Mercurial > vim
annotate src/hashtab.c @ 19671:897cb43a5c72 v8.2.0392
patch 8.2.0392: Coverity warns for using array index out of range
Commit: https://github.com/vim/vim/commit/56cb3378727783da2d246b9c5091784821666cfa
Author: Bram Moolenaar <Bram@vim.org>
Date: Mon Mar 16 20:04:41 2020 +0100
patch 8.2.0392: Coverity warns for using array index out of range
Problem: Coverity warns for using array index out of range.
Solution: Add extra "if" to avoid warning.
| author | Bram Moolenaar <Bram@vim.org> |
|---|---|
| date | Mon, 16 Mar 2020 20:15:04 +0100 |
| parents | f0f9692d4487 |
| children | aadd1cae2ff5 |
| rev | line source |
|---|---|
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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 | |
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33 # define HT_DEBUG // extra checks for table consistency and statistics |
| 799 | 34 |
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35 static long hash_count_lookup = 0; // count number of hashtab lookups |
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36 static long hash_count_perturb = 0; // count number of "misses" |
| 799 | 37 #endif |
| 38 | |
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39 // Magic value for algorithm that walks through the array. |
| 799 | 40 #define PERTURB_SHIFT 5 |
| 41 | |
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42 static int hash_may_resize(hashtab_T *ht, int minitems); |
| 799 | 43 |
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44 #if 0 // currently not used |
| 799 | 45 /* |
| 46 * Create an empty hash table. | |
| 47 * Returns NULL when out of memory. | |
| 48 */ | |
| 49 hashtab_T * | |
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50 hash_create(void) |
| 799 | 51 { |
| 52 hashtab_T *ht; | |
| 53 | |
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54 ht = ALLOC_ONE(hashtab_T); |
| 799 | 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 | |
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65 hash_init(hashtab_T *ht) |
| 799 | 66 { |
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67 // This zeroes all "ht_" entries and all the "hi_key" in "ht_smallarray". |
| 799 | 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 | |
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78 hash_clear(hashtab_T *ht) |
| 799 | 79 { |
| 80 if (ht->ht_array != ht->ht_smallarray) | |
| 81 vim_free(ht->ht_array); | |
| 82 } | |
| 83 | |
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84 #if defined(FEAT_SPELL) || defined(PROTO) |
| 799 | 85 /* |
| 86 * Free the array of a hash table and all the keys it contains. The keys must | |
| 87 * have been allocated. "off" is the offset from the start of the allocate | |
| 88 * memory to the location of the key (it's always positive). | |
| 89 */ | |
| 90 void | |
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91 hash_clear_all(hashtab_T *ht, int off) |
| 799 | 92 { |
| 835 | 93 long todo; |
| 799 | 94 hashitem_T *hi; |
| 95 | |
| 835 | 96 todo = (long)ht->ht_used; |
| 799 | 97 for (hi = ht->ht_array; todo > 0; ++hi) |
| 98 { | |
| 99 if (!HASHITEM_EMPTY(hi)) | |
| 100 { | |
| 101 vim_free(hi->hi_key - off); | |
| 102 --todo; | |
| 103 } | |
| 104 } | |
| 105 hash_clear(ht); | |
| 106 } | |
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107 #endif |
| 799 | 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 | |
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168 ++hash_count_perturb; // count a "miss" for hashtab lookup |
| 799 | 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 | |
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183 #if defined(FEAT_EVAL) || defined(FEAT_SYN_HL) || defined(PROTO) |
| 799 | 184 /* |
| 185 * Print the efficiency of hashtable lookups. | |
| 186 * Useful when trying different hash algorithms. | |
| 187 * Called when exiting. | |
| 188 */ | |
| 189 void | |
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190 hash_debug_results(void) |
| 799 | 191 { |
| 192 #ifdef HT_DEBUG | |
| 193 fprintf(stderr, "\r\n\r\n\r\n\r\n"); | |
| 194 fprintf(stderr, "Number of hashtable lookups: %ld\r\n", hash_count_lookup); | |
| 195 fprintf(stderr, "Number of perturb loops: %ld\r\n", hash_count_perturb); | |
| 196 fprintf(stderr, "Percentage of perturb loops: %ld%%\r\n", | |
| 197 hash_count_perturb * 100 / hash_count_lookup); | |
| 198 #endif | |
| 199 } | |
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200 #endif |
| 799 | 201 |
| 202 /* | |
| 203 * Add item with key "key" to hashtable "ht". | |
| 204 * Returns FAIL when out of memory or the key is already present. | |
| 205 */ | |
| 206 int | |
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207 hash_add(hashtab_T *ht, char_u *key) |
| 799 | 208 { |
| 209 hash_T hash = hash_hash(key); | |
| 210 hashitem_T *hi; | |
| 211 | |
| 212 hi = hash_lookup(ht, key, hash); | |
