--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/track_func.h	Tue Jan 22 21:00:30 2008 +0000
@@ -0,0 +1,519 @@
+/* $Id$ */
+
+/** @file track_func.h Different conversion functions from one kind of track to another. */
+
+#ifndef TRACK_FUNC_H
+#define TRACK_FUNC_H
+
+#include "core/bitmath_func.hpp"
+#include "track_type.h"
+#include "direction_type.h"
+#include "slope_func.h"
+
+/**
+ * Convert an Axis to the corresponding Track
+ * AXIS_X -> TRACK_X
+ * AXIS_Y -> TRACK_Y
+ * Uses the fact that they share the same internal encoding
+ *
+ * @param a the axis to convert
+ * @return the track corresponding to the axis
+ */
+static inline Track AxisToTrack(Axis a)
+{
+	return (Track)a;
+}
+
+
+
+/**
+ * Maps a Track to the corresponding TrackBits value
+ * @param track the track to convert
+ * @return the converted TrackBits value of the track
+ */
+static inline TrackBits TrackToTrackBits(Track track)
+{
+	return (TrackBits)(1 << track);
+}
+
+/**
+ * Maps an Axis to the corresponding TrackBits value
+ * @param a the axis to convert
+ * @return the converted TrackBits value of the axis
+ */
+static inline TrackBits AxisToTrackBits(Axis a)
+{
+	return TrackToTrackBits(AxisToTrack(a));
+}
+
+/**
+ * Returns a single horizontal/vertical trackbit, that is in a specific tile corner.
+ *
+ * @param corner The corner of a tile.
+ * @return The TrackBits of the track in the corner.
+ */
+static inline TrackBits CornerToTrackBits(Corner corner)
+{
+	extern const TrackBits _corner_to_trackbits[];
+	assert(IsValidCorner(corner));
+	return _corner_to_trackbits[corner];
+}
+
+
+
+/**
+ * Maps a Trackdir to the corresponding TrackdirBits value
+ * @param trackdir the track direction to convert
+ * @return the converted TrackdirBits value
+ */
+static inline TrackdirBits TrackdirToTrackdirBits(Trackdir trackdir)
+{
+	return (TrackdirBits)(1 << trackdir);
+}
+
+/**
+ * Removes first Track from TrackBits and returns it
+ *
+ * This function searchs for the first bit in the TrackBits,
+ * remove this bit from the parameter and returns the found
+ * bit as Track value. It returns INVALID_TRACK if the
+ * parameter was TRACK_BIT_NONE or INVALID_TRACK_BIT. This
+ * is basically used in while-loops to get up to 6 possible
+ * tracks on a tile until the parameter becomes TRACK_BIT_NONE.
+ *
+ * @param tracks The value with the TrackBits
+ * @return The first Track from the TrackBits value
+ * @see FindFirstTrack
+ */
+static inline Track RemoveFirstTrack(TrackBits *tracks)
+{
+	if (*tracks != TRACK_BIT_NONE && *tracks != INVALID_TRACK_BIT) {
+		Track first = (Track)FIND_FIRST_BIT(*tracks);
+		ClrBit(*tracks, first);
+		return first;
+	}
+	return INVALID_TRACK;
+}
+
+/**
+ * Removes first Trackdir from TrackdirBits and returns it
+ *
+ * This function searchs for the first bit in the TrackdirBits parameter,
+ * remove this bit from the parameter and returns the fnound bit as
+ * Trackdir value. It returns INVALID_TRACKDIR if the trackdirs is
+ * TRACKDIR_BIT_NONE or INVALID_TRACKDIR_BIT. This is basically used in a
+ * while-loop to get all track-directions step by step until the value
+ * reaches TRACKDIR_BIT_NONE.
