aboutsummaryrefslogtreecommitdiff
path: root/newlib/libm/common/s_logb.c
blob: dbddd19947d135727393313b251105b4974409ab (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42

/* @(#)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.
 * ====================================================
 */

/*
 * double logb(x)
 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
 * Use ilogb instead.
 */

#include "fdlibm.h"

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
	double logb(double x)
#else
	double logb(x)
	double x;
#endif
{
	__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); 
}

#endif /* _DOUBLE_IS_32BITS */