Mercurial > vim
annotate src/hashtab.c @ 14384:6f01954c86e5
Added tag v8.1.0206 for changeset 8846b83444309722d72d62961e6eebe4df5846f2
| author | Christian Brabandt <cb@256bit.org> |
|---|---|
| date | Mon, 23 Jul 2018 05:00:06 +0200 |
| parents | 9279c939391b |
| children | 55ccc2d353bd |
| rev | line source |
|---|---|
|
10042
4aead6a9b7a9
commit https://github.com/vim/vim/commit/edf3f97ae2af024708ebb4ac614227327033ca47
Christian Brabandt <cb@256bit.org>
parents:
9513
diff
changeset
|
1 /* vi:set ts=8 sts=4 sw=4 noet: |
| 799 | 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 0 | |
| 33 # define HT_DEBUG /* extra checks for table consistency and statistics */ | |
| 34 | |
| 35 static long hash_count_lookup = 0; /* count number of hashtab lookups */ | |
| 36 static long hash_count_perturb = 0; /* count number of "misses" */ | |
| 37 #endif | |
| 38 | |
| 39 /* Magic value for algorithm that walks through the array. */ | |
| 40 #define PERTURB_SHIFT 5 | |
| 41 | |
|
7803
37c929c4a073
commit https://github.com/vim/vim/commit/92b8b2d307e34117f146319872010b0ccc9d2713
Christian Brabandt <cb@256bit.org>
parents:
3970
diff
changeset
|
42 static int hash_may_resize(hashtab_T *ht, int minitems); |
| 799 | 43 |
| 44 #if 0 /* currently not used */ | |
| 45 /* | |
| 46 * Create an empty hash table. | |
| 47 * Returns NULL when out of memory. | |
| 48 */ | |
| 49 hashtab_T * | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
50 hash_create(void) |
| 799 | 51 { |
| 52 hashtab_T *ht; | |
| 53 | |
| 54 ht = (hashtab_T *)alloc(sizeof(hashtab_T)); | |
| 55 if (ht != NULL) | |
| 56 hash_init(ht); | |
| 57 return ht; | |
| 58 } | |
| 59 #endif | |
| 60 | |
| 61 /* | |
| 62 * Initialize an empty hash table. | |
| 63 */ | |
| 64 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
65 hash_init(hashtab_T *ht) |
| 799 | 66 { |
| 67 /* This zeroes all "ht_" entries and all the "hi_key" in "ht_smallarray". */ | |
| 68 vim_memset(ht, 0, sizeof(hashtab_T)); | |
| 69 ht->ht_array = ht->ht_smallarray; | |
| 70 ht->ht_mask = HT_INIT_SIZE - 1; | |
| 71 } | |
| 72 | |
| 73 /* | |
| 74 * Free the array of a hash table. Does not free the items it contains! | |
| 75 * If "ht" is not freed then you should call hash_init() next! | |
| 76 */ | |
| 77 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
78 hash_clear(hashtab_T *ht) |
| 799 | 79 { |
| 80 if (ht->ht_array != ht->ht_smallarray) | |
| 81 vim_free(ht->ht_array); | |
| 82 } | |
| 83 | |
| 84 /* | |
| 85 * Free the array of a hash table and all the keys it contains. The keys must | |
| 86 * have been allocated. "off" is the offset from the start of the allocate | |
| 87 * memory to the location of the key (it's always positive). | |
| 88 */ | |
| 89 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
90 hash_clear_all(hashtab_T *ht, int off) |
| 799 | 91 { |
| 835 | 92 long todo; |
| 799 | 93 hashitem_T *hi; |
| 94 | |
| 835 | 95 todo = (long)ht->ht_used; |
| 799 | 96 for (hi = ht->ht_array; todo > 0; ++hi) |
| 97 { | |
| 98 if (!HASHITEM_EMPTY(hi)) | |
| 99 { | |
| 100 vim_free(hi->hi_key - off); | |
| 101 --todo; | |
| 102 } | |
| 103 } | |
| 104 hash_clear(ht); | |
| 105 } | |
| 106 | |
| 107 /* | |
| 108 * Find "key" in hashtable "ht". "key" must not be NULL. | |
| 109 * Always returns a pointer to a hashitem. If the item was not found then | |
| 110 * HASHITEM_EMPTY() is TRUE. The pointer is then the place where the key | |
| 111 * would be added. | |
