53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
/* @(#)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.
|
|
* ====================================================
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
#if defined(LIBM_SCCS) && !defined(lint)
|
|
__RCSID("$NetBSD: s_ilogb.c,v 1.13 2011/07/28 22:32:29 joerg 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"
|
|
|
|
#ifndef __HAVE_LONG_DOUBLE
|
|
__strong_alias(ilogbl,ilogb)
|
|
#endif
|
|
|
|
int
|
|
ilogb(double x)
|
|
{
|
|
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;
|
|
}
|