(svn r3514) -Codechange: Replace direct fiddling of bits for the ground type and density of clear tiles with symbolic names and accessors.

See clear.h for details

clear.h

@@ -0,0 +1,36 @@
+/* $Id$ */
+
+#ifndef CLEAR_H
+#define CLEAR_H
+
+#include "macros.h"
+
+/* ground type, m5 bits 2...4
+ * valid densities (bits 0...1) in comments after the enum
+ */
+typedef enum ClearGround {
+	CL_GRASS  = 0, // 0-3
+	CL_ROUGH  = 1, // 3
+	CL_ROCKS  = 2, // 3
+	CL_FIELDS = 3, // 3
+	CL_SNOW   = 4, // 0-3
+	CL_DESERT = 5  // 1,3
+} ClearGround;
+
+static inline ClearGround GetClearGround(TileIndex t) { return GB(_m[t].m5, 2, 3); }
+static inline bool IsClearGround(TileIndex t, ClearGround ct) { return GetClearGround(t) == ct; }
+
+static inline void AddClearDensity(TileIndex t, int d) { _m[t].m5 += d; }
+static inline uint GetClearDensity(TileIndex t) { return GB(_m[t].m5, 0, 2); }
+
+static inline void AddClearCounter(TileIndex t, int c) { _m[t].m5 += c << 5; }
+static inline uint GetClearCounter(TileIndex t) { return GB(_m[t].m5, 5, 3); }
+static inline void SetClearCounter(TileIndex t, uint c) { SB(_m[t].m5, 5, 3, c); }
+
+/* Sets type and density in one go, also sets the counter to 0 */
+static inline void SetClearGroundDensity(TileIndex t, ClearGround type, uint density)
+{
+	_m[t].m5 = 0 << 5 | type << 2 | density;
+}
+
+#endif