1/*
2 * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26/*
27 * double logb(x)
28 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
29 * Use ilogb instead.
30 */
31
32#include "fdlibm.h"
33
34#ifdef __STDC__
35 double logb(double x)
36#else
37 double logb(x)
38 double x;
39#endif
40{
41 int lx,ix;
42 ix = (__HI(x))&0x7fffffff; /* high |x| */
43 lx = __LO(x); /* low x */
44 if((ix|lx)==0) return -1.0/fabs(x);
45 if(ix>=0x7ff00000) return x*x;
46 if((ix>>=20)==0) /* IEEE 754 logb */
47 return -1022.0;
48 else
49 return (double) (ix-1023);
50}
51