44 lines
1.0 KiB
C
44 lines
1.0 KiB
C
/* @(#)s_logb.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_logb.c,v 1.12 2011/08/03 14:13:07 joerg Exp $");
|
|
#endif
|
|
|
|
/*
|
|
* double logb(x)
|
|
* IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
|
|
* Use ilogb instead.
|
|
*/
|
|
|
|
#include "math.h"
|
|
#include "math_private.h"
|
|
|
|
#ifndef __HAVE_LONG_DOUBLE
|
|
__strong_alias(logbl,logb)
|
|
#endif
|
|
|
|
double
|
|
logb(double x)
|
|
{
|
|
int32_t lx,ix;
|
|
EXTRACT_WORDS(ix,lx,x);
|
|
ix &= 0x7fffffff; /* high |x| */
|
|
if((ix|lx)==0) return -1.0/fabs(x);
|
|
if(ix>=0x7ff00000) return x*x;
|
|
if((ix>>=20)==0) /* IEEE 754 logb */
|
|
return -1022.0;
|
|
else
|
|
return (double) (ix-1023);
|
|
}
|