+ *
+ * @param trackdirs The value with the TrackdirBits
+ * @return The first Trackdir from the TrackdirBits value
+ * @see FindFirstTrackdir
+ */
+static inline Trackdir RemoveFirstTrackdir(TrackdirBits *trackdirs)
+{
+	if (*trackdirs != TRACKDIR_BIT_NONE && *trackdirs != INVALID_TRACKDIR_BIT) {
+		Trackdir first = (Trackdir)FindFirstBit2x64(*trackdirs);
+		ClrBit(*trackdirs, first);
+		return first;
+	}
+	return INVALID_TRACKDIR;
+}
+
+/**
+ * Returns first Track from TrackBits or INVALID_TRACK
+ *
+ * This function returns the first Track found in the TrackBits value as Track-value.
+ * It returns INVALID_TRACK if the parameter is TRACK_BIT_NONE or INVALID_TRACK_BIT.
+ *
+ * @param tracks The TrackBits value
+ * @return The first Track found or INVALID_TRACK
+ * @see RemoveFirstTrack
+ */
+static inline Track FindFirstTrack(TrackBits tracks)
+{
+	return (tracks != TRACK_BIT_NONE && tracks != INVALID_TRACK_BIT) ? (Track)FIND_FIRST_BIT(tracks) : INVALID_TRACK;
+}
+
+/**
+ * Converts TrackBits to Track.
+ *
+ * This function converts a TrackBits value to a Track value. As it
+ * is not possible to convert two or more tracks to one track the
+ * parameter must contain only one track or be the INVALID_TRACK_BIT value.
+ *
+ * @param tracks The TrackBits value to convert
+ * @return The Track from the value or INVALID_TRACK
+ * @pre tracks must contains only one Track or be INVALID_TRACK_BIT
+ */
+static inline Track TrackBitsToTrack(TrackBits tracks)
+{
+	assert(tracks == INVALID_TRACK_BIT || (tracks != TRACK_BIT_NONE && KillFirstBit(tracks & TRACK_BIT_MASK) == TRACK_BIT_NONE));
+	return tracks != INVALID_TRACK_BIT ? (Track)FIND_FIRST_BIT(tracks & TRACK_BIT_MASK) : INVALID_TRACK;
+}
+
+/**
+ * Returns first Trackdir from TrackdirBits or INVALID_TRACKDIR
+ *
+ * This function returns the first Trackdir in the given TrackdirBits value or
+ * INVALID_TRACKDIR if the value is TRACKDIR_BIT_NONE. The TrackdirBits must
+ * not be INVALID_TRACKDIR_BIT.
+ *
+ * @param trackdirs The TrackdirBits value
+ * @return The first Trackdir from the TrackdirBits or INVALID_TRACKDIR on TRACKDIR_BIT_NONE.
+ * @pre trackdirs must not be INVALID_TRACKDIR_BIT
+ * @see RemoveFirstTrackdir
+ */
+static inline Trackdir FindFirstTrackdir(TrackdirBits trackdirs)
+{
+	assert((trackdirs & ~TRACKDIR_BIT_MASK) == TRACKDIR_BIT_NONE);
+	return (trackdirs != TRACKDIR_BIT_NONE) ? (Trackdir)FindFirstBit2x64(trackdirs) : INVALID_TRACKDIR;
+}
+
+/**
+ * Checks if a Track is valid.
+ *
+ * @param track The value to check
+ * @return true if the given value is a valid track.
+ * @note Use this in an assert()
+ */
+static inline bool IsValidTrack(Track track)
+{
+	return track < TRACK_END;
+}
+
+/**
+ * Checks if a Trackdir is valid.
+ *
+ * @param trackdir The value to check
+ * @return true if the given valie is a valid Trackdir
+ * @note Use this in an assert()
+ */
+static inline bool IsValidTrackdir(Trackdir trackdir)
+{
+	return (TrackdirToTrackdirBits(trackdir) & TRACKDIR_BIT_MASK) != 0;
+}
+
+
+/*
+ * Functions describing logical relations between Tracks, TrackBits, Trackdirs
+ * TrackdirBits, Direction and DiagDirections.
