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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: fibrand.c,v 1.5 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * Fibonacci generator |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <stdarg.h> |
33 | #include <stdio.h> |
34 | #include <stdlib.h> |
35 | #include <string.h> |
36 | |
37 | #include <mLib/bits.h> |
38 | #include <mLib/sub.h> |
39 | |
40 | #include "fibrand.h" |
41 | #include "grand.h" |
42 | #include "lcrand.h" |
43 | |
44 | /*----- Main code ---------------------------------------------------------*/ |
45 | |
46 | /* --- @fibrand_step@ --- * |
47 | * |
48 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
49 | * |
50 | * Returns: Next output from generator. |
51 | * |
52 | * Use: Steps the generator. Returns |
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53 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%. |
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54 | */ |
55 | |
56 | uint32 fibrand_step(fibrand *f) |
57 | { |
58 | unsigned i = f->i; |
59 | unsigned j = i + (FIB_SZ - FIB_TAP); |
60 | uint32 x; |
61 | if (j >= FIB_SZ) |
62 | j -= FIB_SZ; |
63 | x = f->x[i] = U32(f->x[i] + f->x[j]); |
64 | i++; |
65 | if (i >= FIB_SZ) |
66 | i = 0; |
67 | f->i = i; |
68 | return (x); |
69 | } |
70 | |
71 | /* --- @fibrand_seed@ --- * |
72 | * |
73 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
74 | * @grand *r@ = random number generator to extract words from |
75 | * |
76 | * Returns: --- |
77 | * |
78 | * Use: Initializes a Fibonacci generator using word outputs from the |
79 | * given random number source @r@. |
80 | */ |
81 | |
82 | void fibrand_seed(fibrand *f, grand *r) |
83 | { |
84 | int i; |
85 | unsigned p = 0; |
86 | |
87 | for (i = 0; i < FIB_SZ; i++) |
88 | p |= f->x[i] = r->ops->word(r); |
89 | if (!(p & 1)) { |
90 | i = r->ops->range(r, FIB_SZ); |
91 | f->x[i] |= 1; |
92 | } |
93 | f->i = 0; |
94 | } |
95 | |
96 | /* --- @fibrand_lcseed@ --- * |
97 | * |
98 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
99 | * @uint32 seed@ = seed value |
100 | * |
101 | * Returns: --- |
102 | * |
103 | * Use: Initializes a Fibonacci generator using outputs from the |
104 | * @lcrand@ generator seeded from @seed@. This is faster than |
105 | * using a generic @lcrand@-based generator and @fibrand_rseed@ |
106 | * because it uses raw outputs rather than uniformly distributed |
107 | * 32-bit words. |
108 | */ |
109 | |
110 | void fibrand_lcseed(fibrand *f, uint32 seed) |
111 | { |
112 | int i; |
113 | unsigned p = 0; |
114 | |
115 | for (i = 0; i < FIB_SZ; i++) |
116 | p |= f->x[i] = seed = lcrand(seed); |
117 | if (!(p & 1)) { |
118 | i = lcrand_range(&seed, FIB_SZ); |
119 | f->x[i] |= 1; |
120 | } |
121 | f->i = 0; |
122 | } |
123 | |
124 | /* --- @fibrand_range@ --- * |
125 | * |
126 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
127 | * @uint32 m@ = limit |
128 | * |
129 | * Returns: A uniformly distributed pseudorandom integer in the interval |
130 | * %$[0, m)$%. |
131 | */ |
132 | |
133 | uint32 fibrand_range(fibrand *f, uint32 m) |
134 | { |
135 | uint32 r = 0xffffffff - (0xffffffff % m); |
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136 | uint32 x; |
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137 | |
138 | /* --- Now generate numbers until a good one comes along --- */ |
139 | |
140 | do x = fibrand_step(f); while (x >= r); |
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141 | return (x % m); |
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142 | } |
143 | |
144 | /*----- Generic interface -------------------------------------------------*/ |
145 | |
146 | typedef struct gctx { |
147 | grand r; |
148 | fibrand f; |
149 | } gctx; |
150 | |
151 | static void gdestroy(grand *r) |
152 | { |
153 | gctx *g = (gctx *)r; |
154 | DESTROY(g); |
155 | } |
156 | |
157 | static int gmisc(grand *r, unsigned op, ...) |
158 | { |
159 | gctx *g = (gctx *)r; |
160 | va_list ap; |
161 | int rc = 0; |
162 | va_start(ap, op); |
163 | |
164 | switch (op) { |
165 | case GRAND_CHECK: |
166 | switch (va_arg(ap, unsigned)) { |
167 | case GRAND_CHECK: |
168 | case GRAND_SEEDINT: |
169 | case GRAND_SEEDUINT32: |
170 | case GRAND_SEEDRAND: |
171 | rc = 1; |
172 | break; |
173 | default: |
174 | rc = 0; |
175 | break; |
176 | } |
177 | break; |
178 | case GRAND_SEEDINT: |
179 | fibrand_lcseed(&g->f, va_arg(ap, unsigned)); |
180 | break; |
181 | case GRAND_SEEDUINT32: |
182 | fibrand_lcseed(&g->f, va_arg(ap, uint32)); |
183 | break; |
184 | case GRAND_SEEDRAND: |
185 | fibrand_seed(&g->f, va_arg(ap, grand *)); |
186 | break; |
187 | default: |
188 | GRAND_BADOP; |
189 | break; |
190 | } |
191 | |
192 | va_end(ap); |
193 | return (rc); |
194 | } |
195 | |
196 | static octet gbyte(grand *r) |
197 | { |
198 | gctx *g = (gctx *)r; |
199 | return (U8(fibrand_step(&g->f))); |
200 | } |
201 | |
202 | static uint32 gword(grand *r) |
203 | { |
204 | gctx *g = (gctx *)r; |
205 | return (fibrand_step(&g->f)); |
206 | } |
207 | |
208 | static uint32 grange(grand *r, uint32 l) |
209 | { |
210 | gctx *g = (gctx *)r; |
211 | return (fibrand_range(&g->f, l)); |
212 | } |
213 | |
214 | static void gfill(grand *r, void *p, size_t sz) |
215 | { |
216 | gctx *g = (gctx *)r; |
217 | octet *q = p; |
218 | while (sz) { |
219 | *q++ = U8(fibrand_step(&g->f)); |
220 | sz--; |
221 | } |
222 | } |
223 | |
224 | static const grand_ops gops = { |
225 | "fibrand", |
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226 | 0, 0, |
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227 | gmisc, gdestroy, |
228 | gword, gbyte, gword, grange, gfill |
229 | }; |
230 | |
231 | /* --- @fibrand_create@ --- * |
232 | * |
233 | * Arguments: @uint32 seed@ = initial seed |
234 | * |
235 | * Returns: Pointer to a generic generator. |
236 | * |
237 | * Use: Constructs a generic generator interface over a Fibonacci |
238 | * generator. The generator is seeded using @fibrand_lcseed@. |
239 | */ |
240 | |
241 | grand *fibrand_create(uint32 seed) |
242 | { |
243 | gctx *g = CREATE(gctx); |
244 | g->r.ops = &gops; |
245 | fibrand_lcseed(&g->f, seed); |
246 | return (&g->r); |
247 | } |
248 | |
249 | /*----- That's all, folks -------------------------------------------------*/ |