3 * $Id: fibrand.c,v 1.3 2000/12/06 20:31:06 mdw Exp $
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.3 2000/12/06 20:31:06 mdw
34 * Simplify uniform range transformation.
36 * Revision 1.2 2000/06/17 10:55:24 mdw
37 * Typesetting fixes. Add flags word to generatic random generator.
39 * Revision 1.1 1999/12/10 23:15:27 mdw
40 * Noncryptographic random number generator.
44 /*----- Header files ------------------------------------------------------*/
51 #include <mLib/bits.h>
58 /*----- Main code ---------------------------------------------------------*/
60 /* --- @fibrand_step@ --- *
62 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
64 * Returns: Next output from generator.
66 * Use: Steps the generator. Returns
67 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
70 uint32 fibrand_step(fibrand *f)
73 unsigned j = i + (FIB_SZ - FIB_TAP);
77 x = f->x[i] = U32(f->x[i] + f->x[j]);
85 /* --- @fibrand_seed@ --- *
87 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
88 * @grand *r@ = random number generator to extract words from
92 * Use: Initializes a Fibonacci generator using word outputs from the
93 * given random number source @r@.
96 void fibrand_seed(fibrand *f, grand *r)
101 for (i = 0; i < FIB_SZ; i++)
102 p |= f->x[i] = r->ops->word(r);
104 i = r->ops->range(r, FIB_SZ);
110 /* --- @fibrand_lcseed@ --- *
112 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
113 * @uint32 seed@ = seed value
117 * Use: Initializes a Fibonacci generator using outputs from the
118 * @lcrand@ generator seeded from @seed@. This is faster than
119 * using a generic @lcrand@-based generator and @fibrand_rseed@
120 * because it uses raw outputs rather than uniformly distributed
124 void fibrand_lcseed(fibrand *f, uint32 seed)
129 for (i = 0; i < FIB_SZ; i++)
130 p |= f->x[i] = seed = lcrand(seed);
132 i = lcrand_range(&seed, FIB_SZ);
138 /* --- @fibrand_range@ --- *
140 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
143 * Returns: A uniformly distributed pseudorandom integer in the interval
147 uint32 fibrand_range(fibrand *f, uint32 m)
149 uint32 r = 0xffffffff - (0xffffffff % m);
152 /* --- Now generate numbers until a good one comes along --- */
154 do x = fibrand_step(f); while (x >= r);
158 /*----- Generic interface -------------------------------------------------*/
160 typedef struct gctx {
165 static void gdestroy(grand *r)
171 static int gmisc(grand *r, unsigned op, ...)
180 switch (va_arg(ap, unsigned)) {
183 case GRAND_SEEDUINT32:
193 fibrand_lcseed(&g->f, va_arg(ap, unsigned));
195 case GRAND_SEEDUINT32:
196 fibrand_lcseed(&g->f, va_arg(ap, uint32));
199 fibrand_seed(&g->f, va_arg(ap, grand *));
210 static octet gbyte(grand *r)
213 return (U8(fibrand_step(&g->f)));
216 static uint32 gword(grand *r)
219 return (fibrand_step(&g->f));
222 static uint32 grange(grand *r, uint32 l)
225 return (fibrand_range(&g->f, l));
228 static void gfill(grand *r, void *p, size_t sz)
233 *q++ = U8(fibrand_step(&g->f));
238 static const grand_ops gops = {
242 gword, gbyte, gword, grange, gfill
245 /* --- @fibrand_create@ --- *
247 * Arguments: @uint32 seed@ = initial seed
249 * Returns: Pointer to a generic generator.
251 * Use: Constructs a generic generator interface over a Fibonacci
252 * generator. The generator is seeded using @fibrand_lcseed@.
255 grand *fibrand_create(uint32 seed)
257 gctx *g = CREATE(gctx);
259 fibrand_lcseed(&g->f, seed);
263 /*----- That's all, folks -------------------------------------------------*/