3 * $Id: fibrand.c,v 1.2 2000/06/17 10:55:24 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 1.2 2000/06/17 10:55:24 mdw
34 * Typesetting fixes. Add flags word to generatic random generator.
36 * Revision 1.1 1999/12/10 23:15:27 mdw
37 * Noncryptographic random number generator.
41 /*----- Header files ------------------------------------------------------*/
48 #include <mLib/bits.h>
55 /*----- Main code ---------------------------------------------------------*/
57 /* --- @fibrand_step@ --- *
59 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
61 * Returns: Next output from generator.
63 * Use: Steps the generator. Returns
64 * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%.
67 uint32
fibrand_step(fibrand
*f
)
70 unsigned j
= i
+ (FIB_SZ
- FIB_TAP
);
74 x
= f
->x
[i
] = U32(f
->x
[i
] + f
->x
[j
]);
82 /* --- @fibrand_seed@ --- *
84 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
85 * @grand *r@ = random number generator to extract words from
89 * Use: Initializes a Fibonacci generator using word outputs from the
90 * given random number source @r@.
93 void fibrand_seed(fibrand
*f
, grand
*r
)
98 for (i
= 0; i
< FIB_SZ
; i
++)
99 p
|= f
->x
[i
] = r
->ops
->word(r
);
101 i
= r
->ops
->range(r
, FIB_SZ
);
107 /* --- @fibrand_lcseed@ --- *
109 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
110 * @uint32 seed@ = seed value
114 * Use: Initializes a Fibonacci generator using outputs from the
115 * @lcrand@ generator seeded from @seed@. This is faster than
116 * using a generic @lcrand@-based generator and @fibrand_rseed@
117 * because it uses raw outputs rather than uniformly distributed
121 void fibrand_lcseed(fibrand
*f
, uint32 seed
)
126 for (i
= 0; i
< FIB_SZ
; i
++)
127 p
|= f
->x
[i
] = seed
= lcrand(seed
);
129 i
= lcrand_range(&seed
, FIB_SZ
);
135 /* --- @fibrand_range@ --- *
137 * Arguments: @fibrand *f@ = pointer to Fibonacci generator context
140 * Returns: A uniformly distributed pseudorandom integer in the interval
144 uint32
fibrand_range(fibrand
*f
, uint32 m
)
146 uint32 r
= 0xffffffff - (0xffffffff % m
);
149 /* --- Now generate numbers until a good one comes along --- */
151 do x
= fibrand_step(f
); while (x
>= r
);
152 return (x
/ (r
/ m
));
155 /*----- Generic interface -------------------------------------------------*/
157 typedef struct gctx
{
162 static void gdestroy(grand
*r
)
168 static int gmisc(grand
*r
, unsigned op
, ...)
177 switch (va_arg(ap
, unsigned)) {
180 case GRAND_SEEDUINT32
:
190 fibrand_lcseed(&g
->f
, va_arg(ap
, unsigned));
192 case GRAND_SEEDUINT32
:
193 fibrand_lcseed(&g
->f
, va_arg(ap
, uint32
));
196 fibrand_seed(&g
->f
, va_arg(ap
, grand
*));
207 static octet
gbyte(grand
*r
)
210 return (U8(fibrand_step(&g
->f
)));
213 static uint32
gword(grand
*r
)
216 return (fibrand_step(&g
->f
));
219 static uint32
grange(grand
*r
, uint32 l
)
222 return (fibrand_range(&g
->f
, l
));
225 static void gfill(grand
*r
, void *p
, size_t sz
)
230 *q
++ = U8(fibrand_step(&g
->f
));
235 static const grand_ops gops
= {
239 gword
, gbyte
, gword
, grange
, gfill
242 /* --- @fibrand_create@ --- *
244 * Arguments: @uint32 seed@ = initial seed
246 * Returns: Pointer to a generic generator.
248 * Use: Constructs a generic generator interface over a Fibonacci
249 * generator. The generator is seeded using @fibrand_lcseed@.
252 grand
*fibrand_create(uint32 seed
)
254 gctx
*g
= CREATE(gctx
);
256 fibrand_lcseed(&g
->f
, seed
);
260 /*----- That's all, folks -------------------------------------------------*/