |
| 153 | if (chunk == NULL) |
| 154 | return NULL; |
| 155 | chunk->next = (struct objalloc_chunk *) o->chunks; |
| 156 | chunk->current_ptr = NULL; |
| 157 | |
| 158 | o->current_ptr = (char *) chunk + CHUNK_HEADER_SIZE; |
| 159 | o->current_space = CHUNK_SIZE - CHUNK_HEADER_SIZE; |
| 160 | |
| 161 | o->chunks = (PTR) chunk; |
| 162 | |
| 163 | return objalloc_alloc (o, len); |
| 164 | } |
| 165 | } |
| 166 | |
| 167 | /* Free an entire objalloc structure. */ |
| 168 | |
| 169 | void |
| 170 | objalloc_free (struct objalloc *o) |
| 171 | { |
| 172 | struct objalloc_chunk *l; |
| 173 | |
| 174 | l = (struct objalloc_chunk *) o->chunks; |
| 175 | while (l != NULL) |
| 176 | { |
| 177 | struct objalloc_chunk *next; |
| 178 | |
| 179 | next = l->next; |
| 180 | free (l); |
| 181 | l = next; |
| 182 | } |
| 183 | |
| 184 | free (o); |
| 185 | } |
| 186 | |
| 187 | /* Free a block from an objalloc structure. This also frees all more |
| 188 | recently allocated blocks. */ |
| 189 | |
| 190 | void |
| 191 | objalloc_free_block (struct objalloc *o, PTR block) |
| 192 | { |
| 193 | struct objalloc_chunk *p, *small; |
| 194 | char *b = (char *) block; |
| 195 | |
| 196 | /* First set P to the chunk which contains the block we are freeing, |
| 197 | and set Q to the last small object chunk we see before P. */ |
| 198 | small = NULL; |
| 199 | for (p = (struct objalloc_chunk *) o->chunks; p != NULL; p = p->next) |
| 200 | { |
| 201 | if (p->current_ptr == NULL) |
| 202 | { |
| 203 | if (b > (char *) p && b < (char *) p + CHUNK_SIZE) |
| 204 | break; |
| 205 | small = p; |
| 206 | } |
| 207 | else |
| 208 | { |
| 209 | if (b == (char *) p + CHUNK_HEADER_SIZE) |
| 210 | break; |
| 211 | } |
| 212 | } |
| 213 | |
| 214 | /* If we can't find the chunk, the caller has made a mistake. */ |
| 215 | if (p == NULL) |
| 216 | abort (); |
| 217 | |
| 218 | if (p->current_ptr == NULL) |
| 219 | { |
| 220 | struct objalloc_chunk *q; |
| 221 | struct objalloc_chunk *first; |
| 222 | |
| 223 | /* The block is in a chunk containing small objects. We can |
| 224 | free every chunk through SMALL, because they have certainly |
| 225 | been allocated more recently. After SMALL, we will not see |
| 226 | any chunks containing small objects; we can free any big |
| 227 | chunk if the current_ptr is greater than or equal to B. We |
| 228 | can then reset the new current_ptr to B. */ |
| 229 | |
| 230 | first = NULL; |
| 231 | q = (struct objalloc_chunk *) o->chunks; |
| 232 | while (q != p) |
| 233 | { |
| 234 | struct objalloc_chunk *next; |
| 235 | |
| 236 | next = q->next; |
| 237 | if (small != NULL) |
| 238 | { |
| 239 | if (small == q) |
| 240 | small = NULL; |
| 241 | free (q); |
| 242 | } |
| 243 | else if (q->current_ptr > b) |
| 244 | free (q); |
| 245 | else if (first == NULL) |
| 246 | first = q; |
| 247 | |
| 248 | q = next; |
| 249 | } |
| 250 | |
| 251 | if (first == NULL) |
| 252 | first = p; |
| 253 | o->chunks = (PTR) first; |
| 254 | |
| 255 | /* Now start allocating from this small block again. */ |
| 256 | o->current_ptr = b; |
| 257 | o->current_space = ((char *) p + CHUNK_SIZE) - b; |
| 258 | } |
| 259 | else |
| 260 | { |
| 261 | struct objalloc_chunk *q; |
| 262 | char *current_ptr; |
| 263 | |
| 264 | /* This block is in a large chunk by itself. We can free |
| 265 | everything on the list up to and including this block. We |
| 266 | then start allocating from the next chunk containing small |
| 267 | objects, setting current_ptr from the value stored with the |
| 268 | large chunk we are freeing. */ |
| 269 | |
| 270 | current_ptr = p->current_ptr; |
| 271 | p = p->next; |
| 272 | |
| 273 | q = (struct objalloc_chunk *) o->chunks; |
| 274 | while (q != p) |
| 275 | { |
| 276 | struct objalloc_chunk *next; |
| 277 | |
| 278 | next = q->next; |
| 279 | free (q); |
| 280 | q = next; |
| 281 | } |
| 282 | |
| 283 | o->chunks = (PTR) p; |
| 284 | |
| 285 | while (p->current_ptr != NULL) |
| 286 | p = p->next; |
| 287 | |
| 288 | o->current_ptr = current_ptr; |
| 289 | o->current_space = ((char *) p + CHUNK_SIZE) - current_ptr; |
| 290 | } |
| 291 | } |