/* @(#)s_ilogb.c 1.3 95/01/18 */

/*

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

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice 

 * is preserved.

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

 */

/* ilogb(double x)

 * return the binary exponent of non-zero x

 * ilogb(0) = 0x80000001

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

 */

#include "fdlibm.h"

#ifdef __STDC__

	int ilogb(double x)

#else

	int ilogb(x)

	double x;

#endif

{

	int hx,lx,ix;

	hx  = (__HI(x))&0x7fffffff;	/* high word of x */

	if(hx<0x00100000) {

	    lx = __LO(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;

}