/* @(#)s_floor.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.

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

 */

/*

 * floor(x)

 * Return x rounded toward -inf to integral value

 * Method:

 *	Bit twiddling.

 * Exception:

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

 */

#include "fdlibm.h"

#ifdef __STDC__

static const double huge = 1.0e300;

#else

static double huge = 1.0e300;

#endif

#ifdef __STDC__

	double floor(double x)

#else

	double floor(x)

	double x;

#endif

{

	int i0,i1,j0;

	unsigned i,j;

	i0 =  __HI(x);

	i1 =  __LO(x);

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

	if(j0<20) {

	    if(j0<0) { 	/* raise inexact if x != 0 */

		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */

		    if(i0>=0) {i0=i1=0;} 

		    else if(((i0&0x7fffffff)|i1)!=0)

			{ i0=0xbff00000;i1=0;}

		}

	    } else {

		i = (0x000fffff)>>j0;

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

		if(huge+x>0.0) {	/* raise inexact flag */

		    if(i0<0) i0 += (0x00100000)>>j0;

		    i0 &= (~i); i1=0;

		}

	    }

	} 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 */

	    if(huge+x>0.0) { 		/* raise inexact flag */

		if(i0<0) {

		    if(j0==20) i0+=1; 

		    else {

			j = i1+(1<<(52-j0));

			if(j<i1) i0 +=1 ; 	/* got a carry */

			i1=j;

		    }

		}

		i1 &= (~i);

	    }

	}

	__HI(x) = i0;

	__LO(x) = i1;

	return x;

}