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/* @(#)e_remainder.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: e_remainder.c,v 1.8 1995/05/10 20:46:05 jtc Exp $";

#endif

/* __ieee754_remainder(x,p)

 * Return :

 *      returns  x REM p  =  x - [x/p]*p as if in infinite

 *      precise arithmetic, where [x/p] is the (infinite bit)

 *      integer nearest x/p (in half way case choose the even one).

 * Method :

 *      Based on fmod() return x-[x/p]chopped*p exactlp.

 */

#include "math.h"

#include "math_private.h"

#ifdef __STDC__

static const double zero = 0.0;

#else

static double zero = 0.0;

#endif

#ifdef __STDC__

        double __ieee754_remainder(double x, double p)

#else

        double __ieee754_remainder(x,p)

        double x,p;

#endif

{

        int32_t hx,hp;

        u_int32_t sx,lx,lp;

        double p_half;

        EXTRACT_WORDS(hx,lx,x);

        EXTRACT_WORDS(hp,lp,p);

        sx = hx&0x80000000;

        hp &= 0x7fffffff;

        hx &= 0x7fffffff;

    /* purge off exception values */

        if((hp|lp)==0) return (x*p)/(x*p);       /* p = 0 */

        if((hx>=0x7ff00000)||                   /* x not finite */

          ((hp>=0x7ff00000)&&                   /* p is NaN */

          (((hp-0x7ff00000)|lp)!=0)))

            return (x*p)/(x*p);

        if (hp<=0x7fdfffff) x = __ieee754_fmod(x,p+p);  /* now x < 2p */

        if (((hx-hp)|(lx-lp))==0) return zero*x;

        x  = fabs(x);

        p  = fabs(p);

        if (hp<0x00200000) {

            if(x+x>p) {

                x-=p;

                if(x+x>=p) x -= p;

            }

        } else {

            p_half = 0.5*p;

            if(x>p_half) {

                x-=p;

                if(x>=p_half) x -= p;

            }

        }

        GET_HIGH_WORD(hx,x);

        SET_HIGH_WORD(x,hx^sx);

        return x;

}