Mercurial > vim
annotate src/hashtab.c @ 7909:6dee75491f5d
Added tag v7.4.1250 for changeset a343a738010e0dd632be30d7e2a02a955dc405ed
| author | Christian Brabandt <cb@256bit.org> |
|---|---|
| date | Wed, 03 Feb 2016 22:00:05 +0100 |
| parents | bcef391c101c |
| children | 9fa567d13551 |
| rev | line source |
|---|---|
| 799 | 1 /* vi:set ts=8 sts=4 sw=4: |
| 2 * | |
| 3 * VIM - Vi IMproved by Bram Moolenaar | |
| 4 * | |
| 5 * Do ":help uganda" in Vim to read copying and usage conditions. | |
| 6 * Do ":help credits" in Vim to see a list of people who contributed. | |
| 7 * See README.txt for an overview of the Vim source code. | |
| 8 */ | |
| 9 | |
| 10 /* | |
| 11 * hashtab.c: Handling of a hashtable with Vim-specific properties. | |
| 12 * | |
| 13 * Each item in a hashtable has a NUL terminated string key. A key can appear | |
| 14 * only once in the table. | |
| 15 * | |
| 16 * A hash number is computed from the key for quick lookup. When the hashes | |
| 17 * of two different keys point to the same entry an algorithm is used to | |
| 18 * iterate over other entries in the table until the right one is found. | |
| 19 * To make the iteration work removed keys are different from entries where a | |
| 20 * key was never present. | |
| 21 * | |
| 22 * The mechanism has been partly based on how Python Dictionaries are | |
| 23 * implemented. The algorithm is from Knuth Vol. 3, Sec. 6.4. | |
| 24 * | |
| 25 * The hashtable grows to accommodate more entries when needed. At least 1/3 | |
| 26 * of the entries is empty to keep the lookup efficient (at the cost of extra | |
| 27 * memory). | |
| 28 */ | |
| 29 | |
| 30 #include "vim.h" | |
| 31 | |
| 32 #if defined(FEAT_EVAL) || defined(FEAT_SYN_HL) || defined(PROTO) | |
| 33 | |
| 34 #if 0 | |
| 35 # define HT_DEBUG /* extra checks for table consistency and statistics */ | |
| 36 | |
| 37 static long hash_count_lookup = 0; /* count number of hashtab lookups */ | |
| 38 static long hash_count_perturb = 0; /* count number of "misses" */ | |
| 39 #endif | |
| 40 | |
| 41 /* Magic value for algorithm that walks through the array. */ | |
| 42 #define PERTURB_SHIFT 5 | |
| 43 | |
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44 static int hash_may_resize(hashtab_T *ht, int minitems); |
| 799 | 45 |
| 46 #if 0 /* currently not used */ | |
| 47 /* | |
| 48 * Create an empty hash table. | |
| 49 * Returns NULL when out of memory. | |
| 50 */ | |
| 51 hashtab_T * | |
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52 hash_create(void) |
| 799 | 53 { |
| 54 hashtab_T *ht; | |
| 55 | |
| 56 ht = (hashtab_T *)alloc(sizeof(hashtab_T)); | |
| 57 if (ht != NULL) | |
| 58 hash_init(ht); | |
| 59 return ht; | |
| 60 } | |
| 61 #endif | |
| 62 | |
| 63 /* | |
| 64 * Initialize an empty hash table. | |
| 65 */ | |
| 66 void | |
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67 hash_init(hashtab_T *ht) |
| 799 | 68 { |
| 69 /* This zeroes all "ht_" entries and all the "hi_key" in "ht_smallarray". */ | |
| 70 vim_memset(ht, 0, sizeof(hashtab_T)); | |
| 71 ht->ht_array = ht->ht_smallarray; | |
| 72 ht->ht_mask = HT_INIT_SIZE - 1; | |
| 73 } | |
| 74 | |
| 75 /* | |
| 76 * Free the array of a hash table. Does not free the items it contains! | |
| 77 * If "ht" is not freed then you should call hash_init() next! | |
| 78 */ | |
| 79 void | |
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80 hash_clear(hashtab_T *ht) |
| 799 | 81 { |
| 82 if (ht->ht_array != ht->ht_smallarray) | |
| 83 vim_free(ht->ht_array); | |
| 84 } | |
| 85 | |
| 86 /* | |
| 87 * Free the array of a hash table and all the keys it contains. The keys must | |
| 88 * have been allocated. "off" is the offset from the start of the allocate | |
