1251875Speter/* Licensed to the Apache Software Foundation (ASF) under one or more 2251875Speter * contributor license agreements. See the NOTICE file distributed with 3251875Speter * this work for additional information regarding copyright ownership. 4251875Speter * The ASF licenses this file to You under the Apache License, Version 2.0 5251875Speter * (the "License"); you may not use this file except in compliance with 6251875Speter * the License. You may obtain a copy of the License at 7251875Speter * 8251875Speter * http://www.apache.org/licenses/LICENSE-2.0 9251875Speter * 10251875Speter * Unless required by applicable law or agreed to in writing, software 11251875Speter * distributed under the License is distributed on an "AS IS" BASIS, 12251875Speter * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13251875Speter * See the License for the specific language governing permissions and 14251875Speter * limitations under the License. 15251875Speter */ 16251875Speter 17251875Speter#include "apr_private.h" 18251875Speter 19251875Speter#include "apr_general.h" 20251875Speter#include "apr_pools.h" 21251875Speter#include "apr_time.h" 22251875Speter 23251875Speter#include "apr_hash.h" 24251875Speter 25251875Speter#if APR_HAVE_STDLIB_H 26251875Speter#include <stdlib.h> 27251875Speter#endif 28251875Speter#if APR_HAVE_STRING_H 29251875Speter#include <string.h> 30251875Speter#endif 31251875Speter 32251875Speter#if APR_POOL_DEBUG && APR_HAVE_STDIO_H 33251875Speter#include <stdio.h> 34251875Speter#endif 35251875Speter 36251875Speter/* 37251875Speter * The internal form of a hash table. 38251875Speter * 39251875Speter * The table is an array indexed by the hash of the key; collisions 40251875Speter * are resolved by hanging a linked list of hash entries off each 41251875Speter * element of the array. Although this is a really simple design it 42251875Speter * isn't too bad given that pools have a low allocation overhead. 43251875Speter */ 44251875Speter 45251875Spetertypedef struct apr_hash_entry_t apr_hash_entry_t; 46251875Speter 47251875Speterstruct apr_hash_entry_t { 48251875Speter apr_hash_entry_t *next; 49251875Speter unsigned int hash; 50251875Speter const void *key; 51251875Speter apr_ssize_t klen; 52251875Speter const void *val; 53251875Speter}; 54251875Speter 55251875Speter/* 56251875Speter * Data structure for iterating through a hash table. 57251875Speter * 58251875Speter * We keep a pointer to the next hash entry here to allow the current 59251875Speter * hash entry to be freed or otherwise mangled between calls to 60251875Speter * apr_hash_next(). 61251875Speter */ 62251875Speterstruct apr_hash_index_t { 63251875Speter apr_hash_t *ht; 64251875Speter apr_hash_entry_t *this, *next; 65251875Speter unsigned int index; 66251875Speter}; 67251875Speter 68251875Speter/* 69251875Speter * The size of the array is always a power of two. We use the maximum 70251875Speter * index rather than the size so that we can use bitwise-AND for 71251875Speter * modular arithmetic. 72251875Speter * The count of hash entries may be greater depending on the chosen 73251875Speter * collision rate. 74251875Speter */ 75251875Speterstruct apr_hash_t { 76251875Speter apr_pool_t *pool; 77251875Speter apr_hash_entry_t **array; 78251875Speter apr_hash_index_t iterator; /* For apr_hash_first(NULL, ...) */ 79251875Speter unsigned int count, max, seed; 80251875Speter apr_hashfunc_t hash_func; 81251875Speter apr_hash_entry_t *free; /* List of recycled entries */ 82251875Speter}; 83251875Speter 84251875Speter#define INITIAL_MAX 15 /* tunable == 2^n - 1 */ 85251875Speter 86251875Speter 87251875Speter/* 88251875Speter * Hash creation functions. 