random.h revision 356345 
1/*
2 * util/random.h - thread safe random generator, which is reasonably secure.
3 *
4 * Copyright (c) 2007, NLnet Labs. All rights reserved.
5 *
6 * This software is open source.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * Redistributions of source code must retain the above copyright notice,
13 * this list of conditions and the following disclaimer.
14 *
15 * Redistributions in binary form must reproduce the above copyright notice,
16 * this list of conditions and the following disclaimer in the documentation
17 * and/or other materials provided with the distribution.
18 *
19 * Neither the name of the NLNET LABS nor the names of its contributors may
20 * be used to endorse or promote products derived from this software without
21 * specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
26 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
27 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
29 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
30 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
31 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
32 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
33 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35
36#ifndef UTIL_RANDOM_H
37#define UTIL_RANDOM_H
38
39/**
40 * \file
41 * Thread safe random functions. Similar to arc4random() with an explicit
42 * initialisation routine.
43 */
44
45/**
46 * random state structure.
47 */
48struct ub_randstate;
49
50/**
51 * Initialize a random generator state for use
52 * @param from: if not NULL, the seed is taken from this random structure.
53 * 	can be used to seed random states via a parent-random-state that
54 * 	is itself seeded with entropy.
55 * @return new state or NULL alloc failure.
56 */
57struct ub_randstate* ub_initstate(struct ub_randstate* from);
58
59/**
60 * Generate next random number from the state passed along.
61 * Thread safe, so random numbers are repeatable.
62 * @param state: must have been initialised with ub_initstate.
63 * @return: random 31 bit value.
64 */
65long int ub_random(struct ub_randstate* state);
66
67/**
68 * Generate random number between 0 and x-1.  No modulo bias.
69 * @param state: must have been initialised with ub_initstate.
70 * @param x: an upper limit. not (negative or zero). must be smaller than 2**31.
71 * @return: random value between 0..x-1. Possibly more than one
72 * random number is picked from the random stream to satisfy this.
73 */
74long int ub_random_max(struct ub_randstate* state, long int x);
75
76/**
77 * Delete the random state.
78 * @param state: to delete.
79 */
80void ub_randfree(struct ub_randstate* state);
81
82#endif /* UTIL_RANDOM_H */
83