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3 (C) 2012 Christian Grothoff (and other contributing authors)
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22 * @file consensus/ibf.c
23 * @brief implementation of the invertible bloom filter
24 * @author Florian Dold
30 * Create a key from a hashcode.
32 * @param hash the hashcode
36 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash)
38 /* FIXME: endianess */
39 return *(struct IBF_Key *) hash;
43 * Create a hashcode from a key, by replicating the key
44 * until the hascode is filled
47 * @param dst hashcode to store the result in
50 ibf_hashcode_from_key (struct IBF_Key key, struct GNUNET_HashCode *dst)
54 const unsigned int keys_per_hashcode = sizeof (struct GNUNET_HashCode) / sizeof (struct IBF_Key);
55 p = (struct IBF_Key *) dst;
56 for (i = 0; i < keys_per_hashcode; i++)
62 * Create an invertible bloom filter.
64 * @param size number of IBF buckets
65 * @param hash_num number of buckets one element is hashed in
66 * @param salt salt for mingling hashes, different salt may
67 * result in less (or more) collisions
68 * @return the newly created invertible bloom filter
70 struct InvertibleBloomFilter *
71 ibf_create (uint32_t size, uint8_t hash_num, uint32_t salt)
73 struct InvertibleBloomFilter *ibf;
75 /* TODO: use malloc_large */
77 ibf = GNUNET_malloc (sizeof (struct InvertibleBloomFilter));
78 ibf->count = GNUNET_malloc (size * sizeof (uint8_t));
79 ibf->key_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
80 ibf->key_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 struct IBF_Key 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;
121 struct IBF_KeyHash key_hash;
122 GNUNET_CRYPTO_hash (&key, sizeof key, &key_hash_sha);
123 key_hash.key_hash_val = key_hash_sha.bits[0];
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 ^= key_hash.key_hash_val;
135 * Insert an element into an IBF.
138 * @param id the element's hash code
141 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key 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].count_val)
159 if (0 != ibf->key_hash_sum[i].key_hash_val)
161 if (0 != ibf->key_sum[i].key_val)
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, struct IBF_Key *ret_id)
184 struct IBF_KeyHash hash;
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].count_val) && (-1 != ibf->count[i].count_val))
200 GNUNET_CRYPTO_hash (&ibf->key_sum[i], sizeof (struct IBF_Key), &key_hash_sha);
201 hash.key_hash_val = key_hash_sha.bits[0];
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;
238 * @param ibf the ibf to write
239 * @param start with which bucket to start
240 * @param count how many buckets to write
241 * @param buf buffer to write the data to, will be updated to point to the
242 * first byte after the written data
243 * @param size pointer to the size of the buffer, will be updated, can be NULL
246 ibf_write_slice (const struct InvertibleBloomFilter *ibf, uint32_t start, uint32_t count, void **buf, size_t *size)
248 struct IBF_Key *key_dst;
249 struct IBF_KeyHash *key_hash_dst;
250 struct IBF_Count *count_dst;
252 /* update size and check for overflow */
257 *size = *size - count * IBF_BUCKET_SIZE;
258 GNUNET_assert (*size < old_size);
261 key_dst = (struct IBF_Key *) *buf;
262 memcpy (key_dst, ibf->key_sum + start, count * sizeof *key_dst);
264 /* copy key hashes */
265 key_hash_dst = (struct IBF_KeyHash *) key_dst;
266 memcpy (key_hash_dst, ibf->key_hash_sum + start, count * sizeof *key_hash_dst);
267 key_hash_dst += count;
269 count_dst = (struct IBF_Count *) key_hash_dst;
270 memcpy (count_dst, ibf->count + start, count * sizeof *count_dst);
272 /* returned buffer is at the end of written data*/
273 *buf = (void *) count_dst;
