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/*
This file is part of GNUnet
Copyright (C) 2017 GNUnet e.V.
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 3, 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., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/
/**
* @file block/bg_bf.c
* @brief implementation of a block group using a Bloom filter
* to drop duplicate blocks
* @author Christian Grothoff
*/
#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_block_group_lib.h"
#include "gnunet_block_plugin.h"
/**
* Internal data structure for a block group.
*/
struct BfGroupInternals
{
/**
* A Bloom filter to weed out duplicate replies probabilistically.
*/
struct GNUNET_CONTAINER_BloomFilter *bf;
/**
* Set from the nonce to mingle the hashes before going into the @e bf.
*/
uint32_t bf_mutator;
/**
* Size of @a bf.
*/
uint32_t bf_size;
};
/**
* Serialize state of a block group.
*
* @param bg group to serialize
* @param[out] raw_data set to the serialized state
* @param[out] raw_data_size set to the number of bytes in @a raw_data
* @return #GNUNET_OK on success, #GNUNET_NO if serialization is not
* supported, #GNUNET_SYSERR on error
*/
static int
bf_group_serialize_cb (struct GNUNET_BLOCK_Group *bg,
void **raw_data,
size_t *raw_data_size)
{
struct BfGroupInternals *gi = bg->internal_cls;
char *raw;
raw = GNUNET_malloc (gi->bf_size);
if (GNUNET_OK !=
GNUNET_CONTAINER_bloomfilter_get_raw_data (gi->bf,
raw,
gi->bf_size))
{
GNUNET_break (0);
return GNUNET_SYSERR;
}
*raw_data = raw;
*raw_data_size = gi->bf_size;
return GNUNET_OK;
}
/**
* Destroy resources used by a block group.
*
* @param bg group to destroy, NULL is allowed
*/
static void
bf_group_destroy_cb (struct GNUNET_BLOCK_Group *bg)
{
struct BfGroupInternals *gi = bg->internal_cls;
GNUNET_CONTAINER_bloomfilter_free (gi->bf);
GNUNET_free (gi);
GNUNET_free (bg);
}
/**
* Create a new block group that filters duplicates using a Bloom filter.
*
* @param ctx block context in which the block group is created
* @param bf_size size of the Bloom filter
* @param bf_k K-value for the Bloom filter
* @param type block type
* @param nonce random value used to seed the group creation
* @param raw_data optional serialized prior state of the group, NULL if unavailable/fresh
* @param raw_data_size number of bytes in @a raw_data, 0 if unavailable/fresh
* @return block group handle, NULL if block groups are not supported
* by this @a type of block (this is not an error)
*/
struct GNUNET_BLOCK_Group *
GNUNET_BLOCK_GROUP_bf_create (void *cls,
size_t bf_size,
unsigned int bf_k,
enum GNUNET_BLOCK_Type type,
uint32_t nonce,
const void *raw_data,
size_t raw_data_size)
{
struct BfGroupInternals *gi;
struct GNUNET_BLOCK_Group *bg;
gi = GNUNET_new (struct BfGroupInternals);
gi->bf = GNUNET_CONTAINER_bloomfilter_init ((bf_size != raw_data_size) ? NULL : raw_data,
bf_size,
bf_k);
gi->bf_mutator = nonce;
gi->bf_size = bf_size;
bg = GNUNET_new (struct GNUNET_BLOCK_Group);
bg->type = type;
bg->serialize_cb = &bf_group_serialize_cb;
bg->destroy_cb = &bf_group_destroy_cb;
bg->internal_cls = gi;
return bg;
}
/**
* Test if @a hc is contained in the Bloom filter of @a bg. If so,
* return #GNUNET_YES. If not, add @a hc to the Bloom filter and
* return #GNUNET_NO.
*
* @param bg block group to use for testing
* @param hc hash of element to evaluate
* @return #GNUNET_YES if @a hc is (likely) a duplicate
* #GNUNET_NO if @a hc was definitively not in @bg (but now is)
*/
int
GNUNET_BLOCK_GROUP_bf_test_and_set (struct GNUNET_BLOCK_Group *bg,
const struct GNUNET_HashCode *hc)
{
struct BfGroupInternals *gi = bg->internal_cls;
struct GNUNET_HashCode mhash;
GNUNET_BLOCK_mingle_hash (hc,
gi->bf_mutator,
&mhash);
if (GNUNET_YES ==
GNUNET_CONTAINER_bloomfilter_test (gi->bf,
&mhash))
return GNUNET_YES;
GNUNET_CONTAINER_bloomfilter_add (gi->bf,
&mhash);
return GNUNET_NO;
}
/* end of bg_bf.c */
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