src/track_func.h

   1 /*
   2  * This file is part of OpenTTD.
   3  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   4  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   6  */
   7
   8 /** @file track_func.h Different conversion functions from one kind of track to another. */
   9
  10 #ifndef TRACK_FUNC_H
  11 #define TRACK_FUNC_H
  12
  13 #include "core/bitmath_func.hpp"
  14 #include "track_type.h"
  15 #include "direction_func.h"
  16 #include "slope_func.h"
  17
  18 using SetTrackBitIterator = SetBitIterator<Track, TrackBits>;
  19 using SetTrackdirBitIterator = SetBitIterator<Trackdir, TrackdirBits>;
  20
  21 /**
  22  * Checks if a Track is valid.
  23  *
  24  * @param track The value to check
  25  * @return true if the given value is a valid track.
  26  * @note Use this in an assert()
  27  */
  28 inline bool IsValidTrack(Track track)
  29 {
  30         return track < TRACK_END;
  31 }
  32
  33 /**
  34  * Checks if a Trackdir is valid for road vehicles.
  35  *
  36  * @param trackdir The value to check
  37  * @return true if the given value is a valid Trackdir
  38  * @note Use this in an assert()
  39  */
  40 inline bool IsValidTrackdirForRoadVehicle(Trackdir trackdir)
  41 {
  42         return trackdir < TRACKDIR_END;
  43 }
  44
  45 /**
  46  * Checks if a Trackdir is valid for non-road vehicles.
  47  *
  48  * @param trackdir The value to check
  49  * @return true if the given value is a valid Trackdir
  50  * @note Use this in an assert()
  51  */
  52 inline bool IsValidTrackdir(Trackdir trackdir)
  53 {
  54         return trackdir != INVALID_TRACKDIR && ((1 << trackdir & TRACKDIR_BIT_MASK) != TRACKDIR_BIT_NONE);
  55 }
  56
  57 /**
  58  * Convert an Axis to the corresponding Track
  59  * AXIS_X -> TRACK_X
  60  * AXIS_Y -> TRACK_Y
  61  * Uses the fact that they share the same internal encoding
  62  *
  63  * @param a the axis to convert
  64  * @return the track corresponding to the axis
  65  */
  66 inline Track AxisToTrack(Axis a)
  67 {
  68         assert(IsValidAxis(a));
  69         return (Track)a;
  70 }
  71
  72 /**
  73  * Maps a Track to the corresponding TrackBits value
  74  * @param track the track to convert
  75  * @return the converted TrackBits value of the track
  76  */
  77 inline TrackBits TrackToTrackBits(Track track)
  78 {
  79         assert(IsValidTrack(track));
  80         return (TrackBits)(1 << track);
  81 }
  82
  83 /**
  84  * Maps an Axis to the corresponding TrackBits value
  85  * @param a the axis to convert
  86  * @return the converted TrackBits value of the axis
  87  */
  88 inline TrackBits AxisToTrackBits(Axis a)
  89 {
  90         return TrackToTrackBits(AxisToTrack(a));
  91 }
  92
  93 /**
  94  * Returns a single horizontal/vertical trackbit that is in a specific tile corner.
  95  *
  96  * @param corner The corner of a tile.
  97  * @return The TrackBits of the track in the corner.
  98  */
  99 inline TrackBits CornerToTrackBits(Corner corner)
 100 {
 101         extern const TrackBits _corner_to_trackbits[];
 102         assert(IsValidCorner(corner));
 103         return _corner_to_trackbits[corner];
 104 }
 105
 106 /**
 107  * Maps a Trackdir to the corresponding TrackdirBits value
 108  * @param trackdir the track direction to convert
 109  * @return the converted TrackdirBits value
 110  */
 111 inline TrackdirBits TrackdirToTrackdirBits(Trackdir trackdir)
 112 {
 113         assert(IsValidTrackdir(trackdir));
 114         return (TrackdirBits)(1 << trackdir);
 115 }
 116
 117 /**
 118  * Removes first Track from TrackBits and returns it
 119  *
 120  * This function searches for the first bit in the TrackBits,
 121  * remove this bit from the parameter and returns the found
 122  * bit as Track value. It returns INVALID_TRACK if the
 123  * parameter was TRACK_BIT_NONE or INVALID_TRACK_BIT. This
 124  * is basically used in while-loops to get up to 6 possible
 125  * tracks on a tile until the parameter becomes TRACK_BIT_NONE.
