3 * $Id: fibrand.c,v 1.1 1999/12/10 23:15:27 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 1.1 1999/12/10 23:15:27 mdw
34 * Noncryptographic random number generator.
38 /*----- Header files ------------------------------------------------------*/
45 #include <mLib/bits.h>
52 /*----- Main code ---------------------------------------------------------*/
54 /* --- @fibrand_step@ --- *
56 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
58 * Returns: Next output from generator.
60 * Use: Steps the generator. Returns
61 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}%$.
64 uint32 fibrand_step(fibrand *f)
67 unsigned j = i + (FIB_SZ - FIB_TAP);
71 x = f->x[i] = U32(f->x[i] + f->x[j]);
79 /* --- @fibrand_seed@ --- *
81 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
82 * @grand *r@ = random number generator to extract words from
86 * Use: Initializes a Fibonacci generator using word outputs from the
87 * given random number source @r@.
90 void fibrand_seed(fibrand *f, grand *r)
95 for (i = 0; i < FIB_SZ; i++)
96 p |= f->x[i] = r->ops->word(r);
98 i = r->ops->range(r, FIB_SZ);
104 /* --- @fibrand_lcseed@ --- *
106 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
107 * @uint32 seed@ = seed value
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
118 void fibrand_lcseed(fibrand *f, uint32 seed)
123 for (i = 0; i < FIB_SZ; i++)
124 p |= f->x[i] = seed = lcrand(seed);
126 i = lcrand_range(&seed, FIB_SZ);
132 /* --- @fibrand_range@ --- *
134 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
137 * Returns: A uniformly distributed pseudorandom integer in the interval
141 uint32 fibrand_range(fibrand *f, uint32 m)
143 uint32 r = 0xffffffff - (0xffffffff % m);
146 /* --- Now generate numbers until a good one comes along --- */
148 do x = fibrand_step(f); while (x >= r);
149 return (x / (r / m));
152 /*----- Generic interface -------------------------------------------------*/
154 typedef struct gctx {
159 static void gdestroy(grand *r)
165 static int gmisc(grand *r, unsigned op, ...)
174 switch (va_arg(ap, unsigned)) {
177 case GRAND_SEEDUINT32:
187 fibrand_lcseed(&g->f, va_arg(ap, unsigned));
189 case GRAND_SEEDUINT32:
190 fibrand_lcseed(&g->f, va_arg(ap, uint32));
193 fibrand_seed(&g->f, va_arg(ap, grand *));
204 static octet gbyte(grand *r)
207 return (U8(fibrand_step(&g->f)));
210 static uint32 gword(grand *r)
213 return (fibrand_step(&g->f));
216 static uint32 grange(grand *r, uint32 l)
219 return (fibrand_range(&g->f, l));
222 static void gfill(grand *r, void *p, size_t sz)
227 *q++ = U8(fibrand_step(&g->f));
232 static const grand_ops gops = {
236 gword, gbyte, gword, grange, gfill
239 /* --- @fibrand_create@ --- *
241 * Arguments: @uint32 seed@ = initial seed
243 * Returns: Pointer to a generic generator.
245 * Use: Constructs a generic generator interface over a Fibonacci
246 * generator. The generator is seeded using @fibrand_lcseed@.
249 grand *fibrand_create(uint32 seed)
251 gctx *g = CREATE(gctx);
253 fibrand_lcseed(&g->f, seed);
257 /*----- That's all, folks -------------------------------------------------*/