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23 * @file consensus/ibf.c
24 * @brief implementation of the invertible bloom filter
25 * @author Florian Dold
33 * Create a key from a hashcode.
35 * @param hash the hashcode
39 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash)
41 return GNUNET_ntohll (*(uint64_t *) hash);
46 * Create a hashcode from a key, by replicating the key
47 * until the hascode is filled
50 * @param dst hashcode to store the result in
53 ibf_hashcode_from_key (uint64_t key, struct GNUNET_HashCode *dst)
58 for (i = 0; i < 8; i++)
64 * Create an invertible bloom filter.
66 * @param size number of IBF buckets
67 * @param hash_num number of buckets one element is hashed in
68 * @param salt salt for mingling hashes, different salt may
69 * result in less (or more) collisions
70 * @return the newly created invertible bloom filter
72 struct InvertibleBloomFilter *
73 ibf_create (uint32_t size, unsigned int hash_num, uint32_t salt)
75 struct InvertibleBloomFilter *ibf;
77 ibf = GNUNET_malloc (sizeof (struct InvertibleBloomFilter));
78 ibf->count = GNUNET_malloc (size * sizeof (uint8_t));
79 ibf->id_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
80 ibf->hash_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
82 ibf->hash_num = hash_num;
88 * Store unique bucket indices for the specified key in dst.
91 ibf_get_indices (const struct InvertibleBloomFilter *ibf,
92 uint64_t key, int *dst)
94 struct GNUNET_HashCode bucket_indices;
95 unsigned int filled = 0;
97 GNUNET_CRYPTO_hash (&key, sizeof key, &bucket_indices);
98 for (i = 0; filled < ibf->hash_num; i++)
102 if ( (0 != i) && (0 == (i % 16)) )
103 GNUNET_CRYPTO_hash (&bucket_indices, sizeof (struct GNUNET_HashCode), &bucket_indices);
104 bucket = bucket_indices.bits[i] % ibf->size;
105 for (j = 0; j < filled; j++)
106 if (dst[j] == bucket)
108 dst[filled++] = bucket;
115 ibf_insert_into (struct InvertibleBloomFilter *ibf,
117 const int *buckets, int side)
120 struct GNUNET_HashCode key_hash_sha;
122 GNUNET_CRYPTO_hash (&key, sizeof key, &key_hash_sha);
123 key_hash = key_hash_sha.bits[0];
124 for (i = 0; i < ibf->hash_num; i++)
126 const int bucket = buckets[i];
127 ibf->count[bucket] += side;
128 ibf->id_sum[bucket] ^= key;
129 ibf->hash_sum[bucket] ^= key_hash;
135 * Insert an element into an IBF.
138 * @param id the element's hash code
141 ibf_insert (struct InvertibleBloomFilter *ibf, uint64_t key)
143 int buckets[ibf->hash_num];
144 ibf_get_indices (ibf, key, buckets);
145 ibf_insert_into (ibf, key, buckets, 1);
149 * Test is the IBF is empty, i.e. all counts, keys and key hashes are zero.
152 ibf_is_empty (struct InvertibleBloomFilter *ibf)
155 for (i = 0; i < ibf->size; i++)
157 if (0 != ibf->count[i])
159 if (0 != ibf->hash_sum[i])
161 if (0 != ibf->id_sum[i])
169 * Decode and remove an element from the IBF, if possible.
171 * @param ibf the invertible bloom filter to decode
172 * @param side sign of the cell's count where the decoded element came from.
173 * A negative sign indicates that the element was recovered
174 * resides in an IBF that was previously subtracted from.
175 * @param ret_id the hash code of the decoded element, if successful
176 * @return GNUNET_YES if decoding an element was successful,
177 * GNUNET_NO if the IBF is empty,
178 * GNUNET_SYSERR if the decoding has failed
181 ibf_decode (struct InvertibleBloomFilter *ibf,
182 int *ret_side, uint64_t *ret_id)
186 struct GNUNET_HashCode key_hash_sha;
187 int buckets[ibf->hash_num];
189 GNUNET_assert (NULL != ibf);
191 for (i = 0; i < ibf->size; i++)
196 /* we can only decode from pure buckets */
197 if ((1 != ibf->count[i]) && (-1 != ibf->count[i]))
200 GNUNET_CRYPTO_hash (&ibf->id_sum[i], sizeof (uint64_t), &key_hash_sha);
201 hash = key_hash_sha.bits[0];
203 /* test if the hash matches the key */
204 if (hash != ibf->hash_sum[i])
207 /* test if key in bucket hits its own location,
208 * if not, the key hash was subject to collision */
210 ibf_get_indices (ibf, ibf->id_sum[i], buckets);
211 for (j = 0; j < ibf->hash_num; j++)
215 if (GNUNET_NO == hit)
218 if (NULL != ret_side)
219 *ret_side = ibf->count[i];
221 *ret_id = ibf->id_sum[i];
223 /* insert on the opposite side, effectively removing the element */
224 ibf_insert_into (ibf, ibf->id_sum[i], buckets, -ibf->count[i]);
229 if (GNUNET_YES == ibf_is_empty (ibf))
231 return GNUNET_SYSERR;
236 * Subtract ibf2 from ibf1, storing the result in ibf1.
237 * The two IBF's must have the same parameters size and hash_num.
239 * @param ibf1 IBF that is subtracted from
240 * @param ibf2 IBF that will be subtracted from ibf1
243 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2)
247 GNUNET_assert (ibf1->size == ibf2->size);
248 GNUNET_assert (ibf1->hash_num == ibf2->hash_num);
249 GNUNET_assert (ibf1->salt == ibf2->salt);
251 for (i = 0; i < ibf1->size; i++)
253 ibf1->count[i] -= ibf2->count[i];
254 ibf1->hash_sum[i] ^= ibf2->hash_sum[i];
255 ibf1->id_sum[i] ^= ibf2->id_sum[i];
260 * Create a copy of an IBF, the copy has to be destroyed properly.
262 * @param ibf the IBF to copy
264 struct InvertibleBloomFilter *
265 ibf_dup (struct InvertibleBloomFilter *ibf)
267 struct InvertibleBloomFilter *copy;
268 copy = GNUNET_malloc (sizeof *copy);
269 copy->hash_num = ibf->hash_num;
270 copy->salt = ibf->salt;
271 copy->size = ibf->size;
272 copy->hash_sum = GNUNET_memdup (ibf->hash_sum, ibf->size * sizeof (struct GNUNET_HashCode));
273 copy->id_sum = GNUNET_memdup (ibf->id_sum, ibf->size * sizeof (struct GNUNET_HashCode));
274 copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (uint8_t));
279 * Destroy all resources associated with the invertible bloom filter.
280 * No more ibf_*-functions may be called on ibf after calling destroy.
282 * @param ibf the intertible bloom filter to destroy
285 ibf_destroy (struct InvertibleBloomFilter *ibf)
287 GNUNET_free (ibf->hash_sum);
288 GNUNET_free (ibf->id_sum);
289 GNUNET_free (ibf->count);