aa1082f2 |
1 | /* -*-c-*- |
2 | * |
3 | * $Id: grand.c,v 1.1 1999/12/10 23:16:01 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 1.1 1999/12/10 23:16:01 mdw |
34 | * Generic interface. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include <stddef.h> |
41 | |
42 | #include <mLib/bits.h> |
43 | |
44 | #include "grand.h" |
45 | |
46 | /*----- Main code ---------------------------------------------------------*/ |
47 | |
48 | /* --- @grand_byte@ --- * |
49 | * |
50 | * Arguments: @grand *r@ = pointet to generic generator |
51 | * |
52 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
53 | * %$[0, 256)$%. |
54 | */ |
55 | |
56 | octet grand_byte(grand *r) |
57 | { |
58 | if (r->ops->byte != grand_byte) |
59 | return (r->ops->byte(r)); |
60 | else if (r->ops->word != grand_word) |
61 | return (r->ops->word(r) & 0xff); |
62 | else if (r->ops->fill != grand_fill) { |
63 | octet o; |
64 | r->ops->fill(r, &o, 1); |
65 | return (o); |
66 | } else |
67 | return (grand_range(r, 256)); |
68 | } |
69 | |
70 | /* --- @grand_word@ --- * |
71 | * |
72 | * Arguments: @grand *r@ = pointet to generic generator |
73 | * |
74 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
75 | * %$[0, 2^{32})$%. |
76 | */ |
77 | |
78 | uint32 grand_word(grand *r) |
79 | { |
80 | if (r->ops->word != grand_word) |
81 | return (r->ops->word(r)); |
82 | else { |
83 | octet b[4]; |
84 | grand_fill(r, b, sizeof(b)); |
85 | return (LOAD32(b)); |
86 | } |
87 | } |
88 | |
89 | /* --- @grand_range@ --- * |
90 | * |
91 | * Arguments: @grand *r@ = pointet to generic generator |
92 | * @uint32 l@ = limit for acceptable results |
93 | * |
94 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
95 | * %$[0, l)$%. |
96 | */ |
97 | |
98 | uint32 grand_range(grand *r, uint32 l) |
99 | { |
100 | if (r->ops->range != grand_range) |
101 | return (r->ops->range(r, l)); |
102 | else { |
103 | uint32 m, z; |
104 | uint32 (*w)(grand */*r*/); |
105 | uint32 x; |
106 | |
107 | /* --- Decide where to get data from --- * |
108 | * |
109 | * The choice of %$2^{32} - 1$% as a limit when using @grand_word@ isn't |
110 | * wonderful, but working with %$2^{32}$% is awkward and the loss of a |
111 | * few return values isn't significant. The algorithm below still |
112 | * successfully returns uniformly distributed results. |
113 | */ |
114 | |
115 | if (r->ops->max) { |
116 | w = r->ops->raw; |
117 | m = r->ops->max; |
118 | } else { |
119 | w = grand_word; |
120 | m = 0xffffffff; |
121 | } |
122 | |
123 | /* --- Work out maximum acceptable return value --- * |
124 | * |
125 | * This will be the highest multiple of @l@ less than @m@. |
126 | */ |
127 | |
128 | z = m - (m % l); |
129 | m = z / l; |
130 | |
131 | /* --- Generate numbers until something acceptable is found --- * |
132 | * |
133 | * This will require an expected number of attempts less than 2. |
134 | */ |
135 | |
136 | do x = w(r); while (x >= z); |
137 | return (x / m); |
138 | } |
139 | } |
140 | |
141 | /* --- @grand_fill@ --- * |
142 | * |
143 | * Arguments: @grand *r@ = pointet to generic generator |
144 | * @void *p@ = pointer to a buffer |
145 | * @size_t sz@ = size of the buffer |
146 | * |
147 | * Returns: --- |
148 | * |
149 | * Use: Fills a buffer with uniformly distributed pseudorandom bytes |
150 | * (see @grand_byte@). |
151 | */ |
152 | |
153 | void grand_fill(grand *r, void *p, size_t sz) |
154 | { |
155 | if (r->ops->fill != grand_fill) |
156 | r->ops->fill(r, p, sz); |
157 | else { |
158 | octet *q = p; |
159 | while (sz) { |
160 | *q++ = r->ops->byte(r); |
161 | sz--; |
162 | } |
163 | } |
164 | } |
165 | |
166 | /*----- That's all, folks -------------------------------------------------*/ |