1 | /* Copyright (C) 1991-2022 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <limits.h> |
19 | #define ffsl __something_else |
20 | #include <string.h> |
21 | |
22 | #undef ffs |
23 | |
24 | /* Find the first bit set in I. */ |
25 | int |
26 | __ffs (int i) |
27 | { |
28 | static const unsigned char table[] = |
29 | { |
30 | 0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5, |
31 | 6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6, |
32 | 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, |
33 | 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, |
34 | 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, |
35 | 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, |
36 | 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, |
37 | 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8 |
38 | }; |
39 | unsigned int a; |
40 | unsigned int x = i & -i; |
41 | |
42 | a = x <= 0xffff ? (x <= 0xff ? 0 : 8) : (x <= 0xffffff ? 16 : 24); |
43 | |
44 | return table[x >> a] + a; |
45 | } |
46 | weak_alias (__ffs, ffs) |
47 | libc_hidden_def (__ffs) |
48 | libc_hidden_builtin_def (ffs) |
49 | |
50 | #if ULONG_MAX == UINT_MAX |
51 | #undef ffsl |
52 | weak_alias (__ffs, ffsl) |
53 | #endif |
54 | |