| 89 * memory to the location of the key (it's always positive). | |
| 90 */ | |
| 91 void | |
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92 hash_clear_all(hashtab_T *ht, int off) |
| 799 | 93 { |
| 835 | 94 long todo; |
| 799 | 95 hashitem_T *hi; |
| 96 | |
| 835 | 97 todo = (long)ht->ht_used; |
| 799 | 98 for (hi = ht->ht_array; todo > 0; ++hi) |
| 99 { | |
| 100 if (!HASHITEM_EMPTY(hi)) | |
| 101 { | |
| 102 vim_free(hi->hi_key - off); | |
| 103 --todo; | |
| 104 } | |
| 105 } | |
| 106 hash_clear(ht); | |
| 107 } | |
| 108 | |
| 109 /* | |
| 110 * Find "key" in hashtable "ht". "key" must not be NULL. | |
| 111 * Always returns a pointer to a hashitem. If the item was not found then | |
| 112 * HASHITEM_EMPTY() is TRUE. The pointer is then the place where the key | |
| 113 * would be added. | |
| 114 * WARNING: The returned pointer becomes invalid when the hashtable is changed | |
| 115 * (adding, setting or removing an item)! | |
| 116 */ | |
| 117 hashitem_T * | |
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118 hash_find(hashtab_T *ht, char_u *key) |
| 799 | 119 { |
| 120 return hash_lookup(ht, key, hash_hash(key)); | |
| 121 } | |
| 122 | |
| 123 /* | |
| 124 * Like hash_find(), but caller computes "hash". | |
| 125 */ | |
| 126 hashitem_T * | |
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127 hash_lookup(hashtab_T *ht, char_u *key, hash_T hash) |
| 799 | 128 { |
| 129 hash_T perturb; | |
| 130 hashitem_T *freeitem; | |
| 131 hashitem_T *hi; | |
| 3970 | 132 unsigned idx; |
| 799 | 133 |
| 134 #ifdef HT_DEBUG | |
| 135 ++hash_count_lookup; | |
| 136 #endif | |
| 137 | |
| 138 /* | |
| 139 * Quickly handle the most common situations: | |
| 140 * - return if there is no item at all | |
| 141 * - skip over a removed item | |
| 142 * - return if the item matches | |
| 143 */ | |
| 3970 | 144 idx = (unsigned)(hash & ht->ht_mask); |
| 799 | 145 hi = &ht->ht_array[idx]; |
| 146 | |
| 147 if (hi->hi_key == NULL) | |
| 148 return hi; | |
| 149 if (hi->hi_key == HI_KEY_REMOVED) | |
| 150 freeitem = hi; | |
| 151 else if (hi->hi_hash == hash && STRCMP(hi->hi_key, key) == 0) | |
| 152 return hi; | |
| 153 else | |
| 154 freeitem = NULL; | |
| 155 | |
| 156 /* | |
| 157 * Need to search through the table to find the key. The algorithm | |
| 158 * to step through the table starts with large steps, gradually becoming | |
| 159 * smaller down to (1/4 table size + 1). This means it goes through all | |
| 160 * table entries in the end. | |
| 161 * When we run into a NULL key it's clear that the key isn't there. | |
| 162 * Return the first available slot found (can be a slot of a removed | |
| 163 * item). | |
| 164 */ | |
| 165 for (perturb = hash; ; perturb >>= PERTURB_SHIFT) | |
| 166 { | |
| 167 #ifdef HT_DEBUG | |
| 168 ++hash_count_perturb; /* count a "miss" for hashtab lookup */ | |
| 169 #endif | |
| 3970 | 170 idx = (unsigned)((idx << 2U) + idx + perturb + 1U); |
| 799 | 171 hi = &ht->ht_array[idx & ht->ht_mask]; |
| 172 if (hi->hi_key == NULL) | |
| 173 return freeitem == NULL ? hi : freeitem; | |
| 174 if (hi->hi_hash == hash | |
| 175 && hi->hi_key != HI_KEY_REMOVED | |
| 176 && STRCMP(hi->hi_key, key) == 0) | |
| 177 return hi; | |
| 178 if (hi->hi_key == HI_KEY_REMOVED && freeitem == NULL) | |
| 179 freeitem = hi; | |
| 180 } | |
| 181 } | |
| 182 | |
| 183 /* | |
| 184 * Print the efficiency of hashtable lookups. | |
| 185 * Useful when trying different hash algorithms. | |
| 186 * Called when exiting. | |
| 187 */ | |
| 188 void | |
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189 hash_debug_results(void) |
| 799 | 190 { |
| 191 #ifdef HT_DEBUG | |
| 192 fprintf(stderr, "\r\n\r\n\r\n\r\n"); | |
