| /* Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "apr_private.h" |
| |
| #include "apr_general.h" |
| #include "apr_pools.h" |
| #include "apr_time.h" |
| |
| #include "apr_hash.h" |
| |
| #if APR_HAVE_STDLIB_H |
| #include <stdlib.h> |
| #endif |
| #if APR_HAVE_STRING_H |
| #include <string.h> |
| #endif |
| |
| #if APR_POOL_DEBUG && APR_HAVE_STDIO_H |
| #include <stdio.h> |
| #endif |
| |
| /* |
| * The internal form of a hash table. |
| * |
| * The table is an array indexed by the hash of the key; collisions |
| * are resolved by hanging a linked list of hash entries off each |
| * element of the array. Although this is a really simple design it |
| * isn't too bad given that pools have a low allocation overhead. |
| */ |
| |
| typedef struct apr_hash_entry_t apr_hash_entry_t; |
| |
| struct apr_hash_entry_t { |
| apr_hash_entry_t *next; |
| unsigned int hash; |
| const void *key; |
| apr_ssize_t klen; |
| const void *val; |
| }; |
| |
| /* |
| * Data structure for iterating through a hash table. |
| * |
| * We keep a pointer to the next hash entry here to allow the current |
| * hash entry to be freed or otherwise mangled between calls to |
| * apr_hash_next(). |
| */ |
| struct apr_hash_index_t { |
| apr_hash_t *ht; |
| apr_hash_entry_t *this, *next; |
| unsigned int index; |
| }; |
| |
| /* |
| * The size of the array is always a power of two. We use the maximum |
| * index rather than the size so that we can use bitwise-AND for |
| * modular arithmetic. |
| * The count of hash entries may be greater depending on the chosen |
| * collision rate. |
| */ |
| struct apr_hash_t { |
| apr_pool_t *pool; |
| apr_hash_entry_t **array; |
| apr_hash_index_t iterator; /* For apr_hash_first(NULL, ...) */ |
| unsigned int count, max, seed; |
| apr_hashfunc_t hash_func; |
| apr_hash_entry_t *free; /* List of recycled entries */ |
| }; |
| |
| #define INITIAL_MAX 15 /* tunable == 2^n - 1 */ |
| |
| |
| /* |
| * Hash creation functions. |
| */ |
| |
| static apr_hash_entry_t **alloc_array(apr_hash_t *ht, unsigned int max) |
| { |
| return apr_pcalloc(ht->pool, sizeof(*ht->array) * (max + 1)); |
| } |
| |
| APR_DECLARE(apr_hash_t *) apr_hash_make(apr_pool_t *pool) |
| { |
| apr_hash_t *ht; |
| apr_time_t now = apr_time_now(); |
| |
| ht = apr_palloc(pool, sizeof(apr_hash_t)); |
| ht->pool = pool; |
| ht->free = NULL; |
| ht->count = 0; |
| ht->max = INITIAL_MAX; |
| ht->seed = (unsigned int)((now >> 32) ^ now ^ (apr_uintptr_t)pool ^ |
| (apr_uintptr_t)ht ^ (apr_uintptr_t)&now) - 1; |
| ht->array = alloc_array(ht, ht->max); |
| ht->hash_func = NULL; |
| |
| return ht; |
| } |
| |
| APR_DECLARE(apr_hash_t *) apr_hash_make_custom(apr_pool_t *pool, |
| apr_hashfunc_t hash_func) |
| { |
| apr_hash_t *ht = apr_hash_make(pool); |
| ht->hash_func = hash_func; |
| return ht; |
| } |
| |
| |
| /* |
| * Hash iteration functions. |
| */ |
| |
| APR_DECLARE(apr_hash_index_t *) apr_hash_next(apr_hash_index_t *hi) |
| { |
| hi->this = hi->next; |
| while (!hi->this) { |
| if (hi->index > hi->ht->max) |
| return NULL; |
