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3 (C) 2012 Christian Grothoff (and other contributing authors)
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13 General Public License for more details.
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23 * @brief implementation of the invertible bloom filter
24 * @author Florian Dold
30 * Compute the key's hash from the key.
31 * Redefine to use a different hash function.
33 #define IBF_KEY_HASH_VAL(k) (GNUNET_CRYPTO_crc32_n (&(k), sizeof (struct IBF_KeyHash)))
36 * Create a key from a hashcode.
38 * @param hash the hashcode
42 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash)
44 /* FIXME: endianess */
45 return *(struct IBF_Key *) hash;
49 * Create a hashcode from a key, by replicating the key
50 * until the hascode is filled
53 * @param dst hashcode to store the result in
56 ibf_hashcode_from_key (struct IBF_Key key, struct GNUNET_HashCode *dst)
60 const unsigned int keys_per_hashcode = sizeof (struct GNUNET_HashCode) / sizeof (struct IBF_Key);
61 p = (struct IBF_Key *) dst;
62 for (i = 0; i < keys_per_hashcode; i++)
68 * Create an invertible bloom filter.
70 * @param size number of IBF buckets
71 * @param hash_num number of buckets one element is hashed in
72 * @return the newly created invertible bloom filter
74 struct InvertibleBloomFilter *
75 ibf_create (uint32_t size, uint8_t hash_num)
77 struct InvertibleBloomFilter *ibf;
79 /* TODO: use malloc_large */
81 ibf = GNUNET_malloc (sizeof (struct InvertibleBloomFilter));
82 ibf->count = GNUNET_malloc (size * sizeof (uint8_t));
83 ibf->key_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
84 ibf->key_hash_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
86 ibf->hash_num = hash_num;
92 * Store unique bucket indices for the specified key in dst.
95 ibf_get_indices (const struct InvertibleBloomFilter *ibf,
96 struct IBF_Key key, int *dst)
100 uint32_t bucket = key.key_val & 0xFFFFFFFF;
102 for (i = 0, filled=0; filled < ibf->hash_num; i++)
106 for (j = 0; j < filled; j++)
107 if (dst[j] == bucket)
109 dst[filled++] = bucket % ibf->size;
111 x = ((uint64_t) bucket << 32) | i;
112 bucket = GNUNET_CRYPTO_crc32_n (&x, sizeof x);
118 ibf_insert_into (struct InvertibleBloomFilter *ibf,
120 const int *buckets, int side)
124 for (i = 0; i < ibf->hash_num; i++)
126 const int bucket = buckets[i];
127 ibf->count[bucket].count_val += side;
128 ibf->key_sum[bucket].key_val ^= key.key_val;
129 ibf->key_hash_sum[bucket].key_hash_val
130 ^= IBF_KEY_HASH_VAL (key);
136 * Insert an element into an IBF.
139 * @param key the element's hash code
142 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key)
144 int buckets[ibf->hash_num];
145 GNUNET_assert (ibf->hash_num <= ibf->size);
146 ibf_get_indices (ibf, key, buckets);
147 ibf_insert_into (ibf, key, buckets, 1);
151 * Test is the IBF is empty, i.e. all counts, keys and key hashes are zero.
154 ibf_is_empty (struct InvertibleBloomFilter *ibf)
157 for (i = 0; i < ibf->size; i++)
159 if (0 != ibf->count[i].count_val)
161 if (0 != ibf->key_hash_sum[i].key_hash_val)
163 if (0 != ibf->key_sum[i].key_val)
171 * Decode and remove an element from the IBF, if possible.
173 * @param ibf the invertible bloom filter to decode
174 * @param ret_side sign of the cell's count where the decoded element came from.
175 * A negative sign indicates that the element was recovered
176 * resides in an IBF that was previously subtracted from.
177 * @param ret_id receives the hash code of the decoded element, if successful
178 * @return GNUNET_YES if decoding an element was successful,
179 * GNUNET_NO if the IBF is empty,
180 * GNUNET_SYSERR if the decoding has failed
183 ibf_decode (struct InvertibleBloomFilter *ibf,
184 int *ret_side, struct IBF_Key *ret_id)
186 struct IBF_KeyHash hash;
188 int buckets[ibf->hash_num];
190 GNUNET_assert (NULL != ibf);
192 for (i = 0; i < ibf->size; i++)
197 /* we can only decode from pure buckets */
198 if ((1 != ibf->count[i].count_val) && (-1 != ibf->count[i].count_val))
201 hash.key_hash_val = IBF_KEY_HASH_VAL (ibf->key_sum[i]);
203 /* test if the hash matches the key */
204 if (hash.key_hash_val != ibf->key_hash_sum[i].key_hash_val)
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->key_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].count_val;
221 *ret_id = ibf->key_sum[i];
223 /* insert on the opposite side, effectively removing the element */
224 ibf_insert_into (ibf, ibf->key_sum[i], buckets, -ibf->count[i].count_val);
229 if (GNUNET_YES == ibf_is_empty (ibf))
231 return GNUNET_SYSERR;
236 * Write buckets from an ibf to a buffer.