| 112 * WARNING: The returned pointer becomes invalid when the hashtable is changed | |
| 113 * (adding, setting or removing an item)! | |
| 114 */ | |
| 115 hashitem_T * | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
116 hash_find(hashtab_T *ht, char_u *key) |
| 799 | 117 { |
| 118 return hash_lookup(ht, key, hash_hash(key)); | |
| 119 } | |
| 120 | |
| 121 /* | |
| 122 * Like hash_find(), but caller computes "hash". | |
| 123 */ | |
| 124 hashitem_T * | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
125 hash_lookup(hashtab_T *ht, char_u *key, hash_T hash) |
| 799 | 126 { |
| 127 hash_T perturb; | |
| 128 hashitem_T *freeitem; | |
| 129 hashitem_T *hi; | |
| 3970 | 130 unsigned idx; |
| 799 | 131 |
| 132 #ifdef HT_DEBUG | |
| 133 ++hash_count_lookup; | |
| 134 #endif | |
| 135 | |
| 136 /* | |
| 137 * Quickly handle the most common situations: | |
| 138 * - return if there is no item at all | |
| 139 * - skip over a removed item | |
| 140 * - return if the item matches | |
| 141 */ | |
| 3970 | 142 idx = (unsigned)(hash & ht->ht_mask); |
| 799 | 143 hi = &ht->ht_array[idx]; |
| 144 | |
| 145 if (hi->hi_key == NULL) | |
| 146 return hi; | |
| 147 if (hi->hi_key == HI_KEY_REMOVED) | |
| 148 freeitem = hi; | |
| 149 else if (hi->hi_hash == hash && STRCMP(hi->hi_key, key) == 0) | |
| 150 return hi; | |
| 151 else | |
| 152 freeitem = NULL; | |
| 153 | |
| 154 /* | |
| 155 * Need to search through the table to find the key. The algorithm | |
| 156 * to step through the table starts with large steps, gradually becoming | |
| 157 * smaller down to (1/4 table size + 1). This means it goes through all | |
| 158 * table entries in the end. | |
| 159 * When we run into a NULL key it's clear that the key isn't there. | |
| 160 * Return the first available slot found (can be a slot of a removed | |
| 161 * item). | |
| 162 */ | |
| 163 for (perturb = hash; ; perturb >>= PERTURB_SHIFT) | |
| 164 { | |
| 165 #ifdef HT_DEBUG | |
| 166 ++hash_count_perturb; /* count a "miss" for hashtab lookup */ | |
| 167 #endif | |
| 3970 | 168 idx = (unsigned)((idx << 2U) + idx + perturb + 1U); |
| 799 | 169 hi = &ht->ht_array[idx & ht->ht_mask]; |
| 170 if (hi->hi_key == NULL) | |
| 171 return freeitem == NULL ? hi : freeitem; | |
| 172 if (hi->hi_hash == hash | |
| 173 && hi->hi_key != HI_KEY_REMOVED | |
| 174 && STRCMP(hi->hi_key, key) == 0) | |
| 175 return hi; | |
| 176 if (hi->hi_key == HI_KEY_REMOVED && freeitem == NULL) | |
| 177 freeitem = hi; | |
| 178 } | |
| 179 } | |
| 180 | |
| 181 /* | |
| 182 * Print the efficiency of hashtable lookups. | |
| 183 * Useful when trying different hash algorithms. | |
| 184 * Called when exiting. | |
| 185 */ | |
| 186 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
187 hash_debug_results(void) |
| 799 | 188 { |
| 189 #ifdef HT_DEBUG | |
| 190 fprintf(stderr, "\r\n\r\n\r\n\r\n"); | |
| 191 fprintf(stderr, "Number of hashtable lookups: %ld\r\n", hash_count_lookup); | |
| 192 fprintf(stderr, "Number of perturb loops: %ld\r\n", hash_count_perturb); | |
| 193 fprintf(stderr, "Percentage of perturb loops: %ld%%\r\n", | |
| 194 hash_count_perturb * 100 / hash_count_lookup); | |
| 195 #endif | |
| 196 } | |
| 197 | |
| 198 /* | |
| 199 * Add item with key "key" to hashtable "ht". | |
| 200 * Returns FAIL when out of memory or the key is already present. | |
| 201 */ | |
| 202 int | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
203 hash_add(hashtab_T *ht, char_u *key) |
