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/*
This file is part of GNUnet
(C) 2012 Christian Grothoff (and other contributing authors)
GNUnet 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, or (at your
option) any later version.
GNUnet 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 GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
/**
* @file consensus/ibf.h
* @brief invertible bloom filter
* @author Florian Dold
*/
#ifndef GNUNET_CONSENSUS_IBF_H
#define GNUNET_CONSENSUS_IBF_H
#include "platform.h"
#include "gnunet_common.h"
#include "gnunet_util_lib.h"
#ifdef __cplusplus
extern "C"
{
#if 0 /* keep Emacsens' auto-indent happy */
}
#endif
#endif
/**
* Size of one ibf bucket in bytes
*/
#define IBF_BUCKET_SIZE (64+64+1)
/**
* Invertible bloom filter (IBF).
*
* An IBF is a counting bloom filter that has the ability to restore
* the hashes of its stored elements with high probability.
*/
struct InvertibleBloomFilter
{
/**
* How many cells does this IBF have?
*/
unsigned int size;
/**
* In how many cells do we hash one element?
* Usually 4 or 3.
*/
unsigned int hash_num;
/**
* Salt for mingling hashes
*/
uint32_t salt;
/**
* xor sums of the elements' hash codes, used to identify the elements.
*/
struct GNUNET_HashCode *id_sum;
/**
* xor sums of the "hash of the hash".
*/
struct GNUNET_HashCode *hash_sum;
/**
* How many times has a bucket been hit?
* Can be negative, as a result of IBF subtraction.
*/
int8_t *count;
};
/**
* Create an invertible bloom filter.
*
* @param size number of IBF buckets
* @param hash_num number of buckets one element is hashed in
* @param salt salt for mingling hashes, different salt may
* result in less (or more) collisions
* @return the newly created invertible bloom filter
*/
struct InvertibleBloomFilter *
ibf_create(unsigned int size, unsigned int hash_num, uint32_t salt);
/**
* Insert an element into an IBF.
*
* @param ibf the IBF
* @param id the element's hash code
*/
void
ibf_insert (struct InvertibleBloomFilter *ibf, const struct GNUNET_HashCode *id);
/**
* Subtract ibf2 from ibf1, storing the result in ibf1.
* The two IBF's must have the same parameters size and hash_num.
*
* @param ibf1 IBF that is subtracted from
* @param ibf2 IBF that will be subtracted from ibf1
*/
void
ibf_subtract (struct InvertibleBloomFilter *ibf1, struct InvertibleBloomFilter *ibf2);
/**
* Decode and remove an element from the IBF, if possible.
*
* @param ibf the invertible bloom filter to decode
* @param side sign of the cell's count where the decoded element came from.
* A negative sign indicates that the element was recovered resides in an IBF
* that was previously subtracted from.
* @param ret_id the hash code of the decoded element, if successful
* @return GNUNET_YES if decoding an element was successful, GNUNET_NO if the IBF is empty,
* GNUNET_SYSERR if the decoding has faile
*/
int
ibf_decode (struct InvertibleBloomFilter *ibf, int *side, struct GNUNET_HashCode *ret_id);
/**
* Create a copy of an IBF, the copy has to be destroyed properly.
*
* @param ibf the IBF to copy
*/
struct InvertibleBloomFilter *
ibf_dup (struct InvertibleBloomFilter *ibf);
/**
* Destroy all resources associated with the invertible bloom filter.
* No more ibf_*-functions may be called on ibf after calling destroy.
*
* @param ibf the intertible bloom filter to destroy
*/
void
ibf_destroy (struct InvertibleBloomFilter *ibf);
#if 0 /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif
#endif
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