diff options
Diffstat (limited to 'p11-kit/hash.c')
| -rw-r--r-- | p11-kit/hash.c | 452 |
1 files changed, 452 insertions, 0 deletions
diff --git a/p11-kit/hash.c b/p11-kit/hash.c new file mode 100644 index 0000000..836e717 --- /dev/null +++ b/p11-kit/hash.c @@ -0,0 +1,452 @@ +/* + * Copyright (c) 2004, Stefan Walter + * Copyright (c) 2011, Collabora Ltd. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * * Redistributions of source code must retain the above + * copyright notice, this list of conditions and the + * following disclaimer. + * * Redistributions in binary form must reproduce the + * above copyright notice, this list of conditions and + * the following disclaimer in the documentation and/or + * other materials provided with the distribution. + * * The names of contributors to this software may not be + * used to endorse or promote products derived from this + * software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF + * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH + * DAMAGE. + */ + +/* + * Originally from apache 2.0 + * Modifications for general use by <stef@memberwebs.com> + */ + +/* Copyright 2000-2004 The Apache Software Foundation + * + * Licensed 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 <sys/types.h> + +#include <assert.h> +#include <stdlib.h> +#include <string.h> + +#include "hash.h" + +/* + * 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 hash_entry hash_entry_t; + +struct hash_entry +{ + hash_entry_t* next; + unsigned int hash; + void* key; + void* val; +}; + +/* + * 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 hash { + hash_entry_t** array; + unsigned int count; + unsigned int max; + hash_hash_func hash_func; + hash_equal_func equal_func; + hash_destroy_func key_destroy_func; + hash_destroy_func value_destroy_func; +}; + +#define INITIAL_MAX 15 /* tunable == 2^n - 1 */ +#define int_malloc malloc +#define int_calloc calloc +#define int_free free + +/* + * Hash creation functions. + */ + +static hash_entry_t** +alloc_array(hash_t* ht, unsigned int max) +{ + return (hash_entry_t**)int_calloc (sizeof (*(ht->array)), (max + 1)); +} + +hash_t* +hash_create (hash_hash_func hash_func, + hash_equal_func equal_func, + hash_destroy_func key_destroy_func, + hash_destroy_func value_destroy_func) +{ + hash_t* ht; + + assert (hash_func); + assert (equal_func); + + ht = int_malloc (sizeof (hash_t)); + if (ht) { + ht->count = 0; + ht->max = INITIAL_MAX; + ht->hash_func = hash_func; + ht->equal_func = equal_func; + ht->key_destroy_func = key_destroy_func; + ht->value_destroy_func = value_destroy_func; + ht->array = alloc_array (ht, ht->max); + if (!ht->array) { + int_free (ht); + return NULL; + } + } + return ht; +} + +void +hash_free (hash_t* ht) +{ + hash_iter_t hi; + + if (!ht) + return; + + hash_iterate (ht, &hi); + while (hash_next (&hi, NULL, NULL)) { + if (ht->key_destroy_func) + ht->key_destroy_func (hi.ths->key); + if (ht->value_destroy_func) + ht->value_destroy_func (hi.ths->val); + } + + if (ht->array) + int_free (ht->array); + + int_free (ht); +} + +/* + * Hash iteration functions. + */ +int +hash_next (hash_iter_t* hi, void **key, void **value) +{ + hi->ths = hi->next; + while (!hi->ths) { + if (hi->index > hi->ht->max) + return 0; + hi->ths = hi->ht->array[hi->index++]; + } + hi->next = hi->ths->next; + if (key) + *key = hi->ths->key; + if (value) + *value = hi->ths->val; + return 1; +} + +void +hash_iterate (hash_t* ht, hash_iter_t *hi) +{ + hi->ht = ht; + hi->index = 0; + hi->ths = NULL; + hi->next = NULL; +} + +/* + * Expanding a hash table + */ + +static int +expand_array (hash_t* ht) +{ + hash_iter_t hi; + hash_entry_t** new_array; + unsigned int new_max; + + new_max = ht->max * 2 + 1; + new_array = alloc_array (ht, new_max); + + if(!new_array) + return 0; + + hash_iterate (ht, &hi); + while (hash_next (&hi, NULL, NULL)) { + unsigned int i = hi.ths->hash & new_max; + hi.ths->next = new_array[i]; + new_array[i] = hi.ths; + } + + if(ht->array) + int_free (ht->array); + + ht->array = new_array; + ht->max = new_max; + return 1; +} + +/* + * 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 hash_entry_t** +find_entry (hash_t* ht, const void* key, void* val) +{ + hash_entry_t** hep; + hash_entry_t* he; + unsigned int hash; + + /* Perform the hashing */ + hash = ht->hash_func (key); + + /* scan linked list */ + for (hep = &ht->array[hash & ht->max], he = *hep; + he; hep = &he->next, he = *hep) { + if(he->hash == hash && ht->equal_func (he->key, key)) + break; + } + + if(he || !val) + return hep; + + /* add a new entry for non-NULL val */ + he = int_malloc (sizeof (*he)); + + if(he) { + he->key = (void*)key; + he->next = NULL; + he->hash = hash; + he->val = val; + + *hep = he; + ht->count++; + } + + return hep; +} + +void* +hash_get (hash_t* ht, const void *key) +{ + hash_entry_t** he = find_entry (ht, key, NULL); + if (he && *he) + return (void*)((*he)->val); + else + return NULL; +} + +int +hash_set (hash_t* ht, void* key, void* val) +{ + hash_entry_t** hep = find_entry (ht, key, val); + if(hep && *hep) { + /* replace entry */ + (*hep)->val = val; + + /* check that the collision rate isn't too high */ + if (ht->count > ht->max) { + if (!expand_array (ht)) + return 0; + } + + return 1; + } + + return 0; +} + +int +hash_remove (hash_t* ht, const void* key) +{ + hash_entry_t** hep = find_entry (ht, key, NULL); + + if (hep && *hep) { + hash_entry_t* old = *hep; + *hep = (*hep)->next; + --ht->count; + if (ht->key_destroy_func) + ht->key_destroy_func (old->key); + if (ht->value_destroy_func) + ht->value_destroy_func (old->val); + free (old); + return 1; + } + + return 0; +} + +void +hash_clear (hash_t* ht) +{ + hash_entry_t *he, *next; + int i; + + /* Free all entries in the array */ + for (i = 0; i < ht->max; ++i) { + he = ht->array[i]; + while (he) { + next = he->next; + if (ht->key_destroy_func) + ht->key_destroy_func (he->key); + if (ht->value_destroy_func) + ht->value_destroy_func (he->val); + free (he); + he = next; + } + } + + memset (ht->array, 0, ht->max * sizeof (hash_entry_t*)); + ht->count = 0; +} + +unsigned int +hash_count (hash_t* ht) +{ + return ht->count; +} + +unsigned int +hash_string_hash (const void *string) +{ + unsigned int hash; + const unsigned char *p; + + assert (string); + + /* + * 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; + + for(p = string; *p; p++) + hash = hash * 33 + *p; + + return hash; +} + +int +hash_string_equal (const void *string_one, const void *string_two) +{ + assert (string_one); + assert (string_two); + + return strcmp (string_one, string_two) == 0; +} + +unsigned int +hash_ulongptr_hash (const void *to_ulong) +{ + assert (to_ulong); + return (unsigned int)*((unsigned long*)to_ulong); +} + +int +hash_ulongptr_equal (const void *ulong_one, const void *ulong_two) +{ + assert (ulong_one); + assert (ulong_two); + return *((unsigned long*)ulong_one) == *((unsigned long*)ulong_two); +} + +unsigned int +hash_intptr_hash (const void *to_int) +{ + assert (to_int); + return (unsigned int)*((unsigned long*)to_int); +} + +int +hash_intptr_equal (const void *int_one, const void *int_two) +{ + assert (int_one); + assert (int_two); + return *((unsigned long*)int_one) == *((unsigned long*)int_two); +} + +unsigned int +hash_direct_hash (const void *ptr) +{ + return (unsigned int)ptr; +} + +int +hash_direct_equal (const void *ptr_one, const void *ptr_two) +{ + return ptr_one == ptr_two; +} |