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e2f6ee2 Oct 27, 2015
charsyam fixing typos
339 lines (293 sloc) 10.3 KB
/* Hash table implementation.
*
* This file implements in memory hash tables with insert/del/replace/find/
* get-random-element operations. Hash tables will auto resize if needed
* tables of power of two in size are used, collisions are handled by
* chaining. See the source code for more information... :)
*
* Copyright (c) 2006-2010, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* 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.
* * Neither the name of Redis nor the names of its contributors may 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.
*/
#include "fmacros.h"
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include "dict.h"
/* -------------------------- private prototypes ---------------------------- */
static int _dictExpandIfNeeded(dict *ht);
static unsigned long _dictNextPower(unsigned long size);
static int _dictKeyIndex(dict *ht, const void *key);
static int _dictInit(dict *ht, dictType *type, void *privDataPtr);
/* -------------------------- hash functions -------------------------------- */
/* Generic hash function (a popular one from Bernstein).
* I tested a few and this was the best. */
static unsigned int dictGenHashFunction(const unsigned char *buf, int len) {
unsigned int hash = 5381;
while (len--)
hash = ((hash << 5) + hash) + (*buf++); /* hash * 33 + c */
return hash;
}
/* ----------------------------- API implementation ------------------------- */
/* Reset an hashtable already initialized with ht_init().
* NOTE: This function should only called by ht_destroy(). */
static void _dictReset(dict *ht) {
ht->table = NULL;
ht->size = 0;
ht->sizemask = 0;
ht->used = 0;
}
/* Create a new hash table */
static dict *dictCreate(dictType *type, void *privDataPtr) {
dict *ht = malloc(sizeof(*ht));
_dictInit(ht,type,privDataPtr);
return ht;
}
/* Initialize the hash table */
static int _dictInit(dict *ht, dictType *type, void *privDataPtr) {
_dictReset(ht);
ht->type = type;
ht->privdata = privDataPtr;
return DICT_OK;
}
/* Expand or create the hashtable */
static int dictExpand(dict *ht, unsigned long size) {
dict n; /* the new hashtable */
unsigned long realsize = _dictNextPower(size), i;
/* the size is invalid if it is smaller than the number of
* elements already inside the hashtable */
if (ht->used > size)
return DICT_ERR;
_dictInit(&n, ht->type, ht->privdata);
n.size = realsize;
n.sizemask = realsize-1;
n.table = calloc(realsize,sizeof(dictEntry*));
/* Copy all the elements from the old to the new table:
* note that if the old hash table is empty ht->size is zero,
* so dictExpand just creates an hash table. */
n.used = ht->used;
for (i = 0; i < ht->size && ht->used > 0; i++) {
dictEntry *he, *nextHe;
if (ht->table[i] == NULL) continue;
/* For each hash entry on this slot... */
he = ht->table[i];
while(he) {
unsigned int h;
nextHe = he->next;
/* Get the new element index */
h = dictHashKey(ht, he->key) & n.sizemask;
he->next = n.table[h];
n.table[h] = he;
ht->used--;
/* Pass to the next element */
he = nextHe;
}
}
assert(ht->used == 0);
free(ht->table);
/* Remap the new hashtable in the old */
*ht = n;
return DICT_OK;
}
/* Add an element to the target hash table */
static int dictAdd(dict *ht, void *key, void *val) {
int index;
dictEntry *entry;
/* Get the index of the new element, or -1 if
* the element already exists. */
if ((index = _dictKeyIndex(ht, key)) == -1)
return DICT_ERR;
/* Allocates the memory and stores key */
entry = malloc(sizeof(*entry));
entry->next = ht->table[index];
ht->table[index] = entry;
/* Set the hash entry fields. */
dictSetHashKey(ht, entry, key);
dictSetHashVal(ht, entry, val);
ht->used++;
return DICT_OK;
}
/* Add an element, discarding the old if the key already exists.