 126  *
 127  * @param tracks The value with the TrackBits
 128  * @return The first Track from the TrackBits value
 129  * @see FindFirstTrack
 130  */
 131 inline Track RemoveFirstTrack(TrackBits *tracks)
 132 {
 133         if (*tracks != TRACK_BIT_NONE && *tracks != INVALID_TRACK_BIT) {
 134                 assert((*tracks & ~TRACK_BIT_MASK) == TRACK_BIT_NONE);
 135                 Track first = (Track)FindFirstBit(*tracks);
 136                 ClrBit(*tracks, first);
 137                 return first;
 138         }
 139         return INVALID_TRACK;
 140 }
 141
 142 /**
 143  * Removes first Trackdir from TrackdirBits and returns it
 144  *
 145  * This function searches for the first bit in the TrackdirBits parameter,
 146  * remove this bit from the parameter and returns the fnound bit as
 147  * Trackdir value. It returns INVALID_TRACKDIR if the trackdirs is
 148  * TRACKDIR_BIT_NONE or INVALID_TRACKDIR_BIT. This is basically used in a
 149  * while-loop to get all track-directions step by step until the value
 150  * reaches TRACKDIR_BIT_NONE.
 151  *
 152  * @param trackdirs The value with the TrackdirBits
 153  * @return The first Trackdir from the TrackdirBits value
 154  * @see FindFirstTrackdir
 155  */
 156 inline Trackdir RemoveFirstTrackdir(TrackdirBits *trackdirs)
 157 {
 158         if (*trackdirs != TRACKDIR_BIT_NONE && *trackdirs != INVALID_TRACKDIR_BIT) {
 159                 assert((*trackdirs & ~TRACKDIR_BIT_MASK) == TRACKDIR_BIT_NONE);
 160                 Trackdir first = (Trackdir)FindFirstBit(*trackdirs);
 161                 ClrBit(*trackdirs, first);
 162                 return first;
 163         }
 164         return INVALID_TRACKDIR;
 165 }
 166
 167 /**
 168  * Returns first Track from TrackBits or INVALID_TRACK
 169  *
 170  * This function returns the first Track found in the TrackBits value as Track-value.
 171  * It returns INVALID_TRACK if the parameter is TRACK_BIT_NONE or INVALID_TRACK_BIT.
 172  *
 173  * @param tracks The TrackBits value
 174  * @return The first Track found or INVALID_TRACK
 175  * @see RemoveFirstTrack
 176  */
 177 inline Track FindFirstTrack(TrackBits tracks)
 178 {
 179         return (tracks != TRACK_BIT_NONE && tracks != INVALID_TRACK_BIT) ? (Track)FindFirstBit(tracks) : INVALID_TRACK;
 180 }
 181
 182 /**
 183  * Converts TrackBits to Track.
 184  *
 185  * This function converts a TrackBits value to a Track value. As it
 186  * is not possible to convert two or more tracks to one track the
 187  * parameter must contain only one track or be the INVALID_TRACK_BIT value.
 188  *
 189  * @param tracks The TrackBits value to convert
 190  * @return The Track from the value or INVALID_TRACK
 191  * @pre tracks must contains only one Track or be INVALID_TRACK_BIT
 192  */
 193 inline Track TrackBitsToTrack(TrackBits tracks)
 194 {
 195         assert(tracks == INVALID_TRACK_BIT || (tracks != TRACK_BIT_NONE && KillFirstBit(tracks & TRACK_BIT_MASK) == TRACK_BIT_NONE));
 196         return tracks != INVALID_TRACK_BIT ? (Track)FindFirstBit(tracks & TRACK_BIT_MASK) : INVALID_TRACK;
 197 }
 198
 199 /**
 200  * Returns first Trackdir from TrackdirBits or INVALID_TRACKDIR
 201  *
 202  * This function returns the first Trackdir in the given TrackdirBits value or
 203  * INVALID_TRACKDIR if the value is TRACKDIR_BIT_NONE. The TrackdirBits must
 204  * not be INVALID_TRACKDIR_BIT.
