ref: 0ec1cfd78b495e9be40e4aa24e35b2aa5d5e5704
dir: /libmath/fdlibm/s_ilogb.c/
/* derived from /netlib/fdlibm */
/* @(#)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"
int ilogb(double x)
{
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;
}