3 * $Id: fibrand.c,v 1.5 2004/04/08 01:36:15 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 /*----- Header files ------------------------------------------------------*/
37 #include <mLib/bits.h>
44 /*----- Main code ---------------------------------------------------------*/
46 /* --- @fibrand_step@ --- *
48 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
50 * Returns: Next output from generator.
52 * Use: Steps the generator. Returns
53 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
56 uint32 fibrand_step(fibrand *f)
59 unsigned j = i + (FIB_SZ - FIB_TAP);
63 x = f->x[i] = U32(f->x[i] + f->x[j]);
71 /* --- @fibrand_seed@ --- *
73 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
74 * @grand *r@ = random number generator to extract words from
78 * Use: Initializes a Fibonacci generator using word outputs from the
79 * given random number source @r@.
82 void fibrand_seed(fibrand *f, grand *r)
87 for (i = 0; i < FIB_SZ; i++)
88 p |= f->x[i] = r->ops->word(r);
90 i = r->ops->range(r, FIB_SZ);
96 /* --- @fibrand_lcseed@ --- *
98 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
99 * @uint32 seed@ = seed value
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
110 void fibrand_lcseed(fibrand *f, uint32 seed)
115 for (i = 0; i < FIB_SZ; i++)
116 p |= f->x[i] = seed = lcrand(seed);
118 i = lcrand_range(&seed, FIB_SZ);
124 /* --- @fibrand_range@ --- *
126 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
129 * Returns: A uniformly distributed pseudorandom integer in the interval
133 uint32 fibrand_range(fibrand *f, uint32 m)
135 uint32 r = 0xffffffff - (0xffffffff % m);
138 /* --- Now generate numbers until a good one comes along --- */
140 do x = fibrand_step(f); while (x >= r);
144 /*----- Generic interface -------------------------------------------------*/
146 typedef struct gctx {
151 static void gdestroy(grand *r)
157 static int gmisc(grand *r, unsigned op, ...)
166 switch (va_arg(ap, unsigned)) {
169 case GRAND_SEEDUINT32:
179 fibrand_lcseed(&g->f, va_arg(ap, unsigned));
181 case GRAND_SEEDUINT32:
182 fibrand_lcseed(&g->f, va_arg(ap, uint32));
185 fibrand_seed(&g->f, va_arg(ap, grand *));
196 static octet gbyte(grand *r)
199 return (U8(fibrand_step(&g->f)));
202 static uint32 gword(grand *r)
205 return (fibrand_step(&g->f));
208 static uint32 grange(grand *r, uint32 l)
211 return (fibrand_range(&g->f, l));
214 static void gfill(grand *r, void *p, size_t sz)
219 *q++ = U8(fibrand_step(&g->f));
224 static const grand_ops gops = {
228 gword, gbyte, gword, grange, gfill
231 /* --- @fibrand_create@ --- *
233 * Arguments: @uint32 seed@ = initial seed
235 * Returns: Pointer to a generic generator.
237 * Use: Constructs a generic generator interface over a Fibonacci
238 * generator. The generator is seeded using @fibrand_lcseed@.
241 grand *fibrand_create(uint32 seed)
243 gctx *g = CREATE(gctx);
245 fibrand_lcseed(&g->f, seed);
249 /*----- That's all, folks -------------------------------------------------*/