1/* Licensed to the Apache Software Foundation (ASF) under one or more 2 * contributor license agreements. See the NOTICE file distributed with 3 * this work for additional information regarding copyright ownership. 4 * The ASF licenses this file to You under the Apache License, Version 2.0 5 * (the "License"); you may not use this file except in compliance with 6 * the License. You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#include "apr_private.h" 18 19#include "apr_general.h" 20#include "apr_pools.h" 21#include "apr_time.h" 22 23#include "apr_hash.h" 24 25#if APR_HAVE_STDLIB_H 26#include <stdlib.h> 27#endif 28#if APR_HAVE_STRING_H 29#include <string.h> 30#endif 31 32#if APR_POOL_DEBUG && APR_HAVE_STDIO_H 33#include <stdio.h> 34#endif 35 36/* 37 * The internal form of a hash table. 38 * 39 * The table is an array indexed by the hash of the key; collisions 40 * are resolved by hanging a linked list of hash entries off each 41 * element of the array. Although this is a really simple design it 42 * isn't too bad given that pools have a low allocation overhead. 43 */ 44 45typedef struct apr_hash_entry_t apr_hash_entry_t; 46 47struct apr_hash_entry_t { 48 apr_hash_entry_t *next; 49 unsigned int hash; 50 const void *key; 51 apr_ssize_t klen; 52 const void *val; 53}; 54 55/* 56 * Data structure for iterating through a hash table. 57 * 58 * We keep a pointer to the next hash entry here to allow the current 59 * hash entry to be freed or otherwise mangled between calls to 60 * apr_hash_next(). 61 */ 62struct apr_hash_index_t { 63 apr_hash_t *ht; 64 apr_hash_entry_t *this, *next; 65 unsigned int index; 66}; 67 68/* 69 * The size of the array is always a power of two. We use the maximum 70 * index rather than the size so that we can use bitwise-AND for 71 * modular arithmetic. 72 * The count of hash entries may be greater depending on the chosen 73 * collision rate. 74 */ 75struct apr_hash_t { 76 apr_pool_t *pool; 77 apr_hash_entry_t **array; 78 apr_hash_index_t iterator; /* For apr_hash_first(NULL, ...) */ 79 unsigned int count, max, seed; 80 apr_hashfunc_t hash_func; 81 apr_hash_entry_t *free; /* List of recycled entries */ 82}; 83 84#define INITIAL_MAX 15 /* tunable == 2^n - 1 */ 85 86 87/* 88 * Hash creation functions. 89 */ 90 91static apr_hash_entry_t **alloc_array(apr_hash_t *ht, unsigned int max) 92{ 93 return apr_pcalloc(ht->pool, sizeof(*ht->array) * (max + 1)); 94} 95 96APR_DECLARE(apr_hash_t *) apr_hash_make(apr_pool_t *pool) 97{ 98 apr_hash_t *ht; 99 apr_time_t now = apr_time_now(); 100 101 ht = apr_palloc(pool, sizeof(apr_hash_t)); 102 ht->pool = pool; 103 ht->free = NULL; 104 ht->count = 0; 105 ht->max = INITIAL_MAX; 106 ht->seed = (unsigned int)((now >> 32) ^ now ^ (apr_uintptr_t)pool ^ 107 (apr_uintptr_t)ht ^ (apr_uintptr_t)&now) - 1; 108 ht->array = alloc_array(ht, ht->max); 109 ht->hash_func = NULL; 110 111 return ht; 112} 113 114APR_DECLARE(apr_hash_t *) apr_hash_make_custom(apr_pool_t *pool, 115 apr_hashfunc_t hash_func) 116{ 117 apr_hash_t *ht = apr_hash_make(pool); 118 ht->hash_func = hash_func; 119 return ht; 120} 121 122 123/* 124 * Hash iteration functions. 