diff options
Diffstat (limited to 'wsutil/bits_ctz.h')
| -rw-r--r-- | wsutil/bits_ctz.h | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/wsutil/bits_ctz.h b/wsutil/bits_ctz.h new file mode 100644 index 0000000000..7fa9cd87ad --- /dev/null +++ b/wsutil/bits_ctz.h @@ -0,0 +1,48 @@ +/* + * bitz_ctz.h + * + * $Id$ + * + * Wireshark - Network traffic analyzer + * By Gerald Combs <gerald@wireshark.org> + * Copyright 1998 Gerald Combs + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ + +#ifndef __WSUTIL_BITS_CTZ_H__ +#define __WSUTIL_BITS_CTZ_H__ + +#include <glib.h> + +static inline int +ws_ctz(guint32 x) +{ +#if defined(__GNUC__) && ((__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)) + g_assert(x != 0); + + return __builtin_ctz(x); +#else + /* From http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightMultLookup */ + static const int table[32] = { + 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, + 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 + }; + + return table[((guint32)((x & -(gint32)x) * 0x077CB531U)) >> 27]; +#endif +} + +#endif /* __WSUTIL_BITS_CTZ_H__ */ |