| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Fibonacci generator |
| 4 | * |
| 5 | * (c) 1999 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 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. |
| 16 | * |
| 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. |
| 21 | * |
| 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, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include <stdarg.h> |
| 31 | #include <stdio.h> |
| 32 | #include <stdlib.h> |
| 33 | #include <string.h> |
| 34 | |
| 35 | #include <mLib/bits.h> |
| 36 | #include <mLib/sub.h> |
| 37 | |
| 38 | #include "fibrand.h" |
| 39 | #include "grand.h" |
| 40 | #include "lcrand.h" |
| 41 | |
| 42 | /*----- Main code ---------------------------------------------------------*/ |
| 43 | |
| 44 | /* --- @fibrand_step@ --- * |
| 45 | * |
| 46 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
| 47 | * |
| 48 | * Returns: Next output from generator. |
| 49 | * |
| 50 | * Use: Steps the generator. Returns |
| 51 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%. |
| 52 | */ |
| 53 | |
| 54 | uint32 fibrand_step(fibrand *f) |
| 55 | { |
| 56 | unsigned i = f->i; |
| 57 | unsigned j = i + (FIB_SZ - FIB_TAP); |
| 58 | uint32 x; |
| 59 | if (j >= FIB_SZ) |
| 60 | j -= FIB_SZ; |
| 61 | x = f->x[i] = U32(f->x[i] + f->x[j]); |
| 62 | i++; |
| 63 | if (i >= FIB_SZ) |
| 64 | i = 0; |
| 65 | f->i = i; |
| 66 | return (x); |
| 67 | } |
| 68 | |
| 69 | /* --- @fibrand_seed@ --- * |
| 70 | * |
| 71 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
| 72 | * @grand *r@ = random number generator to extract words from |
| 73 | * |
| 74 | * Returns: --- |
| 75 | * |
| 76 | * Use: Initializes a Fibonacci generator using word outputs from the |
| 77 | * given random number source @r@. |
| 78 | */ |
| 79 | |
| 80 | void fibrand_seed(fibrand *f, grand *r) |
| 81 | { |
| 82 | int i; |
| 83 | unsigned p = 0; |
| 84 | |
| 85 | for (i = 0; i < FIB_SZ; i++) |
| 86 | p |= f->x[i] = r->ops->word(r); |
| 87 | if (!(p & 1)) { |
| 88 | i = r->ops->range(r, FIB_SZ); |
| 89 | f->x[i] |= 1; |
| 90 | } |
| 91 | f->i = 0; |
| 92 | } |
| 93 | |
| 94 | /* --- @fibrand_lcseed@ --- * |
| 95 | * |
| 96 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
| 97 | * @uint32 seed@ = seed value |
| 98 | * |
| 99 | * Returns: --- |
| 100 | * |
| 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 |
| 105 | * 32-bit words. |
| 106 | */ |
| 107 | |
| 108 | void fibrand_lcseed(fibrand *f, uint32 seed) |
| 109 | { |
| 110 | int i; |
| 111 | unsigned p = 0; |
| 112 | |
| 113 | for (i = 0; i < FIB_SZ; i++) |
| 114 | p |= f->x[i] = seed = lcrand(seed); |
| 115 | if (!(p & 1)) { |
| 116 | i = lcrand_range(&seed, FIB_SZ); |
| 117 | f->x[i] |= 1; |
| 118 | } |
| 119 | f->i = 0; |
| 120 | } |
| 121 | |
| 122 | /* --- @fibrand_range@ --- * |
| 123 | * |
| 124 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
| 125 | * @uint32 m@ = limit |
| 126 | * |
| 127 | * Returns: A uniformly distributed pseudorandom integer in the interval |
| 128 | * %$[0, m)$%. |
| 129 | */ |
| 130 | |
| 131 | uint32 fibrand_range(fibrand *f, uint32 m) |