 205  *
 206  * @param trackdirs The TrackdirBits value
 207  * @return The first Trackdir from the TrackdirBits or INVALID_TRACKDIR on TRACKDIR_BIT_NONE.
 208  * @pre trackdirs must not be INVALID_TRACKDIR_BIT
 209  * @see RemoveFirstTrackdir
 210  */
 211 inline Trackdir FindFirstTrackdir(TrackdirBits trackdirs)
 212 {
 213         assert((trackdirs & ~TRACKDIR_BIT_MASK) == TRACKDIR_BIT_NONE);
 214         return (trackdirs != TRACKDIR_BIT_NONE) ? (Trackdir)FindFirstBit(trackdirs) : INVALID_TRACKDIR;
 215 }
 216
 217 /*
 218  * Functions describing logical relations between Tracks, TrackBits, Trackdirs
 219  * TrackdirBits, Direction and DiagDirections.
 220  */
 221
 222 /**
 223  * Find the opposite track to a given track.
 224  *
 225  * TRACK_LOWER -> TRACK_UPPER and vice versa, likewise for left/right.
 226  * TRACK_X is mapped to TRACK_Y and reversed.
 227  *
 228  * @param t the track to convert
 229  * @return the opposite track
 230  */
 231 inline Track TrackToOppositeTrack(Track t)
 232 {
 233         assert(IsValidTrack(t));
 234         return (Track)(t ^ 1);
 235 }
 236
 237 /**
 238  * Maps a trackdir to the reverse trackdir.
 239  *
 240  * Returns the reverse trackdir of a Trackdir value. The reverse trackdir
 241  * is the same track with the other direction on it.
 242  *
 243  * @param trackdir The Trackdir value
 244  * @return The reverse trackdir
 245  * @pre trackdir must not be INVALID_TRACKDIR
 246  */
 247 inline Trackdir ReverseTrackdir(Trackdir trackdir)
 248 {
 249         assert(IsValidTrackdirForRoadVehicle(trackdir));
 250         return (Trackdir)(trackdir ^ 8);
 251 }
 252
 253 /**
 254  * Returns the Track that a given Trackdir represents
 255  *
 256  * This function filters the Track which is used in the Trackdir value and
 257  * returns it as a Track value.
 258  *
 259  * @param trackdir The trackdir value
 260  * @return The Track which is used in the value
 261  */
 262 inline Track TrackdirToTrack(Trackdir trackdir)
 263 {
 264         assert(IsValidTrackdir(trackdir));
 265         return (Track)(trackdir & 0x7);
 266 }
 267
 268 /**
 269  * Returns a Trackdir for the given Track
 270  *
 271  * Since every Track corresponds to two Trackdirs, we choose the
 272  * one which points between NE and S. Note that the actual
 273  * implementation is quite futile, but this might change
 274  * in the future.
 275  *
 276  * @param track The given Track
 277  * @return The Trackdir from the given Track
 278  */
 279 inline Trackdir TrackToTrackdir(Track track)
 280 {
 281         assert(IsValidTrack(track));
 282         return (Trackdir)track;
 283 }
 284
 285 /**
 286  * Returns a TrackdirBit mask from a given Track
 287  *
 288  * The TrackdirBit mask contains the two TrackdirBits that
 289  * correspond with the given Track (one for each direction).
 290  *
 291  * @param track The track to get the TrackdirBits from
 292  * @return The TrackdirBits which the selected tracks
 293  */
 294 inline TrackdirBits TrackToTrackdirBits(Track track)
 295 {
 296         Trackdir td = TrackToTrackdir(track);
 297         return (TrackdirBits)(TrackdirToTrackdirBits(td) | TrackdirToTrackdirBits(ReverseTrackdir(td)));
 298 }
 299
 300 /**
 301  * Discards all directional information from a TrackdirBits value
 302  *
 303  * Any Track which is present in either direction will be present in the result.
 304  *
 305  * @param bits The TrackdirBits to get the TrackBits from
 306  * @return The TrackBits
 307  */
 308 inline TrackBits TrackdirBitsToTrackBits(TrackdirBits bits)
 309 {
 310         return (TrackBits)((bits | (bits >> 8)) & TRACK_BIT_MASK);
 311 }
 312
 313 /**
 314  * Converts TrackBits to TrackdirBits while allowing both directions.
