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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.
* ====================================================
*/
#ifndef lint
static char rcsid[] = "$FreeBSD$";
#endif
/* ilogb(double x)
* return the binary exponent of non-zero x
* ilogb(0) = FP_ILOGB0
* ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
* ilogb(inf) = INT_MAX (no signal is raised)
*/
#include <limits.h>
#include "math.h"
#include "math_private.h"
int ilogb(double x)
{
int32_t hx,lx,ix;
EXTRACT_WORDS(hx,lx,x);
hx &= 0x7fffffff;
if(hx<0x00100000) {
if((hx|lx)==0)
return FP_ILOGB0;
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 if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN;
else return INT_MAX;
}
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