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-rw-r--r--contrib/apr/tables/apr_hash.c529
1 files changed, 529 insertions, 0 deletions
diff --git a/contrib/apr/tables/apr_hash.c b/contrib/apr/tables/apr_hash.c
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+/* 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;
+}
+
+
+/*
+ * 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(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)
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-27 00:37:23 +0000