(svn r11527) -Codechange: Split the bitmath functions of to their own files

1 files changed, 45 insertions, 0 deletions

diff --git a/src/core/bitmath_func.cpp b/src/core/bitmath_func.cpp
new file mode 100644
index 000000000..9f36ed9a8
--- /dev/null
+++ b/src/core/bitmath_func.cpp
@@ -0,0 +1,45 @@
+/* $Id$ */
+
+/** @file bitmath_func.cpp */
+
+#include "../stdafx.h"
+#include "bitmath_func.hpp"
+
+const uint8 _ffb_64[64] = {
+ 0,  0,  1,  0,  2,  0,  1,  0,
+ 3,  0,  1,  0,  2,  0,  1,  0,
+ 4,  0,  1,  0,  2,  0,  1,  0,
+ 3,  0,  1,  0,  2,  0,  1,  0,
+ 5,  0,  1,  0,  2,  0,  1,  0,
+ 3,  0,  1,  0,  2,  0,  1,  0,
+ 4,  0,  1,  0,  2,  0,  1,  0,
+ 3,  0,  1,  0,  2,  0,  1,  0,
+};
+
+/**
+ * Search the first set bit in a 32 bit variable.
+ *
+ * This algorithm is a static implementation of a log
+ * conguence search algorithm. It checks the first half
+ * if there is a bit set search there further. And this
+ * way further. If no bit is set return 0.
+ *
+ * @param x The value to search
+ * @param The position of the first bit set
+ */
+uint8 FindFirstBit(uint32 x)
+{
+	if (x == 0) return 0;
+	/* The macro FIND_FIRST_BIT is better to use when your x is
+	  not more than 128. */
+
+	uint8 pos = 0;
+
+	if ((x & 0x0000ffff) == 0) { x >>= 16; pos += 16; }
+	if ((x & 0x000000ff) == 0) { x >>= 8;  pos += 8;  }
+	if ((x & 0x0000000f) == 0) { x >>= 4;  pos += 4;  }
+	if ((x & 0x00000003) == 0) { x >>= 2;  pos += 2;  }
+	if ((x & 0x00000001) == 0) { pos += 1; }
+
+	return pos;
+}