/* @(#)e_fmod.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.
 * ====================================================
 */

/*
 * fmodl(x,y)
 * Return x mod y in exact arithmetic
 * Method: shift and subtract
 */

#include <math.h>

#include "math_private.h"

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

long double
fmodl(long double x, long double y)
{
        int64_t n,hx,hy,hz,ix,iy,sx,i;
        u_int64_t lx,ly,lz;

        GET_LDOUBLE_WORDS64(hx,lx,x);
        GET_LDOUBLE_WORDS64(hy,ly,y);
        sx = hx&0x8000000000000000ULL;          /* sign of x */
        hx ^=sx;                                /* |x| */
        hy &= 0x7fffffffffffffffLL;             /* |y| */

    /* purge off exception values */
        if((hy|ly)==0||(hx>=0x7fff000000000000LL)|| /* y=0,or x not finite */
          ((hy|((ly|-ly)>>63))>0x7fff000000000000LL))   /* 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[(u_int64_t)sx>>63]; /* |x|=|y| return x*0*/
        }

    /* determine ix = ilogb(x) */
        if(hx<0x0001000000000000LL) {   /* subnormal x */
            if(hx==0) {
                for (ix = -16431, i=lx; i>0; i<<=1) ix -=1;
            } else {
                for (ix = -16382, i=hx<<15; i>0; i<<=1) ix -=1;
            }
        } else ix = (hx>>48)-0x3fff;

    /* determine iy = ilogb(y) */
        if(hy<0x0001000000000000LL) {   /* subnormal y */
            if(hy==0) {
                for (iy = -16431, i=ly; i>0; i<<=1) iy -=1;
            } else {
                for (iy = -16382, i=hy<<15; i>0; i<<=1) iy -=1;
            }
        } else iy = (hy>>48)-0x3fff;

    /* set up {hx,lx}, {hy,ly} and align y to x */
        if(ix >= -16382)
            hx = 0x0001000000000000LL|(0x0000ffffffffffffLL&hx);
        else {          /* subnormal x, shift x to normal */
            n = -16382-ix;
            if(n<=63) {
                hx = (hx<<n)|(lx>>(64-n));
                lx <<= n;
            } else {
                hx = lx<<(n-64);
                lx = 0;
            }
        }
        if(iy >= -16382)
            hy = 0x0001000000000000LL|(0x0000ffffffffffffLL&hy);
        else {          /* subnormal y, shift y to normal */
            n = -16382-iy;
            if(n<=63) {
                hy = (hy<<n)|(ly>>(64-n));
                ly <<= n;
            } else {
                hy = ly<<(n-64);
                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>>63); lx = lx+lx;}
            else {
                if((hz|lz)==0)          /* return sign(x)*0 */
                    return Zero[(u_int64_t)sx>>63];
                hx = hz+hz+(lz>>63); 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[(u_int64_t)sx>>63];     
        while(hx<0x0001000000000000LL) {        /* normalize x */
            hx = hx+hx+(lx>>63); lx = lx+lx;
            iy -= 1;
        }
        if(iy>= -16382) {       /* normalize output */
            hx = ((hx-0x0001000000000000LL)|((iy+16383)<<48));
            SET_LDOUBLE_WORDS64(x,hx|sx,lx);
        } else {                /* subnormal output */
            n = -16382 - iy;
            if(n<=48) {
                lx = (lx>>n)|((u_int64_t)hx<<(64-n));
                hx >>= n;
            } else if (n<=63) {
                lx = (hx<<(64-n))|(lx>>n); hx = sx;
            } else {
                lx = hx>>(n-64); hx = sx;
            }
            SET_LDOUBLE_WORDS64(x,hx|sx,lx);
            x *= one;           /* create necessary signal */
        }
        return x;               /* exact output */
}