diff options
author | 2015-11-30 01:45:08 -0500 | |
---|---|---|
committer | 2015-11-30 01:45:08 -0500 | |
commit | e8ec7aa8e38a93f5b034ac74cebce5de23710317 (patch) | |
tree | aa031937bf856c1f8d6ad7877b8d2cb0224da5ef /rubbos/app/httpd-2.0.64/srclib/apr/tables/apr_hash.c | |
parent | cc40af334e619bb549038238507407866f774f8f (diff) |
upload http
JIRA: BOTTLENECK-10
Change-Id: I7598427ff904df438ce77c2819ee48ac75ffa8da
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/httpd-2.0.64/srclib/apr/tables/apr_hash.c')
-rw-r--r-- | rubbos/app/httpd-2.0.64/srclib/apr/tables/apr_hash.c | 443 |
1 files changed, 443 insertions, 0 deletions
diff --git a/rubbos/app/httpd-2.0.64/srclib/apr/tables/apr_hash.c b/rubbos/app/httpd-2.0.64/srclib/apr/tables/apr_hash.c new file mode 100644 index 00000000..abc5008c --- /dev/null +++ b/rubbos/app/httpd-2.0.64/srclib/apr/tables/apr_hash.c @@ -0,0 +1,443 @@ +/* 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_hash.h" + +#if APR_HAVE_STDLIB_H +#include <stdlib.h> +#endif +#if APR_HAVE_STRING_H +#include <string.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; + 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; + ht = apr_palloc(pool, sizeof(apr_hash_t)); + ht->pool = pool; + ht->free = NULL; + ht->count = 0; + ht->max = INITIAL_MAX; + ht->array = alloc_array(ht, ht->max); + 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; +} + + +/* + * 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; +} + +/* + * 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; + const unsigned char *p; + unsigned int hash; + 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> + */ + hash = 0; + if (klen == APR_HASH_KEY_STRING) { + for (p = key; *p; p++) { + hash = hash * 33 + *p; + } + klen = p - (const unsigned char *)key; + } + else { + for (p = key, i = klen; i; i--, p++) { + hash = hash * 33 + *p; + } + } + + /* 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->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(unsigned int) apr_hash_count(apr_hash_t *ht) +{ + return ht->count; +} + +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; + +#ifdef 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_overlay: overlay's pool is not an ancestor of p\n"); + abort(); + } + if (!apr_pool_is_ancestor(base->pool, p)) { + fprintf(stderr, + "apr_hash_overlay: 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->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->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) { + i = iter->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 = iter->hash; + new_vals[j].next = res->array[i]; + res->array[i] = &new_vals[j]; + res->count++; + j++; + } + } + } + return res; +} + +APR_POOL_IMPLEMENT_ACCESSOR(hash) |