 315  *
 316  * @param bits The TrackBits
 317  * @return The TrackdirBits containing of bits in both directions.
 318  */
 319 inline TrackdirBits TrackBitsToTrackdirBits(TrackBits bits)
 320 {
 321         return (TrackdirBits)(bits * 0x101);
 322 }
 323
 324 /**
 325  * Checks whether a TrackBits has a given Track.
 326  * @param tracks The track bits.
 327  * @param track The track to check.
 328  */
 329 inline bool HasTrack(TrackBits tracks, Track track)
 330 {
 331         assert(IsValidTrack(track));
 332         return HasBit(tracks, track);
 333 }
 334
 335 /**
 336  * Checks whether a TrackdirBits has a given Trackdir.
 337  * @param trackdirs The trackdir bits.
 338  * @param trackdir The trackdir to check.
 339  */
 340 inline bool HasTrackdir(TrackdirBits trackdirs, Trackdir trackdir)
 341 {
 342         assert(IsValidTrackdir(trackdir));
 343         return HasBit(trackdirs, trackdir);
 344 }
 345
 346 /**
 347  * Returns the present-trackdir-information of a TrackStatus.
 348  *
 349  * @param ts The TrackStatus returned by GetTileTrackStatus()
 350  * @return the present trackdirs
 351  */
 352 inline TrackdirBits TrackStatusToTrackdirBits(TrackStatus ts)
 353 {
 354         return (TrackdirBits)(ts & TRACKDIR_BIT_MASK);
 355 }
 356
 357 /**
 358  * Returns the present-track-information of a TrackStatus.
 359  *
 360  * @param ts The TrackStatus returned by GetTileTrackStatus()
 361  * @return the present tracks
 362  */
 363 inline TrackBits TrackStatusToTrackBits(TrackStatus ts)
 364 {
 365         return TrackdirBitsToTrackBits(TrackStatusToTrackdirBits(ts));
 366 }
 367
 368 /**
 369  * Returns the red-signal-information of a TrackStatus.
 370  *
 371  * Note: The result may contain red signals for non-present tracks.
 372  *
 373  * @param ts The TrackStatus returned by GetTileTrackStatus()
 374  * @return the The trackdirs that are blocked by red-signals
 375  */
 376 inline TrackdirBits TrackStatusToRedSignals(TrackStatus ts)
 377 {
 378         return (TrackdirBits)((ts >> 16) & TRACKDIR_BIT_MASK);
 379 }
 380
 381 /**
 382  * Builds a TrackStatus
 383  *
 384  * @param trackdirbits present trackdirs
 385  * @param red_signals red signals
 386  * @return the TrackStatus representing the given information
 387  */
 388 inline TrackStatus CombineTrackStatus(TrackdirBits trackdirbits, TrackdirBits red_signals)
 389 {
 390         return (TrackStatus)(trackdirbits | (red_signals << 16));
 391 }
 392
 393 /**
 394  * Maps a trackdir to the trackdir that you will end up on if you go straight
 395  * ahead.
 396  *
 397  * This will be the same trackdir for diagonal trackdirs, but a
 398  * different (alternating) one for straight trackdirs
 399  *
 400  * @param trackdir The given trackdir
 401  * @return The next Trackdir value of the next tile.
 402  */
 403 inline Trackdir NextTrackdir(Trackdir trackdir)
 404 {
 405         assert(IsValidTrackdir(trackdir));
 406         extern const Trackdir _next_trackdir[TRACKDIR_END];
 407         return _next_trackdir[trackdir];
 408 }
 409
 410 /**
 411  * Maps a track to all tracks that make 90 deg turns with it.
 412  *
 413  * For the diagonal directions these are the complement of the
 414  * direction, for the straight directions these are the
 415  * two vertical or horizontal tracks, depend on the given direction
 416  *
 417  * @param track The given track
 418  * @return The TrackBits with the tracks marked which cross the given track by 90 deg.
 419  */
 420 inline TrackBits TrackCrossesTracks(Track track)
 421 {
 422         assert(IsValidTrack(track));
 423         extern const TrackBits _track_crosses_tracks[TRACK_END];
 424         return _track_crosses_tracks[track];
 425 }
 426
 427 /**
 428  * Maps a trackdir to the (4-way) direction the tile is exited when following
 429  * that trackdir.