| 799 | 204 { |
| 205 hash_T hash = hash_hash(key); | |
| 206 hashitem_T *hi; | |
| 207 | |
| 208 hi = hash_lookup(ht, key, hash); | |
| 209 if (!HASHITEM_EMPTY(hi)) | |
| 210 { | |
|
10359
66f1b5bf3fa6
commit https://github.com/vim/vim/commit/95f096030ed1a8afea028f2ea295d6f6a70f466f
Christian Brabandt <cb@256bit.org>
parents:
10042
diff
changeset
|
211 internal_error("hash_add()"); |
| 799 | 212 return FAIL; |
| 213 } | |
| 214 return hash_add_item(ht, hi, key, hash); | |
| 215 } | |
| 216 | |
| 217 /* | |
| 218 * Add item "hi" with "key" to hashtable "ht". "key" must not be NULL and | |
| 219 * "hi" must have been obtained with hash_lookup() and point to an empty item. | |
| 220 * "hi" is invalid after this! | |
| 221 * Returns OK or FAIL (out of memory). | |
| 222 */ | |
| 223 int | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
224 hash_add_item( |
|
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
225 hashtab_T *ht, |
|
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
226 hashitem_T *hi, |
|
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
227 char_u *key, |
|
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
228 hash_T hash) |
| 799 | 229 { |
| 230 /* If resizing failed before and it fails again we can't add an item. */ | |
| 231 if (ht->ht_error && hash_may_resize(ht, 0) == FAIL) | |
| 232 return FAIL; | |
| 233 | |
| 234 ++ht->ht_used; | |
| 235 if (hi->hi_key == NULL) | |
| 236 ++ht->ht_filled; | |
| 237 hi->hi_key = key; | |
| 238 hi->hi_hash = hash; | |
| 239 | |
| 240 /* When the space gets low may resize the array. */ | |
| 241 return hash_may_resize(ht, 0); | |
| 242 } | |
| 243 | |
| 244 #if 0 /* not used */ | |
| 245 /* | |
| 246 * Overwrite hashtable item "hi" with "key". "hi" must point to the item that | |
| 247 * is to be overwritten. Thus the number of items in the hashtable doesn't | |
| 248 * change. | |
| 249 * Although the key must be identical, the pointer may be different, thus it's | |
| 250 * set anyway (the key is part of an item with that key). | |
| 251 * The caller must take care of freeing the old item. | |
| 252 * "hi" is invalid after this! | |
| 253 */ | |
| 254 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
255 hash_set(hashitem_T *hi, char_u *key) |
| 799 | 256 { |
| 257 hi->hi_key = key; | |
| 258 } | |
| 259 #endif | |
| 260 | |
| 261 /* | |
| 262 * Remove item "hi" from hashtable "ht". "hi" must have been obtained with | |
| 263 * hash_lookup(). | |
| 264 * The caller must take care of freeing the item itself. | |
| 265 */ | |
| 266 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
267 hash_remove(hashtab_T *ht, hashitem_T *hi) |
| 799 | 268 { |
| 269 --ht->ht_used; | |
| 270 hi->hi_key = HI_KEY_REMOVED; | |
| 271 hash_may_resize(ht, 0); | |
| 272 } | |
| 273 | |
| 274 /* | |
| 275 * Lock a hashtable: prevent that ht_array changes. | |
| 276 * Don't use this when items are to be added! | |
| 277 * Must call hash_unlock() later. | |
| 278 */ | |
| 279 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
280 hash_lock(hashtab_T *ht) |
| 799 | 281 { |
| 282 ++ht->ht_locked; | |
| 283 } | |
| 284 | |
| 285 #if 0 /* currently not used */ | |
| 286 /* | |
| 287 * Lock a hashtable at the specified number of entries. | |
| 288 * Caller must make sure no more than "size" entries will be added. | |
| 289 * Must call hash_unlock() later. | |
| 290 */ | |
| 291 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