| |
| hi->this = hi->ht->array[hi->index++]; |
| } |
| hi->next = hi->this->next; |
| return hi; |
| } |
| |
| APR_DECLARE(apr_hash_index_t *) apr_hash_first(apr_pool_t *p, apr_hash_t *ht) |
| { |
| apr_hash_index_t *hi; |
| if (p) |
| hi = apr_palloc(p, sizeof(*hi)); |
| else |
| hi = &ht->iterator; |
| |
| hi->ht = ht; |
| hi->index = 0; |
| hi->this = NULL; |
| hi->next = NULL; |
| return apr_hash_next(hi); |
| } |
| |
| APR_DECLARE(void) apr_hash_this(apr_hash_index_t *hi, |
| const void **key, |
| apr_ssize_t *klen, |
| void **val) |
| { |
| if (key) *key = hi->this->key; |
| if (klen) *klen = hi->this->klen; |
| if (val) *val = (void *)hi->this->val; |
| } |
| |
| APR_DECLARE(const void *) apr_hash_this_key(apr_hash_index_t *hi) |
| { |
| const void *key; |
| |
| apr_hash_this(hi, &key, NULL, NULL); |
| return key; |
| } |
| |
| APR_DECLARE(apr_ssize_t) apr_hash_this_key_len(apr_hash_index_t *hi) |
| { |
| apr_ssize_t klen; |
| |
| apr_hash_this(hi, NULL, &klen, NULL); |
| return klen; |
| } |
| |
| APR_DECLARE(void *) apr_hash_this_val(apr_hash_index_t *hi) |
| { |
| void *val; |
| |
| apr_hash_this(hi, NULL, NULL, &val); |
| return val; |
| } |
| |
| /* |
| * Expanding a hash table |
| */ |
| |
| static void expand_array(apr_hash_t *ht) |
| { |
| apr_hash_index_t *hi; |
| apr_hash_entry_t **new_array; |
| unsigned int new_max; |
| |
| new_max = ht->max * 2 + 1; |
| new_array = alloc_array(ht, new_max); |
| for (hi = apr_hash_first(NULL, ht); hi; hi = apr_hash_next(hi)) { |
| unsigned int i = hi->this->hash & new_max; |
| hi->this->next = new_array[i]; |
| new_array[i] = hi->this; |
| } |
| ht->array = new_array; |
| ht->max = new_max; |
| } |
| |
| static unsigned int hashfunc_default(const char *char_key, apr_ssize_t *klen, |
| unsigned int hash) |
| { |
| const unsigned char *key = (const unsigned char *)char_key; |
| const unsigned char *p; |
| apr_ssize_t i; |
| |
| /* |
| * This is the popular `times 33' hash algorithm which is used by |
| * perl and also appears in Berkeley DB. This is one of the best |
| * known hash functions for strings because it is both computed |
| * very fast and distributes very well. |
| * |
| * The originator may be Dan Bernstein but the code in Berkeley DB |
| * cites Chris Torek as the source. The best citation I have found |
| * is "Chris Torek, Hash function for text in C, Usenet message |
| * <27038@mimsy.umd.edu> in comp.lang.c , October, 1990." in Rich |
| * Salz's USENIX 1992 paper about INN which can be found at |
| * <http://citeseer.nj.nec.com/salz92internetnews.html>. |
| * |
| * The magic of number 33, i.e. why it works better than many other |
| * constants, prime or not, has never been adequately explained by |
| * anyone. So I try an explanation: if one experimentally tests all |
| * multipliers between 1 and 256 (as I did while writing a low-level |
| * data structure library some time ago) one detects that even |
| * numbers are not useable at all. The remaining 128 odd numbers |
| * (except for the number 1) work more or less all equally well. |
