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