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e6e0e332 MW |
1 | /* -*-c-*- |
2 | * | |
3 | * $Id: fibrand.c,v 1.1 2000/05/21 11:28:30 mdw Exp $ | |
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 | |
34 | * NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, | |
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 $ | |
53 | * Revision 1.1 2000/05/21 11:28:30 mdw | |
54 | * Initial check-in. | |
55 | * | |
56 | * --- Past lives (Catacomb) --- * | |
57 | * | |
58 | * Revision 1.1 1999/12/10 23:15:27 mdw | |
59 | * Noncryptographic random number generator. | |
60 | * | |
61 | */ | |
62 | ||
63 | /*----- Header files ------------------------------------------------------*/ | |
64 | ||
65 | #include <stdio.h> | |
66 | #include <stdlib.h> | |
67 | #include <string.h> | |
68 | ||
69 | #include "bits.h" | |
70 | #include "fibrand.h" | |
71 | #include "lcrand.h" | |
72 | ||
73 | /*----- Main code ---------------------------------------------------------*/ | |
74 | ||
75 | /* --- @fibrand_step@ --- * | |
76 | * | |
77 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context | |
78 | * | |
79 | * Returns: Next output from generator. | |
80 | * | |
81 | * Use: Steps the generator. Returns | |
82 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%. | |
83 | */ | |
84 | ||
85 | uint32 fibrand_step(fibrand *f) | |
86 | { | |
87 | unsigned i = f->i; | |
88 | unsigned j = i + (FIB_SZ - FIB_TAP); | |
89 | uint32 x; | |
90 | if (j >= FIB_SZ) | |
91 | j -= FIB_SZ; | |
92 | x = f->x[i] = U32(f->x[i] + f->x[j]); | |
93 | i++; | |
94 | if (i >= FIB_SZ) | |
95 | i = 0; | |
96 | f->i = i; | |
97 | return (x); | |
98 | } | |
99 | ||
100 | /* --- @fibrand_lcseed@ --- * | |
101 | * | |
102 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context | |
103 | * @uint32 seed@ = seed value | |
104 | * | |
105 | * Returns: --- | |
106 | * | |
107 | * Use: Initializes a Fibonacci generator using outputs from the | |
108 | * @lcrand@ generator seeded from @seed@. This is faster than | |
109 | * using a generic @lcrand@-based generator and @fibrand_rseed@ | |
110 | * because it uses raw outputs rather than uniformly distributed | |
111 | * 32-bit words. | |
112 | */ | |
113 | ||
114 | void fibrand_lcseed(fibrand *f, uint32 seed) | |
115 | { | |
116 | int i; | |
117 | unsigned p = 0; | |
118 | ||
119 | for (i = 0; i < FIB_SZ; i++) | |
120 | p |= f->x[i] = seed = lcrand(seed); | |
121 | if (!(p & 1)) { | |
122 | i = lcrand_range(&seed, FIB_SZ); | |
123 | f->x[i] |= 1; | |
124 | } | |
125 | f->i = 0; | |
126 | } | |
127 | ||
128 | /* --- @fibrand_range@ --- * | |
129 | * | |
130 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context | |
131 | * @uint32 m@ = limit | |
132 | * | |
133 | * Returns: A uniformly distributed pseudorandom integer in the interval | |
134 | * %$[0, m)$%. | |
135 | */ | |
136 | ||
137 | uint32 fibrand_range(fibrand *f, uint32 m) | |
138 | { | |
139 | uint32 r = 0xffffffff - (0xffffffff % m); | |
140 | uint x; | |
141 | ||
142 | /* --- Now generate numbers until a good one comes along --- */ | |
143 | ||
144 | do x = fibrand_step(f); while (x >= r); | |
145 | return (x / (r / m)); | |
146 | } | |
147 | ||
148 | /*----- That's all, folks -------------------------------------------------*/ |