292 hash_lock_size(hashtab_T *ht, int size) |
| 799 | 293 { |
| 294 (void)hash_may_resize(ht, size); | |
| 295 ++ht->ht_locked; | |
| 296 } | |
| 297 #endif | |
| 298 | |
| 299 /* | |
| 300 * Unlock a hashtable: allow ht_array changes again. | |
| 301 * Table will be resized (shrink) when necessary. | |
| 302 * This must balance a call to hash_lock(). | |
| 303 */ | |
| 304 void | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
305 hash_unlock(hashtab_T *ht) |
| 799 | 306 { |
| 307 --ht->ht_locked; | |
| 308 (void)hash_may_resize(ht, 0); | |
| 309 } | |
| 310 | |
| 311 /* | |
| 312 * Shrink a hashtable when there is too much empty space. | |
| 313 * Grow a hashtable when there is not enough empty space. | |
| 314 * Returns OK or FAIL (out of memory). | |
| 315 */ | |
| 316 static int | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
317 hash_may_resize( |
|
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
318 hashtab_T *ht, |
|
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
319 int minitems) /* minimal number of items */ |
| 799 | 320 { |
| 321 hashitem_T temparray[HT_INIT_SIZE]; | |
| 322 hashitem_T *oldarray, *newarray; | |
| 323 hashitem_T *olditem, *newitem; | |
| 3970 | 324 unsigned newi; |
| 799 | 325 int todo; |
| 326 long_u oldsize, newsize; | |
| 327 long_u minsize; | |
| 328 long_u newmask; | |
| 329 hash_T perturb; | |
| 330 | |
| 331 /* Don't resize a locked table. */ | |
| 332 if (ht->ht_locked > 0) | |
| 333 return OK; | |
| 334 | |
| 335 #ifdef HT_DEBUG | |
| 336 if (ht->ht_used > ht->ht_filled) | |
| 337 EMSG("hash_may_resize(): more used than filled"); | |
| 338 if (ht->ht_filled >= ht->ht_mask + 1) | |
| 339 EMSG("hash_may_resize(): table completely filled"); | |
| 340 #endif | |
| 341 | |
| 342 if (minitems == 0) | |
| 343 { | |
| 344 /* Return quickly for small tables with at least two NULL items. NULL | |
| 345 * items are required for the lookup to decide a key isn't there. */ | |
| 346 if (ht->ht_filled < HT_INIT_SIZE - 1 | |
| 347 && ht->ht_array == ht->ht_smallarray) | |
| 348 return OK; | |
| 349 | |
| 350 /* | |
| 351 * Grow or refill the array when it's more than 2/3 full (including | |
| 352 * removed items, so that they get cleaned up). | |
| 353 * Shrink the array when it's less than 1/5 full. When growing it is | |
| 354 * at least 1/4 full (avoids repeated grow-shrink operations) | |
| 355 */ | |
| 356 oldsize = ht->ht_mask + 1; | |
| 357 if (ht->ht_filled * 3 < oldsize * 2 && ht->ht_used > oldsize / 5) | |
| 358 return OK; | |
| 359 | |
| 360 if (ht->ht_used > 1000) | |
| 361 minsize = ht->ht_used * 2; /* it's big, don't make too much room */ | |
| 362 else | |
| 363 minsize = ht->ht_used * 4; /* make plenty of room */ | |
| 364 } | |
| 365 else | |
| 366 { | |
| 367 /* Use specified size. */ | |
| 368 if ((long_u)minitems < ht->ht_used) /* just in case... */ | |
| 835 | 369 minitems = (int)ht->ht_used; |
| 799 | 370 minsize = minitems * 3 / 2; /* array is up to 2/3 full */ |
| 371 } | |
| 372 | |
| 373 newsize = HT_INIT_SIZE; | |
| 374 while (newsize < minsize) | |
| 375 { | |
| 376 newsize <<= 1; /* make sure it's always a power of 2 */ | |
| 377 if (newsize == 0) | |
| 378 return FAIL; /* overflow */ | |
| 379 } | |
| 380 | |
| 381 if (newsize == HT_INIT_SIZE) | |
| 382 { | |
| 383 /* Use the small array inside the hashdict structure. */ | |
| 384 newarray = ht->ht_smallarray; | |
| 385 if (ht->ht_array == newarray) | |
| 386 { | |
