5 * (c) 1999 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Catacomb.
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.
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.
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,
28 /*----- Header files ------------------------------------------------------*/
35 #include <mLib/bits.h>
42 /*----- Main code ---------------------------------------------------------*/
44 /* --- @fibrand_step@ --- *
46 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
48 * Returns: Next output from generator.
50 * Use: Steps the generator. Returns
51 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
54 uint32 fibrand_step(fibrand *f)
57 unsigned j = i + (FIB_SZ - FIB_TAP);
61 x = f->x[i] = U32(f->x[i] + f->x[j]);
69 /* --- @fibrand_seed@ --- *
71 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
72 * @grand *r@ = random number generator to extract words from
76 * Use: Initializes a Fibonacci generator using word outputs from the
77 * given random number source @r@.
80 void fibrand_seed(fibrand *f, grand *r)
85 for (i = 0; i < FIB_SZ; i++)
86 p |= f->x[i] = r->ops->word(r);
88 i = r->ops->range(r, FIB_SZ);
94 /* --- @fibrand_lcseed@ --- *
96 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
97 * @uint32 seed@ = seed value
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
108 void fibrand_lcseed(fibrand *f, uint32 seed)
113 for (i = 0; i < FIB_SZ; i++)
114 p |= f->x[i] = seed = lcrand(seed);
116 i = lcrand_range(&seed, FIB_SZ);
122 /* --- @fibrand_range@ --- *
124 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
127 * Returns: A uniformly distributed pseudorandom integer in the interval
131 uint32 fibrand_range(fibrand *f, uint32 m)
133 uint32 r = 0xffffffff - (0xffffffff % m);
136 /* --- Now generate numbers until a good one comes along --- */
138 do x = fibrand_step(f); while (x >= r);
142 /*----- Generic interface -------------------------------------------------*/
144 typedef struct gctx {
149 static void gdestroy(grand *r)
155 static int gmisc(grand *r, unsigned op, ...)
164 switch (va_arg(ap, unsigned)) {
167 case GRAND_SEEDUINT32:
177 fibrand_lcseed(&g->f, va_arg(ap, unsigned));
179 case GRAND_SEEDUINT32:
180 fibrand_lcseed(&g->f, va_arg(ap, uint32));
183 fibrand_seed(&g->f, va_arg(ap, grand *));
194 static octet gbyte(grand *r)
197 return (U8(fibrand_step(&g->f)));
200 static uint32 gword(grand *r)
203 return (fibrand_step(&g->f));
206 static uint32 grange(grand *r, uint32 l)
209 return (fibrand_range(&g->f, l));
212 static void gfill(grand *r, void *p, size_t sz)
217 *q++ = U8(fibrand_step(&g->f));
222 static const grand_ops gops = {
226 gword, gbyte, gword, grange, gfill
229 /* --- @fibrand_create@ --- *
231 * Arguments: @uint32 seed@ = initial seed
233 * Returns: Pointer to a generic generator.
235 * Use: Constructs a generic generator interface over a Fibonacci
236 * generator. The generator is seeded using @fibrand_lcseed@.
239 grand *fibrand_create(uint32 seed)
241 gctx *g = CREATE(gctx);
243 fibrand_lcseed(&g->f, seed);
247 /*----- That's all, folks -------------------------------------------------*/