| 213 if (!HASHITEM_EMPTY(hi)) | |
| 214 { | |
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215 internal_error("hash_add()"); |
| 799 | 216 return FAIL; |
| 217 } | |
| 218 return hash_add_item(ht, hi, key, hash); | |
| 219 } | |
| 220 | |
| 221 /* | |
| 222 * Add item "hi" with "key" to hashtable "ht". "key" must not be NULL and | |
| 223 * "hi" must have been obtained with hash_lookup() and point to an empty item. | |
| 224 * "hi" is invalid after this! | |
| 225 * Returns OK or FAIL (out of memory). | |
| 226 */ | |
| 227 int | |
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228 hash_add_item( |
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229 hashtab_T *ht, |
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230 hashitem_T *hi, |
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231 char_u *key, |
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232 hash_T hash) |
| 799 | 233 { |
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234 // If resizing failed before and it fails again we can't add an item. |
| 799 | 235 if (ht->ht_error && hash_may_resize(ht, 0) == FAIL) |
| 236 return FAIL; | |
| 237 | |
| 238 ++ht->ht_used; | |
| 239 if (hi->hi_key == NULL) | |
| 240 ++ht->ht_filled; | |
| 241 hi->hi_key = key; | |
| 242 hi->hi_hash = hash; | |
| 243 | |
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244 // When the space gets low may resize the array. |
| 799 | 245 return hash_may_resize(ht, 0); |
| 246 } | |
| 247 | |
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248 #if 0 // not used |
| 799 | 249 /* |
| 250 * Overwrite hashtable item "hi" with "key". "hi" must point to the item that | |
| 251 * is to be overwritten. Thus the number of items in the hashtable doesn't | |
| 252 * change. | |
| 253 * Although the key must be identical, the pointer may be different, thus it's | |
| 254 * set anyway (the key is part of an item with that key). | |
| 255 * The caller must take care of freeing the old item. | |
| 256 * "hi" is invalid after this! | |
| 257 */ | |
| 258 void | |
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259 hash_set(hashitem_T *hi, char_u *key) |
| 799 | 260 { |
| 261 hi->hi_key = key; | |
| 262 } | |
| 263 #endif | |
| 264 | |
| 265 /* | |
| 266 * Remove item "hi" from hashtable "ht". "hi" must have been obtained with | |
| 267 * hash_lookup(). | |
| 268 * The caller must take care of freeing the item itself. | |
| 269 */ | |
| 270 void | |
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271 hash_remove(hashtab_T *ht, hashitem_T *hi) |
| 799 | 272 { |
| 273 --ht->ht_used; | |
| 274 hi->hi_key = HI_KEY_REMOVED; | |
| 275 hash_may_resize(ht, 0); | |
| 276 } | |
| 277 | |
| 278 /* | |
| 279 * Lock a hashtable: prevent that ht_array changes. | |
| 280 * Don't use this when items are to be added! | |
| 281 * Must call hash_unlock() later. | |
| 282 */ | |
| 283 void | |
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284 hash_lock(hashtab_T *ht) |
| 799 | 285 { |
| 286 ++ht->ht_locked; | |
| 287 } | |
| 288 | |
| 289 /* | |
| 290 * Lock a hashtable at the specified number of entries. | |
| 291 * Caller must make sure no more than "size" entries will be added. | |
| 292 * Must call hash_unlock() later. | |
| 293 */ | |
| 294 void | |
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295 hash_lock_size(hashtab_T *ht, int size) |
| 799 | 296 { |
| 297 (void)hash_may_resize(ht, size); | |
| 298 ++ht->ht_locked; | |
| 299 } | |
| 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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320 hashtab_T *ht, |
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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 | |
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333 // Don't resize a locked table. |
| 799 | 334 if (ht->ht_locked > 0) |
| 335 return OK; | |
| 336 | |
| 337 #ifdef HT_DEBUG | |
| 338 if (ht->ht_used > ht->ht_filled) | |
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339 emsg("hash_may_resize(): more used than filled"); |
| 799 | 340 if (ht->ht_filled >= ht->ht_mask + 1) |
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341 emsg("hash_may_resize(): table completely filled"); |
| 799 | 342 #endif |
| 343 | |
| 344 if (minitems == 0) | |
| 345 { | |
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346 // Return quickly for small tables with at least two NULL items. NULL |
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347 // items are required for the lookup to decide a key isn't there. |
| 799 | 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) | |
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363 minsize = ht->ht_used * 2; // it's big, don't make too much room |
| 799 | 364 else |
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365 minsize = ht->ht_used * 4; // make plenty of room |
| 799 | 366 } |
| 367 else | |
