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22 * @file consensus/ibf.h
23 * @brief invertible bloom filter
24 * @author Florian Dold
27 #ifndef GNUNET_CONSENSUS_IBF_H
28 #define GNUNET_CONSENSUS_IBF_H
31 #include "gnunet_common.h"
32 #include "gnunet_util_lib.h"
37 #if 0 /* keep Emacsens' auto-indent happy */
50 uint32_t key_hash_val;
59 * Size of one ibf bucket in bytes
61 #define IBF_BUCKET_SIZE (sizeof (struct IBF_Count) + sizeof (struct IBF_Key) + \
62 sizeof (struct IBF_KeyHash))
65 * Invertible bloom filter (IBF).
67 * An IBF is a counting bloom filter that has the ability to restore
68 * the hashes of its stored elements with high probability.
70 struct InvertibleBloomFilter
73 * How many cells does this IBF have?
78 * In how many cells do we hash one element?
84 * Xor sums of the elements' keys, used to identify the elements.
85 * Array of 'size' elements.
87 struct IBF_Key *key_sum;
90 * Xor sums of the hashes of the keys of inserted elements.
91 * Array of 'size' elements.
93 struct IBF_KeyHash *key_hash_sum;
96 * How many times has a bucket been hit?
97 * Can be negative, as a result of IBF subtraction.
98 * Array of 'size' elements.
100 struct IBF_Count *count;
105 * Write buckets from an ibf to a buffer.
106 * Exactly (IBF_BUCKET_SIZE*ibf->size) bytes are written to buf.
108 * @param ibf the ibf to write
109 * @param start with which bucket to start
110 * @param count how many buckets to write
111 * @param buf buffer to write the data to
114 ibf_write_slice (const struct InvertibleBloomFilter *ibf, uint32_t start, uint32_t count, void *buf);
118 * Read buckets from a buffer into an ibf.
120 * @param buf pointer to the buffer to read from
121 * @param start which bucket to start at
122 * @param count how many buckets to read
123 * @param ibf the ibf to read from
126 ibf_read_slice (const void *buf, uint32_t start, uint32_t count, struct InvertibleBloomFilter *ibf);
130 * Create a key from a hashcode.
132 * @param hash the hashcode
136 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash);
140 * Create a hashcode from a key, by replicating the key
141 * until the hascode is filled
144 * @param dst hashcode to store the result in
147 ibf_hashcode_from_key (struct IBF_Key key, struct GNUNET_HashCode *dst);
151 * Create an invertible bloom filter.
153 * @param size number of IBF buckets
154 * @param hash_num number of buckets one element is hashed in, usually 3 or 4
155 * @return the newly created invertible bloom filter
157 struct InvertibleBloomFilter *
158 ibf_create (uint32_t size, uint8_t hash_num);
162 * Insert an element into an IBF.
165 * @param key the element's hash code
168 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key);
172 * Subtract ibf2 from ibf1, storing the result in ibf1.
173 * The two IBF's must have the same parameters size and hash_num.
175 * @param ibf1 IBF that is subtracted from
176 * @param ibf2 IBF that will be subtracted from ibf1
179 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2);
183 * Decode and remove an element from the IBF, if possible.
185 * @param ibf the invertible bloom filter to decode
186 * @param ret_side sign of the cell's count where the decoded element came from.
187 * A negative sign indicates that the element was recovered
188 * resides in an IBF that was previously subtracted from.
189 * @param ret_id receives the hash code of the decoded element, if successful
190 * @return GNUNET_YES if decoding an element was successful,
191 * GNUNET_NO if the IBF is empty,
192 * GNUNET_SYSERR if the decoding has failed
195 ibf_decode (struct InvertibleBloomFilter *ibf, int *ret_side, struct IBF_Key *ret_id);
199 * Create a copy of an IBF, the copy has to be destroyed properly.
201 * @param ibf the IBF to copy
203 struct InvertibleBloomFilter *
204 ibf_dup (const struct InvertibleBloomFilter *ibf);
207 * Destroy all resources associated with the invertible bloom filter.
208 * No more ibf_*-functions may be called on ibf after calling destroy.
210 * @param ibf the intertible bloom filter to destroy
213 ibf_destroy (struct InvertibleBloomFilter *ibf);
216 #if 0 /* keep Emacsens' auto-indent happy */