 430  *
 431  * For the diagonal directions these are the same directions. For
 432  * the straight directions these are the directions from the imagined
 433  * base-tile to the bordering tile which will be joined if the given
 434  * straight direction is leaved from the base-tile.
 435  *
 436  * @param trackdir The given track direction
 437  * @return The direction which points to the resulting tile if following the Trackdir
 438  */
 439 inline DiagDirection TrackdirToExitdir(Trackdir trackdir)
 440 {
 441         assert(IsValidTrackdirForRoadVehicle(trackdir));
 442         extern const DiagDirection _trackdir_to_exitdir[TRACKDIR_END];
 443         return _trackdir_to_exitdir[trackdir];
 444 }
 445
 446 /**
 447  * Maps a track and an (4-way) dir to the trackdir that represents the track
 448  * with the exit in the given direction.
 449  *
 450  * For the diagonal tracks the resulting track direction are clear for a given
 451  * DiagDirection. It either matches the direction or it returns INVALID_TRACKDIR,
 452  * as a TRACK_X cannot be applied with DIAG_SE.
 453  * For the straight tracks the resulting track direction will be the
 454  * direction which the DiagDirection is pointing. But this will be INVALID_TRACKDIR
 455  * if the DiagDirection is pointing 'away' the track.
 456  *
 457  * @param track The track to apply an direction on
 458  * @param diagdir The DiagDirection to apply on
 459  * @return The resulting track direction or INVALID_TRACKDIR if not possible.
 460  */
 461 inline Trackdir TrackExitdirToTrackdir(Track track, DiagDirection diagdir)
 462 {
 463         assert(IsValidTrack(track));
 464         assert(IsValidDiagDirection(diagdir));
 465         extern const Trackdir _track_exitdir_to_trackdir[TRACK_END][DIAGDIR_END];
 466         return _track_exitdir_to_trackdir[track][diagdir];
 467 }
 468
 469 /**
 470  * Maps a track and an (4-way) dir to the trackdir that represents the track
 471  * with the entry in the given direction.
 472  *
 473  * For the diagonal tracks the return value is clear, its either the matching
 474  * track direction or INVALID_TRACKDIR.
 475  * For the straight tracks this returns the track direction which results if
 476  * you follow the DiagDirection and then turn by 45 deg left or right on the
 477  * next tile. The new direction on the new track will be the returning Trackdir
 478  * value. If the parameters makes no sense like the track TRACK_UPPER and the
 479  * direction DIAGDIR_NE (target track cannot be reached) this function returns
 480  * INVALID_TRACKDIR.
 481  *
 482  * @param track The target track
 483  * @param diagdir The direction to "come from"
 484  * @return the resulting Trackdir or INVALID_TRACKDIR if not possible.
 485  */
 486 inline Trackdir TrackEnterdirToTrackdir(Track track, DiagDirection diagdir)
 487 {
 488         assert(IsValidTrack(track));
 489         assert(IsValidDiagDirection(diagdir));
 490         extern const Trackdir _track_enterdir_to_trackdir[TRACK_END][DIAGDIR_END];
 491         return _track_enterdir_to_trackdir[track][diagdir];
 492 }
 493
 494 /**
 495  * Maps a track and a full (8-way) direction to the trackdir that represents
 496  * the track running in the given direction.
 497  */
 498 inline Trackdir TrackDirectionToTrackdir(Track track, Direction dir)
 499 {
 500         assert(IsValidTrack(track));
 501         assert(IsValidDirection(dir));
 502         extern const Trackdir _track_direction_to_trackdir[TRACK_END][DIR_END];
 503         return _track_direction_to_trackdir[track][dir];
 504 }
 505
 506 /**
 507  * Maps a (4-way) direction to the diagonal track incidating with that diagdir
 508  *
 509  * @param diagdir The direction
 510  * @return The resulting Track
 511  */
 512 inline Track DiagDirToDiagTrack(DiagDirection diagdir)
 513 {
 514         assert(IsValidDiagDirection(diagdir));
 515         return (Track)(diagdir & 1);
 516 }
 517
 518 /**
 519  * Maps a (4-way) direction to the diagonal track bits incidating with that diagdir
 520  *
 521  * @param diagdir The direction
 522  * @return The resulting TrackBits
 523  */
 524 inline TrackBits DiagDirToDiagTrackBits(DiagDirection diagdir)
 525 {
 526         assert(IsValidDiagDirection(diagdir));
 527         return TrackToTrackBits(DiagDirToDiagTrack(diagdir));
 528 }
 529
 530 /**
 531  * Maps a (4-way) direction to the diagonal trackdir that runs in that
 532  * direction.