| 368 { | |
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369 // Use specified size. |
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370 if ((long_u)minitems < ht->ht_used) // just in case... |
| 835 | 371 minitems = (int)ht->ht_used; |
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372 minsize = (minitems * 3 + 1) / 2; // array is up to 2/3 full |
| 799 | 373 } |
| 374 | |
| 375 newsize = HT_INIT_SIZE; | |
| 376 while (newsize < minsize) | |
| 377 { | |
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378 newsize <<= 1; // make sure it's always a power of 2 |
| 799 | 379 if (newsize == 0) |
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380 return FAIL; // overflow |
| 799 | 381 } |
| 382 | |
| 383 if (newsize == HT_INIT_SIZE) | |
| 384 { | |
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385 // Use the small array inside the hashdict structure. |
| 799 | 386 newarray = ht->ht_smallarray; |
| 387 if (ht->ht_array == newarray) | |
| 388 { | |
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389 // Moving from ht_smallarray to ht_smallarray! Happens when there |
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390 // are many removed items. Copy the items to be able to clean up |
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391 // removed items. |
| 799 | 392 mch_memmove(temparray, newarray, sizeof(temparray)); |
| 393 oldarray = temparray; | |
| 394 } | |
| 395 else | |
| 396 oldarray = ht->ht_array; | |
| 397 } | |
| 398 else | |
| 399 { | |
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400 // Allocate an array. |
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401 newarray = ALLOC_MULT(hashitem_T, newsize); |
| 799 | 402 if (newarray == NULL) |
| 403 { | |
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404 // Out of memory. When there are NULL items still return OK. |
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405 // Otherwise set ht_error, because lookup may result in a hang if |
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406 // we add another item. |
| 799 | 407 if (ht->ht_filled < ht->ht_mask) |
| 408 return OK; | |
| 409 ht->ht_error = TRUE; | |
| 410 return FAIL; | |
| 411 } | |
| 412 oldarray = ht->ht_array; | |
| 413 } | |
| 414 vim_memset(newarray, 0, (size_t)(sizeof(hashitem_T) * newsize)); | |
| 415 | |
| 416 /* | |
| 417 * Move all the items from the old array to the new one, placing them in | |
| 418 * the right spot. The new array won't have any removed items, thus this | |
| 419 * is also a cleanup action. | |
| 420 */ | |
| 421 newmask = newsize - 1; | |
| 835 | 422 todo = (int)ht->ht_used; |
| 799 | 423 for (olditem = oldarray; todo > 0; ++olditem) |
| 424 if (!HASHITEM_EMPTY(olditem)) | |
| 425 { | |
| 426 /* | |
| 427 * The algorithm to find the spot to add the item is identical to | |
| 428 * the algorithm to find an item in hash_lookup(). But we only | |
| 429 * need to search for a NULL key, thus it's simpler. | |
| 430 */ | |
| 3970 | 431 newi = (unsigned)(olditem->hi_hash & newmask); |
| 799 | 432 newitem = &newarray[newi]; |
| 433 | |
| 434 if (newitem->hi_key != NULL) | |
| 435 for (perturb = olditem->hi_hash; ; perturb >>= PERTURB_SHIFT) | |
| 436 { | |
| 3970 | 437 newi = (unsigned)((newi << 2U) + newi + perturb + 1U); |
| 799 | 438 newitem = &newarray[newi & newmask]; |
| 439 if (newitem->hi_key == NULL) | |
| 440 break; | |
| 441 } | |
| 442 *newitem = *olditem; | |
| 443 --todo; | |
| 444 } | |
| 445 | |
| 446 if (ht->ht_array != ht->ht_smallarray) | |
| 447 vim_free(ht->ht_array); | |
| 448 ht->ht_array = newarray; | |
| 449 ht->ht_mask = newmask; | |
| 450 ht->ht_filled = ht->ht_used; | |
| 451 ht->ht_error = FALSE; | |
| 452 | |
| 453 return OK; | |
| 454 } | |
| 455 | |
| 456 /* | |
| 457 * Get the hash number for a key. | |
| 458 * If you think you know a better hash function: Compile with HT_DEBUG set and | |
| 459 * run a script that uses hashtables a lot. Vim will then print statistics | |
| 460 * when exiting. Try that with the current hash algorithm and yours. The | |
| 461 * lower the percentage the better. | |
| 462 */ | |
| 463 hash_T | |
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commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
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464 hash_hash(char_u *key) |
| 799 | 465 { |
| 466 hash_T hash; | |
| 467 char_u *p; | |
| 468 | |
| 469 if ((hash = *key) == 0) | |
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470 return (hash_T)0; |
| 799 | 471 p = key + 1; |
| 472 | |
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473 // A simplistic algorithm that appears to do very well. |
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474 // Suggested by George Reilly. |
| 799 | 475 while (*p != NUL) |
| 476 hash = hash * 101 + *p++; | |
| 477 | |
| 478 return hash; | |
| 479 } |