125 */ 126 127APR_DECLARE(apr_hash_index_t *) apr_hash_next(apr_hash_index_t *hi) 128{ 129 hi->this = hi->next; 130 while (!hi->this) { 131 if (hi->index > hi->ht->max) 132 return NULL; 133 134 hi->this = hi->ht->array[hi->index++]; 135 } 136 hi->next = hi->this->next; 137 return hi; 138} 139 140APR_DECLARE(apr_hash_index_t *) apr_hash_first(apr_pool_t *p, apr_hash_t *ht) 141{ 142 apr_hash_index_t *hi; 143 if (p) 144 hi = apr_palloc(p, sizeof(*hi)); 145 else 146 hi = &ht->iterator; 147 148 hi->ht = ht; 149 hi->index = 0; 150 hi->this = NULL; 151 hi->next = NULL; 152 return apr_hash_next(hi); 153} 154 155APR_DECLARE(void) apr_hash_this(apr_hash_index_t *hi, 156 const void **key, 157 apr_ssize_t *klen, 158 void **val) 159{ 160 if (key) *key = hi->this->key; 161 if (klen) *klen = hi->this->klen; 162 if (val) *val = (void *)hi->this->val; 163} 164 165 166/* 167 * Expanding a hash table 168 */ 169 170static void expand_array(apr_hash_t *ht) 171{ 172 apr_hash_index_t *hi; 173 apr_hash_entry_t **new_array; 174 unsigned int new_max; 175 176 new_max = ht->max * 2 + 1; 177 new_array = alloc_array(ht, new_max); 178 for (hi = apr_hash_first(NULL, ht); hi; hi = apr_hash_next(hi)) { 179 unsigned int i = hi->this->hash & new_max; 180 hi->this->next = new_array[i]; 181 new_array[i] = hi->this; 182 } 183 ht->array = new_array; 184 ht->max = new_max; 185} 186 187static unsigned int hashfunc_default(const char *char_key, apr_ssize_t *klen, 188 unsigned int hash) 189{ 190 const unsigned char *key = (const unsigned char *)char_key; 191 const unsigned char *p; 192 apr_ssize_t i; 193 194 /* 195 * This is the popular `times 33' hash algorithm which is used by 196 * perl and also appears in Berkeley DB. This is one of the best 197 * known hash functions for strings because it is both computed 198 * very fast and distributes very well. 199 * 200 * The originator may be Dan Bernstein but the code in Berkeley DB 201 * cites Chris Torek as the source. The best citation I have found 202 * is "Chris Torek, Hash function for text in C, Usenet message 203 * <27038@mimsy.umd.edu> in comp.lang.c , October, 1990." in Rich 204 * Salz's USENIX 1992 paper about INN which can be found at 205 * <http://citeseer.nj.nec.com/salz92internetnews.html>. 206 * 207 * The magic of number 33, i.e. why it works better than many other 208 * constants, prime or not, has never been adequately explained by 209 * anyone. So I try an explanation: if one experimentally tests all 210 * multipliers between 1 and 256 (as I did while writing a low-level 211 * data structure library some time ago) one detects that even 212 * numbers are not useable at all. The remaining 128 odd numbers 213 * (except for the number 1) work more or less all equally well. 214 * They all distribute in an acceptable way and this way fill a hash 215 * table with an average percent of approx. 86%. 216 * 217 * If one compares the chi^2 values of the variants (see 218 * Bob Jenkins ``Hashing Frequently Asked Questions'' at 219 * http://burtleburtle.net/bob/hash/hashfaq.html for a description 220 * of chi^2), the number 33 not even has the best value. But the 221 * number 33 and a few other equally good numbers like 17, 31, 63, 222 * 127 and 129 have nevertheless a great advantage to the remaining 223 * numbers in the large set of possible multipliers: their multiply 224 * operation can be replaced by a faster operation based on just one 225 * shift plus either a single addition or subtraction operation. And 226 * because a hash function has to both distribute good _and_ has to 227 * be very fast to compute, those few numbers should be preferred. 228 * 229 * -- Ralf S. Engelschall <rse@engelschall.com> 230 */ 231 232 if (*klen == APR_HASH_KEY_STRING) { 233 for (p = key; *p; p++) { 234 hash = hash * 33 + *p; 235 } 236 *klen = p - key; 237 } 238 else { 239 for (p = key, i = *klen; i; i--, p++) { 240 hash = hash * 33 + *p; 241 } 242 } 243 244 return hash; 245} 246 247APR_DECLARE_NONSTD(unsigned int) apr_hashfunc_default(const char *char_key, 248 apr_ssize_t *klen) 249{ 250 return hashfunc_default(char_key, klen, 0); 251} 252 253/* 254 * This is where we keep the details of the hash function and control 255 * the maximum collision rate. 256 * 257 * If val is non-NULL it creates and initializes a new hash entry if 258 * there isn't already one there; it returns an updatable pointer so 259 * that hash entries can be removed. 