280 * @param buf pointer to the buffer to write to, will point to first
281 * byte after the written data
282 * @param size size of the buffer, will be updated
283 * @param start which bucket to start at
284 * @param count how many buckets to read
285 * @param dst ibf to write buckets to
286 * @return GNUNET_OK on success
289 ibf_read_slice (void **buf, size_t *size, uint32_t start, uint32_t count, struct InvertibleBloomFilter *ibf)
291 struct IBF_Key *key_src;
292 struct IBF_KeyHash *key_hash_src;
293 struct IBF_Count *count_src;
295 /* update size and check for overflow */
300 *size = *size - count * IBF_BUCKET_SIZE;
301 if (*size > old_size)
302 return GNUNET_SYSERR;
305 key_src = (struct IBF_Key *) *buf;
306 memcpy (ibf->key_sum + start, key_src, count * sizeof *key_src);
308 /* copy key hashes */
309 key_hash_src = (struct IBF_KeyHash *) key_src;
310 memcpy (ibf->key_hash_sum + start, key_hash_src, count * sizeof *key_hash_src);
311 key_hash_src += count;
313 count_src = (struct IBF_Count *) key_hash_src;
314 memcpy (ibf->count + start, count_src, count * sizeof *count_src);
316 /* returned buffer is at the end of written data*/
317 *buf = (void *) count_src;
325 * @param ibf the ibf to write
326 * @param start with which bucket to start
327 * @param count how many buckets to write
328 * @param buf buffer to write the data to, will be updated to point to the
329 * first byte after the written data
330 * @param size pointer to the size of the buffer, will be updated, can be NULL
333 ibf_write (const struct InvertibleBloomFilter *ibf, void **buf, size_t *size)
335 ibf_write_slice (ibf, 0, ibf->size, buf, size);
342 * @param buf pointer to the buffer to write to, will point to first
343 * byte after the written data
344 * @param size size of the buffer, will be updated
345 * @param start which bucket to start at
346 * @param count how many buckets to read
347 * @param dst ibf to write buckets to
348 * @return GNUNET_OK on success
351 ibf_read (void **buf, size_t *size, struct InvertibleBloomFilter *dst)
353 return ibf_read_slice (buf, size, 0, dst->size, dst);
358 * Subtract ibf2 from ibf1, storing the result in ibf1.
359 * The two IBF's must have the same parameters size and hash_num.
361 * @param ibf1 IBF that is subtracted from
362 * @param ibf2 IBF that will be subtracted from ibf1
365 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2)
369 GNUNET_assert (ibf1->size == ibf2->size);
370 GNUNET_assert (ibf1->hash_num == ibf2->hash_num);
371 GNUNET_assert (ibf1->salt == ibf2->salt);
373 for (i = 0; i < ibf1->size; i++)
375 ibf1->count[i].count_val -= ibf2->count[i].count_val;
376 ibf1->key_hash_sum[i].key_hash_val ^= ibf2->key_hash_sum[i].key_hash_val;
377 ibf1->key_sum[i].key_val ^= ibf2->key_sum[i].key_val;
383 * Create a copy of an IBF, the copy has to be destroyed properly.
385 * @param ibf the IBF to copy
387 struct InvertibleBloomFilter *
388 ibf_dup (const struct InvertibleBloomFilter *ibf)
390 struct InvertibleBloomFilter *copy;
391 copy = GNUNET_malloc (sizeof *copy);
392 copy->hash_num = ibf->hash_num;
393 copy->salt = ibf->salt;
394 copy->size = ibf->size;
395 copy->key_hash_sum = GNUNET_memdup (ibf->key_hash_sum, ibf->size * sizeof (struct IBF_KeyHash));
396 copy->key_sum = GNUNET_memdup (ibf->key_sum, ibf->size * sizeof (struct IBF_Key));
397 copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (struct IBF_Count));
403 * Destroy all resources associated with the invertible bloom filter.
404 * No more ibf_*-functions may be called on ibf after calling destroy.
406 * @param ibf the intertible bloom filter to destroy
409 ibf_destroy (struct InvertibleBloomFilter *ibf)
411 GNUNET_free (ibf->key_sum);
412 GNUNET_free (ibf->key_hash_sum);
413 GNUNET_free (ibf->count);