07871354 |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: fibrand.c,v 1.1 1999/12/10 23:15:27 mdw Exp $ |
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 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: fibrand.c,v $ |
33 | * Revision 1.1 1999/12/10 23:15:27 mdw |
34 | * Noncryptographic random number generator. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include <stdarg.h> |
41 | #include <stdio.h> |
42 | #include <stdlib.h> |
43 | #include <string.h> |
44 | |
45 | #include <mLib/bits.h> |
46 | #include <mLib/sub.h> |
47 | |
48 | #include "fibrand.h" |
49 | #include "grand.h" |
50 | #include "lcrand.h" |
51 | |
52 | /*----- Main code ---------------------------------------------------------*/ |
53 | |
54 | /* --- @fibrand_step@ --- * |
55 | * |
56 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
57 | * |
58 | * Returns: Next output from generator. |
59 | * |
60 | * Use: Steps the generator. Returns |
61 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}%$. |
62 | */ |
63 | |
64 | uint32 fibrand_step(fibrand *f) |
65 | { |
66 | unsigned i = f->i; |
67 | unsigned j = i + (FIB_SZ - FIB_TAP); |
68 | uint32 x; |
69 | if (j >= FIB_SZ) |
70 | j -= FIB_SZ; |
71 | x = f->x[i] = U32(f->x[i] + f->x[j]); |
72 | i++; |
73 | if (i >= FIB_SZ) |
74 | i = 0; |
75 | f->i = i; |
76 | return (x); |
77 | } |
78 | |
79 | /* --- @fibrand_seed@ --- * |
80 | * |
81 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
82 | * @grand *r@ = random number generator to extract words from |
83 | * |
84 | * Returns: --- |
85 | * |
86 | * Use: Initializes a Fibonacci generator using word outputs from the |
87 | * given random number source @r@. |
88 | */ |
89 | |
90 | void fibrand_seed(fibrand *f, grand *r) |
91 | { |
92 | int i; |
93 | unsigned p = 0; |
94 | |
95 | for (i = 0; i < FIB_SZ; i++) |
96 | p |= f->x[i] = r->ops->word(r); |
97 | if (!(p & 1)) { |
98 | i = r->ops->range(r, FIB_SZ); |
99 | f->x[i] |= 1; |
100 | } |
101 | f->i = 0; |
102 | } |
103 | |
104 | /* --- @fibrand_lcseed@ --- * |
105 | * |
106 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
107 | * @uint32 seed@ = seed value |
108 | * |
109 | * Returns: --- |
110 | * |
111 | * Use: Initializes a Fibonacci generator using outputs from the |
112 | * @lcrand@ generator seeded from @seed@. This is faster than |
113 | * using a generic @lcrand@-based generator and @fibrand_rseed@ |
114 | * because it uses raw outputs rather than uniformly distributed |
115 | * 32-bit words. |
116 | */ |
117 | |
118 | void fibrand_lcseed(fibrand *f, uint32 seed) |
119 | { |
120 | int i; |
121 | unsigned p = 0; |
122 | |
123 | for (i = 0; i < FIB_SZ; i++) |
124 | p |= f->x[i] = seed = lcrand(seed); |
125 | if (!(p & 1)) { |
126 | i = lcrand_range(&seed, FIB_SZ); |
127 | f->x[i] |= 1; |
128 | } |
129 | f->i = 0; |
130 | } |
131 | |
132 | /* --- @fibrand_range@ --- * |
133 | * |
134 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
135 | * @uint32 m@ = limit |
136 | * |
137 | * Returns: A uniformly distributed pseudorandom integer in the interval |
138 | * %$[0, m)$%. |
139 | */ |
140 | |
141 | uint32 fibrand_range(fibrand *f, uint32 m) |
142 | { |
143 | uint32 r = 0xffffffff - (0xffffffff % m); |
144 | uint x; |
145 | |
146 | /* --- Now generate numbers until a good one comes along --- */ |
147 | |
148 | do x = fibrand_step(f); while (x >= r); |
149 | return (x / (r / m)); |
150 | } |
151 | |
152 | /*----- Generic interface -------------------------------------------------*/ |
153 | |
154 | typedef struct gctx { |
155 | grand r; |
156 | fibrand f; |
157 | } gctx; |
158 | |
159 | static void gdestroy(grand *r) |
160 | { |
161 | gctx *g = (gctx *)r; |
162 | DESTROY(g); |
163 | } |
164 | |
165 | static int gmisc(grand *r, unsigned op, ...) |
166 | { |
167 | gctx *g = (gctx *)r; |
168 | va_list ap; |
169 | int rc = 0; |
170 | va_start(ap, op); |
171 | |
172 | switch (op) { |
173 | case GRAND_CHECK: |
174 | switch (va_arg(ap, unsigned)) { |
175 | case GRAND_CHECK: |
176 | case GRAND_SEEDINT: |
177 | case GRAND_SEEDUINT32: |
178 | case GRAND_SEEDRAND: |
179 | rc = 1; |
180 | break; |
181 | default: |
182 | rc = 0; |
183 | break; |
184 | } |
185 | break; |
186 | case GRAND_SEEDINT: |
187 | fibrand_lcseed(&g->f, va_arg(ap, unsigned)); |
188 | break; |
189 | case GRAND_SEEDUINT32: |
190 | fibrand_lcseed(&g->f, va_arg(ap, uint32)); |
191 | break; |
192 | case GRAND_SEEDRAND: |
193 | fibrand_seed(&g->f, va_arg(ap, grand *)); |
194 | break; |
195 | default: |
196 | GRAND_BADOP; |
197 | break; |
198 | } |
199 | |
200 | va_end(ap); |
201 | return (rc); |
202 | } |
203 | |
204 | static octet gbyte(grand *r) |
205 | { |
206 | gctx *g = (gctx *)r; |
207 | return (U8(fibrand_step(&g->f))); |
208 | } |
209 | |
210 | static uint32 gword(grand *r) |
211 | { |
212 | gctx *g = (gctx *)r; |
213 | return (fibrand_step(&g->f)); |
214 | } |
215 | |
216 | static uint32 grange(grand *r, uint32 l) |
217 | { |
218 | gctx *g = (gctx *)r; |
219 | return (fibrand_range(&g->f, l)); |
220 | } |
221 | |
222 | static void gfill(grand *r, void *p, size_t sz) |
223 | { |
224 | gctx *g = (gctx *)r; |
225 | octet *q = p; |
226 | while (sz) { |
227 | *q++ = U8(fibrand_step(&g->f)); |
228 | sz--; |
229 | } |
230 | } |
231 | |
232 | static const grand_ops gops = { |
233 | "fibrand", |
234 | 0, |
235 | gmisc, gdestroy, |
236 | gword, gbyte, gword, grange, gfill |
237 | }; |
238 | |
239 | /* --- @fibrand_create@ --- * |
240 | * |
241 | * Arguments: @uint32 seed@ = initial seed |
242 | * |
243 | * Returns: Pointer to a generic generator. |
244 | * |
245 | * Use: Constructs a generic generator interface over a Fibonacci |
246 | * generator. The generator is seeded using @fibrand_lcseed@. |
247 | */ |
248 | |
249 | grand *fibrand_create(uint32 seed) |
250 | { |
251 | gctx *g = CREATE(gctx); |
252 | g->r.ops = &gops; |
253 | fibrand_lcseed(&g->f, seed); |
254 | return (&g->r); |
255 | } |
256 | |
257 | /*----- That's all, folks -------------------------------------------------*/ |