260 */ 261 262static apr_hash_entry_t **find_entry(apr_hash_t *ht, 263 const void *key, 264 apr_ssize_t klen, 265 const void *val) 266{ 267 apr_hash_entry_t **hep, *he; 268 unsigned int hash; 269 270 if (ht->hash_func) 271 hash = ht->hash_func(key, &klen); 272 else 273 hash = hashfunc_default(key, &klen, ht->seed); 274 275 /* scan linked list */ 276 for (hep = &ht->array[hash & ht->max], he = *hep; 277 he; hep = &he->next, he = *hep) { 278 if (he->hash == hash 279 && he->klen == klen 280 && memcmp(he->key, key, klen) == 0) 281 break; 282 } 283 if (he || !val) 284 return hep; 285 286 /* add a new entry for non-NULL values */ 287 if ((he = ht->free) != NULL) 288 ht->free = he->next; 289 else 290 he = apr_palloc(ht->pool, sizeof(*he)); 291 he->next = NULL; 292 he->hash = hash; 293 he->key = key; 294 he->klen = klen; 295 he->val = val; 296 *hep = he; 297 ht->count++; 298 return hep; 299} 300 301APR_DECLARE(apr_hash_t *) apr_hash_copy(apr_pool_t *pool, 302 const apr_hash_t *orig) 303{ 304 apr_hash_t *ht; 305 apr_hash_entry_t *new_vals; 306 unsigned int i, j; 307 308 ht = apr_palloc(pool, sizeof(apr_hash_t) + 309 sizeof(*ht->array) * (orig->max + 1) + 310 sizeof(apr_hash_entry_t) * orig->count); 311 ht->pool = pool; 312 ht->free = NULL; 313 ht->count = orig->count; 314 ht->max = orig->max; 315 ht->seed = orig->seed; 316 ht->hash_func = orig->hash_func; 317 ht->array = (apr_hash_entry_t **)((char *)ht + sizeof(apr_hash_t)); 318 319 new_vals = (apr_hash_entry_t *)((char *)(ht) + sizeof(apr_hash_t) + 320 sizeof(*ht->array) * (orig->max + 1)); 321 j = 0; 322 for (i = 0; i <= ht->max; i++) { 323 apr_hash_entry_t **new_entry = &(ht->array[i]); 324 apr_hash_entry_t *orig_entry = orig->array[i]; 325 while (orig_entry) { 326 *new_entry = &new_vals[j++]; 327 (*new_entry)->hash = orig_entry->hash; 328 (*new_entry)->key = orig_entry->key; 329 (*new_entry)->klen = orig_entry->klen; 330 (*new_entry)->val = orig_entry->val; 331 new_entry = &((*new_entry)->next); 332 orig_entry = orig_entry->next; 333 } 334 *new_entry = NULL; 335 } 336 return ht; 337} 338 339APR_DECLARE(void *) apr_hash_get(apr_hash_t *ht, 340 const void *key, 341 apr_ssize_t klen) 342{ 343 apr_hash_entry_t *he; 344 he = *find_entry(ht, key, klen, NULL); 345 if (he) 346 return (void *)he->val; 347 else 348 return NULL; 349} 350 351APR_DECLARE(void) apr_hash_set(apr_hash_t *ht, 352 const void *key, 353 apr_ssize_t klen, 354 const void *val) 355{ 356 apr_hash_entry_t **hep; 357 hep = find_entry(ht, key, klen, val); 358 if (*hep) { 359 if (!val) { 360 /* delete entry */ 361 apr_hash_entry_t *old = *hep; 362 *hep = (*hep)->next; 363 old->next = ht->free; 364 ht->free = old; 365 --ht->count; 366 } 367 else { 368 /* replace entry */ 369 (*hep)->val = val; 370 /* check that the collision rate isn't too high */ 371 if (ht->count > ht->max) { 372 expand_array(ht); 373 } 374 } 375 } 376 /* else key not present and val==NULL */ 377} 378 379APR_DECLARE(unsigned int) apr_hash_count(apr_hash_t *ht) 380{ 381 return ht->count; 382} 383 384APR_DECLARE(void) apr_hash_clear(apr_hash_t *ht) 385{ 386 apr_hash_index_t *hi; 387 for (hi = apr_hash_first(NULL, ht); hi; hi = apr_hash_next(hi)) 388 apr_hash_set(ht, hi->this->key, hi->this->klen, NULL); 389} 390 391APR_DECLARE(apr_hash_t*) apr_hash_overlay(apr_pool_t *p, 392 const apr_hash_t *overlay, 393 const apr_hash_t *base) 394{ 395 return apr_hash_merge(p, overlay, base, NULL, NULL); 396} 397 398APR_DECLARE(apr_hash_t *) apr_hash_merge(apr_pool_t *p, 399 const apr_hash_t *overlay, 400 const apr_hash_t *base, 401 void * (*merger)(apr_pool_t *p, 402 const void *key, 403 apr_ssize_t klen, 404 const void *h1_val, 405 const void *h2_val, 406 const void *data), 407 const void *data) 408{ 409 apr_hash_t *res; 410 apr_hash_entry_t *new_vals = NULL; 411 apr_hash_entry_t *iter; 412 apr_hash_entry_t *ent; 413 unsigned int i, j, k, hash; 414 415#if APR_POOL_DEBUG 416 /* we don't copy keys and values, so it's necessary that 417 * overlay->a.pool and base->a.pool have a life span at least 418 * as long as p 419 */ 420 if (!apr_pool_is_ancestor(overlay->pool, p)) { 421 fprintf(stderr, 422 "apr_hash_merge: overlay's pool is not an ancestor of p\n"); 423 abort(); 424 } 425 if (!apr_pool_is_ancestor(base->pool, p)) { 426 fprintf(stderr, 427 "apr_hash_merge: base's pool is not an ancestor of p\n"); 428 abort(); 429 } 430#endif 431 432 res = apr_palloc(p, sizeof(apr_hash_t)); 433 res->pool = p; 434 res->free = NULL; 435 res->hash_func = base->hash_func; 436 res->count = base->count; 437 res->max = (overlay->max > base->max) ? overlay->max : base->max; 438 if (base->count + overlay->count > res->max) { 439 res->max = res->max * 2 + 1; 440 } 441 res->seed = base->seed; 442 res->array = alloc_array(res, res->max); 443 if (base->count + overlay->count) { 444 new_vals = apr_palloc(p, sizeof(apr_hash_entry_t) * 445 (base->count + overlay->count)); 446 } 447 j = 0; 448 for (k = 0; k <= base->max; k++) { 449 for (iter = base->array[k]; iter; iter = iter->next) { 450 i = iter->hash & res->max; 451 new_vals[j].klen = iter->klen; 452 new_vals[j].key = iter->key; 453 new_vals[j].val = iter->val; 454 new_vals[j].hash = iter->hash; 455 new_vals[j].next = res->array[i]; 456 res->array[i] = &new_vals[j]; 457 j++; 458 } 459 } 460 461 for (k = 0; k <= overlay->max; k++) { 462 for (iter = overlay->array[k]; iter; iter = iter->next) { 463 if (res->hash_func) 464 hash = res->hash_func(iter->key, &iter->klen); 465 else 466 hash = hashfunc_default(iter->key, &iter->klen, res->seed); 467 i = hash & res->max; 468 for (ent = res->array[i]; ent; ent = ent->next) { 469 if ((ent->klen == iter->klen) && 470 (memcmp(ent->key, iter->key, iter->klen) == 0)) { 471 if (merger) { 472 ent->val = (*merger)(p, iter->key, iter->klen, 473 iter->val, ent->val, data); 474 } 475 else { 476 ent->val = iter->val; 477 } 478 break; 479 } 480 } 481 if (!ent) { 482 new_vals[j].klen = iter->klen; 483 new_vals[j].key = iter->key; 484 new_vals[j].val = iter->val; 485 new_vals[j].hash = hash; 486 new_vals[j].next = res->array[i]; 487 res->array[i] = &new_vals[j]; 488 res->count++; 489 j++; 490 } 491 } 492 } 493 return res; 494} 495 496/* This is basically the following... 497 * for every element in hash table { 498 * comp elemeny.key, element.value 499 * } 500 * 501 * Like with apr_table_do, the comp callback is called for each and every 502 * element of the hash table. 503 */ 504APR_DECLARE(int) apr_hash_do(apr_hash_do_callback_fn_t *comp, 505 void *rec, const apr_hash_t *ht) 506{ 507 apr_hash_index_t hix; 508 apr_hash_index_t *hi; 509 int rv, dorv = 1; 510 511 hix.ht = (apr_hash_t *)ht; 512 hix.index = 0; 513 hix.this = NULL; 514 hix.next = NULL; 515 516 if ((hi = apr_hash_next(&hix))) { 517 /* Scan the entire table */ 518 do { 519 rv = (*comp)(rec, hi->this->key, hi->this->klen, hi->this->val); 520 } while (rv && (hi = apr_hash_next(hi))); 521 522 if (rv == 0) { 523 dorv = 0; 524 } 525 } 526 return dorv; 527} 528 529APR_POOL_IMPLEMENT_ACCESSOR(hash) 530