/* @(#)s_rint.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.

 * ====================================================

 */

/*

 * rint(x)

 * Return x rounded to integral value according to the prevailing

 * rounding mode.

 * Method:

 *	Using floating addition.

 * Exception:

 *	Inexact flag raised if x not equal to rint(x).

 */

#include "fdlibm.h"

#ifdef __STDC__

static const double

#else

static double 

#endif

TWO52[2]={

  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */

 -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */

};

#ifdef __STDC__

	double rint(double x)

#else

	double rint(x)

	double x;

#endif

{

	int i0,j0,sx;

	unsigned i,i1;

	double w,t;

	i0 =  __HI(x);

	sx = (i0>>31)&1;

	i1 =  __LO(x);

	j0 = ((i0>>20)&0x7ff)-0x3ff;

	if(j0<20) {

	    if(j0<0) { 	

		if(((i0&0x7fffffff)|i1)==0) return x;

		i1 |= (i0&0x0fffff);

		i0 &= 0xfffe0000;

		i0 |= ((i1|-i1)>>12)&0x80000;

		__HI(x)=i0;

	        w = TWO52[sx]+x;

	        t =  w-TWO52[sx];

	        i0 = __HI(t);

	        __HI(t) = (i0&0x7fffffff)|(sx<<31);

	        return t;

	    } else {

		i = (0x000fffff)>>j0;

		if(((i0&i)|i1)==0) return x; /* x is integral */

		i>>=1;

		if(((i0&i)|i1)!=0) {

		    if(j0==19) i1 = 0x40000000; else

		    i0 = (i0&(~i))|((0x20000)>>j0);

		}

	    }

	} else if (j0>51) {

	    if(j0==0x400) return x+x;	/* inf or NaN */

	    else return x;		/* x is integral */

	} else {

	    i = ((unsigned)(0xffffffff))>>(j0-20);

	    if((i1&i)==0) return x;	/* x is integral */

	    i>>=1;

	    if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));

	}

	__HI(x) = i0;

	__LO(x) = i1;

	w = TWO52[sx]+x;

	return w-TWO52[sx];

}