3 * $Id: fibrand.c,v 1.2 2000/07/02 15:21:20 mdw Exp $
7 * (c) 1999 Straylight/Edgeware
8 * (c) 2000 Mark Wooding
11 /*----- Licensing notice --------------------------------------------------*
13 * Copyright (c) 2000 Mark Wooding
14 * All rights reserved.
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions are
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
23 * 2, Redistributions in binary form must reproduce the above copyright
24 * notice, this list of conditions and the following disclaimer in the
25 * documentation and/or other materials provided with the distribution.
27 * 3. The name of the authors may not be used to endorse or promote
28 * products derived from this software without specific prior written
31 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
32 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
33 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
34 * NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
35 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
36 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
37 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
40 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
41 * POSSIBILITY OF SUCH DAMAGE.
43 * Instead of accepting the above terms, you may redistribute and/or modify
44 * this software under the terms of either the GNU General Public License,
45 * or the GNU Library General Public License, published by the Free
46 * Software Foundation; either version 2 of the License, or (at your
47 * option) any later version.
50 /*----- Revision history --------------------------------------------------*
53 * Revision 1.2 2000/07/02 15:21:20 mdw
56 * Revision 1.1 2000/05/21 11:28:30 mdw
59 * --- Past lives (Catacomb) --- *
61 * Revision 1.1 1999/12/10 23:15:27 mdw
62 * Noncryptographic random number generator.
66 /*----- Header files ------------------------------------------------------*/
76 /*----- Main code ---------------------------------------------------------*/
78 /* --- @fibrand_step@ --- *
80 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
82 * Returns: Next output from generator.
84 * Use: Steps the generator. Returns
85 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
88 uint32
fibrand_step(fibrand
*f
)
91 unsigned j
= i
+ (FIB_SZ
- FIB_TAP
);
95 x
= f
->x
[i
] = U32(f
->x
[i
] + f
->x
[j
]);
103 /* --- @fibrand_lcseed@ --- *
105 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
106 * @uint32 seed@ = seed value
110 * Use: Initializes a Fibonacci generator using outputs from the
111 * @lcrand@ generator seeded from @seed@. This is faster than
112 * using a generic @lcrand@-based generator and @fibrand_rseed@
113 * because it uses raw outputs rather than uniformly distributed
117 void fibrand_lcseed(fibrand
*f
, uint32 seed
)
122 for (i
= 0; i
< FIB_SZ
; i
++)
123 p
|= f
->x
[i
] = seed
= lcrand(seed
);
125 i
= lcrand_range(&seed
, FIB_SZ
);
131 /* --- @fibrand_range@ --- *
133 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
136 * Returns: A uniformly distributed pseudorandom integer in the interval
140 uint32
fibrand_range(fibrand
*f
, uint32 m
)
142 uint32 r
= 0xffffffff - (0xffffffff % m
);
145 /* --- Now generate numbers until a good one comes along --- */
147 do x
= fibrand_step(f
); while (x
>= r
);
148 return (x
/ (r
/ m
));
151 /*----- That's all, folks -------------------------------------------------*/