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1 | /* -*-c-*- |
2 | * | |
05dfc037 | 3 | * $Id$ |
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4 | * |
5 | * Fibonacci generator | |
6 | * | |
7 | * (c) 1999 Straylight/Edgeware | |
8 | * (c) 2000 Mark Wooding | |
9 | */ | |
10 | ||
11 | /*----- Licensing notice --------------------------------------------------* | |
12 | * | |
13 | * Copyright (c) 2000 Mark Wooding | |
14 | * All rights reserved. | |
15 | * | |
16 | * Redistribution and use in source and binary forms, with or without | |
17 | * modification, are permitted provided that the following conditions are | |
18 | * met: | |
19 | * | |
20 | * 1. Redistributions of source code must retain the above copyright | |
21 | * notice, this list of conditions and the following disclaimer. | |
22 | * | |
23 | * 2, Redistributions in binary form must reproduce the above copyright | |
24 | * notice, this list of conditions and the following disclaimer in the | |
25 | * documentation and/or other materials provided with the distribution. | |
26 | * | |
27 | * 3. The name of the authors may not be used to endorse or promote | |
28 | * products derived from this software without specific prior written | |
29 | * permission. | |
30 | * | |
31 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED | |
32 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF | |
33 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN | |
6b2d9d76 | 34 | * NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
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35 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
36 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | |
37 | * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
38 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |
39 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN | |
40 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |
41 | * POSSIBILITY OF SUCH DAMAGE. | |
42 | * | |
43 | * Instead of accepting the above terms, you may redistribute and/or modify | |
44 | * this software under the terms of either the GNU General Public License, | |
45 | * or the GNU Library General Public License, published by the Free | |
46 | * Software Foundation; either version 2 of the License, or (at your | |
47 | * option) any later version. | |
48 | */ | |
49 | ||
50 | /*----- Revision history --------------------------------------------------* | |
51 | * | |
52 | * $Log: fibrand.c,v $ | |
6b2d9d76 MW |
53 | * Revision 1.2 2000/07/02 15:21:20 mdw |
54 | * Fix licence text. | |
55 | * | |
e6e0e332 MW |
56 | * Revision 1.1 2000/05/21 11:28:30 mdw |
57 | * Initial check-in. | |
58 | * | |
59 | * --- Past lives (Catacomb) --- * | |
60 | * | |
61 | * Revision 1.1 1999/12/10 23:15:27 mdw | |
62 | * Noncryptographic random number generator. | |
63 | * | |
64 | */ | |
65 | ||
66 | /*----- Header files ------------------------------------------------------*/ | |
67 | ||
68 | #include <stdio.h> | |
69 | #include <stdlib.h> | |
70 | #include <string.h> | |
71 | ||
72 | #include "bits.h" | |
73 | #include "fibrand.h" | |
74 | #include "lcrand.h" | |
75 | ||
76 | /*----- Main code ---------------------------------------------------------*/ | |
77 | ||
78 | /* --- @fibrand_step@ --- * | |
79 | * | |
80 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context | |
81 | * | |
82 | * Returns: Next output from generator. | |
83 | * | |
84 | * Use: Steps the generator. Returns | |
85 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%. | |
86 | */ | |
87 | ||
88 | uint32 fibrand_step(fibrand *f) | |
89 | { | |
90 | unsigned i = f->i; | |
91 | unsigned j = i + (FIB_SZ - FIB_TAP); | |
92 | uint32 x; | |
93 | if (j >= FIB_SZ) | |
94 | j -= FIB_SZ; | |
95 | x = f->x[i] = U32(f->x[i] + f->x[j]); | |
96 | i++; | |
97 | if (i >= FIB_SZ) | |
98 | i = 0; | |
99 | f->i = i; | |
100 | return (x); | |
101 | } | |
102 | ||
103 | /* --- @fibrand_lcseed@ --- * | |
104 | * | |
105 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context | |
106 | * @uint32 seed@ = seed value | |
107 | * | |
108 | * Returns: --- | |
109 | * | |
110 | * Use: Initializes a Fibonacci generator using outputs from the | |
111 | * @lcrand@ generator seeded from @seed@. This is faster than | |
112 | * using a generic @lcrand@-based generator and @fibrand_rseed@ | |
113 | * because it uses raw outputs rather than uniformly distributed | |
114 | * 32-bit words. | |
115 | */ | |
116 | ||
117 | void fibrand_lcseed(fibrand *f, uint32 seed) | |
118 | { | |
119 | int i; | |
120 | unsigned p = 0; | |
121 | ||
122 | for (i = 0; i < FIB_SZ; i++) | |
123 | p |= f->x[i] = seed = lcrand(seed); | |
124 | if (!(p & 1)) { | |
125 | i = lcrand_range(&seed, FIB_SZ); | |
126 | f->x[i] |= 1; | |
127 | } | |
128 | f->i = 0; | |
129 | } | |
130 | ||
131 | /* --- @fibrand_range@ --- * | |
132 | * | |
133 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context | |
134 | * @uint32 m@ = limit | |
135 | * | |
136 | * Returns: A uniformly distributed pseudorandom integer in the interval | |
137 | * %$[0, m)$%. | |
138 | */ | |
139 | ||
140 | uint32 fibrand_range(fibrand *f, uint32 m) | |
141 | { | |
142 | uint32 r = 0xffffffff - (0xffffffff % m); | |
143 | uint x; | |
144 | ||
145 | /* --- Now generate numbers until a good one comes along --- */ | |
146 | ||
147 | do x = fibrand_step(f); while (x >= r); | |
148 | return (x / (r / m)); | |
149 | } | |
150 | ||
151 | /*----- That's all, folks -------------------------------------------------*/ |