223706d52f
Remove the struct hash_entry and define a new type for hash values. Most likely we will only need one member in this struct. and instead of just using unsinged int. let's name a new type for clarity.
138 lines
2.8 KiB
C
138 lines
2.8 KiB
C
/* hash.c
|
|
*
|
|
* Copyright (C) 2011-2012 Henrik Hautakoski <henrik@fiktivkod.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
|
|
* MA 02110-1301, USA.
|
|
*/
|
|
|
|
#include "hash.h"
|
|
#include <stdlib.h>
|
|
|
|
#define TABLE_MIN_SIZE 128
|
|
|
|
hash_t hash_sdbm(const char *s) {
|
|
|
|
hash_t h;
|
|
|
|
for(h = 0; *s; s++)
|
|
h = ((hash_t)*s) + (h << 6) + (h << 16) - h;
|
|
return h;
|
|
}
|
|
|
|
void hash_init(struct hash_table *table) {
|
|
|
|
table->ptr = NULL;
|
|
table->size = 0;
|
|
table->count = 0;
|
|
}
|
|
|
|
void hash_free(struct hash_table *table) {
|
|
|
|
if (table->ptr)
|
|
free(table->ptr);
|
|
hash_init(table);
|
|
}
|
|
|
|
static hash_t** lookup(const struct hash_table *t, hash_t hash) {
|
|
|
|
unsigned i = hash % t->size;
|
|
hash_t **table = t->ptr;
|
|
|
|
while(table[i]) {
|
|
if (*table[i] == hash)
|
|
break;
|
|
i = (i + 1) % t->size;
|
|
}
|
|
return table + i;
|
|
}
|
|
|
|
void* hash_lookup(const struct hash_table *t, hash_t hash) {
|
|
|
|
if (t->size < 1)
|
|
return NULL;
|
|
return *lookup(t, hash);
|
|
}
|
|
|
|
static void* insert(struct hash_table *t, hash_t hash, void *ptr) {
|
|
|
|
hash_t **dest = lookup(t, hash);
|
|
|
|
if (!*dest) {
|
|
*dest = ptr;
|
|
**dest = hash;
|
|
t->count++;
|
|
return NULL;
|
|
}
|
|
return *dest;
|
|
}
|
|
|
|
static unsigned needs_resize(const struct hash_table *t) {
|
|
|
|
if (t->size) {
|
|
double load = t->count / t->size;
|
|
return ((load >= 0.5 && load <= 0.75) == 0) &&
|
|
(t->size > TABLE_MIN_SIZE);
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
static void resize(struct hash_table *t) {
|
|
|
|
unsigned int i, old_size = t->size;
|
|
hash_t **old = t->ptr;
|
|
|
|
/*
|
|
* set size to a load factor that is in the
|
|
* middle in the valid range.
|
|
*/
|
|
t->size = t->count / 0.625;
|
|
if (t->size < TABLE_MIN_SIZE)
|
|
t->size = TABLE_MIN_SIZE;
|
|
|
|
t->count = 0;
|
|
t->ptr = calloc(sizeof(t->ptr), t->size);
|
|
|
|
if (old) {
|
|
for(i=0; i < old_size; i++) {
|
|
hash_t *entry = old[i];
|
|
if (entry)
|
|
insert(t, *entry, entry);
|
|
}
|
|
free(old);
|
|
}
|
|
}
|
|
|
|
void* hash_insert(struct hash_table *t, hash_t hash, void *ptr) {
|
|
|
|
if (needs_resize(t))
|
|
resize(t);
|
|
return insert(t, hash, ptr);
|
|
}
|
|
|
|
void* hash_remove(struct hash_table *t, hash_t hash) {
|
|
|
|
hash_t **dest = lookup(t, hash);
|
|
|
|
if (*dest) {
|
|
void *ptr = *dest;
|
|
*dest = NULL;
|
|
t->count--;
|
|
if (needs_resize(t))
|
|
resize(t);
|
|
return ptr;
|
|
}
|
|
return NULL;
|
|
}
|