* Return 1 if the key was added from scratch, 0 if there was already an
* element with such key and dictReplace() just performed a value update
* operation. */
static int dictReplace(dict *ht, void *key, void *val) {
dictEntry *entry, auxentry;
/* Try to add the element. If the key
* does not exists dictAdd will succeed. */
if (dictAdd(ht, key, val) == DICT_OK)
return 1;
/* It already exists, get the entry */
entry = dictFind(ht, key);
/* Free the old value and set the new one */
/* Set the new value and free the old one. Note that it is important
* to do that in this order, as the value may just be exactly the same
* as the previous one. In this context, think to reference counting,
* you want to increment (set), and then decrement (free), and not the
* reverse. */
auxentry = *entry;
dictSetHashVal(ht, entry, val);
dictFreeEntryVal(ht, &auxentry);
return 0;
}
/* Search and remove an element */
static int dictDelete(dict *ht, const void *key) {
unsigned int h;
dictEntry *de, *prevde;
if (ht->size == 0)
return DICT_ERR;
h = dictHashKey(ht, key) & ht->sizemask;
de = ht->table[h];
prevde = NULL;
while(de) {
if (dictCompareHashKeys(ht,key,de->key)) {
/* Unlink the element from the list */
if (prevde)
prevde->next = de->next;
else
ht->table[h] = de->next;
dictFreeEntryKey(ht,de);
dictFreeEntryVal(ht,de);
free(de);
ht->used--;
return DICT_OK;
}
prevde = de;
de = de->next;
}
return DICT_ERR; /* not found */
}
/* Destroy an entire hash table */
static int _dictClear(dict *ht) {
unsigned long i;
/* Free all the elements */
for (i = 0; i < ht->size && ht->used > 0; i++) {
dictEntry *he, *nextHe;
if ((he = ht->table[i]) == NULL) continue;
while(he) {
nextHe = he->next;
dictFreeEntryKey(ht, he);
dictFreeEntryVal(ht, he);
free(he);
ht->used--;
he = nextHe;
}
}
/* Free the table and the allocated cache structure */
free(ht->table);
/* Re-initialize the table */
_dictReset(ht);
return DICT_OK; /* never fails */
}
/* Clear & Release the hash table */
static void dictRelease(dict *ht) {
_dictClear(ht);
free(ht);
}
static dictEntry *dictFind(dict *ht, const void *key) {
dictEntry *he;
unsigned int h;
if (ht->size == 0) return NULL;
h = dictHashKey(ht, key) & ht->sizemask;
he = ht->table[h];
while(he) {
if (dictCompareHashKeys(ht, key, he->key))
return he;
he = he->next;
}
return NULL;
}
static dictIterator *dictGetIterator(dict *ht) {
dictIterator *iter = malloc(sizeof(*iter));
iter->ht = ht;
iter->index = -1;
iter->entry = NULL;
iter->nextEntry = NULL;
return iter;
}
static dictEntry *dictNext(dictIterator *iter) {
while (1) {
if (iter->entry == NULL) {
iter->index++;
if (iter->index >=
(signed)iter->ht->size) break;
iter->entry = iter->ht->table[iter->index];
} else {
iter->entry = iter->nextEntry;
}
if (iter->entry) {
/* We need to save the 'next' here, the iterator user
* may delete the entry we are returning. */
iter->nextEntry = iter->entry->next;
return iter->entry;
}
}
return NULL;
}
static void dictReleaseIterator(dictIterator *iter) {
free(iter);
}
/* ------------------------- private functions ------------------------------ */
/* Expand the hash table if needed */
static int _dictExpandIfNeeded(dict *ht) {
/* If the hash table is empty expand it to the initial size,
* if the table is "full" dobule its size. */
if (ht->size == 0)
return dictExpand(ht, DICT_HT_INITIAL_SIZE);
if (ht->used == ht->size)
return dictExpand(ht, ht->size*2);
return DICT_OK;
}
/* Our hash table capability is a power of two */
static unsigned long _dictNextPower(unsigned long size) {
unsigned long i = DICT_HT_INITIAL_SIZE;
if (size >= LONG_MAX) return LONG_MAX;
while(1) {
if (i >= size)
return i;
i *= 2;
}
}
/* Returns the index of a free slot that can be populated with
* an hash entry for the given 'key'.
* If the key already exists, -1 is returned. */
static int _dictKeyIndex(dict *ht, const void *key) {
unsigned int h;
dictEntry *he;
/* Expand the hashtable if needed */
if (_dictExpandIfNeeded(ht) == DICT_ERR)
return -1;
/* Compute the key hash value */
h = dictHashKey(ht, key) & ht->sizemask;
/* Search if this slot does not already contain the given key */
he = ht->table[h];
while(he) {
if (dictCompareHashKeys(ht, key, he->key))
return -1;
he = he->next;
}
return h;
}