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

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

#include "fdlibm.h"

#ifdef _NEED_FLOAT64

static const __float64
    one = _F_64(1.0),
    Zero[] = { _F_64(0.0), _F_64(-0.0) };

__float64
fmod64(__float64 x, __float64 y)
{
    __int32_t n, hx, hy, hz, ix, iy, sx, i;
    __uint32_t lx, ly, lz;

    EXTRACT_WORDS(hx, lx, x);
    EXTRACT_WORDS(hy, ly, y);
    sx = hx & 0x80000000; /* sign of x */
    hx ^= sx; /* |x| */
    hy &= 0x7fffffff; /* |y| */

    /* purge off exception values */
    if (isnan(x) || isnan(y)) /* x or y nan, return nan */
        return x + y;

    if (isinf(x)) /* x == inf, domain error */
        return __math_invalid(x);

    if ((hy | ly) == 0) /* y=0, domain error */
        return __math_invalid(y);

    if (hx <= hy) {
        if ((hx < hy) || (lx < ly))
            return x; /* |x|<|y| return x */
        if (lx == ly)
            return Zero[(__uint32_t)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[(__uint32_t)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[(__uint32_t)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));
        INSERT_WORDS(x, hx | sx, lx);
    } else { /* subnormal output */
        n = -1022 - iy;
        if (n <= 20) {
            lx = (lx >> n) | ((__uint32_t)hx << (32 - n));
            hx >>= n;
        } else if (n <= 31) {
            lx = (hx << (32 - n)) | (lx >> n);
            hx = sx;
        } else {
            lx = hx >> (n - 32);
            hx = sx;
        }
        INSERT_WORDS(x, hx | sx, lx);
        x *= one; /* create necessary signal */
    }
    return x; /* exact output */
}

_MATH_ALIAS_d_dd(fmod)

#endif /* _NEED_FLOAT64 */
