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3 (C) 2012 Christian Grothoff (and other contributing authors)
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23 * @brief invertible bloom filter
24 * @author Florian Dold
27 #ifndef GNUNET_CONSENSUS_IBF_H
28 #define GNUNET_CONSENSUS_IBF_H
31 #include "gnunet_util_lib.h"
36 #if 0 /* keep Emacsens' auto-indent happy */
49 uint32_t key_hash_val;
58 * Size of one ibf bucket in bytes
60 #define IBF_BUCKET_SIZE (sizeof (struct IBF_Count) + sizeof (struct IBF_Key) + \
61 sizeof (struct IBF_KeyHash))
64 * Invertible bloom filter (IBF).
66 * An IBF is a counting bloom filter that has the ability to restore
67 * the hashes of its stored elements with high probability.
69 struct InvertibleBloomFilter
72 * How many cells does this IBF have?
77 * In how many cells do we hash one element?
83 * Xor sums of the elements' keys, used to identify the elements.
84 * Array of 'size' elements.
86 struct IBF_Key *key_sum;
89 * Xor sums of the hashes of the keys of inserted elements.
90 * Array of 'size' elements.
92 struct IBF_KeyHash *key_hash_sum;
95 * How many times has a bucket been hit?
96 * Can be negative, as a result of IBF subtraction.
97 * Array of 'size' elements.
99 struct IBF_Count *count;
104 * Write buckets from an ibf to a buffer.
105 * Exactly (IBF_BUCKET_SIZE*ibf->size) bytes are written to buf.
107 * @param ibf the ibf to write
108 * @param start with which bucket to start
109 * @param count how many buckets to write
110 * @param buf buffer to write the data to
113 ibf_write_slice (const struct InvertibleBloomFilter *ibf, uint32_t start, uint32_t count, void *buf);
117 * Read buckets from a buffer into an ibf.
119 * @param buf pointer to the buffer to read from
120 * @param start which bucket to start at
121 * @param count how many buckets to read
122 * @param ibf the ibf to read from
125 ibf_read_slice (const void *buf, uint32_t start, uint32_t count, struct InvertibleBloomFilter *ibf);
129 * Create a key from a hashcode.
131 * @param hash the hashcode
135 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash);
139 * Create a hashcode from a key, by replicating the key
140 * until the hascode is filled
143 * @param dst hashcode to store the result in
146 ibf_hashcode_from_key (struct IBF_Key key, struct GNUNET_HashCode *dst);
150 * Create an invertible bloom filter.
152 * @param size number of IBF buckets
153 * @param hash_num number of buckets one element is hashed in, usually 3 or 4
154 * @return the newly created invertible bloom filter
156 struct InvertibleBloomFilter *
157 ibf_create (uint32_t size, uint8_t hash_num);
161 * Insert an element into an IBF.
164 * @param key the element's hash code
167 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key);
171 * Subtract ibf2 from ibf1, storing the result in ibf1.
172 * The two IBF's must have the same parameters size and hash_num.
174 * @param ibf1 IBF that is subtracted from
175 * @param ibf2 IBF that will be subtracted from ibf1
178 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2);
182 * Decode and remove an element from the IBF, if possible.
184 * @param ibf the invertible bloom filter to decode
185 * @param ret_side sign of the cell's count where the decoded element came from.
186 * A negative sign indicates that the element was recovered
187 * resides in an IBF that was previously subtracted from.
188 * @param ret_id receives the hash code of the decoded element, if successful
189 * @return GNUNET_YES if decoding an element was successful,
190 * GNUNET_NO if the IBF is empty,
191 * GNUNET_SYSERR if the decoding has failed
194 ibf_decode (struct InvertibleBloomFilter *ibf, int *ret_side, struct IBF_Key *ret_id);
198 * Create a copy of an IBF, the copy has to be destroyed properly.
200 * @param ibf the IBF to copy
202 struct InvertibleBloomFilter *
203 ibf_dup (const struct InvertibleBloomFilter *ibf);
206 * Destroy all resources associated with the invertible bloom filter.
207 * No more ibf_*-functions may be called on ibf after calling destroy.
209 * @param ibf the intertible bloom filter to destroy
212 ibf_destroy (struct InvertibleBloomFilter *ibf);
215 #if 0 /* keep Emacsens' auto-indent happy */