| 193 fprintf(stderr, "Number of hashtable lookups: %ld\r\n", hash_count_lookup); | |
| 194 fprintf(stderr, "Number of perturb loops: %ld\r\n", hash_count_perturb); | |
| 195 fprintf(stderr, "Percentage of perturb loops: %ld%%\r\n", | |
| 196 hash_count_perturb * 100 / hash_count_lookup); | |
| 197 #endif | |
| 198 } | |
| 199 | |
| 200 /* | |
| 201 * Add item with key "key" to hashtable "ht". | |
| 202 * Returns FAIL when out of memory or the key is already present. | |
| 203 */ | |
| 204 int | |
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205 hash_add(hashtab_T *ht, char_u *key) |
| 799 | 206 { |
| 207 hash_T hash = hash_hash(key); | |
| 208 hashitem_T *hi; | |
| 209 | |
| 210 hi = hash_lookup(ht, key, hash); | |
| 211 if (!HASHITEM_EMPTY(hi)) | |
| 212 { | |
| 213 EMSG2(_(e_intern2), "hash_add()"); | |
| 214 return FAIL; | |
| 215 } | |
| 216 return hash_add_item(ht, hi, key, hash); | |
| 217 } | |
| 218 | |
| 219 /* | |
| 220 * Add item "hi" with "key" to hashtable "ht". "key" must not be NULL and | |
| 221 * "hi" must have been obtained with hash_lookup() and point to an empty item. | |
| 222 * "hi" is invalid after this! | |
| 223 * Returns OK or FAIL (out of memory). | |
| 224 */ | |
| 225 int | |
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226 hash_add_item( |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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227 hashtab_T *ht, |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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228 hashitem_T *hi, |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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229 char_u *key, |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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230 hash_T hash) |
| 799 | 231 { |
| 232 /* If resizing failed before and it fails again we can't add an item. */ | |
| 233 if (ht->ht_error && hash_may_resize(ht, 0) == FAIL) | |
| 234 return FAIL; | |
| 235 | |
| 236 ++ht->ht_used; | |
| 237 if (hi->hi_key == NULL) | |
| 238 ++ht->ht_filled; | |
| 239 hi->hi_key = key; | |
| 240 hi->hi_hash = hash; | |
| 241 | |
| 242 /* When the space gets low may resize the array. */ | |
| 243 return hash_may_resize(ht, 0); | |
| 244 } | |
| 245 | |
| 246 #if 0 /* not used */ | |
| 247 /* | |
| 248 * Overwrite hashtable item "hi" with "key". "hi" must point to the item that | |
| 249 * is to be overwritten. Thus the number of items in the hashtable doesn't | |
| 250 * change. | |
| 251 * Although the key must be identical, the pointer may be different, thus it's | |
| 252 * set anyway (the key is part of an item with that key). | |
| 253 * The caller must take care of freeing the old item. | |
| 254 * "hi" is invalid after this! | |
| 255 */ | |
| 256 void | |
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257 hash_set(hashitem_T *hi, char_u *key) |
| 799 | 258 { |
| 259 hi->hi_key = key; | |
| 260 } | |
| 261 #endif | |
| 262 | |
| 263 /* | |
| 264 * Remove item "hi" from hashtable "ht". "hi" must have been obtained with | |
| 265 * hash_lookup(). | |
| 266 * The caller must take care of freeing the item itself. | |
| 267 */ | |
| 268 void | |
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269 hash_remove(hashtab_T *ht, hashitem_T *hi) |
| 799 | 270 { |
| 271 --ht->ht_used; | |
| 272 hi->hi_key = HI_KEY_REMOVED; | |
| 273 hash_may_resize(ht, 0); | |
| 274 } | |
| 275 | |
| 276 /* | |
| 277 * Lock a hashtable: prevent that ht_array changes. | |
| 278 * Don't use this when items are to be added! | |
| 279 * Must call hash_unlock() later. | |
| 280 */ | |
| 281 void | |
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282 hash_lock(hashtab_T *ht) |
