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/* @(#)s_ilogb.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.

 * ====================================================

 */

#if defined(LIBM_SCCS) && !defined(lint)

static char rcsid[] = "$NetBSD: s_ilogb.c,v 1.9 1995/05/10 20:47:28 jtc Exp $";

#endif

/* ilogb(double x)

 * return the binary exponent of non-zero x

 * ilogb(0) = 0x80000001

 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)

 */

#include "math.h"

#include "math_private.h"

#ifdef __STDC__

        int ilogb(double x)

#else

        int ilogb(x)

        double x;

#endif

{

        int32_t hx,lx,ix;

        GET_HIGH_WORD(hx,x);

        hx &= 0x7fffffff;

        if(hx<0x00100000) {

            GET_LOW_WORD(lx,x);

            if((hx|lx)==0)

                return 0x80000001;      /* ilogb(0) = 0x80000001 */

            else                        /* subnormal x */

                if(hx==0) {

                    for (ix = -1043; lx>0; lx<<=1) ix -=1;

                } else {

                    for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;

                }

            return ix;

        }

        else if (hx<0x7ff00000) return (hx>>20)-1023;

        else return 0x7fffffff;

}