(svn r16550) -Codechange: move definition of ScaleByMapSize to header file, use shifts instead of mults

1 files changed, 24 insertions, 4 deletions

diff --git a/src/map_func.h b/src/map_func.h
index 038942cd9..265b88741 100644
--- a/src/map_func.h
+++ b/src/map_func.h
@@ -111,14 +111,34 @@ static inline uint MapMaxY()
 }
 
 /**
- * Scales relative to the number of tiles.
+ * Scales the given value by the map size, where the given value is
+ * for a 256 by 256 map.
+ * @param n the value to scale
+ * @return the scaled size
  */
-uint ScaleByMapSize(uint);
+static inline uint ScaleByMapSize(uint n)
+{
+	/* Subtract 12 from shift in order to prevent integer overflow
+	 * for large values of n. It's safe since the min mapsize is 64x64.
+	 * Add (1<<4)-1 to round upwards. */
+	return ((n << (MapLogX() + MapLogY() - 12)) + (1 << 4) - 1) >> 4;
+}
+
 
 /**
- * Scale relative to the circumference of the map.
+ * Scales the given value by the maps circumference, where the given
+ * value is for a 256 by 256 map
+ * @param n the value to scale
+ * @return the scaled size
  */
-uint ScaleByMapSize1D(uint);
+static inline uint ScaleByMapSize1D(uint n)
+{
+	/* Normal circumference for the X+Y is 256+256 = 1<<9
+	 * Note, not actually taking the full circumference into account,
+	 * just half of it.
+	 * (1<<9) - 1 is there to scale upwards. */
+	return ((n << MapLogX()) + (n << MapLogY()) + (1 << 9) - 1) >> 9;
+}
 
 /**
  * An offset value between to tiles.