 533  *
 534  * @param diagdir The direction
 535  * @return The resulting Trackdir direction
 536  */
 537 inline Trackdir DiagDirToDiagTrackdir(DiagDirection diagdir)
 538 {
 539         assert(IsValidDiagDirection(diagdir));
 540         extern const Trackdir _dir_to_diag_trackdir[DIAGDIR_END];
 541         return _dir_to_diag_trackdir[diagdir];
 542 }
 543
 544 /**
 545  * Returns all trackdirs that can be reached when entering a tile from a given
 546  * (diagonal) direction.
 547  *
 548  * This will obviously include 90 degree turns, since no information is available
 549  * about the exact angle of entering
 550  *
 551  * @param diagdir The joining direction
 552  * @return The TrackdirBits which can be used from the given direction
 553  * @see DiagdirReachesTracks
 554  */
 555 inline TrackdirBits DiagdirReachesTrackdirs(DiagDirection diagdir)
 556 {
 557         assert(IsValidDiagDirection(diagdir));
 558         extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
 559         return _exitdir_reaches_trackdirs[diagdir];
 560 }
 561
 562 /**
 563  * Returns all tracks that can be reached when entering a tile from a given
 564  * (diagonal) direction.
 565  *
 566  * This will obviously include 90 degree turns, since no
 567  * information is available about the exact angle of entering
 568  *
 569  * @param diagdir The joining direction
 570  * @return The tracks which can be used
 571  * @see DiagdirReachesTrackdirs
 572  */
 573 inline TrackBits DiagdirReachesTracks(DiagDirection diagdir) { return TrackdirBitsToTrackBits(DiagdirReachesTrackdirs(diagdir)); }
 574
 575 /**
 576  * Maps a trackdir to the trackdirs that can be reached from it (ie, when
 577  * entering the next tile.
 578  *
 579  * This will include 90 degree turns!
 580  *
 581  * @param trackdir The track direction which will be leaved
 582  * @return The track directions which can be used from this direction (in the next tile)
 583  */
 584 inline TrackdirBits TrackdirReachesTrackdirs(Trackdir trackdir)
 585 {
 586         assert(IsValidTrackdir(trackdir));
 587         extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
 588         return _exitdir_reaches_trackdirs[TrackdirToExitdir(trackdir)];
 589 }
 590 /* Note that there is no direct table for this function (there used to be),
 591  * but it uses two simpler tables to achieve the result */
 592
 593 /**
 594  * Maps a trackdir to all trackdirs that make 90 deg turns with it.
 595  *
 596  * For the diagonal tracks this returns the track direction bits
 597  * of the other axis in both directions, which cannot be joined by
 598  * the given track direction.
 599  * For the straight tracks this returns all possible 90 deg turns
 600  * either on the current tile (which no train can joined) or on the
 601  * bordering tiles.
 602  *
 603  * @param trackdir The track direction
 604  * @return The TrackdirBits which are (more or less) 90 deg turns.
 605  */
 606 inline TrackdirBits TrackdirCrossesTrackdirs(Trackdir trackdir)
 607 {
 608         assert(IsValidTrackdirForRoadVehicle(trackdir));
 609         extern const TrackdirBits _track_crosses_trackdirs[TRACK_END];
 610         return _track_crosses_trackdirs[TrackdirToTrack(trackdir)];
 611 }
 612
 613 /**
 614  * Checks if a given Track is diagonal
 615  *
 616  * @param track The given track to check
 617  * @return true if diagonal, else false
 618  */
 619 inline bool IsDiagonalTrack(Track track)
 620 {
 621         assert(IsValidTrack(track));
 622         return (track == TRACK_X) || (track == TRACK_Y);
 623 }
 624
 625 /**
 626  * Checks if a given Trackdir is diagonal.
