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21 * @brief implementation of the invertible bloom filter
22 * @author Florian Dold
28 * Compute the key's hash from the key.
29 * Redefine to use a different hash function.
31 #define IBF_KEY_HASH_VAL(k) (GNUNET_CRYPTO_crc32_n (&(k), sizeof (struct IBF_KeyHash)))
34 * Create a key from a hashcode.
36 * @param hash the hashcode
40 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash)
42 return *(struct IBF_Key *) 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 (struct IBF_Key key,
54 struct GNUNET_HashCode *dst)
58 const unsigned int keys_per_hashcode = sizeof (struct GNUNET_HashCode) / sizeof (struct IBF_Key);
60 p = (struct IBF_Key *) dst;
61 for (i = 0; i < keys_per_hashcode; i++)
67 * Create an invertible bloom filter.
69 * @param size number of IBF buckets
70 * @param hash_num number of buckets one element is hashed in
71 * @return the newly created invertible bloom filter, NULL on error
73 struct InvertibleBloomFilter *
74 ibf_create (uint32_t size, uint8_t hash_num)
76 struct InvertibleBloomFilter *ibf;
78 GNUNET_assert (0 != size);
80 ibf = GNUNET_new (struct InvertibleBloomFilter);
81 ibf->count = GNUNET_malloc_large (size * sizeof (uint8_t));
82 if (NULL == ibf->count)
87 ibf->key_sum = GNUNET_malloc_large (size * sizeof (struct IBF_Key));
88 if (NULL == ibf->key_sum)
90 GNUNET_free (ibf->count);
94 ibf->key_hash_sum = GNUNET_malloc_large (size * sizeof (struct IBF_KeyHash));
95 if (NULL == ibf->key_hash_sum)
97 GNUNET_free (ibf->key_sum);
98 GNUNET_free (ibf->count);
103 ibf->hash_num = hash_num;
110 * Store unique bucket indices for the specified key in dst.
113 ibf_get_indices (const struct InvertibleBloomFilter *ibf,
121 bucket = GNUNET_CRYPTO_crc32_n (&key, sizeof key);
122 for (i = 0, filled=0; filled < ibf->hash_num; i++)
126 for (j = 0; j < filled; j++)
127 if (dst[j] == bucket)
129 dst[filled++] = bucket % ibf->size;
131 x = ((uint64_t) bucket << 32) | i;
132 bucket = GNUNET_CRYPTO_crc32_n (&x, sizeof x);
138 ibf_insert_into (struct InvertibleBloomFilter *ibf,
140 const int *buckets, int side)
144 for (i = 0; i < ibf->hash_num; i++)
146 const int bucket = buckets[i];
147 ibf->count[bucket].count_val += side;
148 ibf->key_sum[bucket].key_val ^= key.key_val;
149 ibf->key_hash_sum[bucket].key_hash_val
150 ^= IBF_KEY_HASH_VAL (key);
156 * Insert a key into an IBF.
159 * @param key the element's hash code
162 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key)
164 int buckets[ibf->hash_num];
165 GNUNET_assert (ibf->hash_num <= ibf->size);
166 ibf_get_indices (ibf, key, buckets);
167 ibf_insert_into (ibf, key, buckets, 1);
172 * Remove a key from an IBF.
175 * @param key the element's hash code
178 ibf_remove (struct InvertibleBloomFilter *ibf, struct IBF_Key key)
180 int buckets[ibf->hash_num];
181 GNUNET_assert (ibf->hash_num <= ibf->size);
182 ibf_get_indices (ibf, key, buckets);
183 ibf_insert_into (ibf, key, buckets, -1);
188 * Test is the IBF is empty, i.e. all counts, keys and key hashes are zero.
191 ibf_is_empty (struct InvertibleBloomFilter *ibf)
194 for (i = 0; i < ibf->size; i++)
196 if (0 != ibf->count[i].count_val)
198 if (0 != ibf->key_hash_sum[i].key_hash_val)
200 if (0 != ibf->key_sum[i].key_val)
208 * Decode and remove an element from the IBF, if possible.
210 * @param ibf the invertible bloom filter to decode
211 * @param ret_side sign of the cell's count where the decoded element came from.
212 * A negative sign indicates that the element was recovered
213 * resides in an IBF that was previously subtracted from.