| 132 | { |
| 133 | uint32 r = 0xffffffff - (0xffffffff % m); |
| 134 | uint32 x; |
| 135 | |
| 136 | /* --- Now generate numbers until a good one comes along --- */ |
| 137 | |
| 138 | do x = fibrand_step(f); while (x >= r); |
| 139 | return (x % m); |
| 140 | } |
| 141 | |
| 142 | /*----- Generic interface -------------------------------------------------*/ |
| 143 | |
| 144 | typedef struct gctx { |
| 145 | grand r; |
| 146 | fibrand f; |
| 147 | } gctx; |
| 148 | |
| 149 | static void gdestroy(grand *r) |
| 150 | { |
| 151 | gctx *g = (gctx *)r; |
| 152 | DESTROY(g); |
| 153 | } |
| 154 | |
| 155 | static int gmisc(grand *r, unsigned op, ...) |
| 156 | { |
| 157 | gctx *g = (gctx *)r; |
| 158 | va_list ap; |
| 159 | int rc = 0; |
| 160 | va_start(ap, op); |
| 161 | |
| 162 | switch (op) { |
| 163 | case GRAND_CHECK: |
| 164 | switch (va_arg(ap, unsigned)) { |
| 165 | case GRAND_CHECK: |
| 166 | case GRAND_SEEDINT: |
| 167 | case GRAND_SEEDUINT32: |
| 168 | case GRAND_SEEDRAND: |
| 169 | rc = 1; |
| 170 | break; |
| 171 | default: |
| 172 | rc = 0; |
| 173 | break; |
| 174 | } |
| 175 | break; |
| 176 | case GRAND_SEEDINT: |
| 177 | fibrand_lcseed(&g->f, va_arg(ap, unsigned)); |
| 178 | break; |
| 179 | case GRAND_SEEDUINT32: |
| 180 | fibrand_lcseed(&g->f, va_arg(ap, uint32)); |
| 181 | break; |
| 182 | case GRAND_SEEDRAND: |
| 183 | fibrand_seed(&g->f, va_arg(ap, grand *)); |
| 184 | break; |
| 185 | default: |
| 186 | GRAND_BADOP; |
| 187 | break; |
| 188 | } |
| 189 | |
| 190 | va_end(ap); |
| 191 | return (rc); |
| 192 | } |
| 193 | |
| 194 | static octet gbyte(grand *r) |
| 195 | { |
| 196 | gctx *g = (gctx *)r; |
| 197 | return (U8(fibrand_step(&g->f))); |
| 198 | } |
| 199 | |
| 200 | static uint32 gword(grand *r) |
| 201 | { |
| 202 | gctx *g = (gctx *)r; |
| 203 | return (fibrand_step(&g->f)); |
| 204 | } |
| 205 | |
| 206 | static uint32 grange(grand *r, uint32 l) |
| 207 | { |
| 208 | gctx *g = (gctx *)r; |
| 209 | return (fibrand_range(&g->f, l)); |
| 210 | } |
| 211 | |
| 212 | static void gfill(grand *r, void *p, size_t sz) |
| 213 | { |
| 214 | gctx *g = (gctx *)r; |
| 215 | octet *q = p; |
| 216 | while (sz) { |
| 217 | *q++ = U8(fibrand_step(&g->f)); |
| 218 | sz--; |
| 219 | } |
| 220 | } |
| 221 | |
| 222 | static const grand_ops gops = { |
| 223 | "fibrand", |
| 224 | 0, 0, |
| 225 | gmisc, gdestroy, |
| 226 | gword, gbyte, gword, grange, gfill |
| 227 | }; |
| 228 | |
| 229 | /* --- @fibrand_create@ --- * |
| 230 | * |
| 231 | * Arguments: @uint32 seed@ = initial seed |
| 232 | * |
| 233 | * Returns: Pointer to a generic generator. |
| 234 | * |
| 235 | * Use: Constructs a generic generator interface over a Fibonacci |
| 236 | * generator. The generator is seeded using @fibrand_lcseed@. |
| 237 | */ |
| 238 | |
| 239 | grand *fibrand_create(uint32 seed) |
| 240 | { |
| 241 | gctx *g = CREATE(gctx); |
| 242 | g->r.ops = &gops; |
| 243 | fibrand_lcseed(&g->f, seed); |
| 244 | return (&g->r); |
| 245 | } |
| 246 | |
| 247 | /*----- That's all, folks -------------------------------------------------*/ |