adtools/clib2

/*
 * $Id: math_scalbn.c,v 1.3 2006-01-08 12:04:24 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)

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

static const double
two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
huge   = 1.0e+300,
tiny   = 1.0e-300;

double
scalbn (double x, int n)
{
    LONG  k,hx,lx;
    EXTRACT_WORDS(hx,lx,x);
        k = (hx&0x7ff00000)>>20;        /* extract exponent */
        if (k==0) {                /* 0 or subnormal x */
            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
        x *= two54; 
        GET_HIGH_WORD(hx,x);
        k = ((hx&0x7ff00000)>>20) - 54; 
            if (n< -50000) return tiny*x;     /*underflow*/
        }
        if (k==0x7ff) return x+x;        /* NaN or Inf */
        k = k+n; 
        if (k >  0x7fe) return copysign(HUGE_VAL,x); /* overflow  */
        if (k > 0)                 /* normal result */
        {SET_HIGH_WORD(x,(hx&0x800fffffU)|(k<<20)); return x;}
        if (k <= -54) {
            if (n > 50000)     /* in case integer overflow in n+k */
        return copysign(HUGE_VAL,x);    /*overflow*/
        else return tiny*copysign(tiny,x);     /*underflow*/
    }
        k += 54;                /* subnormal result */
    SET_HIGH_WORD(x,(hx&0x800fffffU)|(k<<20));
        return x*twom54;
}

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

#endif /* FLOATING_POINT_SUPPORT */