214 * @param ret_id receives the hash code of the decoded element, if successful
215 * @return GNUNET_YES if decoding an element was successful,
216 * GNUNET_NO if the IBF is empty,
217 * GNUNET_SYSERR if the decoding has failed
220 ibf_decode (struct InvertibleBloomFilter *ibf,
221 int *ret_side, struct IBF_Key *ret_id)
223 struct IBF_KeyHash hash;
225 int buckets[ibf->hash_num];
227 GNUNET_assert (NULL != ibf);
229 for (i = 0; i < ibf->size; i++)
234 /* we can only decode from pure buckets */
235 if ((1 != ibf->count[i].count_val) && (-1 != ibf->count[i].count_val))
238 hash.key_hash_val = IBF_KEY_HASH_VAL (ibf->key_sum[i]);
240 /* test if the hash matches the key */
241 if (hash.key_hash_val != ibf->key_hash_sum[i].key_hash_val)
244 /* test if key in bucket hits its own location,
245 * if not, the key hash was subject to collision */
247 ibf_get_indices (ibf, ibf->key_sum[i], buckets);
248 for (j = 0; j < ibf->hash_num; j++)
252 if (GNUNET_NO == hit)
255 if (NULL != ret_side)
256 *ret_side = ibf->count[i].count_val;
258 *ret_id = ibf->key_sum[i];
260 /* insert on the opposite side, effectively removing the element */
261 ibf_insert_into (ibf, ibf->key_sum[i], buckets, -ibf->count[i].count_val);
266 if (GNUNET_YES == ibf_is_empty (ibf))
268 return GNUNET_SYSERR;
273 * Write buckets from an ibf to a buffer.
274 * Exactly (IBF_BUCKET_SIZE*ibf->size) bytes are written to buf.
276 * @param ibf the ibf to write
277 * @param start with which bucket to start
278 * @param count how many buckets to write
279 * @param buf buffer to write the data to
282 ibf_write_slice (const struct InvertibleBloomFilter *ibf, uint32_t start, uint32_t count, void *buf)
284 struct IBF_Key *key_dst;
285 struct IBF_KeyHash *key_hash_dst;
286 struct IBF_Count *count_dst;
288 GNUNET_assert (start + count <= ibf->size);
291 key_dst = (struct IBF_Key *) buf;
292 GNUNET_memcpy (key_dst, ibf->key_sum + start, count * sizeof *key_dst);
294 /* copy key hashes */
295 key_hash_dst = (struct IBF_KeyHash *) key_dst;
296 GNUNET_memcpy (key_hash_dst, ibf->key_hash_sum + start, count * sizeof *key_hash_dst);
297 key_hash_dst += count;
299 count_dst = (struct IBF_Count *) key_hash_dst;
300 GNUNET_memcpy (count_dst, ibf->count + start, count * sizeof *count_dst);
305 * Read buckets from a buffer into an ibf.
307 * @param buf pointer to the buffer to read from
308 * @param start which bucket to start at
309 * @param count how many buckets to read
310 * @param ibf the ibf to read from
313 ibf_read_slice (const void *buf, uint32_t start, uint32_t count, struct InvertibleBloomFilter *ibf)
315 struct IBF_Key *key_src;
316 struct IBF_KeyHash *key_hash_src;
317 struct IBF_Count *count_src;
319 GNUNET_assert (count > 0);
320 GNUNET_assert (start + count <= ibf->size);
323 key_src = (struct IBF_Key *) buf;
324 GNUNET_memcpy (ibf->key_sum + start, key_src, count * sizeof *key_src);
326 /* copy key hashes */
327 key_hash_src = (struct IBF_KeyHash *) key_src;
328 GNUNET_memcpy (ibf->key_hash_sum + start, key_hash_src, count * sizeof *key_hash_src);
329 key_hash_src += count;
331 count_src = (struct IBF_Count *) key_hash_src;
332 GNUNET_memcpy (ibf->count + start, count_src, count * sizeof *count_src);
337 * Subtract ibf2 from ibf1, storing the result in ibf1.
338 * The two IBF's must have the same parameters size and hash_num.
340 * @param ibf1 IBF that is subtracted from
341 * @param ibf2 IBF that will be subtracted from ibf1
344 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2)
348 GNUNET_assert (ibf1->size == ibf2->size);
349 GNUNET_assert (ibf1->hash_num == ibf2->hash_num);
351 for (i = 0; i < ibf1->size; i++)
353 ibf1->count[i].count_val -= ibf2->count[i].count_val;
354 ibf1->key_hash_sum[i].key_hash_val ^= ibf2->key_hash_sum[i].key_hash_val;
355 ibf1->key_sum[i].key_val ^= ibf2->key_sum[i].key_val;
361 * Create a copy of an IBF, the copy has to be destroyed properly.
363 * @param ibf the IBF to copy
365 struct InvertibleBloomFilter *
366 ibf_dup (const struct InvertibleBloomFilter *ibf)
368 struct InvertibleBloomFilter *copy;
369 copy = GNUNET_malloc (sizeof *copy);
370 copy->hash_num = ibf->hash_num;
371 copy->size = ibf->size;
372 copy->key_hash_sum = GNUNET_memdup (ibf->key_hash_sum, ibf->size * sizeof (struct IBF_KeyHash));
373 copy->key_sum = GNUNET_memdup (ibf->key_sum, ibf->size * sizeof (struct IBF_Key));
374 copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (struct IBF_Count));
380 * Destroy all resources associated with the invertible bloom filter.
381 * No more ibf_*-functions may be called on ibf after calling destroy.
383 * @param ibf the intertible bloom filter to destroy
386 ibf_destroy (struct InvertibleBloomFilter *ibf)
388 GNUNET_free (ibf->key_sum);
389 GNUNET_free (ibf->key_hash_sum);
390 GNUNET_free (ibf->count);