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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 * @return the newly created invertible bloom filter
68 struct InvertibleBloomFilter *
69 ibf_create (uint32_t size, uint8_t hash_num)
71 struct InvertibleBloomFilter *ibf;
73 /* TODO: use malloc_large */
75 ibf = GNUNET_malloc (sizeof (struct InvertibleBloomFilter));
76 ibf->count = GNUNET_malloc (size * sizeof (uint8_t));
77 ibf->key_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
78 ibf->key_hash_sum = GNUNET_malloc (size * sizeof (struct GNUNET_HashCode));
80 ibf->hash_num = hash_num;
86 * Store unique bucket indices for the specified key in dst.
89 ibf_get_indices (const struct InvertibleBloomFilter *ibf,
90 struct IBF_Key key, int *dst)
92 struct GNUNET_HashCode bucket_indices;
95 GNUNET_CRYPTO_hash (&key, sizeof key, &bucket_indices);
97 for (i = 0; filled < ibf->hash_num; i++)
101 if ( (0 != i) && (0 == (i % 16)) )
102 GNUNET_CRYPTO_hash (&bucket_indices, sizeof (struct GNUNET_HashCode), &bucket_indices);
103 bucket = bucket_indices.bits[i % 16] % ibf->size;
104 for (j = 0; j < filled; j++)
105 if (dst[j] == bucket)
107 dst[filled++] = bucket;
114 ibf_insert_into (struct InvertibleBloomFilter *ibf,
116 const int *buckets, int side)
119 struct GNUNET_HashCode key_hash_sha;
120 struct IBF_KeyHash key_hash;
121 GNUNET_CRYPTO_hash (&key, sizeof key, &key_hash_sha);
122 key_hash.key_hash_val = key_hash_sha.bits[0];
123 for (i = 0; i < ibf->hash_num; i++)
125 const int bucket = buckets[i];
126 ibf->count[bucket].count_val += side;
127 ibf->key_sum[bucket].key_val ^= key.key_val;
128 ibf->key_hash_sum[bucket].key_hash_val ^= key_hash.key_hash_val;
134 * Insert an element into an IBF.
137 * @param key the element's hash code
140 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key)
142 int buckets[ibf->hash_num];
143 GNUNET_assert (ibf->hash_num <= ibf->size);
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 ret_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 receives 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;
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 (start + count <= ibf->size);
286 key_src = (struct IBF_Key *) buf;
287 memcpy (ibf->key_sum + start, key_src, count * sizeof *key_src);
289 /* copy key hashes */
290 key_hash_src = (struct IBF_KeyHash *) key_src;
291 memcpy (ibf->key_hash_sum + start, key_hash_src, count * sizeof *key_hash_src);
292 key_hash_src += count;
294 count_src = (struct IBF_Count *) key_hash_src;
295 memcpy (ibf->count + start, count_src, count * sizeof *count_src);
301 * Subtract ibf2 from ibf1, storing the result in ibf1.
302 * The two IBF's must have the same parameters size and hash_num.
304 * @param ibf1 IBF that is subtracted from
305 * @param ibf2 IBF that will be subtracted from ibf1
308 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2)
312 GNUNET_assert (ibf1->size == ibf2->size);
313 GNUNET_assert (ibf1->hash_num == ibf2->hash_num);
315 for (i = 0; i < ibf1->size; i++)
317 ibf1->count[i].count_val -= ibf2->count[i].count_val;
318 ibf1->key_hash_sum[i].key_hash_val ^= ibf2->key_hash_sum[i].key_hash_val;
319 ibf1->key_sum[i].key_val ^= ibf2->key_sum[i].key_val;
325 * Create a copy of an IBF, the copy has to be destroyed properly.
327 * @param ibf the IBF to copy
329 struct InvertibleBloomFilter *
330 ibf_dup (const struct InvertibleBloomFilter *ibf)
332 struct InvertibleBloomFilter *copy;
333 copy = GNUNET_malloc (sizeof *copy);
334 copy->hash_num = ibf->hash_num;
335 copy->size = ibf->size;
336 copy->key_hash_sum = GNUNET_memdup (ibf->key_hash_sum, ibf->size * sizeof (struct IBF_KeyHash));
337 copy->key_sum = GNUNET_memdup (ibf->key_sum, ibf->size * sizeof (struct IBF_Key));
338 copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (struct IBF_Count));
344 * Destroy all resources associated with the invertible bloom filter.
345 * No more ibf_*-functions may be called on ibf after calling destroy.
347 * @param ibf the intertible bloom filter to destroy
350 ibf_destroy (struct InvertibleBloomFilter *ibf)
352 GNUNET_free (ibf->key_sum);
353 GNUNET_free (ibf->key_hash_sum);
354 GNUNET_free (ibf->count);