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/* ilogb(double x)
27 * return the binary exponent of non-zero x
28 * ilogb(0) = 0x80000001
29 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
30 */
31
32#include "fdlibm.h"
33
34#ifdef __STDC__
35 int ilogb(double x)
36#else
37 int ilogb(x)
38 double x;
39#endif
40{
41 int hx,lx,ix;
42
43 hx = (__HI(x))&0x7fffffff; /* high word of x */
44 if(hx<0x00100000) {
45 lx = __LO(x);
46 if((hx|lx)==0)
47 return 0x80000001; /* ilogb(0) = 0x80000001 */
48 else /* subnormal x */
49 if(hx==0) {
50 for (ix = -1043; lx>0; lx<<=1) ix -=1;
51 } else {
52 for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
53 }
54 return ix;
55 }
56 else if (hx<0x7ff00000) return (hx>>20)-1023;
57 else return 0x7fffffff;
58}
59