| 387 /* Moving from ht_smallarray to ht_smallarray! Happens when there | |
| 388 * are many removed items. Copy the items to be able to clean up | |
| 389 * removed items. */ | |
| 390 mch_memmove(temparray, newarray, sizeof(temparray)); | |
| 391 oldarray = temparray; | |
| 392 } | |
| 393 else | |
| 394 oldarray = ht->ht_array; | |
| 395 } | |
| 396 else | |
| 397 { | |
| 398 /* Allocate an array. */ | |
| 399 newarray = (hashitem_T *)alloc((unsigned) | |
| 400 (sizeof(hashitem_T) * newsize)); | |
| 401 if (newarray == NULL) | |
| 402 { | |
| 403 /* Out of memory. When there are NULL items still return OK. | |
| 404 * Otherwise set ht_error, because lookup may result in a hang if | |
| 405 * we add another item. */ | |
| 406 if (ht->ht_filled < ht->ht_mask) | |
| 407 return OK; | |
| 408 ht->ht_error = TRUE; | |
| 409 return FAIL; | |
| 410 } | |
| 411 oldarray = ht->ht_array; | |
| 412 } | |
| 413 vim_memset(newarray, 0, (size_t)(sizeof(hashitem_T) * newsize)); | |
| 414 | |
| 415 /* | |
| 416 * Move all the items from the old array to the new one, placing them in | |
| 417 * the right spot. The new array won't have any removed items, thus this | |
| 418 * is also a cleanup action. | |
| 419 */ | |
| 420 newmask = newsize - 1; | |
| 835 | 421 todo = (int)ht->ht_used; |
| 799 | 422 for (olditem = oldarray; todo > 0; ++olditem) |
| 423 if (!HASHITEM_EMPTY(olditem)) | |
| 424 { | |
| 425 /* | |
| 426 * The algorithm to find the spot to add the item is identical to | |
| 427 * the algorithm to find an item in hash_lookup(). But we only | |
| 428 * need to search for a NULL key, thus it's simpler. | |
| 429 */ | |
| 3970 | 430 newi = (unsigned)(olditem->hi_hash & newmask); |
| 799 | 431 newitem = &newarray[newi]; |
| 432 | |
| 433 if (newitem->hi_key != NULL) | |
| 434 for (perturb = olditem->hi_hash; ; perturb >>= PERTURB_SHIFT) | |
| 435 { | |
| 3970 | 436 newi = (unsigned)((newi << 2U) + newi + perturb + 1U); |
| 799 | 437 newitem = &newarray[newi & newmask]; |
| 438 if (newitem->hi_key == NULL) | |
| 439 break; | |
| 440 } | |
| 441 *newitem = *olditem; | |
| 442 --todo; | |
| 443 } | |
| 444 | |
| 445 if (ht->ht_array != ht->ht_smallarray) | |
| 446 vim_free(ht->ht_array); | |
| 447 ht->ht_array = newarray; | |
| 448 ht->ht_mask = newmask; | |
| 449 ht->ht_filled = ht->ht_used; | |
| 450 ht->ht_error = FALSE; | |
| 451 | |
| 452 return OK; | |
| 453 } | |
| 454 | |
| 455 /* | |
| 456 * Get the hash number for a key. | |
| 457 * If you think you know a better hash function: Compile with HT_DEBUG set and | |
| 458 * run a script that uses hashtables a lot. Vim will then print statistics | |
| 459 * when exiting. Try that with the current hash algorithm and yours. The | |
| 460 * lower the percentage the better. | |
| 461 */ | |
| 462 hash_T | |
|
7823
bcef391c101c
commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents:
7803
diff
changeset
|
463 hash_hash(char_u *key) |
| 799 | 464 { |
| 465 hash_T hash; | |
| 466 char_u *p; | |
| 467 | |
| 468 if ((hash = *key) == 0) | |
|
8839
9fa567d13551
commit https://github.com/vim/vim/commit/0921ecff1c5a74541bad6c073e8ade32247403d8
Christian Brabandt <cb@256bit.org>
parents:
7823
diff
changeset
|
469 return (hash_T)0; |
| 799 | 470 p = key + 1; |
| 471 | |
| 472 /* A simplistic algorithm that appears to do very well. | |
| 473 * Suggested by George Reilly. */ | |
| 474 while (*p != NUL) | |
| 475 hash = hash * 101 + *p++; | |
| 476 | |
| 477 return hash; | |
| 478 } |