89251875Speter */ 90251875Speter 91251875Speterstatic apr_hash_entry_t **alloc_array(apr_hash_t *ht, unsigned int max) 92251875Speter{ 93251875Speter return apr_pcalloc(ht->pool, sizeof(*ht->array) * (max + 1)); 94251875Speter} 95251875Speter 96251875SpeterAPR_DECLARE(apr_hash_t *) apr_hash_make(apr_pool_t *pool) 97251875Speter{ 98251875Speter apr_hash_t *ht; 99251875Speter apr_time_t now = apr_time_now(); 100251875Speter 101251875Speter ht = apr_palloc(pool, sizeof(apr_hash_t)); 102251875Speter ht->pool = pool; 103251875Speter ht->free = NULL; 104251875Speter ht->count = 0; 105251875Speter ht->max = INITIAL_MAX; 106251875Speter ht->seed = (unsigned int)((now >> 32) ^ now ^ (apr_uintptr_t)pool ^ 107251875Speter (apr_uintptr_t)ht ^ (apr_uintptr_t)&now) - 1; 108251875Speter ht->array = alloc_array(ht, ht->max); 109251875Speter ht->hash_func = NULL; 110251875Speter 111251875Speter return ht; 112251875Speter} 113251875Speter 114251875SpeterAPR_DECLARE(apr_hash_t *) apr_hash_make_custom(apr_pool_t *pool, 115251875Speter apr_hashfunc_t hash_func) 116251875Speter{ 117251875Speter apr_hash_t *ht = apr_hash_make(pool); 118251875Speter ht->hash_func = hash_func; 119251875Speter return ht; 120251875Speter} 121251875Speter 122251875Speter 123251875Speter/* 124251875Speter * Hash iteration functions. 125251875Speter */ 126251875Speter 127251875SpeterAPR_DECLARE(apr_hash_index_t *) apr_hash_next(apr_hash_index_t *hi) 128251875Speter{ 129251875Speter hi->this = hi->next; 130251875Speter while (!hi->this) { 131251875Speter if (hi->index > hi->ht->max) 132251875Speter return NULL; 133251875Speter 134251875Speter hi->this = hi->ht->array[hi->index++]; 135251875Speter } 136251875Speter hi->next = hi->this->next; 137251875Speter return hi; 138251875Speter} 139251875Speter 140251875SpeterAPR_DECLARE(apr_hash_index_t *) apr_hash_first(apr_pool_t *p, apr_hash_t *ht) 141251875Speter{ 142251875Speter apr_hash_index_t *hi; 143251875Speter if (p) 144251875Speter hi = apr_palloc(p, sizeof(*hi)); 145251875Speter else 146251875Speter hi = &ht->iterator; 147251875Speter 148251875Speter hi->ht = ht; 149251875Speter hi->index = 0; 150251875Speter hi->this = NULL; 151251875Speter hi->next = NULL; 152251875Speter return apr_hash_next(hi); 153251875Speter} 154251875Speter 155251875SpeterAPR_DECLARE(void) apr_hash_this(apr_hash_index_t *hi, 156251875Speter const void **key, 157251875Speter apr_ssize_t *klen, 158251875Speter void **val) 159251875Speter{ 160251875Speter if (key) *key = hi->this->key; 161251875Speter if (klen) *klen = hi->this->klen; 162251875Speter if (val) *val = (void *)hi->this->val; 163251875Speter} 164251875Speter 165269847SpeterAPR_DECLARE(const void *) apr_hash_this_key(apr_hash_index_t *hi) 166269847Speter{ 167269847Speter const void *key; 168251875Speter 169269847Speter apr_hash_this(hi, &key, NULL, NULL); 170269847Speter return key; 171269847Speter} 172269847Speter 173269847SpeterAPR_DECLARE(apr_ssize_t) apr_hash_this_key_len(apr_hash_index_t *hi) 174269847Speter{ 175269847Speter apr_ssize_t klen; 176269847Speter 177269847Speter apr_hash_this(hi, NULL, &klen, NULL); 178269847Speter return klen; 179269847Speter} 180269847Speter 181269847SpeterAPR_DECLARE(void *) apr_hash_this_val(apr_hash_index_t *hi) 182269847Speter{ 183269847Speter void *val; 184269847Speter 185269847Speter apr_hash_this(hi, NULL, NULL, &val); 186269847Speter return val; 187269847Speter} 188269847Speter 189251875Speter/* 190251875Speter * Expanding a hash table 191251875Speter */ 192251875Speter 193251875Speterstatic void expand_array(apr_hash_t *ht) 194251875Speter{ 195251875Speter apr_hash_index_t *hi; 196251875Speter apr_hash_entry_t **new_array; 197251875Speter unsigned int new_max; 198251875Speter 199251875Speter new_max = ht->max * 2 + 1; 200251875Speter new_array = alloc_array(ht, new_max); 201251875Speter for (hi = apr_hash_first(NULL, ht); hi; hi = apr_hash_next(hi)) { 202251875Speter unsigned int i = hi->this->hash & new_max; 203251875Speter hi->this->next = new_array[i]; 204251875Speter new_array[i] = hi->this; 205251875Speter } 206251875Speter ht->array = new_array; 207251875Speter ht->max = new_max; 208251875Speter} 209251875Speter 210251875Speterstatic unsigned int hashfunc_default(const char *char_key, apr_ssize_t *klen, 211251875Speter unsigned int hash) 212251875Speter{ 213251875Speter const unsigned char *key = (const unsigned char *)char_key; 214251875Speter const unsigned char *p; 215251875Speter apr_ssize_t i; 216251875Speter 217251875Speter /* 218251875Speter * This is the popular `times 33' hash algorithm which is used by 219251875Speter * perl and also appears in Berkeley DB. This is one of the best 220251875Speter * known hash functions for strings because it is both computed 221251875Speter * very fast and distributes very well. 222251875Speter * 223251875Speter * The originator may be Dan Bernstein but the code in Berkeley DB 224251875Speter * cites Chris Torek as the source. The best citation I have found 225251875Speter * is "Chris Torek, Hash function for text in C, Usenet message 226251875Speter * <27038@mimsy.umd.edu> in comp.lang.c , October, 1990." in Rich 227251875Speter * Salz's USENIX 1992 paper about INN which can be found at 228251875Speter * <http://citeseer.nj.nec.com/salz92internetnews.html>. 229251875Speter * 230251875Speter * The magic of number 33, i.e. why it works better than many other 231251875Speter * constants, prime or not, has never been adequately explained by 232251875Speter * anyone. So I try an explanation: if one experimentally tests all 233251875Speter * multipliers between 1 and 256 (as I did while writing a low-level 234251875Speter * data structure library some time ago) one detects that even 235251875Speter * numbers are not useable at all. The remaining 128 odd numbers 236251875Speter * (except for the number 1) work more or less all equally well. 237251875Speter * They all distribute in an acceptable way and this way fill a hash 238251875Speter * table with an average percent of approx. 86%. 239251875Speter * 240251875Speter * If one compares the chi^2 values of the variants (see 241251875Speter * Bob Jenkins ``Hashing Frequently Asked Questions'' at 242251875Speter * http://burtleburtle.net/bob/hash/hashfaq.html for a description 243251875Speter * of chi^2), the number 33 not even has the best value. But the 244251875Speter * number 33 and a few other equally good numbers like 17, 31, 63, 245251875Speter * 127 and 129 have nevertheless a great advantage to the remaining 246251875Speter * numbers in the large set of possible multipliers: their multiply 247251875Speter * operation can be replaced by a faster operation based on just one 248251875Speter * shift plus either a single addition or subtraction operation. And 249251875Speter * because a hash function has to both distribute good _and_ has to 250251875Speter * be very fast to compute, those few numbers should be preferred. 