+++ /dev/null
-/* -*-c-*-
- *
- * $Id: fibrand.c,v 1.5 2004/04/08 01:36:15 mdw Exp $
- *
- * Fibonacci generator
- *
- * (c) 1999 Straylight/Edgeware
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of Catacomb.
- *
- * Catacomb is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * Catacomb is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with Catacomb; if not, write to the Free
- * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- * MA 02111-1307, USA.
- */
-
-/*----- Header files ------------------------------------------------------*/
-
-#include <stdarg.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <mLib/bits.h>
-#include <mLib/sub.h>
-
-#include "fibrand.h"
-#include "grand.h"
-#include "lcrand.h"
-
-/*----- Main code ---------------------------------------------------------*/
-
-/* --- @fibrand_step@ --- *
- *
- * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
- *
- * Returns: Next output from generator.
- *
- * Use: Steps the generator. Returns
- * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
- */
-
-uint32 fibrand_step(fibrand *f)
-{
- unsigned i = f->i;
- unsigned j = i + (FIB_SZ - FIB_TAP);
- uint32 x;
- if (j >= FIB_SZ)
- j -= FIB_SZ;
- x = f->x[i] = U32(f->x[i] + f->x[j]);
- i++;
- if (i >= FIB_SZ)
- i = 0;
- f->i = i;
- return (x);
-}
-
-/* --- @fibrand_seed@ --- *
- *
- * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
- * @grand *r@ = random number generator to extract words from
- *
- * Returns: ---
- *
- * Use: Initializes a Fibonacci generator using word outputs from the
- * given random number source @r@.
- */
-
-void fibrand_seed(fibrand *f, grand *r)
-{
- int i;
- unsigned p = 0;
-
- for (i = 0; i < FIB_SZ; i++)
- p |= f->x[i] = r->ops->word(r);
- if (!(p & 1)) {
- i = r->ops->range(r, FIB_SZ);
- f->x[i] |= 1;
- }
- f->i = 0;
-}
-
-/* --- @fibrand_lcseed@ --- *
- *
- * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
- * @uint32 seed@ = seed value
- *
- * Returns: ---
- *
- * Use: Initializes a Fibonacci generator using outputs from the
- * @lcrand@ generator seeded from @seed@. This is faster than
- * using a generic @lcrand@-based generator and @fibrand_rseed@
- * because it uses raw outputs rather than uniformly distributed
- * 32-bit words.
- */
-
-void fibrand_lcseed(fibrand *f, uint32 seed)
-{
- int i;
- unsigned p = 0;
-
- for (i = 0; i < FIB_SZ; i++)
- p |= f->x[i] = seed = lcrand(seed);
- if (!(p & 1)) {
- i = lcrand_range(&seed, FIB_SZ);
- f->x[i] |= 1;
- }
- f->i = 0;
-}
-
-/* --- @fibrand_range@ --- *
- *
- * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
- * @uint32 m@ = limit
- *
- * Returns: A uniformly distributed pseudorandom integer in the interval
- * %$[0, m)$%.
- */
-
-uint32 fibrand_range(fibrand *f, uint32 m)
-{
- uint32 r = 0xffffffff - (0xffffffff % m);
- uint32 x;
-
- /* --- Now generate numbers until a good one comes along --- */
-
- do x = fibrand_step(f); while (x >= r);
- return (x % m);
-}
-
-/*----- Generic interface -------------------------------------------------*/
-
-typedef struct gctx {
- grand r;
- fibrand f;
-} gctx;
-
-static void gdestroy(grand *r)
-{
- gctx *g = (gctx *)r;
- DESTROY(g);
-}
-
-static int gmisc(grand *r, unsigned op, ...)
-{
- gctx *g = (gctx *)r;
- va_list ap;
- int rc = 0;
- va_start(ap, op);
-
- switch (op) {
- case GRAND_CHECK:
- switch (va_arg(ap, unsigned)) {
- case GRAND_CHECK:
- case GRAND_SEEDINT:
- case GRAND_SEEDUINT32:
- case GRAND_SEEDRAND:
- rc = 1;
- break;
- default:
- rc = 0;
- break;
- }
- break;
- case GRAND_SEEDINT:
- fibrand_lcseed(&g->f, va_arg(ap, unsigned));
- break;
- case GRAND_SEEDUINT32:
- fibrand_lcseed(&g->f, va_arg(ap, uint32));
- break;
- case GRAND_SEEDRAND:
- fibrand_seed(&g->f, va_arg(ap, grand *));
- break;
- default:
- GRAND_BADOP;
- break;
- }
-
- va_end(ap);
- return (rc);
-}
-
-static octet gbyte(grand *r)
-{
- gctx *g = (gctx *)r;
- return (U8(fibrand_step(&g->f)));
-}
-
-static uint32 gword(grand *r)
-{
- gctx *g = (gctx *)r;
- return (fibrand_step(&g->f));
-}
-
-static uint32 grange(grand *r, uint32 l)
-{
- gctx *g = (gctx *)r;
- return (fibrand_range(&g->f, l));
-}
-
-static void gfill(grand *r, void *p, size_t sz)
-{
- gctx *g = (gctx *)r;
- octet *q = p;
- while (sz) {
- *q++ = U8(fibrand_step(&g->f));
- sz--;
- }
-}
-
-static const grand_ops gops = {
- "fibrand",
- 0, 0,
- gmisc, gdestroy,
- gword, gbyte, gword, grange, gfill
-};
-
-/* --- @fibrand_create@ --- *
- *
- * Arguments: @uint32 seed@ = initial seed
- *
- * Returns: Pointer to a generic generator.
- *
- * Use: Constructs a generic generator interface over a Fibonacci
- * generator. The generator is seeded using @fibrand_lcseed@.
- */
-
-grand *fibrand_create(uint32 seed)
-{
- gctx *g = CREATE(gctx);
- g->r.ops = &gops;
- fibrand_lcseed(&g->f, seed);
- return (&g->r);
-}
-
-/*----- That's all, folks -------------------------------------------------*/
projects / u / mdw / catacomb / blobdiff