+ */
+
+/**
+ * Maps a trackdir to the reverse trackdir.
+ *
+ * Returns the reverse trackdir of a Trackdir value. The reverse trackdir
+ * is the same track with the other direction on it.
+ *
+ * @param trackdir The Trackdir value
+ * @return The reverse trackdir
+ * @pre trackdir must not be INVALID_TRACKDIR
+ */
+static inline Trackdir ReverseTrackdir(Trackdir trackdir)
+{
+	assert(trackdir != INVALID_TRACKDIR);
+	return (Trackdir)(trackdir ^ 8);
+}
+
+/**
+ * Returns the Track that a given Trackdir represents
+ *
+ * This function filters the Track which is used in the Trackdir value and
+ * returns it as a Track value.
+ *
+ * @param trackdir The trackdir value
+ * @return The Track which is used in the value
+ */
+static inline Track TrackdirToTrack(Trackdir trackdir)
+{
+	return (Track)(trackdir & 0x7);
+}
+
+/**
+ * Returns a Trackdir for the given Track
+ *
+ * Since every Track corresponds to two Trackdirs, we choose the
+ * one which points between NE and S. Note that the actual
+ * implementation is quite futile, but this might change
+ * in the future.
+ *
+ * @param track The given Track
+ * @return The Trackdir from the given Track
+ */
+static inline Trackdir TrackToTrackdir(Track track)
+{
+	return (Trackdir)track;
+}
+
+/**
+ * Returns a TrackdirBit mask from a given Track
+ *
+ * The TrackdirBit mask contains the two TrackdirBits that
+ * correspond with the given Track (one for each direction).
+ *
+ * @param track The track to get the TrackdirBits from
+ * @return The TrackdirBits which the selected tracks
+ */
+static inline TrackdirBits TrackToTrackdirBits(Track track)
+{
+	Trackdir td = TrackToTrackdir(track);
+	return (TrackdirBits)(TrackdirToTrackdirBits(td) | TrackdirToTrackdirBits(ReverseTrackdir(td)));
+}
+
+/**
+ * Discards all directional information from a TrackdirBits value
+ *
+ * Any Track which is present in either direction will be present in the result.
+ *
+ * @param bits The TrackdirBits to get the TrackBits from
+ * @return The TrackBits
+ */
+static inline TrackBits TrackdirBitsToTrackBits(TrackdirBits bits)
+{
+	return (TrackBits)((bits | (bits >> 8)) & TRACK_BIT_MASK);
+}
+
+/**
+ * Maps a trackdir to the trackdir that you will end up on if you go straight
+ * ahead.
+ *
+ * This will be the same trackdir for diagonal trackdirs, but a
+ * different (alternating) one for straight trackdirs
+ *
+ * @param trackdir The given trackdir
+ * @return The next Trackdir value of the next tile.
+ */
+static inline Trackdir NextTrackdir(Trackdir trackdir)
+{
+	extern const Trackdir _next_trackdir[TRACKDIR_END];
+	return _next_trackdir[trackdir];
+}
+
+/**
+ * Maps a track to all tracks that make 90 deg turns with it.
+ *
+ * For the diagonal directions these are the complement of the
+ * direction, for the straight directions these are the
+ * two vertical or horizontal tracks, depend on the given direction
+ *
+ * @param track The given track
+ * @return The TrackBits with the tracks marked which cross the given track by 90 deg.
+ */
+static inline TrackBits TrackCrossesTracks(Track track)
+{
+	extern const TrackBits _track_crosses_tracks[TRACK_END];
+	return _track_crosses_tracks[track];
+}
+
+/**
+ * Maps a trackdir to the (4-way) direction the tile is exited when following
+ * that trackdir.
+ *
+ * For the diagonal directions these are the same directions. For
+ * the straight directions these are the directions from the imagined
+ * base-tile to the bordering tile which will be joined if the given
+ * straight direction is leaved from the base-tile.