251251875Speter * 252251875Speter * -- Ralf S. Engelschall <rse@engelschall.com> 253251875Speter */ 254251875Speter 255251875Speter if (*klen == APR_HASH_KEY_STRING) { 256251875Speter for (p = key; *p; p++) { 257251875Speter hash = hash * 33 + *p; 258251875Speter } 259251875Speter *klen = p - key; 260251875Speter } 261251875Speter else { 262251875Speter for (p = key, i = *klen; i; i--, p++) { 263251875Speter hash = hash * 33 + *p; 264251875Speter } 265251875Speter } 266251875Speter 267251875Speter return hash; 268251875Speter} 269251875Speter 270251875SpeterAPR_DECLARE_NONSTD(unsigned int) apr_hashfunc_default(const char *char_key, 271251875Speter apr_ssize_t *klen) 272251875Speter{ 273251875Speter return hashfunc_default(char_key, klen, 0); 274251875Speter} 275251875Speter 276251875Speter/* 277251875Speter * This is where we keep the details of the hash function and control 278251875Speter * the maximum collision rate. 279251875Speter * 280251875Speter * If val is non-NULL it creates and initializes a new hash entry if 281251875Speter * there isn't already one there; it returns an updatable pointer so 282251875Speter * that hash entries can be removed. 283251875Speter */ 284251875Speter 285251875Speterstatic apr_hash_entry_t **find_entry(apr_hash_t *ht, 286251875Speter const void *key, 287251875Speter apr_ssize_t klen, 288251875Speter const void *val) 289251875Speter{ 290251875Speter apr_hash_entry_t **hep, *he; 291251875Speter unsigned int hash; 292251875Speter 293251875Speter if (ht->hash_func) 294251875Speter hash = ht->hash_func(key, &klen); 295251875Speter else 296251875Speter hash = hashfunc_default(key, &klen, ht->seed); 297251875Speter 298251875Speter /* scan linked list */ 299251875Speter for (hep = &ht->array[hash & ht->max], he = *hep; 300251875Speter he; hep = &he->next, he = *hep) { 301251875Speter if (he->hash == hash 302251875Speter && he->klen == klen 303251875Speter && memcmp(he->key, key, klen) == 0) 304251875Speter break; 305251875Speter } 306251875Speter if (he || !val) 307251875Speter return hep; 308251875Speter 309251875Speter /* add a new entry for non-NULL values */ 310251875Speter if ((he = ht->free) != NULL) 311251875Speter ht->free = he->next; 312251875Speter else 313251875Speter he = apr_palloc(ht->pool, sizeof(*he)); 314251875Speter he->next = NULL; 315251875Speter he->hash = hash; 316251875Speter he->key = key; 317251875Speter he->klen = klen; 318251875Speter he->val = val; 319251875Speter *hep = he; 320251875Speter ht->count++; 321251875Speter return hep; 322251875Speter} 323251875Speter 324251875SpeterAPR_DECLARE(apr_hash_t *) apr_hash_copy(apr_pool_t *pool, 325251875Speter const apr_hash_t *orig) 326251875Speter{ 327251875Speter apr_hash_t *ht; 328251875Speter apr_hash_entry_t *new_vals; 329251875Speter unsigned int i, j; 330251875Speter 331251875Speter ht = apr_palloc(pool, sizeof(apr_hash_t) + 332251875Speter sizeof(*ht->array) * (orig->max + 1) + 333251875Speter sizeof(apr_hash_entry_t) * orig->count); 334251875Speter ht->pool = pool; 335251875Speter ht->free = NULL; 336251875Speter ht->count = orig->count; 337251875Speter ht->max = orig->max; 338251875Speter ht->seed = orig->seed; 339251875Speter ht->hash_func = orig->hash_func; 340251875Speter ht->array = (apr_hash_entry_t **)((char *)ht + sizeof(apr_hash_t)); 341251875Speter 342251875Speter new_vals = (apr_hash_entry_t *)((char *)(ht) + sizeof(apr_hash_t) + 343251875Speter sizeof(*ht->array) * (orig->max + 1)); 344251875Speter j = 0; 345251875Speter for (i = 0; i <= ht->max; i++) { 346251875Speter apr_hash_entry_t **new_entry = &(ht->array[i]); 347251875Speter apr_hash_entry_t *orig_entry = orig->array[i]; 348251875Speter while (orig_entry) { 349251875Speter *new_entry = &new_vals[j++]; 350251875Speter (*new_entry)->hash = orig_entry->hash; 351251875Speter (*new_entry)->key = orig_entry->key; 352251875Speter (*new_entry)->klen = orig_entry->klen; 353251875Speter (*new_entry)->val = orig_entry->val; 354251875Speter new_entry = &((*new_entry)->next); 355251875Speter orig_entry = orig_entry->next; 