1 files changed, 41 insertions, 0 deletions
diff --git a/src/slope.h b/src/slope.h
new file mode 100644
index 000000000..0708bc5d5
--- /dev/null
+++ b/src/slope.h
@@ -0,0 +1,41 @@
+/* $Id$ */
+
+#ifndef SLOPE_H
+#define SLOPE_H
+
+typedef enum Slope {
+	SLOPE_FLAT     = 0x00,
+	SLOPE_W        = 0x01,
+	SLOPE_S        = 0x02,
+	SLOPE_E        = 0x04,
+	SLOPE_N        = 0x08,
+	SLOPE_STEEP    = 0x10,
+	SLOPE_NW       = SLOPE_N | SLOPE_W,
+	SLOPE_SW       = SLOPE_S | SLOPE_W,
+	SLOPE_SE       = SLOPE_S | SLOPE_E,
+	SLOPE_NE       = SLOPE_N | SLOPE_E,
+	SLOPE_EW       = SLOPE_E | SLOPE_W,
+	SLOPE_NS       = SLOPE_N | SLOPE_S,
+	SLOPE_ELEVATED = SLOPE_N | SLOPE_E | SLOPE_S | SLOPE_W,
+	SLOPE_NWS      = SLOPE_N | SLOPE_W | SLOPE_S,
+	SLOPE_WSE      = SLOPE_W | SLOPE_S | SLOPE_E,
+	SLOPE_SEN      = SLOPE_S | SLOPE_E | SLOPE_N,
+	SLOPE_ENW      = SLOPE_E | SLOPE_N | SLOPE_W,
+	SLOPE_STEEP_W  = SLOPE_STEEP | SLOPE_NWS,
+	SLOPE_STEEP_S  = SLOPE_STEEP | SLOPE_WSE,
+	SLOPE_STEEP_E  = SLOPE_STEEP | SLOPE_SEN,
+	SLOPE_STEEP_N  = SLOPE_STEEP | SLOPE_ENW
+} Slope;
+
+static inline bool IsSteepSlope(Slope s)
+{
+	return (s & SLOPE_STEEP) != 0;
+}
+
+static inline Slope ComplementSlope(Slope s)
+{
+	assert(!IsSteepSlope(s));
+	return (Slope)(0xF ^ s);
+}
+
+#endif /* SLOPE_H */