| 799 | 283 { |
| 284 ++ht->ht_locked; | |
| 285 } | |
| 286 | |
| 287 #if 0 /* currently not used */ | |
| 288 /* | |
| 289 * Lock a hashtable at the specified number of entries. | |
| 290 * Caller must make sure no more than "size" entries will be added. | |
| 291 * Must call hash_unlock() later. | |
| 292 */ | |
| 293 void | |
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294 hash_lock_size(hashtab_T *ht, int size) |
| 799 | 295 { |
| 296 (void)hash_may_resize(ht, size); | |
| 297 ++ht->ht_locked; | |
| 298 } | |
| 299 #endif | |
| 300 | |
| 301 /* | |
| 302 * Unlock a hashtable: allow ht_array changes again. | |
| 303 * Table will be resized (shrink) when necessary. | |
| 304 * This must balance a call to hash_lock(). | |
| 305 */ | |
| 306 void | |
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307 hash_unlock(hashtab_T *ht) |
| 799 | 308 { |
| 309 --ht->ht_locked; | |
| 310 (void)hash_may_resize(ht, 0); | |
| 311 } | |
| 312 | |
| 313 /* | |
| 314 * Shrink a hashtable when there is too much empty space. | |
| 315 * Grow a hashtable when there is not enough empty space. | |
| 316 * Returns OK or FAIL (out of memory). | |
| 317 */ | |
| 318 static int | |
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319 hash_may_resize( |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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320 hashtab_T *ht, |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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parents:
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diff
changeset
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321 int minitems) /* minimal number of items */ |
| 799 | 322 { |
| 323 hashitem_T temparray[HT_INIT_SIZE]; | |
| 324 hashitem_T *oldarray, *newarray; | |
| 325 hashitem_T *olditem, *newitem; | |
| 3970 | 326 unsigned newi; |
| 799 | 327 int todo; |
| 328 long_u oldsize, newsize; | |
| 329 long_u minsize; | |
| 330 long_u newmask; | |
| 331 hash_T perturb; | |
| 332 | |
| 333 /* Don't resize a locked table. */ | |
| 334 if (ht->ht_locked > 0) | |
| 335 return OK; | |
| 336 | |
| 337 #ifdef HT_DEBUG | |
| 338 if (ht->ht_used > ht->ht_filled) | |
| 339 EMSG("hash_may_resize(): more used than filled"); | |
| 340 if (ht->ht_filled >= ht->ht_mask + 1) | |
| 341 EMSG("hash_may_resize(): table completely filled"); | |
| 342 #endif | |
| 343 | |
| 344 if (minitems == 0) | |
| 345 { | |
| 346 /* Return quickly for small tables with at least two NULL items. NULL | |
| 347 * items are required for the lookup to decide a key isn't there. */ | |
| 348 if (ht->ht_filled < HT_INIT_SIZE - 1 | |
| 349 && ht->ht_array == ht->ht_smallarray) | |
| 350 return OK; | |
| 351 | |
| 352 /* | |
| 353 * Grow or refill the array when it's more than 2/3 full (including | |
| 354 * removed items, so that they get cleaned up). | |
| 355 * Shrink the array when it's less than 1/5 full. When growing it is | |
| 356 * at least 1/4 full (avoids repeated grow-shrink operations) | |
| 357 */ | |
| 358 oldsize = ht->ht_mask + 1; | |
| 359 if (ht->ht_filled * 3 < oldsize * 2 && ht->ht_used > oldsize / 5) | |
| 360 return OK; | |
| 361 | |
| 362 if (ht->ht_used > 1000) | |
| 363 minsize = ht->ht_used * 2; /* it's big, don't make too much room */ | |
| 364 else | |
| 365 minsize = ht->ht_used * 4; /* make plenty of room */ | |
| 366 } | |
| 367 else | |
| 368 { | |
| 369 /* Use specified size. */ | |
| 370 if ((long_u)minitems < ht->ht_used) /* just in case... */ | |
| 835 | 371 minitems = (int)ht->ht_used; |
| 799 | 372 minsize = minitems * 3 / 2; /* array is up to 2/3 full */ |
| 373 } | |
| 374 | |
| 375 newsize = HT_INIT_SIZE; | |
| 376 while (newsize < minsize) | |
| 377 { | |
