/* 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.c * @brief implementation of the invertible bloom filter * @author Florian Dold */ #include "ibf.h" /** * 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) { struct InvertibleBloomFilter *ibf; ibf = GNUNET_malloc (sizeof (struct InvertibleBloomFilter)); ibf->count = GNUNET_malloc (size * sizeof (uint8_t)); ibf->id_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode)); ibf->hash_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode)); ibf->size = size; ibf->hash_num = hash_num; return ibf; } /** * Insert an element into an IBF, with either positive or negative sign. * * @param ibf the IBF * @param id the element's hash code * @param side the sign of side determines the sign of the * inserted element. */ void ibf_insert_on_side (struct InvertibleBloomFilter *ibf, const struct GNUNET_HashCode *key, int side) { struct GNUNET_HashCode bucket_indices; struct GNUNET_HashCode key_copy; struct GNUNET_HashCode key_hash; unsigned int i; GNUNET_assert ((1 == side) || (-1 == side)); GNUNET_assert (NULL != ibf); { int used_buckets[ibf->hash_num]; /* copy the key, if key and an entry in the IBF alias */ key_copy = *key; bucket_indices = key_copy; GNUNET_CRYPTO_hash (key, sizeof (struct GNUNET_HashCode), &key_hash); for (i = 0; i < ibf->hash_num; i++) { unsigned int bucket; unsigned int j; int collided; if ( (0 != i) && (0 == (i % 16)) ) GNUNET_CRYPTO_hash (&bucket_indices, sizeof (struct GNUNET_HashCode), &bucket_indices); bucket = bucket_indices.bits[i%16] % ibf->size; collided = GNUNET_NO; for (j = 0; j < i; j++) if (used_buckets[j] == bucket) collided = GNUNET_YES; if (GNUNET_YES == collided) { used_buckets[i] = -1; continue; } used_buckets[i] = bucket; ibf->count[bucket] += side; GNUNET_log_from(GNUNET_ERROR_TYPE_INFO, "ibf", "inserting in bucket %d \n", bucket); GNUNET_CRYPTO_hash_xor (&key_copy, &ibf->id_sum[bucket], &ibf->id_sum[bucket]); GNUNET_CRYPTO_hash_xor (&key_hash, &ibf->hash_sum[bucket], &ibf->hash_sum[bucket]); } } } /** * 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 *key) { ibf_insert_on_side (ibf, key, 1); } static int ibf_is_empty (struct InvertibleBloomFilter *ibf) { int i; for (i = 0; i < ibf->size; i++) { int j; if (0 != ibf->count[i]) return GNUNET_NO; for (j = 0; j < 16; ++j) { if (0 != ibf->hash_sum[i].bits[j]) return GNUNET_NO; if (0 != ibf->id_sum[i].bits[j]) return GNUNET_NO; } } return GNUNET_YES; } /** * 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 failed */ int ibf_decode (struct InvertibleBloomFilter *ibf, int *ret_side, struct GNUNET_HashCode *ret_id) { struct GNUNET_HashCode hash; int i; GNUNET_assert (NULL != ibf); for (i = 0; i < ibf->size; i++) { if ((1 != ibf->count[i]) && (-1 != ibf->count[i])) continue; GNUNET_CRYPTO_hash (&ibf->id_sum[i], sizeof (struct GNUNET_HashCode), &hash); if (0 != memcmp (&hash, &ibf->hash_sum[i], sizeof (struct GNUNET_HashCode))) continue; if (NULL != ret_side) *ret_side = ibf->count[i]; if (NULL != ret_id) *ret_id = ibf->id_sum[i]; /* insert on the opposite side, effectively removing the element */ ibf_insert_on_side (ibf, &ibf->id_sum[i], -ibf->count[i]); return GNUNET_YES; } if (GNUNET_YES == ibf_is_empty (ibf)) return GNUNET_NO; return GNUNET_SYSERR; } /** * 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) { int i; GNUNET_assert (ibf1->size == ibf2->size); GNUNET_assert (ibf1->hash_num == ibf2->hash_num); GNUNET_assert (ibf1->salt == ibf2->salt); for (i = 0; i < ibf1->size; i++) { ibf1->count[i] -= ibf2->count[i]; GNUNET_CRYPTO_hash_xor (&ibf1->id_sum[i], &ibf2->id_sum[i], &ibf1->id_sum[i]); GNUNET_CRYPTO_hash_xor (&ibf1->hash_sum[i], &ibf2->hash_sum[i], &ibf1->hash_sum[i]); } } /** * 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) { struct InvertibleBloomFilter *copy; copy = GNUNET_malloc (sizeof *copy); copy->hash_num = ibf->hash_num; copy->salt = ibf->salt; copy->size = ibf->size; copy->hash_sum = GNUNET_memdup (ibf->hash_sum, ibf->size * sizeof (struct GNUNET_HashCode)); copy->id_sum = GNUNET_memdup (ibf->id_sum, ibf->size * sizeof (struct GNUNET_HashCode)); copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (uint8_t)); return copy; } /** * 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) { GNUNET_free (ibf->hash_sum); GNUNET_free (ibf->id_sum); GNUNET_free (ibf->count); GNUNET_free (ibf); }