| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: grand.c,v 1.3 2004/04/08 01:36:15 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 | /*----- Header files ------------------------------------------------------*/ |
| 31 | |
| 32 | #include <stddef.h> |
| 33 | |
| 34 | #include <mLib/bits.h> |
| 35 | |
| 36 | #include "grand.h" |
| 37 | |
| 38 | /*----- Main code ---------------------------------------------------------*/ |
| 39 | |
| 40 | /* --- @grand_byte@ --- * |
| 41 | * |
| 42 | * Arguments: @grand *r@ = pointet to generic generator |
| 43 | * |
| 44 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
| 45 | * %$[0, 256)$%. |
| 46 | */ |
| 47 | |
| 48 | octet grand_byte(grand *r) |
| 49 | { |
| 50 | if (r->ops->byte != grand_byte) |
| 51 | return (r->ops->byte(r)); |
| 52 | else if (r->ops->word != grand_word) |
| 53 | return (r->ops->word(r) & 0xff); |
| 54 | else if (r->ops->fill != grand_fill) { |
| 55 | octet o; |
| 56 | r->ops->fill(r, &o, 1); |
| 57 | return (o); |
| 58 | } else |
| 59 | return (grand_range(r, 256)); |
| 60 | } |
| 61 | |
| 62 | /* --- @grand_word@ --- * |
| 63 | * |
| 64 | * Arguments: @grand *r@ = pointet to generic generator |
| 65 | * |
| 66 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
| 67 | * %$[0, 2^{32})$%. |
| 68 | */ |
| 69 | |
| 70 | uint32 grand_word(grand *r) |
| 71 | { |
| 72 | if (r->ops->word != grand_word) |
| 73 | return (r->ops->word(r)); |
| 74 | else { |
| 75 | octet b[4]; |
| 76 | grand_fill(r, b, sizeof(b)); |
| 77 | return (LOAD32(b)); |
| 78 | } |
| 79 | } |
| 80 | |
| 81 | /* --- @grand_range@ --- * |
| 82 | * |
| 83 | * Arguments: @grand *r@ = pointet to generic generator |
| 84 | * @uint32 l@ = limit for acceptable results |
| 85 | * |
| 86 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
| 87 | * %$[0, l)$%. |
| 88 | */ |
| 89 | |
| 90 | uint32 grand_range(grand *r, uint32 l) |
| 91 | { |
| 92 | if (r->ops->range != grand_range) |
| 93 | return (r->ops->range(r, l)); |
| 94 | else { |
| 95 | uint32 m, z; |
| 96 | uint32 (*w)(grand */*r*/); |
| 97 | uint32 x; |
| 98 | |
| 99 | /* --- Decide where to get data from --- * |
| 100 | * |
| 101 | * The choice of %$2^{32} - 1$% as a limit when using @grand_word@ isn't |
| 102 | * wonderful, but working with %$2^{32}$% is awkward and the loss of a |
| 103 | * few return values isn't significant. The algorithm below still |
| 104 | * successfully returns uniformly distributed results. |
| 105 | */ |
| 106 | |
| 107 | if (r->ops->max) { |
| 108 | w = r->ops->raw; |
| 109 | m = r->ops->max; |
| 110 | } else { |
| 111 | w = grand_word; |
| 112 | m = 0xffffffff; |
| 113 | } |
| 114 | |
| 115 | /* --- Work out maximum acceptable return value --- * |
| 116 | * |
| 117 | * This will be the highest multiple of @l@ less than @m@. |
| 118 | */ |
| 119 | |
| 120 | z = m - (m % l); |
| 121 | |
| 122 | /* --- Generate numbers until something acceptable is found --- * |
| 123 | * |
| 124 | * This will require an expected number of attempts less than 2. |
| 125 | */ |
| 126 | |
| 127 | do x = w(r); while (x >= z); |
| 128 | return (x % l); |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | /* --- @grand_fill@ --- * |
| 133 | * |
| 134 | * Arguments: @grand *r@ = pointet to generic generator |
| 135 | * @void *p@ = pointer to a buffer |
| 136 | * @size_t sz@ = size of the buffer |
| 137 | * |
| 138 | * Returns: --- |
| 139 | * |
| 140 | * Use: Fills a buffer with uniformly distributed pseudorandom bytes |
| 141 | * (see @grand_byte@). |
| 142 | */ |
| 143 | |
| 144 | void grand_fill(grand *r, void *p, size_t sz) |
| 145 | { |
| 146 | if (r->ops->fill != grand_fill) |
| 147 | r->ops->fill(r, p, sz); |
| 148 | else { |
| 149 | octet *q = p; |
| 150 | while (sz) { |
| 151 | *q++ = r->ops->byte(r); |
| 152 | sz--; |
| 153 | } |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | /*----- That's all, folks -------------------------------------------------*/ |