| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: grand.c,v 1.2 2000/12/06 20:31:06 mdw Exp $ |
| 4 | * |
| 5 | * Generic interface to random number generators |
| 6 | * |
| 7 | * (c) 1999 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of Catacomb. |
| 13 | * |
| 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. |
| 18 | * |
| 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. |
| 23 | * |
| 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, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Revision history --------------------------------------------------* |
| 31 | * |
| 32 | * $Log: grand.c,v $ |
| 33 | * Revision 1.2 2000/12/06 20:31:06 mdw |
| 34 | * Simplify uniform range transformation. |
| 35 | * |
| 36 | * Revision 1.1 1999/12/10 23:16:01 mdw |
| 37 | * Generic interface. |
| 38 | * |
| 39 | */ |
| 40 | |
| 41 | /*----- Header files ------------------------------------------------------*/ |
| 42 | |
| 43 | #include <stddef.h> |
| 44 | |
| 45 | #include <mLib/bits.h> |
| 46 | |
| 47 | #include "grand.h" |
| 48 | |
| 49 | /*----- Main code ---------------------------------------------------------*/ |
| 50 | |
| 51 | /* --- @grand_byte@ --- * |
| 52 | * |
| 53 | * Arguments: @grand *r@ = pointet to generic generator |
| 54 | * |
| 55 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
| 56 | * %$[0, 256)$%. |
| 57 | */ |
| 58 | |
| 59 | octet grand_byte(grand *r) |
| 60 | { |
| 61 | if (r->ops->byte != grand_byte) |
| 62 | return (r->ops->byte(r)); |
| 63 | else if (r->ops->word != grand_word) |
| 64 | return (r->ops->word(r) & 0xff); |
| 65 | else if (r->ops->fill != grand_fill) { |
| 66 | octet o; |
| 67 | r->ops->fill(r, &o, 1); |
| 68 | return (o); |
| 69 | } else |
| 70 | return (grand_range(r, 256)); |
| 71 | } |
| 72 | |
| 73 | /* --- @grand_word@ --- * |
| 74 | * |
| 75 | * Arguments: @grand *r@ = pointet to generic generator |
| 76 | * |
| 77 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
| 78 | * %$[0, 2^{32})$%. |
| 79 | */ |
| 80 | |
| 81 | uint32 grand_word(grand *r) |
| 82 | { |
| 83 | if (r->ops->word != grand_word) |
| 84 | return (r->ops->word(r)); |
| 85 | else { |
| 86 | octet b[4]; |
| 87 | grand_fill(r, b, sizeof(b)); |
| 88 | return (LOAD32(b)); |
| 89 | } |
| 90 | } |
| 91 | |
| 92 | /* --- @grand_range@ --- * |
| 93 | * |
| 94 | * Arguments: @grand *r@ = pointet to generic generator |
| 95 | * @uint32 l@ = limit for acceptable results |
| 96 | * |
| 97 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
| 98 | * %$[0, l)$%. |
| 99 | */ |
| 100 | |
| 101 | uint32 grand_range(grand *r, uint32 l) |
| 102 | { |
| 103 | if (r->ops->range != grand_range) |
| 104 | return (r->ops->range(r, l)); |
| 105 | else { |
| 106 | uint32 m, z; |
| 107 | uint32 (*w)(grand */*r*/); |
| 108 | uint32 x; |
| 109 | |
| 110 | /* --- Decide where to get data from --- * |
| 111 | * |
| 112 | * The choice of %$2^{32} - 1$% as a limit when using @grand_word@ isn't |
| 113 | * wonderful, but working with %$2^{32}$% is awkward and the loss of a |
| 114 | * few return values isn't significant. The algorithm below still |
| 115 | * successfully returns uniformly distributed results. |
| 116 | */ |
| 117 | |
| 118 | if (r->ops->max) { |
| 119 | w = r->ops->raw; |
| 120 | m = r->ops->max; |
| 121 | } else { |
| 122 | w = grand_word; |
| 123 | m = 0xffffffff; |
| 124 | } |
| 125 | |
| 126 | /* --- Work out maximum acceptable return value --- * |
| 127 | * |
| 128 | * This will be the highest multiple of @l@ less than @m@. |
| 129 | */ |
| 130 | |
| 131 | z = m - (m % l); |
| 132 | |
| 133 | /* --- Generate numbers until something acceptable is found --- * |
| 134 | * |
| 135 | * This will require an expected number of attempts less than 2. |
| 136 | */ |
| 137 | |
| 138 | do x = w(r); while (x >= z); |
| 139 | return (x % l); |
| 140 | } |
| 141 | } |
| 142 | |
| 143 | /* --- @grand_fill@ --- * |
| 144 | * |
| 145 | * Arguments: @grand *r@ = pointet to generic generator |
| 146 | * @void *p@ = pointer to a buffer |
| 147 | * @size_t sz@ = size of the buffer |
| 148 | * |
| 149 | * Returns: --- |
| 150 | * |
| 151 | * Use: Fills a buffer with uniformly distributed pseudorandom bytes |
| 152 | * (see @grand_byte@). |
| 153 | */ |
| 154 | |
| 155 | void grand_fill(grand *r, void *p, size_t sz) |
| 156 | { |
| 157 | if (r->ops->fill != grand_fill) |
| 158 | r->ops->fill(r, p, sz); |
| 159 | else { |
| 160 | octet *q = p; |
| 161 | while (sz) { |
| 162 | *q++ = r->ops->byte(r); |
| 163 | sz--; |
| 164 | } |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | /*----- That's all, folks -------------------------------------------------*/ |