3 * $Id: fibrand.c,v 1.3 2000/12/06 20:31:06 mdw Exp $
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of Catacomb.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.3 2000/12/06 20:31:06 mdw
34 * Simplify uniform range transformation.
36 * Revision 1.2 2000/06/17 10:55:24 mdw
37 * Typesetting fixes. Add flags word to generatic random generator.
39 * Revision 1.1 1999/12/10 23:15:27 mdw
40 * Noncryptographic random number generator.
44 /*----- Header files ------------------------------------------------------*/
51 #include <mLib/bits.h>
58 /*----- Main code ---------------------------------------------------------*/
60 /* --- @fibrand_step@ --- *
62 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
64 * Returns: Next output from generator.
66 * Use: Steps the generator. Returns
67 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
70 uint32
fibrand_step(fibrand
*f
)
73 unsigned j
= i
+ (FIB_SZ
- FIB_TAP
);
77 x
= f
->x
[i
] = U32(f
->x
[i
] + f
->x
[j
]);
85 /* --- @fibrand_seed@ --- *
87 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
88 * @grand *r@ = random number generator to extract words from
92 * Use: Initializes a Fibonacci generator using word outputs from the
93 * given random number source @r@.
96 void fibrand_seed(fibrand
*f
, grand
*r
)
101 for (i
= 0; i
< FIB_SZ
; i
++)
102 p
|= f
->x
[i
] = r
->ops
->word(r
);
104 i
= r
->ops
->range(r
, FIB_SZ
);
110 /* --- @fibrand_lcseed@ --- *
112 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
113 * @uint32 seed@ = seed value
117 * Use: Initializes a Fibonacci generator using outputs from the
118 * @lcrand@ generator seeded from @seed@. This is faster than
119 * using a generic @lcrand@-based generator and @fibrand_rseed@
120 * because it uses raw outputs rather than uniformly distributed
124 void fibrand_lcseed(fibrand
*f
, uint32 seed
)
129 for (i
= 0; i
< FIB_SZ
; i
++)
130 p
|= f
->x
[i
] = seed
= lcrand(seed
);
132 i
= lcrand_range(&seed
, FIB_SZ
);
138 /* --- @fibrand_range@ --- *
140 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
143 * Returns: A uniformly distributed pseudorandom integer in the interval
147 uint32
fibrand_range(fibrand
*f
, uint32 m
)
149 uint32 r
= 0xffffffff - (0xffffffff % m
);
152 /* --- Now generate numbers until a good one comes along --- */
154 do x
= fibrand_step(f
); while (x
>= r
);
158 /*----- Generic interface -------------------------------------------------*/
160 typedef struct gctx
{
165 static void gdestroy(grand
*r
)
171 static int gmisc(grand
*r
, unsigned op
, ...)
180 switch (va_arg(ap
, unsigned)) {
183 case GRAND_SEEDUINT32
:
193 fibrand_lcseed(&g
->f
, va_arg(ap
, unsigned));
195 case GRAND_SEEDUINT32
:
196 fibrand_lcseed(&g
->f
, va_arg(ap
, uint32
));
199 fibrand_seed(&g
->f
, va_arg(ap
, grand
*));
210 static octet
gbyte(grand
*r
)
213 return (U8(fibrand_step(&g
->f
)));
216 static uint32
gword(grand
*r
)
219 return (fibrand_step(&g
->f
));
222 static uint32
grange(grand
*r
, uint32 l
)
225 return (fibrand_range(&g
->f
, l
));
228 static void gfill(grand
*r
, void *p
, size_t sz
)
233 *q
++ = U8(fibrand_step(&g
->f
));
238 static const grand_ops gops
= {
242 gword
, gbyte
, gword
, grange
, gfill
245 /* --- @fibrand_create@ --- *
247 * Arguments: @uint32 seed@ = initial seed
249 * Returns: Pointer to a generic generator.
251 * Use: Constructs a generic generator interface over a Fibonacci
252 * generator. The generator is seeded using @fibrand_lcseed@.
255 grand
*fibrand_create(uint32 seed
)
257 gctx
*g
= CREATE(gctx
);
259 fibrand_lcseed(&g
->f
, seed
);
263 /*----- That's all, folks -------------------------------------------------*/