Try to split ws_ctz() from hfinfo_bitshift().

svn path=/trunk/; revision=53176

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__ */