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1 | /* -*-c-*- |
2 | * |
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3 | * Generic interface to random number generators |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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16 | * |
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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. |
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21 | * |
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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 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <stddef.h> |
31 | |
32 | #include <mLib/bits.h> |
33 | |
34 | #include "grand.h" |
35 | |
36 | /*----- Main code ---------------------------------------------------------*/ |
37 | |
38 | /* --- @grand_byte@ --- * |
39 | * |
40 | * Arguments: @grand *r@ = pointet to generic generator |
41 | * |
42 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
43 | * %$[0, 256)$%. |
44 | */ |
45 | |
46 | octet grand_byte(grand *r) |
47 | { |
48 | if (r->ops->byte != grand_byte) |
49 | return (r->ops->byte(r)); |
50 | else if (r->ops->word != grand_word) |
51 | return (r->ops->word(r) & 0xff); |
52 | else if (r->ops->fill != grand_fill) { |
53 | octet o; |
54 | r->ops->fill(r, &o, 1); |
55 | return (o); |
56 | } else |
57 | return (grand_range(r, 256)); |
58 | } |
59 | |
60 | /* --- @grand_word@ --- * |
61 | * |
62 | * Arguments: @grand *r@ = pointet to generic generator |
63 | * |
64 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
65 | * %$[0, 2^{32})$%. |
66 | */ |
67 | |
68 | uint32 grand_word(grand *r) |
69 | { |
70 | if (r->ops->word != grand_word) |
71 | return (r->ops->word(r)); |
72 | else { |
73 | octet b[4]; |
74 | grand_fill(r, b, sizeof(b)); |
75 | return (LOAD32(b)); |
76 | } |
77 | } |
78 | |
79 | /* --- @grand_range@ --- * |
80 | * |
81 | * Arguments: @grand *r@ = pointet to generic generator |
82 | * @uint32 l@ = limit for acceptable results |
83 | * |
84 | * Returns: A uniformly-distributed pseudorandom integer in the interval |
85 | * %$[0, l)$%. |
86 | */ |
87 | |
88 | uint32 grand_range(grand *r, uint32 l) |
89 | { |
90 | if (r->ops->range != grand_range) |
91 | return (r->ops->range(r, l)); |
92 | else { |
93 | uint32 m, z; |
94 | uint32 (*w)(grand */*r*/); |
95 | uint32 x; |
96 | |
97 | /* --- Decide where to get data from --- * |
98 | * |
99 | * The choice of %$2^{32} - 1$% as a limit when using @grand_word@ isn't |
100 | * wonderful, but working with %$2^{32}$% is awkward and the loss of a |
101 | * few return values isn't significant. The algorithm below still |
102 | * successfully returns uniformly distributed results. |
103 | */ |
104 | |
105 | if (r->ops->max) { |
106 | w = r->ops->raw; |
107 | m = r->ops->max; |
108 | } else { |
109 | w = grand_word; |
110 | m = 0xffffffff; |
111 | } |
112 | |
113 | /* --- Work out maximum acceptable return value --- * |
114 | * |
115 | * This will be the highest multiple of @l@ less than @m@. |
116 | */ |
117 | |
118 | z = m - (m % l); |
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119 | |
120 | /* --- Generate numbers until something acceptable is found --- * |
121 | * |
122 | * This will require an expected number of attempts less than 2. |
123 | */ |
124 | |
125 | do x = w(r); while (x >= z); |
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126 | return (x % l); |
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127 | } |
128 | } |
129 | |
130 | /* --- @grand_fill@ --- * |
131 | * |
132 | * Arguments: @grand *r@ = pointet to generic generator |
133 | * @void *p@ = pointer to a buffer |
134 | * @size_t sz@ = size of the buffer |
135 | * |
136 | * Returns: --- |
137 | * |
138 | * Use: Fills a buffer with uniformly distributed pseudorandom bytes |
139 | * (see @grand_byte@). |
140 | */ |
141 | |
142 | void grand_fill(grand *r, void *p, size_t sz) |
143 | { |
144 | if (r->ops->fill != grand_fill) |
145 | r->ops->fill(r, p, sz); |
146 | else { |
147 | octet *q = p; |
148 | while (sz) { |
149 | *q++ = r->ops->byte(r); |
150 | sz--; |
151 | } |
152 | } |
153 | } |
154 | |
155 | /*----- That's all, folks -------------------------------------------------*/ |