--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/direction_func.h	Tue Jan 22 21:00:30 2008 +0000
@@ -0,0 +1,214 @@
+/* $Id$ */
+
+/** @file direction_func.h Different functions related to conversions between directions. */
+
+#ifndef DIRECTION_FUNC_H
+#define DIRECTION_FUNC_H
+
+#include "direction_type.h"
+
+/**
+ * Return the reverse of a direction
+ *
+ * @param d The direction to get the reverse from
+ * @return The reverse Direction
+ */
+static inline Direction ReverseDir(Direction d)
+{
+	return (Direction)(4 ^ d);
+}
+
+
+/**
+ * Calculate the difference between to directions
+ *
+ * @param d0 The first direction as the base
+ * @param d1 The second direction as the offset from the base
+ * @return The difference how the second directions drifts of the first one.
+ */
+static inline DirDiff DirDifference(Direction d0, Direction d1)
+{
+	return (DirDiff)((d0 + 8 - d1) % 8);
+}
+
+/**
+ * Applies two differences together
+ *
+ * This function adds two differences together and return the resulting
+ * difference. So adding two DIRDIFF_REVERSE together results in the
+ * DIRDIFF_SAME difference.
+ *
+ * @param d The first difference
+ * @param delta The second difference to add on
+ * @return The resulting difference
+ */
+static inline DirDiff ChangeDirDiff(DirDiff d, DirDiff delta)
+{
+	return (DirDiff)((d + delta) % 8);
+}
+
+/**
+ * Change a direction by a given difference
+ *
+ * This functions returns a new direction of the given direction
+ * which is rotated by the given difference.
+ *
+ * @param d The direction to get a new direction from
+ * @param delta The offset/drift applied to the direction
+ * @return The new direction
+ */
+static inline Direction ChangeDir(Direction d, DirDiff delta)
+{
+	return (Direction)((d + delta) % 8);
+}
+
+
+/**
+ * Returns the reverse direction of the given DiagDirection
+ *
+ * @param d The DiagDirection to get the reverse from
+ * @return The reverse direction
+ */
+static inline DiagDirection ReverseDiagDir(DiagDirection d)
+{
+	return (DiagDirection)(2 ^ d);
+}
+
+
+/**
+ * Applies a difference on a DiagDirection
+ *
+ * This function applies a difference on a DiagDirection and returns
+ * the new DiagDirection.
+ *
+ * @param d The DiagDirection
+ * @param delta The difference to applie on
+ * @return The new direction which was calculated
+ */
+static inline DiagDirection ChangeDiagDir(DiagDirection d, DiagDirDiff delta)
+{
+	return (DiagDirection)((d + delta) % 4);
+}
+
+/**
+ * Convert a Direction to a DiagDirection.
+ *
+ * This function can be used to convert the 8-way Direction to
+ * the 4-way DiagDirection. If the direction cannot be mapped its
+ * "rounded clockwise". So DIR_N becomes DIAGDIR_NE.
+ *
+ * @param dir The direction to convert
+ * @return The resulting DiagDirection, maybe "rounded clockwise".
+ */
+static inline DiagDirection DirToDiagDir(Direction dir)
+{
+	return (DiagDirection)(dir >> 1);
+}
+
+/**
+ * Convert a DiagDirection to a Direction.
+ *
+ * This function can be used to convert the 4-way DiagDirection
+ * to the 8-way Direction. As 4-way are less than 8-way not all
+ * possible directions can be calculated.
+ *
+ * @param dir The direction to convert
+ * @return The resulting Direction
+ */
+static inline Direction DiagDirToDir(DiagDirection dir)
+{
+	return (Direction)(dir * 2 + 1);
+}
+
+
+/**
+ * Select the other axis as provided.
+ *
+ * This is basically the not-operator for the axis.
+ *
+ * @param a The given axis
+ * @return The other axis
+ */
+static inline Axis OtherAxis(Axis a)
+{
+	return (Axis)(a ^ 1);
+}
+
+
+/**
+ * Convert a DiagDirection to the axis.
+ *
+ * This function returns the axis which belongs to the given
+ * DiagDirection. The axis X belongs to the DiagDirection
+ * north-east and south-west.
+ *
+ * @param d The DiagDirection
+ * @return The axis which belongs to the direction
+ */
+static inline Axis DiagDirToAxis(DiagDirection d)
+{
+	return (Axis)(d & 1);
+}
+
+
+/**
+ * Converts an Axis to a DiagDirection
+ *
+ * This function returns the DiagDirection which
+ * belongs to the axis. As 2 directions are mapped to an axis
+ * this function returns the one which points to south,
+ * either south-west (on X axis) or south-east (on Y axis)
+ *
+ * @param a The axis
+ * @return The direction pointed to south
+ */
+static inline DiagDirection AxisToDiagDir(Axis a)
+{
+	return (DiagDirection)(2 - a);
+}
+
+/**
+ * Convert an axis and a flag for north/south into a DiagDirection
+ * @param xy axis to convert
+ * @param ns north -> 0, south -> 1
+ * @return the desired DiagDirection
+ */
+static inline DiagDirection XYNSToDiagDir(Axis xy, uint ns)
+{
+	return (DiagDirection)(xy * 3 ^ ns * 2);
+}
+
+/**
+ * Checks if an interger value is a valid DiagDirection
+ *
+ * @param d The value to check
+ * @return True if the value belongs to a DiagDirection, else false
+ */
+static inline bool IsValidDiagDirection(DiagDirection d)
+{
+	return d < DIAGDIR_END;
+}
+
+/**
+ * Checks if an integer value is a valid Direction
+ *
+ * @param d The value to check
+ * @return True if the value belongs to a Direction, else false
+ */
+static inline bool IsValidDirection(Direction d)
+{
+	return d < DIR_END;
+}
+
+/**
+ * Checks if an integer value is a valid Axis
+ *
+ * @param d The value to check
+ * @return True if the value belongs to an Axis, else false
+ */
+static inline bool IsValidAxis(Axis d)
+{
+	return d < AXIS_END;
+}
+
+#endif /* DIRECTION_H */