1
2/* @(#)s_logb.c 1.3 95/01/18 */
3/*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunSoft, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
12 */
13
14/*
15 * double ieee_logb(x)
16 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
17 * Use ilogb instead.
18 */
19
20#include "fdlibm.h"
21
22#ifdef __STDC__
23	double ieee_logb(double x)
24#else
25	double ieee_logb(x)
26	double x;
27#endif
28{
29	int lx,ix;
30	ix = (__HI(x))&0x7fffffff;	/* high |x| */
31	lx = __LO(x);			/* low x */
32	if((ix|lx)==0) return -1.0/ieee_fabs(x);
33	if(ix>=0x7ff00000) return x*x;
34	if((ix>>=20)==0) 			/* IEEE 754 logb */
35		return -1022.0;
36	else
37		return (double) (ix-1023);
38}
39