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bloom.h (6598B)
1 /*
2 * Copyright (c) 2012-2022, Jyri J. Virkki
3 * All rights reserved.
4 *
5 * This file is under BSD license. See LICENSE file.
6 */
7
8 #ifndef _BLOOM_H
9 #define _BLOOM_H
10
11 #ifdef __cplusplus
12 extern "C" {
13 #endif
14
15 #define BLOOM_VERSION_MAJOR 2
16 #define BLOOM_VERSION_MINOR 0
17
18 #define NULL_BLOOM_FILTER { 0, 0, 0, 0, 0.0, 0, 0, 0, 0.0, NULL }
19
20 #define ENTRIES_T unsigned int
21 #define BYTES_T unsigned long int
22 #define BITS_T unsigned long int
23
24
25 /** ***************************************************************************
26 * Structure to keep track of one bloom filter. Caller needs to
27 * allocate this and pass it to the functions below. First call for
28 * every struct must be to bloom_init().
29 *
30 */
31 struct bloom
32 {
33 // These fields are part of the public interface of this structure.
34 // Client code may read these values if desired. Client code MUST NOT
35 // modify any of these.
36 unsigned int entries;
37 unsigned long int bits;
38 unsigned long int bytes;
39 unsigned char hashes;
40 double error;
41
42 // Fields below are private to the implementation. These may go away or
43 // change incompatibly at any moment. Client code MUST NOT access or rely
44 // on these.
45 unsigned char ready;
46 unsigned char major;
47 unsigned char minor;
48 double bpe;
49 unsigned char * bf;
50 };
51
52
53 /** ***************************************************************************
54 * Initialize the bloom filter for use.
55 *
56 * The filter is initialized with a bit field and number of hash functions
57 * according to the computations from the wikipedia entry:
58 * http://en.wikipedia.org/wiki/Bloom_filter
59 *
60 * Optimal number of bits is:
61 * bits = (entries * ln(error)) / ln(2)^2
62 *
63 * Optimal number of hash functions is:
64 * hashes = bpe * ln(2)
65 *
66 * Parameters:
67 * -----------
68 * bloom - Pointer to an allocated struct bloom (see above).
69 * entries - The expected number of entries which will be inserted.
70 * Must be at least 1000 (in practice, likely much larger).
71 * error - Probability of collision (as long as entries are not
72 * exceeded).
73 *
74 * Return:
75 * -------
76 * 0 - on success
77 * 1 - on failure
78 *
79 */
80 int bloom_init2(struct bloom * bloom, unsigned int entries, double error);
81
82
83 /**
84 * DEPRECATED.
85 * Kept for compatibility with libbloom v.1. To be removed in v3.0.
86 *
87 */
88 int bloom_init(struct bloom * bloom, int entries, double error);
89
90
91 /** ***************************************************************************
92 * Check if the given element is in the bloom filter. Remember this may
93 * return false positive if a collision occurred.
94 *
95 * Parameters:
96 * -----------
97 * bloom - Pointer to an allocated struct bloom (see above).
98 * buffer - Pointer to buffer containing element to check.
99 * len - Size of 'buffer'.
100 *
101 * Return:
102 * -------
103 * 0 - element is not present
104 * 1 - element is present (or false positive due to collision)
105 * -1 - bloom not initialized
106 *
107 */
108 int bloom_check(struct bloom * bloom, const void * buffer, int len);
109
110
111 /** ***************************************************************************
112 * Add the given element to the bloom filter.
113 * The return code indicates if the element (or a collision) was already in,
114 * so for the common check+add use case, no need to call check separately.
115 *
116 * Parameters:
117 * -----------
118 * bloom - Pointer to an allocated struct bloom (see above).
119 * buffer - Pointer to buffer containing element to add.
120 * len - Size of 'buffer'.
121 *
122 * Return:
123 * -------
124 * 0 - element was not present and was added
125 * 1 - element (or a collision) had already been added previously
126 * -1 - bloom not initialized
127 *
128 */
129 int bloom_add(struct bloom * bloom, const void * buffer, int len);
130
131
132 /** ***************************************************************************
133 * Print (to stdout) info about this bloom filter. Debugging aid.
134 *
135 */
136 void bloom_print(struct bloom * bloom);
137
138
139 /** ***************************************************************************
140 * Deallocate internal storage.
141 *
142 * Upon return, the bloom struct is no longer usable. You may call bloom_init
143 * again on the same struct to reinitialize it again.
144 *
145 * Parameters:
146 * -----------
147 * bloom - Pointer to an allocated struct bloom (see above).
148 *
149 * Return: none
150 *
151 */
152 void bloom_free(struct bloom * bloom);
153
154
155 /** ***************************************************************************
156 * Erase internal storage.
157 *
158 * Erases all elements. Upon return, the bloom struct returns to its initial
159 * (initialized) state.
160 *
161 * Parameters:
162 * -----------
163 * bloom - Pointer to an allocated struct bloom (see above).
164 *
165 * Return:
166 * 0 - on success
167 * 1 - on failure
168 *
169 */
170 int bloom_reset(struct bloom * bloom);
171
172
173 /** ***************************************************************************
174 * Save a bloom filter to a file.
175 *
176 * Parameters:
177 * -----------
178 * bloom - Pointer to an allocated struct bloom (see above).
179 * filename - Create (or overwrite) bloom data to this file.
180 *
181 * Return:
182 * 0 - on success
183 * 1 - on failure
184 *
185 */
186 int bloom_save(struct bloom * bloom, char * filename);
187
188
189 /** ***************************************************************************
190 * Load a bloom filter from a file.
191 *
192 * This functions loads a file previously saved with bloom_save().
193 *
194 * Parameters:
195 * -----------
196 * bloom - Pointer to an allocated struct bloom (see above).
197 * filename - Load bloom filter data from this file.
198 *
199 * Return:
200 * 0 - on success
201 * > 0 - on failure
202 *
203 */
204 int bloom_load(struct bloom * bloom, char * filename);
205
206
207 /** ***************************************************************************
208 * Merge two compatible bloom filters.
209 *
210 * On success, bloom_dest will contain all elements of bloom_src in addition
211 * to its own. The bloom_src bloom filter is never modified.
212 *
213 * Both bloom_dest and bloom_src must be initialized and both must have
214 * identical parameters.
215 *
216 * Parameters:
217 * -----------
218 * bloom_dest - will contain the merged elements from bloom_src
219 * bloom_src - its elements will be merged into bloom_dest
220 *
221 * Return:
222 * -------
223 * 0 - on success
224 * 1 - incompatible bloom filters
225 * -1 - bloom not initialized
226 *
227 */
228 int bloom_merge(struct bloom * bloom_dest, struct bloom * bloom_src);
229
230
231 /** ***************************************************************************
232 * Returns version string compiled into library.
233 *
234 * Return: version string
235 *
236 */
237 const char * bloom_version();
238
239 #ifdef __cplusplus
240 }
241 #endif
242
243 #endif