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/* @(#)s_floor.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.

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

 */

#if defined(LIBM_SCCS) && !defined(lint)

static char rcsid[] = "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";

#endif

/*

 * 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 "math.h"

#include "math_private.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

{

        int32_t i0,i1,j0;

        u_int32_t i,j;

        EXTRACT_WORDS(i0,i1,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 = ((u_int32_t)(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);

            }

        }

        INSERT_WORDS(x,i0,i1);

        return x;

}