+ *
+ * @param trackdir The given track direction
+ * @return The direction which points to the resulting tile if following the Trackdir
+ */
+static inline DiagDirection TrackdirToExitdir(Trackdir trackdir)
+{
+	extern const DiagDirection _trackdir_to_exitdir[TRACKDIR_END];
+	return _trackdir_to_exitdir[trackdir];
+}
+
+/**
+ * Maps a track and an (4-way) dir to the trackdir that represents the track
+ * with the exit in the given direction.
+ *
+ * For the diagonal tracks the resulting track direction are clear for a given
+ * DiagDirection. It either matches the direction or it returns INVALID_TRACKDIR,
+ * as a TRACK_X cannot be applied with DIAG_SE.
+ * For the straight tracks the resulting track direction will be the
+ * direction which the DiagDirection is pointing. But this will be INVALID_TRACKDIR
+ * if the DiagDirection is pointing 'away' the track.
+ *
+ * @param track The track to applie an direction on
+ * @param diagdir The DiagDirection to applie on
+ * @return The resulting track direction or INVALID_TRACKDIR if not possible.
+ */
+static inline Trackdir TrackExitdirToTrackdir(Track track, DiagDirection diagdir)
+{
+	extern const Trackdir _track_exitdir_to_trackdir[TRACK_END][DIAGDIR_END];
+	return _track_exitdir_to_trackdir[track][diagdir];
+}
+
+/**
+ * Maps a track and an (4-way) dir to the trackdir that represents the track
+ * with the entry in the given direction.
+ *
+ * For the diagonal tracks the return value is clear, its either the matching
+ * track direction or INVALID_TRACKDIR.
+ * For the straight tracks this returns the track direction which results if
+ * you follow the DiagDirection and then turn by 45 deg left or right on the
+ * next tile. The new direction on the new track will be the returning Trackdir
+ * value. If the parameters makes no sense like the track TRACK_UPPER and the
+ * diraction DIAGDIR_NE (target track cannot be reached) this function returns
+ * INVALID_TRACKDIR.
+ *
+ * @param track The target track
+ * @param diagdir The direction to "come from"
+ * @return the resulting Trackdir or INVALID_TRACKDIR if not possible.
+ */
+static inline Trackdir TrackEnterdirToTrackdir(Track track, DiagDirection diagdir)
+{
+	extern const Trackdir _track_enterdir_to_trackdir[TRACK_END][DIAGDIR_END];
+	return _track_enterdir_to_trackdir[track][diagdir];
+}
+
+/**
+ * Maps a track and a full (8-way) direction to the trackdir that represents
+ * the track running in the given direction.
+ */
+static inline Trackdir TrackDirectionToTrackdir(Track track, Direction dir)
+{
+	extern const Trackdir _track_direction_to_trackdir[TRACK_END][DIR_END];
+	return _track_direction_to_trackdir[track][dir];
+}
+
+/**
+ * Maps a (4-way) direction to the diagonal trackdir that runs in that
+ * direction.
+ *
+ * @param diagdir The direction
+ * @return The resulting Trackdir direction
+ */
+static inline Trackdir DiagdirToDiagTrackdir(DiagDirection diagdir)
+{
+	extern const Trackdir _dir_to_diag_trackdir[DIAGDIR_END];
+	return _dir_to_diag_trackdir[diagdir];
+}
+
+/**
+ * Returns all trackdirs that can be reached when entering a tile from a given
+ * (diagonal) direction.
+ *
+ * This will obviously include 90 degree turns, since no information is available
+ * about the exact angle of entering
+ *
+ * @param diagdir The joining direction
+ * @return The TrackdirBits which can be used from the given direction
+ * @see DiagdirReachesTracks
+ */
+static inline TrackdirBits DiagdirReachesTrackdirs(DiagDirection diagdir)
+{
+	extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
+	return _exitdir_reaches_trackdirs[diagdir];
+}
+
+/**
+ * Returns all tracks that can be reached when entering a tile from a given
+ * (diagonal) direction.
