/*
 * ====================================================
 * 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.
 * ====================================================
 */

/* 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 <float.h>

#include "math.h"
#include "math_private.h"

static const double zero = 0.0;


double
remainder(double x, double p)
{
        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)||                       /* p = 0 */
          (hx>=0x7ff00000)||                    /* x not finite */
          ((hp>=0x7ff00000)&&                   /* p is NaN */
          (((hp-0x7ff00000)|lp)!=0)))
            return nan_mix_op(x, p, *)/nan_mix_op(x, p, *);


        if (hp<=0x7fdfffff) x = 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;
            }
        }
        EXTRACT_WORDS(hx, lx, x);
        if (((hx&0x7fffffff)|lx) == 0) hx = 0;
        SET_HIGH_WORD(x,hx^sx);
        return x;
}

#if LDBL_MANT_DIG == 53
__weak_reference(remainder, remainderl);
#endif