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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License, Version 1.0 only
      6  * (the "License").  You may not use this file except in compliance
      7  * with the License.
      8  *
      9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
     10  * or http://www.opensolaris.org/os/licensing.
     11  * See the License for the specific language governing permissions
     12  * and limitations under the License.
     13  *
     14  * When distributing Covered Code, include this CDDL HEADER in each
     15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     16  * If applicable, add the following below this CDDL HEADER, with the
     17  * fields enclosed by brackets "[]" replaced with your own identifying
     18  * information: Portions Copyright [yyyy] [name of copyright owner]
     19  *
     20  * CDDL HEADER END
     21  */
     22 /*
     23  * Copyright 1996 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 /*      Copyright (c) 1984 AT&T */
     28 /*        All Rights Reserved   */
     29 
     30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     31 
     32 /*LINTLIBRARY*/
     33 /*
     34  *	drand48, etc. pseudo-random number generator
     35  *	This implementation assumes unsigned short integers of at least
     36  *	16 bits, long integers of at least 32 bits, and ignores
     37  *	overflows on adding or multiplying two unsigned integers.
     38  *	Two's-complement representation is assumed in a few places.
     39  *	Some extra masking is done if unsigneds are exactly 16 bits
     40  *	or longs are exactly 32 bits, but so what?
     41  *	An assembly-language implementation would run significantly faster.
     42  */
     43 #define	N	16
     44 #define	MASK	((unsigned)(1 << (N - 1)) + (1 << (N - 1)) - 1)
     45 #define	LOW(x)	((unsigned)(x) & MASK)
     46 #define	HIGH(x)	LOW((x) >> N)
     47 #define	MUL(x, y, z)	{ long l = (long)(x) * (long)(y); \
     48 		(z)[0] = LOW(l); (z)[1] = HIGH(l); }
     49 #define	CARRY(x, y)	((long)(x) + (long)(y) > MASK)
     50 #define	ADDEQU(x, y, z)	(z = CARRY(x, (y)), x = LOW(x + (y)))
     51 #define	X0	0x330E
     52 #define	X1	0xABCD
     53 #define	X2	0x1234
     54 #define	A0	0xE66D
     55 #define	A1	0xDEEC
     56 #define	A2	0x5
     57 #define	C	0xB
     58 #define	SET3(x, x0, x1, x2)	((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2))
     59 #define	SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2]))
     60 #define	SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C)
     61 #define	REST(v)							\
     62 	for (i = 0; i < 3; i++) {				\
     63 		xsubi[i] = x[i];				\
     64 		x[i] = temp[i];					\
     65 	}							\
     66 	return (v)
     67 
     68 #define	NEST(TYPE, f, F)					\
     69 	TYPE f(xsubi)						\
     70 	register unsigned short *xsubi;				\
     71 	{							\
     72 		register int i;					\
     73 		register TYPE v;				\
     74 		unsigned temp[3];				\
     75 								\
     76 		for (i = 0; i < 3; i++) {			\
     77 			temp[i] = x[i];				\
     78 			x[i] = LOW(xsubi[i]);			\
     79 		}						\
     80 		v = F();					\
     81 		REST(v);					\
     82 	}
     83 
     84 static unsigned x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C;
     85 static unsigned short lastx[3];
     86 static void next();
     87 
     88 double
     89 drand48()
     90 {
     91 	static double two16m = 1.0 / (1L << N);
     92 
     93 	next();
     94 	return (two16m * (two16m * (two16m * x[0] + x[1]) + x[2]));
     95 }
     96 
     97 NEST(double, erand48, drand48)
     98 
     99 long
    100 lrand48()
    101 {
    102 	next();
    103 	return (((long)x[2] << (N - 1)) + (x[1] >> 1));
    104 }
    105 
    106 long
    107 mrand48()
    108 {
    109 	next();
    110 	return (((long)x[2] << N) + x[1]);
    111 }
    112 
    113 static void
    114 next()
    115 {
    116 	unsigned p[2], q[2], r[2], carry0, carry1;
    117 
    118 	MUL(a[0], x[0], p);
    119 	ADDEQU(p[0], c, carry0);
    120 	ADDEQU(p[1], carry0, carry1);
    121 	MUL(a[0], x[1], q);
    122 	ADDEQU(p[1], q[0], carry0);
    123 	MUL(a[1], x[0], r);
    124 	x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] +
    125 		a[0] * x[2] + a[1] * x[1] + a[2] * x[0]);
    126 	x[1] = LOW(p[1] + r[0]);
    127 	x[0] = LOW(p[0]);
    128 }
    129 
    130 void
    131 srand48(seedval)
    132 long seedval;
    133 {
    134 	SEED(X0, LOW(seedval), HIGH(seedval));
    135 }
    136 
    137 unsigned short *
    138 seed48(seed16v)
    139 unsigned short seed16v[3];
    140 {
    141 	SETLOW(lastx, x, 0);
    142 	SEED(LOW(seed16v[0]), LOW(seed16v[1]), LOW(seed16v[2]));
    143 	return (lastx);
    144 }
    145 
    146 void
    147 lcong48(param)
    148 unsigned short param[7];
    149 {
    150 	SETLOW(x, param, 0);
    151 	SETLOW(a, param, 3);
    152 	c = LOW(param[6]);
    153 }
    154 
    155 NEST(long, nrand48, lrand48)
    156 
    157 NEST(long, jrand48, mrand48)
    158 
    159 #ifdef DRIVER
    160 /*
    161  *	This should print the sequences of integers in Tables 2
    162  *		and 1 of the TM:
    163  *	1623, 3442, 1447, 1829, 1305, ...
    164  *	657EB7255101, D72A0C966378, 5A743C062A23, ...
    165  */
    166 #include <stdio.h>
    167 
    168 main()
    169 {
    170 	int i;
    171 
    172 	for (i = 0; i < 80; i++) {
    173 		printf("%4d ", (int)(4096 * drand48()));
    174 		printf("%.4X%.4X%.4X\n", x[2], x[1], x[0]);
    175 	}
    176 }
    177 #endif
    178