adtools/clib2

/*
 * $Id: math_logb.c,v 1.9 2006-01-08 12:04:23 obarthel Exp $
 *
 * :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.
 */

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

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

#if defined(FLOATING_POINT_SUPPORT)

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

#if defined(IEEE_FLOATING_POINT_SUPPORT) || defined(M68881_FLOATING_POINT_SUPPORT)

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

INLINE STATIC const double
__logb(double x)
{
    double result;

    result = log(x) / log((double)FLT_RADIX);

    return(result);
}

#endif /* IEEE_FLOATING_POINT_SUPPORT || M68881_FLOATING_POINT_SUPPORT */

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

#if defined(PPC_FLOATING_POINT_SUPPORT)

INLINE STATIC double
__logb(double x)
{
    unsigned int lx,ix;

    EXTRACT_WORDS(ix,lx,x);

    ix &= 0x7fffffff;    /* high |x| */
    if((ix|lx)==0)
        return -1.0/fabs(x);

    if(ix>=0x7ff00000)
        return x*x;

    if((ix>>=20)==0)    /* IEEE 754 logb */
        return -1022.0;
    else
        return (double) (ix-1023);
}

#endif /* PPC_FLOATING_POINT_SUPPORT */

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

double
logb(double x)
{
    double result;

    if(x == 0.0)
    {
        result = -__inf();
        goto out;
    }

    if(isnan(x))
    {
        result = x;
        goto out;
    }

    if(isinf(x))
    {
        if(x < 0)
            result = (-x);
        else
            result = x;

        goto out;
    }

    result = __logb(x);

 out:

    return(result);
}

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

#endif /* FLOATING_POINT_SUPPORT */