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Add direction func: DirToDiagDirAlongAxis

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This commit is contained in:
Jonathan G Rennison
2018-07-08 23:00:29 +01:00
parent 2419974f19
commit 8f574881e8
1 changed files with 23 additions and 0 deletions
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23
src/direction_func.h
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@@ -278,4 +278,27 @@ static inline bool IsDiagonalDirection(Direction dir)
return (dir & 1) != 0;
}
/**
* Convert a Direction to a DiagDirection, along an Axis.
*
* This function can be used to convert the 8-way Direction to
* the 2-way DiagDirection along an axis. If the direction cannot be
* mapped INVALID_DIAGDIR is returned.
*
* @param dir The direction to convert
* @param axis axis to convert
* @return The resulting DiagDirection, may be INVALID_DIAGDIR
*/
static inline DiagDirection DirToDiagDirAlongAxis(Direction dir, Axis axis)
{
assert(IsValidDirection(dir));
assert(IsValidAxis(axis));
if ((dir & 3) == (3 ^ (axis << 1))) return INVALID_DIAGDIR;
/* Mapping:
* X 4, 5, 6 -> 2 0, 1, 2 -> 0
* Y 2, 3, 4 -> 1 0, 6, 7 -> 3
*/
return (DiagDirection)((((dir - axis) & 4) >> 1) | axis);
}
#endif /* DIRECTION_FUNC_H */