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/* @(#)s_modf.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#ifndef lint
static char rcsid[] = "$Id: s_modf.c,v 1.4 1994/03/03 17:04:42 jtc Exp $";
#endif
/*
* modf(double x, double *iptr)
* return fraction part of x, and return x's integral part in *iptr.
* Method:
* Bit twiddling.
*
* Exception:
* No exception.
*/
#include <math.h>
#include <machine/endian.h>
#if BYTE_ORDER == LITTLE_ENDIAN
#define n0 1
#define n1 0
#else
#define n0 0
#define n1 1
#endif
#ifdef __STDC__
static const double one = 1.0;
#else
static double one = 1.0;
#endif
#ifdef __STDC__
double modf(double x, double *iptr)
#else
double modf(x, iptr)
double x,*iptr;
#endif
{
int i0,i1,j0;
unsigned i;
i0 = *(n0+(int*)&x); /* high x */
i1 = *(n1+(int*)&x); /* low x */
j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
if(j0<20) { /* integer part in high x */
if(j0<0) { /* |x|<1 */
*(n0+(int*)iptr) = i0&0x80000000;
*(n1+(int*)iptr) = 0; /* *iptr = +-0 */
return x;
} else {
i = (0x000fffff)>>j0;
if(((i0&i)|i1)==0) { /* x is integral */
*iptr = x;
*(n0+(int*)&x) &= 0x80000000;
*(n1+(int*)&x) = 0; /* return +-0 */
return x;
} else {
*(n0+(int*)iptr) = i0&(~i);
*(n1+(int*)iptr) = 0;
return x - *iptr;
}
}
} else if (j0>51) { /* no fraction part */
*iptr = x*one;
*(n0+(int*)&x) &= 0x80000000;
*(n1+(int*)&x) = 0; /* return +-0 */
return x;
} else { /* fraction part in low x */
i = ((unsigned)(0xffffffff))>>(j0-20);
if((i1&i)==0) { /* x is integral */
*iptr = x;
*(n0+(int*)&x) &= 0x80000000;
*(n1+(int*)&x) = 0; /* return +-0 */
return x;
} else {
*(n0+(int*)iptr) = i0;
*(n1+(int*)iptr) = i1&(~i);
return x - *iptr;
}
}
}
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