| 378 newsize <<= 1; /* make sure it's always a power of 2 */ | |
| 379 if (newsize == 0) | |
| 380 return FAIL; /* overflow */ | |
| 381 } | |
| 382 | |
| 383 if (newsize == HT_INIT_SIZE) | |
| 384 { | |
| 385 /* Use the small array inside the hashdict structure. */ | |
| 386 newarray = ht->ht_smallarray; | |
| 387 if (ht->ht_array == newarray) | |
| 388 { | |
| 389 /* Moving from ht_smallarray to ht_smallarray! Happens when there | |
| 390 * are many removed items. Copy the items to be able to clean up | |
| 391 * removed items. */ | |
| 392 mch_memmove(temparray, newarray, sizeof(temparray)); | |
| 393 oldarray = temparray; | |
| 394 } | |
| 395 else | |
| 396 oldarray = ht->ht_array; | |
| 397 } | |
| 398 else | |
| 399 { | |
| 400 /* Allocate an array. */ | |
| 401 newarray = (hashitem_T *)alloc((unsigned) | |
| 402 (sizeof(hashitem_T) * newsize)); | |
| 403 if (newarray == NULL) | |
| 404 { | |
| 405 /* Out of memory. When there are NULL items still return OK. | |
| 406 * Otherwise set ht_error, because lookup may result in a hang if | |
| 407 * we add another item. */ | |
| 408 if (ht->ht_filled < ht->ht_mask) | |
| 409 return OK; | |
| 410 ht->ht_error = TRUE; | |
| 411 return FAIL; | |
| 412 } | |
| 413 oldarray = ht->ht_array; | |
| 414 } | |
| 415 vim_memset(newarray, 0, (size_t)(sizeof(hashitem_T) * newsize)); | |
| 416 | |
| 417 /* | |
| 418 * Move all the items from the old array to the new one, placing them in | |
| 419 * the right spot. The new array won't have any removed items, thus this | |
| 420 * is also a cleanup action. | |
| 421 */ | |
| 422 newmask = newsize - 1; | |
| 835 | 423 todo = (int)ht->ht_used; |
| 799 | 424 for (olditem = oldarray; todo > 0; ++olditem) |
| 425 if (!HASHITEM_EMPTY(olditem)) | |
| 426 { | |
| 427 /* | |
| 428 * The algorithm to find the spot to add the item is identical to | |
| 429 * the algorithm to find an item in hash_lookup(). But we only | |
| 430 * need to search for a NULL key, thus it's simpler. | |
| 431 */ | |
| 3970 | 432 newi = (unsigned)(olditem->hi_hash & newmask); |
| 799 | 433 newitem = &newarray[newi]; |
| 434 | |
| 435 if (newitem->hi_key != NULL) | |
| 436 for (perturb = olditem->hi_hash; ; perturb >>= PERTURB_SHIFT) | |
| 437 { | |
| 3970 | 438 newi = (unsigned)((newi << 2U) + newi + perturb + 1U); |
| 799 | 439 newitem = &newarray[newi & newmask]; |
| 440 if (newitem->hi_key == NULL) | |
| 441 break; | |
| 442 } | |
| 443 *newitem = *olditem; | |
| 444 --todo; | |
| 445 } | |
| 446 | |
| 447 if (ht->ht_array != ht->ht_smallarray) | |
| 448 vim_free(ht->ht_array); | |
| 449 ht->ht_array = newarray; | |
| 450 ht->ht_mask = newmask; | |
| 451 ht->ht_filled = ht->ht_used; | |
| 452 ht->ht_error = FALSE; | |
| 453 | |
| 454 return OK; | |
| 455 } | |
| 456 | |
| 457 /* | |
| 458 * Get the hash number for a key. | |
| 459 * If you think you know a better hash function: Compile with HT_DEBUG set and | |
| 460 * run a script that uses hashtables a lot. Vim will then print statistics | |
| 461 * when exiting. Try that with the current hash algorithm and yours. The | |
| 462 * lower the percentage the better. | |
| 463 */ | |
| 464 hash_T | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
465 hash_hash(char_u *key) |
| 799 | 466 { |
| 467 hash_T hash; | |
| 468 char_u *p; | |
| 469 | |
| 470 if ((hash = *key) == 0) | |
| 471 return (hash_T)0; /* Empty keys are not allowed, but we don't | |
| 472 want to crash if we get one. */ | |
| 473 p = key + 1; | |
| 474 | |
| 475 /* A simplistic algorithm that appears to do very well. | |
| 476 * Suggested by George Reilly. */ | |
| 477 while (*p != NUL) | |
| 478 hash = hash * 101 + *p++; | |
| 479 | |
| 480 return hash; | |
| 481 } | |
| 482 | |
| 483 #endif |