+ *
+ * This will obviously include 90 degree turns, since no
+ * information is available about the exact angle of entering
+ *
+ * @param diagdir The joining irection
+ * @return The tracks which can be used
+ * @see DiagdirReachesTrackdirs
+ */
+static inline TrackBits DiagdirReachesTracks(DiagDirection diagdir) { return TrackdirBitsToTrackBits(DiagdirReachesTrackdirs(diagdir)); }
+
+/**
+ * Maps a trackdir to the trackdirs that can be reached from it (ie, when
+ * entering the next tile.
+ *
+ * This will include 90 degree turns!
+ *
+ * @param trackdir The track direction which will be leaved
+ * @return The track directions which can be used from this direction (in the next tile)
+ */
+static inline TrackdirBits TrackdirReachesTrackdirs(Trackdir trackdir)
+{
+	extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
+	return _exitdir_reaches_trackdirs[TrackdirToExitdir(trackdir)];
+}
+/* Note that there is no direct table for this function (there used to be),
+ * but it uses two simpeler tables to achieve the result */
+
+/**
+ * Maps a trackdir to all trackdirs that make 90 deg turns with it.
+ *
+ * For the diagonal tracks this returns the track direction bits
+ * of the other axis in both directions, which cannot be joined by
+ * the given track direction.
+ * For the straight tracks this returns all possible 90 deg turns
+ * either on the current tile (which no train can joined) or on the
+ * bordering tiles.
+ *
+ * @param trackdir The track direction
+ * @return The TrackdirBits which are (more or less) 90 deg turns.
+ */
+static inline TrackdirBits TrackdirCrossesTrackdirs(Trackdir trackdir)
+{
+	extern const TrackdirBits _track_crosses_trackdirs[TRACKDIR_END];
+	return _track_crosses_trackdirs[TrackdirToTrack(trackdir)];
+}
+
+/**
+ * Checks if a given Track is diagonal
+ *
+ * @param track The given track to check
+ * @return true if diagonal, else false
+ */
+static inline bool IsDiagonalTrack(Track track)
+{
+	return (track == TRACK_X) || (track == TRACK_Y);
+}
+
+/**
+ * Checks if a given Trackdir is diagonal.
+ *
+ * @param trackdir The given trackdir
+ * @return true if the trackdir use a diagonal track
+ */
+static inline bool IsDiagonalTrackdir(Trackdir trackdir)
+{
+	return IsDiagonalTrack(TrackdirToTrack(trackdir));
+}
+
+
+/**
+ * Checks if the given tracks overlap, ie form a crossing. Basically this
+ * means when there is more than one track on the tile, exept when there are
+ * two parallel tracks.
+ * @param  bits The tracks present.
+ * @return Whether the tracks present overlap in any way.
+ */
+static inline bool TracksOverlap(TrackBits bits)
+{
+	/* With no, or only one track, there is no overlap */
+	if (bits == TRACK_BIT_NONE || KillFirstBit(bits) == TRACK_BIT_NONE) return false;
+	/* We know that there are at least two tracks present. When there are more
+	 * than 2 tracks, they will surely overlap. When there are two, they will
+	 * always overlap unless they are lower & upper or right & left. */
+	return bits != TRACK_BIT_HORZ && bits != TRACK_BIT_VERT;
+}
+
+/**
+ * Checks whether the trackdir means that we are reversing.
+ * @param dir the trackdir to check
+ * @return true if it is a reversing road trackdir
+ */
+static inline bool IsReversingRoadTrackdir(Trackdir dir)
+{
+	return (dir & 0x07) >= 6;
+}
+
+/**
+ * Checks whether the given trackdir is a straight road
+ * @param dir the trackdir to check
+ * @return true if it is a straight road trackdir
+ */
+static inline bool IsStraightRoadTrackdir(Trackdir dir)
+{
+	return (dir & 0x06) == 0;
+}
+
+#endif /* TRACK_FUNC_H */