/* @(#)e_fmod.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.

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

 */

/* 

 * __ieee754_fmod(x,y)

 * Return x mod y in exact arithmetic

 * Method: shift and subtract

 */

#include "fdlibm.h"

#ifdef __STDC__

static const double one = 1.0, Zero[] = {0.0, -0.0,};

#else

static double one = 1.0, Zero[] = {0.0, -0.0,};

#endif

#ifdef __STDC__

	double __ieee754_fmod(double x, double y)

#else

	double __ieee754_fmod(x,y)

	double x,y ;

#endif

{

	int n,hx,hy,hz,ix,iy,sx,i;

	unsigned lx,ly,lz;

	hx = __HI(x);		/* high word of x */

	lx = __LO(x);		/* low  word of x */

	hy = __HI(y);		/* high word of y */

	ly = __LO(y);		/* low  word of y */

	sx = hx&0x80000000;		/* sign of x */

	hx ^=sx;		/* |x| */

	hy &= 0x7fffffff;	/* |y| */

    /* purge off exception values */

	if((hy|ly)==0||(hx>=0x7ff00000)||	/* y=0,or x not finite */

	  ((hy|((ly|-ly)>>31))>0x7ff00000))	/* or y is NaN */

	    return (x*y)/(x*y);

	if(hx<=hy) {

	    if((hx<hy)||(lx<ly)) return x;	/* |x|<|y| return x */

	    if(lx==ly) 

		return Zero[(unsigned)sx>>31];	/* |x|=|y| return x*0*/

	}

    /* determine ix = ilogb(x) */

	if(hx<0x00100000) {	/* subnormal x */

	    if(hx==0) {

		for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;

	    } else {

		for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;

	    }

	} else ix = (hx>>20)-1023;

    /* determine iy = ilogb(y) */

	if(hy<0x00100000) {	/* subnormal y */

	    if(hy==0) {

		for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;

	    } else {

		for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;

	    }

	} else iy = (hy>>20)-1023;

    /* set up {hx,lx}, {hy,ly} and align y to x */

	if(ix >= -1022) 

	    hx = 0x00100000|(0x000fffff&hx);

	else {		/* subnormal x, shift x to normal */

	    n = -1022-ix;

	    if(n<=31) {

	        hx = (hx<<n)|(lx>>(32-n));

	        lx <<= n;

	    } else {

		hx = lx<<(n-32);

		lx = 0;

	    }

	}

	if(iy >= -1022) 

	    hy = 0x00100000|(0x000fffff&hy);

	else {		/* subnormal y, shift y to normal */

	    n = -1022-iy;

	    if(n<=31) {

	        hy = (hy<<n)|(ly>>(32-n));

	        ly <<= n;

	    } else {

		hy = ly<<(n-32);

		ly = 0;

	    }

	}

    /* fix point fmod */

	n = ix - iy;

	while(n--) {

	    hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;

	    if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}

	    else {

	    	if((hz|lz)==0) 		/* return sign(x)*0 */

		    return Zero[(unsigned)sx>>31];

	    	hx = hz+hz+(lz>>31); lx = lz+lz;

	    }

	}

	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;

	if(hz>=0) {hx=hz;lx=lz;}

    /* convert back to floating value and restore the sign */

	if((hx|lx)==0) 			/* return sign(x)*0 */

	    return Zero[(unsigned)sx>>31];	

	while(hx<0x00100000) {		/* normalize x */

	    hx = hx+hx+(lx>>31); lx = lx+lx;

	    iy -= 1;

	}

	if(iy>= -1022) {	/* normalize output */

	    hx = ((hx-0x00100000)|((iy+1023)<<20));

	    __HI(x) = hx|sx;

	    __LO(x) = lx;

	} else {		/* subnormal output */

	    n = -1022 - iy;

	    if(n<=20) {

		lx = (lx>>n)|((unsigned)hx<<(32-n));

		hx >>= n;

	    } else if (n<=31) {

		lx = (hx<<(32-n))|(lx>>n); hx = sx;

	    } else {

		lx = hx>>(n-32); hx = sx;

	    }

	    __HI(x) = hx|sx;

	    __LO(x) = lx;

	    x *= one;		/* create necessary signal */

	}

	return x;		/* exact output */

}