You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
112 lines
2.5 KiB
112 lines
2.5 KiB
/*
|
|
* Copyright 2013 Rob Kendrick <rjek@netsurf-browser.org>
|
|
*
|
|
* This file is part of NetSurf, http://www.netsurf-browser.org/
|
|
*
|
|
* NetSurf 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; version 2 of the License.
|
|
*
|
|
* NetSurf 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, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
/**
|
|
* \file
|
|
* Trivial bloom filter
|
|
*/
|
|
|
|
#include <stdlib.h>
|
|
#include "utils/bloom.h"
|
|
#include "utils/utils.h"
|
|
|
|
/**
|
|
* Hash a string, returning a 32bit value. The hash algorithm used is
|
|
* Fowler Noll Vo - a very fast and simple hash, ideal for short strings.
|
|
* See http://en.wikipedia.org/wiki/Fowler_Noll_Vo_hash for more details.
|
|
*
|
|
* \param datum The string to hash.
|
|
* \param len size_t of data length.
|
|
* \return The calculated hash value for the datum.
|
|
*/
|
|
|
|
static inline uint32_t fnv(const char *datum, size_t len)
|
|
{
|
|
uint32_t z = 0x811c9dc5;
|
|
|
|
if (datum == NULL)
|
|
return 0;
|
|
|
|
while (len--) {
|
|
z *= 0x01000193;
|
|
z ^= *datum++;
|
|
}
|
|
|
|
return z;
|
|
}
|
|
|
|
struct bloom_filter {
|
|
size_t size;
|
|
uint32_t items;
|
|
uint8_t filter[FLEX_ARRAY_LEN_DECL];
|
|
};
|
|
|
|
struct bloom_filter *bloom_create(size_t size)
|
|
{
|
|
struct bloom_filter *r = calloc(sizeof(*r) + size, 1);
|
|
|
|
if (r == NULL)
|
|
return NULL;
|
|
|
|
r->size = size;
|
|
|
|
return r;
|
|
}
|
|
|
|
void bloom_destroy(struct bloom_filter *b)
|
|
{
|
|
free(b);
|
|
}
|
|
|
|
void bloom_insert_str(struct bloom_filter *b, const char *s, size_t z)
|
|
{
|
|
uint32_t hash = fnv(s, z);
|
|
bloom_insert_hash(b, hash);
|
|
}
|
|
|
|
void bloom_insert_hash(struct bloom_filter *b, uint32_t hash)
|
|
{
|
|
unsigned int index = hash % (b->size << 3);
|
|
unsigned int byte_index = index >> 3;
|
|
unsigned int bit_index = index & 7;
|
|
|
|
b->filter[byte_index] |= (1 << bit_index);
|
|
b->items++;
|
|
}
|
|
|
|
bool bloom_search_str(struct bloom_filter *b, const char *s, size_t z)
|
|
{
|
|
uint32_t hash = fnv(s, z);
|
|
return bloom_search_hash(b, hash);
|
|
}
|
|
|
|
bool bloom_search_hash(struct bloom_filter *b, uint32_t hash)
|
|
{
|
|
unsigned int index = hash % (b->size << 3);
|
|
unsigned int byte_index = index >> 3;
|
|
unsigned int bit_index = index & 7;
|
|
|
|
return (b->filter[byte_index] & (1 << bit_index)) != 0;
|
|
}
|
|
|
|
uint32_t bloom_items(struct bloom_filter *b)
|
|
{
|
|
return b->items;
|
|
}
|
|
|