ref: 7a29422cfefaf76315eafa82ca606f9ded9517b3
dir: /libmath/fdlibm/s_modf.c/
/* derived from /netlib/fdlibm */
/* @(#)s_modf.c 1.3 95/01/18 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunSoft, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* 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 "fdlibm.h"
static const double one = 1.0;
double modf(double x, double *iptr)
{
int i0,i1,j0;
unsigned i;
i0 = __HI(x); /* high x */
i1 = __LO(x); /* low x */
j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
if(j0<20) { /* integer part in high x */
if(j0<0) { /* |x|<1 */
__HIp(iptr) = i0&0x80000000;
__LOp(iptr) = 0; /* *iptr = +-0 */
return x;
} else {
i = (0x000fffff)>>j0;
if(((i0&i)|i1)==0) { /* x is integral */
*iptr = x;
__HI(x) &= 0x80000000;
__LO(x) = 0; /* return +-0 */
return x;
} else {
__HIp(iptr) = i0&(~i);
__LOp(iptr) = 0;
return x - *iptr;
}
}
} else if (j0>51) { /* no fraction part */
*iptr = x*one;
__HI(x) &= 0x80000000;
__LO(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;
__HI(x) &= 0x80000000;
__LO(x) = 0; /* return +-0 */
return x;
} else {
__HIp(iptr) = i0;
__LOp(iptr) = i1&(~i);
return x - *iptr;
}
}
}