| * They all distribute in an acceptable way and this way fill a hash |
| * table with an average percent of approx. 86%. |
| * |
| * If one compares the chi^2 values of the variants (see |
| * Bob Jenkins ``Hashing Frequently Asked Questions'' at |
| * http://burtleburtle.net/bob/hash/hashfaq.html for a description |
| * of chi^2), the number 33 not even has the best value. But the |
| * number 33 and a few other equally good numbers like 17, 31, 63, |
| * 127 and 129 have nevertheless a great advantage to the remaining |
| * numbers in the large set of possible multipliers: their multiply |
| * operation can be replaced by a faster operation based on just one |
| * shift plus either a single addition or subtraction operation. And |
| * because a hash function has to both distribute good _and_ has to |
| * be very fast to compute, those few numbers should be preferred. |
| * |
| * -- Ralf S. Engelschall <rse@engelschall.com> |
| */ |
| |
| if (*klen == APR_HASH_KEY_STRING) { |
| for (p = key; *p; p++) { |
| hash = hash * 33 + *p; |
| } |
| *klen = p - key; |
| } |
| else { |
| for (p = key, i = *klen; i; i--, p++) { |
| hash = hash * 33 + *p; |
| } |
| } |
| |
| return hash; |
| } |
| |
| APR_DECLARE_NONSTD(unsigned int) apr_hashfunc_default(const char *char_key, |
| apr_ssize_t *klen) |
| { |
| return hashfunc_default(char_key, klen, 0); |
| } |
| |
| /* |
| * This is where we keep the details of the hash function and control |
| * the maximum collision rate. |
| * |
| * If val is non-NULL it creates and initializes a new hash entry if |
| * there isn't already one there; it returns an updatable pointer so |
| * that hash entries can be removed. |
| */ |
| |
| static apr_hash_entry_t **find_entry(apr_hash_t *ht, |
| const void *key, |
| apr_ssize_t klen, |
| const void *val) |
| { |
| apr_hash_entry_t **hep, *he; |
| unsigned int hash; |
| |
| if (ht->hash_func) |
| hash = ht->hash_func(key, &klen); |
| else |
| hash = hashfunc_default(key, &klen, ht->seed); |
| |
| /* scan linked list */ |
| for (hep = &ht->array[hash & ht->max], he = *hep; |
| he; hep = &he->next, he = *hep) { |
| if (he->hash == hash |
| && he->klen == klen |
| && memcmp(he->key, key, klen) == 0) |
| break; |
| } |
| if (he || !val) |
| return hep; |
| |
| /* add a new entry for non-NULL values */ |
| if ((he = ht->free) != NULL) |
| ht->free = he->next; |
| else |
| he = apr_palloc(ht->pool, sizeof(*he)); |
| he->next = NULL; |
| he->hash = hash; |
| he->key = key; |
| he->klen = klen; |
| he->val = val; |
| *hep = he; |
| ht->count++; |
| return hep; |
| } |
| |
| APR_DECLARE(apr_hash_t *) apr_hash_copy(apr_pool_t *pool, |
| const apr_hash_t *orig) |
| { |
| apr_hash_t *ht; |
| apr_hash_entry_t *new_vals; |
| unsigned int i, j; |
| |
| ht = apr_palloc(pool, sizeof(apr_hash_t) + |
| sizeof(*ht->array) * (orig->max + 1) + |
| sizeof(apr_hash_entry_t) * orig->count); |
| ht->pool = pool; |
| ht->free = NULL; |
| ht->count = orig->count; |
| ht->max = orig->max; |
| ht->seed = orig->seed; |
| ht->hash_func = orig->hash_func; |