 627  *
 628  * @param trackdir The given trackdir
 629  * @return true if the trackdir use a diagonal track
 630  */
 631 inline bool IsDiagonalTrackdir(Trackdir trackdir)
 632 {
 633         assert(IsValidTrackdir(trackdir));
 634         return IsDiagonalTrack(TrackdirToTrack(trackdir));
 635 }
 636
 637
 638 /**
 639  * Checks if the given tracks overlap, ie form a crossing. Basically this
 640  * means when there is more than one track on the tile, except when there are
 641  * two parallel tracks.
 642  * @param  bits The tracks present.
 643  * @return Whether the tracks present overlap in any way.
 644  */
 645 inline bool TracksOverlap(TrackBits bits)
 646 {
 647         /* With no, or only one track, there is no overlap */
 648         if (bits == TRACK_BIT_NONE || KillFirstBit(bits) == TRACK_BIT_NONE) return false;
 649         /* We know that there are at least two tracks present. When there are more
 650          * than 2 tracks, they will surely overlap. When there are two, they will
 651          * always overlap unless they are lower & upper or right & left. */
 652         return bits != TRACK_BIT_HORZ && bits != TRACK_BIT_VERT;
 653 }
 654
 655 /**
 656  * Check if a given track is contained within or overlaps some other tracks.
 657  *
 658  * @param tracks Tracks to be tested against
 659  * @param track The track to test
 660  * @return true if the track is already in the tracks or overlaps the tracks.
 661  */
 662 inline bool TrackOverlapsTracks(TrackBits tracks, Track track)
 663 {
 664         if (HasBit(tracks, track)) return true;
 665         return TracksOverlap(tracks | TrackToTrackBits(track));
 666 }
 667
 668 /**
 669  * Checks whether the trackdir means that we are reversing.
 670  * @param dir the trackdir to check
 671  * @return true if it is a reversing road trackdir
 672  */
 673 inline bool IsReversingRoadTrackdir(Trackdir dir)
 674 {
 675         assert(IsValidTrackdirForRoadVehicle(dir));
 676         return (dir & 0x07) >= 6;
 677 }
 678
 679 /**
 680  * Checks whether the given trackdir is a straight road
 681  * @param dir the trackdir to check
 682  * @return true if it is a straight road trackdir
 683  */
 684 inline bool IsStraightRoadTrackdir(Trackdir dir)
 685 {
 686         assert(IsValidTrackdirForRoadVehicle(dir));
 687         return (dir & 0x06) == 0;
 688 }
 689
 690 /**
 691  * Checks whether a trackdir on a specific slope is going uphill.
 692  *
 693  * Valid for rail and road tracks.
 694  * Valid for tile-slopes (under foundation) and foundation-slopes (on foundation).
 695  *
 696  * @param slope The slope of the tile.
 697  * @param dir The trackdir of interest.
 698  * @return true iff the track goes upwards.
 699  */
 700 inline bool IsUphillTrackdir(Slope slope, Trackdir dir)
 701 {
 702         assert(IsValidTrackdirForRoadVehicle(dir));
 703         extern const TrackdirBits _uphill_trackdirs[];
 704         return HasBit(_uphill_trackdirs[RemoveHalftileSlope(slope)], dir);
 705 }
 706
 707 /**
 708  * Determine the side in which the vehicle will leave the tile
 709  *
 710  * @param direction vehicle direction
 711  * @param track vehicle track bits
 712  * @return side of tile the vehicle will leave
 713  */
 714 inline DiagDirection VehicleExitDir(Direction direction, TrackBits track)
 715 {
 716         static const TrackBits state_dir_table[DIAGDIR_END] = { TRACK_BIT_RIGHT, TRACK_BIT_LOWER, TRACK_BIT_LEFT, TRACK_BIT_UPPER };
 717
 718         DiagDirection diagdir = DirToDiagDir(direction);
 719
 720         /* Determine the diagonal direction in which we will exit this tile */
 721         if (!HasBit(direction, 0) && track != state_dir_table[diagdir]) {
 722                 diagdir = ChangeDiagDir(diagdir, DIAGDIRDIFF_90LEFT);
 723         }
 724
 725         return diagdir;
 726 }
 727
 728 #endif /* TRACK_FUNC_H */