356251875Speter } 357251875Speter *new_entry = NULL; 358251875Speter } 359251875Speter return ht; 360251875Speter} 361251875Speter 362251875SpeterAPR_DECLARE(void *) apr_hash_get(apr_hash_t *ht, 363251875Speter const void *key, 364251875Speter apr_ssize_t klen) 365251875Speter{ 366251875Speter apr_hash_entry_t *he; 367251875Speter he = *find_entry(ht, key, klen, NULL); 368251875Speter if (he) 369251875Speter return (void *)he->val; 370251875Speter else 371251875Speter return NULL; 372251875Speter} 373251875Speter 374251875SpeterAPR_DECLARE(void) apr_hash_set(apr_hash_t *ht, 375251875Speter const void *key, 376251875Speter apr_ssize_t klen, 377251875Speter const void *val) 378251875Speter{ 379251875Speter apr_hash_entry_t **hep; 380251875Speter hep = find_entry(ht, key, klen, val); 381251875Speter if (*hep) { 382251875Speter if (!val) { 383251875Speter /* delete entry */ 384251875Speter apr_hash_entry_t *old = *hep; 385251875Speter *hep = (*hep)->next; 386251875Speter old->next = ht->free; 387251875Speter ht->free = old; 388251875Speter --ht->count; 389251875Speter } 390251875Speter else { 391251875Speter /* replace entry */ 392251875Speter (*hep)->val = val; 393251875Speter /* check that the collision rate isn't too high */ 394251875Speter if (ht->count > ht->max) { 395251875Speter expand_array(ht); 396251875Speter } 397251875Speter } 398251875Speter } 399251875Speter /* else key not present and val==NULL */ 400251875Speter} 401251875Speter 402251875SpeterAPR_DECLARE(unsigned int) apr_hash_count(apr_hash_t *ht) 403251875Speter{ 404251875Speter return ht->count; 405251875Speter} 406251875Speter 407251875SpeterAPR_DECLARE(void) apr_hash_clear(apr_hash_t *ht) 408251875Speter{ 409251875Speter apr_hash_index_t *hi; 410251875Speter for (hi = apr_hash_first(NULL, ht); hi; hi = apr_hash_next(hi)) 411251875Speter apr_hash_set(ht, hi->this->key, hi->this->klen, NULL); 412251875Speter} 413251875Speter 414251875SpeterAPR_DECLARE(apr_hash_t*) apr_hash_overlay(apr_pool_t *p, 415251875Speter const apr_hash_t *overlay, 416251875Speter const apr_hash_t *base) 417251875Speter{ 418251875Speter return apr_hash_merge(p, overlay, base, NULL, NULL); 419251875Speter} 420251875Speter 421251875SpeterAPR_DECLARE(apr_hash_t *) apr_hash_merge(apr_pool_t *p, 422251875Speter const apr_hash_t *overlay, 423251875Speter const apr_hash_t *base, 424251875Speter void * (*merger)(apr_pool_t *p, 425251875Speter const void *key, 426251875Speter apr_ssize_t klen, 427251875Speter const void *h1_val, 428251875Speter const void *h2_val, 429251875Speter const void *data), 430251875Speter const void *data) 431251875Speter{ 432251875Speter apr_hash_t *res; 433251875Speter apr_hash_entry_t *new_vals = NULL; 434251875Speter apr_hash_entry_t *iter; 435251875Speter apr_hash_entry_t *ent; 436251875Speter unsigned int i, j, k, hash; 437251875Speter 438251875Speter#if APR_POOL_DEBUG 439251875Speter /* we don't copy keys and values, so it's necessary that 440251875Speter * overlay->a.pool and base->a.pool have a life span at least 441251875Speter * as long as p 442251875Speter */ 443251875Speter if (!apr_pool_is_ancestor(overlay->pool, p)) { 444251875Speter fprintf(stderr, 445251875Speter "apr_hash_merge: overlay's pool is not an ancestor of p\n"); 446251875Speter abort(); 447251875Speter } 448251875Speter if (!apr_pool_is_ancestor(base->pool, p)) { 449251875Speter fprintf(stderr, 450251875Speter "apr_hash_merge: base's pool is not an ancestor of p\n"); 451251875Speter abort(); 452251875Speter } 453251875Speter#endif 454251875Speter 455251875Speter res = apr_palloc(p, sizeof(apr_hash_t)); 456251875Speter res->pool = p; 457251875Speter res->free = NULL; 