forked from AuroraMiddleware/gtk
158 lines
5.0 KiB
C
158 lines
5.0 KiB
C
/*
|
|
* Copyright © 2020 Benjamin Otte
|
|
*
|
|
* This library is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* This library 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
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
|
|
*
|
|
* Authors: Benjamin Otte <otte@gnome.org>
|
|
*/
|
|
|
|
#ifndef __GTK_COUNTING_BLOOM_FILTER_PRIVATE_H__
|
|
#define __GTK_COUNTING_BLOOM_FILTER_PRIVATE_H__
|
|
|
|
#include <glib.h>
|
|
|
|
|
|
G_BEGIN_DECLS
|
|
|
|
/*
|
|
* GtkCountingBloomFilter:
|
|
*
|
|
* This implements a counting bloom filter. A bloom filter is a space-efficient
|
|
* probabilistic data structure that is used to test whether an element may be
|
|
* a member of a set.
|
|
* The Wikipedia links provide a lot more details into how and why this data
|
|
* structure works and when to use it.
|
|
*
|
|
* This implementation is based on similar implementations in web browsers, because it's
|
|
* original use case is the same: Making CSS lookups fast.
|
|
*
|
|
* As such, the number of bits is hardcoded to 12 and the elements in the set
|
|
* are 16bit hash values.
|
|
* It is possible to use 32bit hash values or a different number of bits, should this
|
|
* be considered useful.
|
|
*
|
|
* See: [Bloom filter](https://en.wikipedia.org/wiki/Bloom_filter),
|
|
* [Counting Bloom filter](https://en.wikipedia.org/wiki/Counting_Bloom_filter)
|
|
*/
|
|
|
|
/* The number of bits from the hash we care about */
|
|
#define GTK_COUNTING_BLOOM_FILTER_BITS (12)
|
|
|
|
/* The necessary size of the filter */
|
|
#define GTK_COUNTING_BLOOM_FILTER_SIZE (1 << GTK_COUNTING_BLOOM_FILTER_BITS)
|
|
|
|
typedef struct _GtkCountingBloomFilter GtkCountingBloomFilter;
|
|
|
|
struct _GtkCountingBloomFilter
|
|
{
|
|
guint8 buckets[GTK_COUNTING_BLOOM_FILTER_SIZE];
|
|
};
|
|
|
|
static inline void gtk_counting_bloom_filter_add (GtkCountingBloomFilter *self,
|
|
guint16 hash);
|
|
static inline void gtk_counting_bloom_filter_remove (GtkCountingBloomFilter *self,
|
|
guint16 hash);
|
|
static inline gboolean gtk_counting_bloom_filter_may_contain (const GtkCountingBloomFilter *self,
|
|
guint16 hash);
|
|
|
|
|
|
/*
|
|
* GTK_COUNTING_BLOOM_FILTER_INIT:
|
|
*
|
|
* Initialize the bloom filter. As bloom filters are always stack-allocated,
|
|
* initialization should happen when defining them, like:
|
|
* ```c
|
|
* GtkCountingBloomFilter filter = GTK_COUNTING_BLOOM_FILTER_INIT;
|
|
* ```
|
|
*
|
|
* The filter does not need to be freed.
|
|
*/
|
|
#define GTK_COUNTING_BLOOM_FILTER_INIT {{0}}
|
|
|
|
/*
|
|
* gtk_counting_bloom_filter_add:
|
|
* @self: a #GtkCountingBloomFilter
|
|
* @hash: a hash value to add to the filter
|
|
*
|
|
* Adds the hash value to the filter.
|
|
*
|
|
* If the same hash value gets added multiple times, it will
|
|
* be considered as contained in the hash until it has been
|
|
* removed as many times.
|
|
**/
|
|
static inline void
|
|
gtk_counting_bloom_filter_add (GtkCountingBloomFilter *self,
|
|
guint16 hash)
|
|
{
|
|
guint16 bucket = hash % GTK_COUNTING_BLOOM_FILTER_SIZE;
|
|
|
|
if (self->buckets[bucket] == 255)
|
|
return;
|
|
|
|
self->buckets[bucket]++;
|
|
}
|
|
|
|
/*
|
|
* gtk_counting_bloom_filter_remove:
|
|
* @self: a #GtkCountingBloomFilter
|
|
* @hash: a hash value to remove from the filter
|
|
*
|
|
* Removes a hash value from the filter that has previously
|
|
* been added via gtk_counting_bloom_filter_add().
|
|
**/
|
|
static inline void
|
|
gtk_counting_bloom_filter_remove (GtkCountingBloomFilter *self,
|
|
guint16 hash)
|
|
{
|
|
guint16 bucket = hash % GTK_COUNTING_BLOOM_FILTER_SIZE;
|
|
|
|
if (self->buckets[bucket] == 255)
|
|
return;
|
|
|
|
g_assert (self->buckets[bucket] > 0);
|
|
|
|
self->buckets[bucket]--;
|
|
}
|
|
|
|
/*
|
|
* gtk_counting_bloom_filter_may_contain:
|
|
* @self: a #GtkCountingBloomFilter
|
|
* @hash: the hash value to check
|
|
*
|
|
* Checks if @hash may be contained in @self.
|
|
*
|
|
* A return value of %FALSE means that @hash is definitely not part
|
|
* of @self.
|
|
*
|
|
* A return value of %TRUE means that @hash may or may not have been
|
|
* added to @self. In that case a different method must be used to
|
|
* confirm that @hash is indeed part of the set.
|
|
*
|
|
* Returns: %FALSE if @hash is not part of @self.
|
|
**/
|
|
static inline gboolean
|
|
gtk_counting_bloom_filter_may_contain (const GtkCountingBloomFilter *self,
|
|
guint16 hash)
|
|
{
|
|
guint16 bucket = hash % GTK_COUNTING_BLOOM_FILTER_SIZE;
|
|
|
|
return self->buckets[bucket] != 0;
|
|
}
|
|
|
|
|
|
G_END_DECLS
|
|
|
|
|
|
#endif /* __GTK_COUNTING_BLOOM_FILTER_PRIVATE_H_ */
|