| ht->array = (apr_hash_entry_t **)((char *)ht + sizeof(apr_hash_t)); |
| |
| new_vals = (apr_hash_entry_t *)((char *)(ht) + sizeof(apr_hash_t) + |
| sizeof(*ht->array) * (orig->max + 1)); |
| j = 0; |
| for (i = 0; i <= ht->max; i++) { |
| apr_hash_entry_t **new_entry = &(ht->array[i]); |
| apr_hash_entry_t *orig_entry = orig->array[i]; |
| while (orig_entry) { |
| *new_entry = &new_vals[j++]; |
| (*new_entry)->hash = orig_entry->hash; |
| (*new_entry)->key = orig_entry->key; |
| (*new_entry)->klen = orig_entry->klen; |
| (*new_entry)->val = orig_entry->val; |
| new_entry = &((*new_entry)->next); |
| orig_entry = orig_entry->next; |
| } |
| *new_entry = NULL; |
| } |
| return ht; |
| } |
| |
| APR_DECLARE(void *) apr_hash_get(apr_hash_t *ht, |
| const void *key, |
| apr_ssize_t klen) |
| { |
| apr_hash_entry_t *he; |
| he = *find_entry(ht, key, klen, NULL); |
| if (he) |
| return (void *)he->val; |
| else |
| return NULL; |
| } |
| |
| APR_DECLARE(void) apr_hash_set(apr_hash_t *ht, |
| const void *key, |
| apr_ssize_t klen, |
| const void *val) |
| { |
| apr_hash_entry_t **hep; |
| hep = find_entry(ht, key, klen, val); |
| if (*hep) { |
| if (!val) { |
| /* delete entry */ |
| apr_hash_entry_t *old = *hep; |
| *hep = (*hep)->next; |
| old->next = ht->free; |
| ht->free = old; |
| --ht->count; |
| } |
| else { |
| /* replace entry */ |
| (*hep)->val = val; |
| /* check that the collision rate isn't too high */ |
| if (ht->count > ht->max) { |
| expand_array(ht); |
| } |
| } |
| } |
| /* else key not present and val==NULL */ |
| } |
| |
| APR_DECLARE(void *) apr_hash_get_or_set(apr_hash_t *ht, |
| const void *key, |
| apr_ssize_t klen, |
| const void *val) |
| { |
| apr_hash_entry_t **hep; |
| hep = find_entry(ht, key, klen, val); |
| if (*hep) { |
| val = (*hep)->val; |
| /* check that the collision rate isn't too high */ |
| if (ht->count > ht->max) { |
| expand_array(ht); |
| } |
| return (void *)val; |
| } |
| /* else key not present and val==NULL */ |
| return NULL; |
| } |
| |
| APR_DECLARE(unsigned int) apr_hash_count(apr_hash_t *ht) |
| { |
| return ht->count; |
| } |
| |
| APR_DECLARE(void) apr_hash_clear(apr_hash_t *ht) |
| { |
| apr_hash_index_t *hi; |
| for (hi = apr_hash_first(NULL, ht); hi; hi = apr_hash_next(hi)) |
| apr_hash_set(ht, hi->this->key, hi->this->klen, NULL); |
| } |
| |
| APR_DECLARE(apr_hash_t*) apr_hash_overlay(apr_pool_t *p, |
| const apr_hash_t *overlay, |
| const apr_hash_t *base) |
| { |
| return apr_hash_merge(p, overlay, base, NULL, NULL); |
| } |
| |
| APR_DECLARE(apr_hash_t *) apr_hash_merge(apr_pool_t *p, |
| const apr_hash_t *overlay, |
| const apr_hash_t *base, |
| void * (*merger)(apr_pool_t *p, |
| const void *key, |
| apr_ssize_t klen, |
| const void *h1_val, |
| const void *h2_val, |
| const void *data), |
| const void *data) |
| { |
| apr_hash_t *res; |
| apr_hash_entry_t *new_vals = NULL; |
| apr_hash_entry_t *iter; |
| apr_hash_entry_t *ent; |
| unsigned int i, j, k, hash; |
| |
| #if APR_POOL_DEBUG |
| /* we don't copy keys and values, so it's necessary that |