458251875Speter res->hash_func = base->hash_func; 459251875Speter res->count = base->count; 460251875Speter res->max = (overlay->max > base->max) ? overlay->max : base->max; 461251875Speter if (base->count + overlay->count > res->max) { 462251875Speter res->max = res->max * 2 + 1; 463251875Speter } 464251875Speter res->seed = base->seed; 465251875Speter res->array = alloc_array(res, res->max); 466251875Speter if (base->count + overlay->count) { 467251875Speter new_vals = apr_palloc(p, sizeof(apr_hash_entry_t) * 468251875Speter (base->count + overlay->count)); 469251875Speter } 470251875Speter j = 0; 471251875Speter for (k = 0; k <= base->max; k++) { 472251875Speter for (iter = base->array[k]; iter; iter = iter->next) { 473251875Speter i = iter->hash & res->max; 474251875Speter new_vals[j].klen = iter->klen; 475251875Speter new_vals[j].key = iter->key; 476251875Speter new_vals[j].val = iter->val; 477251875Speter new_vals[j].hash = iter->hash; 478251875Speter new_vals[j].next = res->array[i]; 479251875Speter res->array[i] = &new_vals[j]; 480251875Speter j++; 481251875Speter } 482251875Speter } 483251875Speter 484251875Speter for (k = 0; k <= overlay->max; k++) { 485251875Speter for (iter = overlay->array[k]; iter; iter = iter->next) { 486251875Speter if (res->hash_func) 487251875Speter hash = res->hash_func(iter->key, &iter->klen); 488251875Speter else 489251875Speter hash = hashfunc_default(iter->key, &iter->klen, res->seed); 490251875Speter i = hash & res->max; 491251875Speter for (ent = res->array[i]; ent; ent = ent->next) { 492251875Speter if ((ent->klen == iter->klen) && 493251875Speter (memcmp(ent->key, iter->key, iter->klen) == 0)) { 494251875Speter if (merger) { 495251875Speter ent->val = (*merger)(p, iter->key, iter->klen, 496251875Speter iter->val, ent->val, data); 497251875Speter } 498251875Speter else { 499251875Speter ent->val = iter->val; 500251875Speter } 501251875Speter break; 502251875Speter } 503251875Speter } 504251875Speter if (!ent) { 505251875Speter new_vals[j].klen = iter->klen; 506251875Speter new_vals[j].key = iter->key; 507251875Speter new_vals[j].val = iter->val; 508251875Speter new_vals[j].hash = hash; 509251875Speter new_vals[j].next = res->array[i]; 510251875Speter res->array[i] = &new_vals[j]; 511251875Speter res->count++; 512251875Speter j++; 513251875Speter } 514251875Speter } 515251875Speter } 516251875Speter return res; 517251875Speter} 518251875Speter 519251875Speter/* This is basically the following... 520251875Speter * for every element in hash table { 521251875Speter * comp elemeny.key, element.value 522251875Speter * } 523251875Speter * 524251875Speter * Like with apr_table_do, the comp callback is called for each and every 525251875Speter * element of the hash table. 526251875Speter */ 527251875SpeterAPR_DECLARE(int) apr_hash_do(apr_hash_do_callback_fn_t *comp, 528251875Speter void *rec, const apr_hash_t *ht) 529251875Speter{ 530251875Speter apr_hash_index_t hix; 531251875Speter apr_hash_index_t *hi; 532251875Speter int rv, dorv = 1; 533251875Speter 534251875Speter hix.ht = (apr_hash_t *)ht; 535251875Speter hix.index = 0; 536251875Speter hix.this = NULL; 537251875Speter hix.next = NULL; 538251875Speter 539251875Speter if ((hi = apr_hash_next(&hix))) { 540251875Speter /* Scan the entire table */ 541251875Speter do { 542251875Speter rv = (*comp)(rec, hi->this->key, hi->this->klen, hi->this->val); 543251875Speter } while (rv && (hi = apr_hash_next(hi))); 544251875Speter 545251875Speter if (rv == 0) { 546251875Speter dorv = 0; 547251875Speter } 548251875Speter } 549251875Speter return dorv; 550251875Speter} 551251875Speter 552251875SpeterAPR_POOL_IMPLEMENT_ACCESSOR(hash) 553