Improve exposure mask calculation.

[rrace.git] / src / game.h

diff --git a/src/game.h b/src/game.h
index 958cc60f94168489d966fc5ff21466d93c7ff2df..7640b415d0bd6aba2c67f98bd3692439f556c43c 100644 (file)
--- a/src/game.h
+++ b/src/game.h
@@ -121,9 +121,7 @@ static inline uint_fast32_t board_mask_v(int x, int y0, int y1)
  */
 static inline uint_fast32_t board_above(int y)
 {
-       uint_fast32_t val = board_row(y);
-
-       return val | (val-1);
+       return ( 0x20ul << 5*y ) - 1;
 }
 
 /*
@@ -131,9 +129,7 @@ static inline uint_fast32_t board_above(int y)
  */
 static inline uint_fast32_t board_below(int y)
 {
-       uint_fast32_t val = board_row(y);
-
-       return val | (~val + 1);
+       return ~( 1ul << 5*y ) + 1;
 }
 
 /*
@@ -156,6 +152,21 @@ static inline uint_fast32_t board_right(int x)
        return ~val + 0x108421;
 }
 
+/*
+ * Return the board bitmap setting the rectangle of locations that are:
+ *
+ *   - on or right of column x1, and
+ *   - on or left of column x2, and
+ *   - on or below row y1, and
+ *   - on or above row y2.
+ *
+ * It must be the case that x2 >= x1 and y2 >= y1.
+ */
+static inline uint_fast32_t board_rect(int x1, int y1, int x2, int y2)
+{
+       return (board_left(x2-x1) << x1) & (board_above(y2-y1) << 5*y1);
+}
+
 /*
  * Move the bits in the game bitmaps according to a move at position (x, y),
  * and update the location of the empty position which, if the move was valid