diff options
author | Stef Walter <stefw@collabora.co.uk> | 2011-03-31 12:41:43 +0200 |
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committer | Stef Walter <stefw@collabora.co.uk> | 2011-03-31 12:41:43 +0200 |
commit | 479cbd55ee5739d3cd2566379575451dbecf4c54 (patch) | |
tree | ec6730dfbd1855dc6193fe2b5df2d09e208200a3 /module/hash.c | |
parent | 6132cd99c39739ef5360e41e92f22d287007577e (diff) |
Documentation and API cleanup.
* Rename source directory
* More consistent with return values from URI functions.
* Allow formatting URI to take a uri type.
Diffstat (limited to 'module/hash.c')
-rw-r--r-- | module/hash.c | 453 |
1 files changed, 0 insertions, 453 deletions
diff --git a/module/hash.c b/module/hash.c deleted file mode 100644 index 30efced..0000000 --- a/module/hash.c +++ /dev/null @@ -1,453 +0,0 @@ -/* - * 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; -} - |