237 * Exactly (IBF_BUCKET_SIZE*ibf->size) bytes are written to buf.
239 * @param ibf the ibf to write
240 * @param start with which bucket to start
241 * @param count how many buckets to write
242 * @param buf buffer to write the data to
245 ibf_write_slice (const struct InvertibleBloomFilter *ibf, uint32_t start, uint32_t count, void *buf)
247 struct IBF_Key *key_dst;
248 struct IBF_KeyHash *key_hash_dst;
249 struct IBF_Count *count_dst;
251 GNUNET_assert (start + count <= ibf->size);
254 key_dst = (struct IBF_Key *) buf;
255 memcpy (key_dst, ibf->key_sum + start, count * sizeof *key_dst);
257 /* copy key hashes */
258 key_hash_dst = (struct IBF_KeyHash *) key_dst;
259 memcpy (key_hash_dst, ibf->key_hash_sum + start, count * sizeof *key_hash_dst);
260 key_hash_dst += count;
262 count_dst = (struct IBF_Count *) key_hash_dst;
263 memcpy (count_dst, ibf->count + start, count * sizeof *count_dst);
269 * Read buckets from a buffer into an ibf.
271 * @param buf pointer to the buffer to read from
272 * @param start which bucket to start at
273 * @param count how many buckets to read
274 * @param ibf the ibf to read from
277 ibf_read_slice (const void *buf, uint32_t start, uint32_t count, struct InvertibleBloomFilter *ibf)
279 struct IBF_Key *key_src;
280 struct IBF_KeyHash *key_hash_src;
281 struct IBF_Count *count_src;
283 GNUNET_assert (count > 0);
284 GNUNET_assert (start + count <= ibf->size);
287 key_src = (struct IBF_Key *) buf;
288 memcpy (ibf->key_sum + start, key_src, count * sizeof *key_src);
290 /* copy key hashes */
291 key_hash_src = (struct IBF_KeyHash *) key_src;
292 memcpy (ibf->key_hash_sum + start, key_hash_src, count * sizeof *key_hash_src);
293 key_hash_src += count;
295 count_src = (struct IBF_Count *) key_hash_src;
296 memcpy (ibf->count + start, count_src, count * sizeof *count_src);
302 * Subtract ibf2 from ibf1, storing the result in ibf1.
303 * The two IBF's must have the same parameters size and hash_num.
305 * @param ibf1 IBF that is subtracted from
306 * @param ibf2 IBF that will be subtracted from ibf1
309 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2)
313 GNUNET_assert (ibf1->size == ibf2->size);
314 GNUNET_assert (ibf1->hash_num == ibf2->hash_num);
316 for (i = 0; i < ibf1->size; i++)
318 ibf1->count[i].count_val -= ibf2->count[i].count_val;
319 ibf1->key_hash_sum[i].key_hash_val ^= ibf2->key_hash_sum[i].key_hash_val;
320 ibf1->key_sum[i].key_val ^= ibf2->key_sum[i].key_val;
326 * Create a copy of an IBF, the copy has to be destroyed properly.
328 * @param ibf the IBF to copy
330 struct InvertibleBloomFilter *
331 ibf_dup (const struct InvertibleBloomFilter *ibf)
333 struct InvertibleBloomFilter *copy;
334 copy = GNUNET_malloc (sizeof *copy);
335 copy->hash_num = ibf->hash_num;
336 copy->size = ibf->size;
337 copy->key_hash_sum = GNUNET_memdup (ibf->key_hash_sum, ibf->size * sizeof (struct IBF_KeyHash));
338 copy->key_sum = GNUNET_memdup (ibf->key_sum, ibf->size * sizeof (struct IBF_Key));
339 copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (struct IBF_Count));
345 * Destroy all resources associated with the invertible bloom filter.
346 * No more ibf_*-functions may be called on ibf after calling destroy.
348 * @param ibf the intertible bloom filter to destroy
351 ibf_destroy (struct InvertibleBloomFilter *ibf)
353 GNUNET_free (ibf->key_sum);
354 GNUNET_free (ibf->key_hash_sum);
355 GNUNET_free (ibf->count);