adtools/clib2

/*
 * $Id$
 *
 * :ts=4
 *
 * Portable ISO 'C' (1994) runtime library for the Amiga computer
 * Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Neither the name of Olaf Barthel nor the names of contributors
 *     may be used to endorse or promote products derived from this
 *     software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * PowerPC math library based in part on work by Sun Microsystems
 * 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.
 *
 *
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

#ifndef _MATH_HEADERS_H
#include "math_headers.h"
#endif /* _MATH_HEADERS_H */

/****************************************************************************/

#if defined(FLOATING_POINT_SUPPORT)

/****************************************************************************/

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

float
fmodf(float x, float y)
{
    LONG n,hx,hy,hz,ix,iy,sx,i;

    GET_FLOAT_WORD(hx,x);
    GET_FLOAT_WORD(hy,y);
    sx = hx&0x80000000U;        /* sign of x */
    hx ^=sx;        /* |x| */
    hy &= 0x7fffffff;    /* |y| */

    /* purge off exception values */
    if(hy==0||(hx>=0x7f800000)||        /* y=0,or x not finite */
       (hy>0x7f800000))            /* or y is NaN */
        return (x*y)/(x*y);
    if(hx<hy) return x;            /* |x|<|y| return x */
    if(hx==hy)
        return Zero[(ULONG)sx>>31];    /* |x|=|y| return x*0*/

    /* determine ix = ilogb(x) */
    if(hx<0x00800000) {    /* subnormal x */
        for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1;
    } else ix = (hx>>23)-127;

    /* determine iy = ilogb(y) */
    if(hy<0x00800000) {    /* subnormal y */
        for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1;
    } else iy = (hy>>23)-127;

    /* set up {hx,lx}, {hy,ly} and align y to x */
    if(ix >= -126) 
        hx = 0x00800000|(0x007fffff&hx);
    else {        /* subnormal x, shift x to normal */
        n = -126-ix;
        hx = hx<<n;
    }
    if(iy >= -126) 
        hy = 0x00800000|(0x007fffff&hy);
    else {        /* subnormal y, shift y to normal */
        n = -126-iy;
        hy = hy<<n;
    }

    /* fix point fmod */
    n = ix - iy;
    while(n--) {
        hz=hx-hy;
        if(hz<0){hx = hx+hx;}
        else {
            if(hz==0)         /* return sign(x)*0 */
            return Zero[(ULONG)sx>>31];
            hx = hz+hz;
        }
    }
    hz=hx-hy;
    if(hz>=0) {hx=hz;}

    /* convert back to floating value and restore the sign */
    if(hx==0)             /* return sign(x)*0 */
        return Zero[(ULONG)sx>>31];    
    while(hx<0x00800000) {        /* normalize x */
        hx = hx+hx;
        iy -= 1;
    }
    if(iy>= -126) {        /* normalize output */
        hx = ((hx-0x00800000)|((iy+127)<<23));
        SET_FLOAT_WORD(x,hx|sx);
    } else {        /* subnormal output */
        n = -126 - iy;
        hx >>= n;
        SET_FLOAT_WORD(x,hx|sx);
        x *= one;        /* create necessary signal */
    }
    return x;        /* exact output */
}

/****************************************************************************/

#endif /* FLOATING_POINT_SUPPORT */