libast/uwin/rand48.c

	rand48.c revision 3f54fd611f536639ec30dd53c48e5ec1897cc7d9
/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*          Copyright (c) 1985-2011 AT&T Intellectual Property          *
*                      and is licensed under the                       *
*                 Eclipse Public License, Version 1.0                  *
*                    by AT&T Intellectual Property                     *
*                                                                      *
*                A copy of the License is available at                 *
*          http://www.eclipse.org/org/documents/epl-v10.html           *
*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#include "FEATURE/uwin"

#if !_UWIN || _lib_srand48

void _STUB_srand48(){}

#else

#define drand48 ______drand48
#define erand48 ______erand48
#define jrand48 ______jrand48
#define lcong48 ______lcong48
#define lrand48 ______lrand48
#define mrand48 ______mrand48
#define nrand48 ______nrand48
#define seed48  ______seed48
#define srand48 ______srand48

#include    <stdlib.h>

#undef  drand48
#undef  erand48
#undef  jrand48
#undef  lcong48
#undef  lrand48
#undef  mrand48
#undef  nrand48
#undef  seed48
#undef  srand48

#if defined(__EXPORT__)
#define extern      __EXPORT__
#endif

#define A   0x5DEECE66D
#define A0  0X5
#define A1  0xDEEC
#define A2  0xE66D
#define C   0xB
#define XINIT   0x330E
#define SCALE   3.55271e-15

static unsigned short oldval[3];
static unsigned short X[3] = { 0, 0, XINIT};
static unsigned short a[3] = { A0, A1, A2};
static unsigned short c = C;

static void multadd(unsigned short x[3], unsigned short a[3], unsigned short c)
{
    register unsigned long r = c;
    unsigned short x2 = x[2];
    unsigned short x1 = x[1];
    r += a[2]*x2;
    x[2] = (unsigned short)r;
    r >>= 16;
    r += a[1]*x2;
    r += a[2]*x1;
    x[1] = (unsigned short)r;
    r >>= 16;
    r += a[2]*x[0];
    r += a[1]*x1;
    r += a[0]*x2;
    x[0] = (unsigned short)r;
}

extern double drand48(void)
{
    double d;
    unsigned long u;
    multadd(X,a,c);
    u = (X[0]<<16) + X[1];
    d = (u*65536.) + X[2];
    return(d*SCALE);
}

extern double erand48(unsigned short xsubi[3])
{
    double d;
    unsigned long u;
    multadd(xsubi,a,c);
    u = (xsubi[0]<<16) + xsubi[1];
    d = (u*65536.) + xsubi[2];
    return(d*SCALE);
}

extern long jrand48(unsigned short xsubi[3])
{
    long u;
    multadd(xsubi,a,c);
    u = (xsubi[0]<<16) | xsubi[1];
    return((long)u);
}

extern void lcong48(unsigned short param[7])
{
    X[0] = param[0];
    X[1] = param[1];
    X[2] = param[2];
    a[0] = param[3];
    a[1] = param[4];
    a[2] = param[5];
    c = param[6];
}

extern long lrand48(void)
{
    long l;
    multadd(X,a,c);
    l = (X[0]<<15)|(X[1]>>1);
    return(l);
}

extern long mrand48(void)
{
    unsigned long u;
    multadd(X,a,c);
    u = (X[0]<<16) | X[1];
    return((long)u);
}

extern long nrand48(unsigned short xsubi[3])
{
    long l;
    multadd(xsubi,a,c);
    l = (xsubi[0]<<15)|(xsubi[1]>>1);
    return(l);
}

extern unsigned short *seed48(unsigned short seed[3])
{
    unsigned short *sp = (unsigned short*)&X;
    a[0] = A0;
    a[1] = A1;
    a[2] = A2;
    c = C;
    oldval[0] = X[2];
    oldval[1] = X[1];
    oldval[2] = X[0];
    X[0] = seed[2];
    X[1] = seed[1];
    X[2] = seed[0];
    return(oldval);
}

extern void srand48(long seedval)
{
    a[0] = A0;
    a[1] = A1;
    a[2] = A2;
    c = C;
    X[0] = (unsigned short)(((unsigned long)seedval) >> 16);
    X[1] = (unsigned short)seedval;
    X[2] = XINIT;
}

#endif