| * overlay->a.pool and base->a.pool have a life span at least |
| * as long as p |
| */ |
| if (!apr_pool_is_ancestor(overlay->pool, p)) { |
| fprintf(stderr, |
| "apr_hash_merge: overlay's pool is not an ancestor of p\n"); |
| abort(); |
| } |
| if (!apr_pool_is_ancestor(base->pool, p)) { |
| fprintf(stderr, |
| "apr_hash_merge: base's pool is not an ancestor of p\n"); |
| abort(); |
| } |
| #endif |
| |
| res = apr_palloc(p, sizeof(apr_hash_t)); |
| res->pool = p; |
| res->free = NULL; |
| res->hash_func = base->hash_func; |
| res->count = base->count; |
| res->max = (overlay->max > base->max) ? overlay->max : base->max; |
| if (base->count + overlay->count > res->max) { |
| res->max = res->max * 2 + 1; |
| } |
| res->seed = base->seed; |
| res->array = alloc_array(res, res->max); |
| if (base->count + overlay->count) { |
| new_vals = apr_palloc(p, sizeof(apr_hash_entry_t) * |
| (base->count + overlay->count)); |
| } |
| j = 0; |
| for (k = 0; k <= base->max; k++) { |
| for (iter = base->array[k]; iter; iter = iter->next) { |
| i = iter->hash & res->max; |
| new_vals[j].klen = iter->klen; |
| new_vals[j].key = iter->key; |
| new_vals[j].val = iter->val; |
| new_vals[j].hash = iter->hash; |
| new_vals[j].next = res->array[i]; |
| res->array[i] = &new_vals[j]; |
| j++; |
| } |
| } |
| |
| for (k = 0; k <= overlay->max; k++) { |
| for (iter = overlay->array[k]; iter; iter = iter->next) { |
| if (res->hash_func) |
| hash = res->hash_func(iter->key, &iter->klen); |
| else |
| hash = hashfunc_default(iter->key, &iter->klen, res->seed); |
| i = hash & res->max; |
| for (ent = res->array[i]; ent; ent = ent->next) { |
| if ((ent->klen == iter->klen) && |
| (memcmp(ent->key, iter->key, iter->klen) == 0)) { |
| if (merger) { |
| ent->val = (*merger)(p, iter->key, iter->klen, |
| iter->val, ent->val, data); |
| } |
| else { |
| ent->val = iter->val; |
| } |
| break; |
| } |
| } |
| if (!ent) { |
| new_vals[j].klen = iter->klen; |
| new_vals[j].key = iter->key; |
| new_vals[j].val = iter->val; |
| new_vals[j].hash = hash; |
| new_vals[j].next = res->array[i]; |
| res->array[i] = &new_vals[j]; |
| res->count++; |
| j++; |
| } |
| } |
| } |
| return res; |
| } |
| |
| /* This is basically the following... |
| * for every element in hash table { |
| * comp elemeny.key, element.value |
| * } |
| * |
| * Like with apr_table_do, the comp callback is called for each and every |
| * element of the hash table. |
| */ |
| APR_DECLARE(int) apr_hash_do(apr_hash_do_callback_fn_t *comp, |
| void *rec, const apr_hash_t *ht) |
| { |
| apr_hash_index_t hix; |
| apr_hash_index_t *hi; |
| int rv, dorv = 1; |
| |
| hix.ht = (apr_hash_t *)ht; |
| hix.index = 0; |
| hix.this = NULL; |
| hix.next = NULL; |
| |
| if ((hi = apr_hash_next(&hix))) { |
| /* Scan the entire table */ |
| do { |
| rv = (*comp)(rec, hi->this->key, hi->this->klen, hi->this->val); |
| } while (rv && (hi = apr_hash_next(hi))); |
| |
| if (rv == 0) { |
| dorv = 0; |
| } |
| } |
| return dorv; |
| } |
| |
| APR_POOL_IMPLEMENT_ACCESSOR(hash) |