1 /*
2 * Copyright (C) 2013 Tim Mayberry <mojofunk@gmail.com>
3 * Copyright (C) 2013-2015 Paul Davis <paul@linuxaudiosystems.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License along
16 * with this program; if not, write to the Free Software Foundation, Inc.,
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18 */
19
20 #include "pbd/ffs.h"
21
22 #ifndef COMPILER_MSVC
23 #include <strings.h>
24 #endif
25
26 namespace PBD {
27 int
ffs(int x)28 ffs (int x)
29 {
30 #if defined (COMPILER_MINGW)
31 return __builtin_ffs(x);
32 #elif defined (COMPILER_MSVC)
33 unsigned long index;
34 #ifdef WIN64
35 if (0 != _BitScanForward64(&index, (__int64)x))
36 #else
37 if (0 != _BitScanForward(&index, (unsigned long)x))
38 #endif
39 index++; // Make the result 1-based
40 else
41 index = 0; // All bits were zero
42
43 return (int)index;
44 #else
45 return ::ffs(x);
46 #endif
47 }
48
49 }
50