src/track_func.h

   1 /* $Id$ */
   2
   3 /*
   4  * This file is part of OpenTTD.
   5  * 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.
   6  * 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.
   7  * 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/>.
   8  */
   9
  10 /** @file track_func.h Different conversion functions from one kind of track to another. */
  11
  12 #ifndef TRACK_FUNC_H
  13 #define TRACK_FUNC_H
  14
  15 #include "core/bitmath_func.hpp"
  16 #include "track_type.h"
  17 #include "slope_func.h"
  18
  19 /**
  20  * Iterate through each set Track in a TrackBits value.
  21  * For more informations see FOR_EACH_SET_BIT_EX.
  22  *
  23  * @param var Loop index variable that stores fallowing set track. Must be of type Track.
  24  * @param track_bits The value to iterate through (any expression).
  25  *
  26  * @see FOR_EACH_SET_BIT_EX
  27  */
  28 #define FOR_EACH_SET_TRACK(var, track_bits) FOR_EACH_SET_BIT_EX(Track, var, TrackBits, track_bits)
  29
  30 /**
  31  * Convert an Axis to the corresponding Track
  32  * AXIS_X -> TRACK_X
  33  * AXIS_Y -> TRACK_Y
  34  * Uses the fact that they share the same internal encoding
  35  *
  36  * @param a the axis to convert
  37  * @return the track corresponding to the axis
  38  */
  39 static inline Track AxisToTrack(Axis a)
  40 {
  41         return (Track)a;
  42 }
  43
  44 /**
  45  * Maps a Track to the corresponding TrackBits value
  46  * @param track the track to convert
  47  * @return the converted TrackBits value of the track
  48  */
  49 static inline TrackBits TrackToTrackBits(Track track)
  50 {
  51         return (TrackBits)(1 << track);
  52 }
  53
  54 /**
  55  * Maps an Axis to the corresponding TrackBits value
  56  * @param a the axis to convert
  57  * @return the converted TrackBits value of the axis
  58  */
  59 static inline TrackBits AxisToTrackBits(Axis a)
  60 {
  61         return TrackToTrackBits(AxisToTrack(a));
  62 }
  63
  64 /**
  65  * Returns a single horizontal/vertical trackbit that is in a specific tile corner.
  66  *
  67  * @param corner The corner of a tile.
  68  * @return The TrackBits of the track in the corner.
  69  */
  70 static inline TrackBits CornerToTrackBits(Corner corner)
  71 {
  72         extern const TrackBits _corner_to_trackbits[];
  73         assert(IsValidCorner(corner));
  74         return _corner_to_trackbits[corner];
  75 }
  76
  77
  78
  79 /**
  80  * Maps a Trackdir to the corresponding TrackdirBits value
  81  * @param trackdir the track direction to convert
  82  * @return the converted TrackdirBits value
  83  */
  84 static inline TrackdirBits TrackdirToTrackdirBits(Trackdir trackdir)
  85 {
  86         return (TrackdirBits)(1 << trackdir);
  87 }
  88
  89 /**
  90  * Removes first Track from TrackBits and returns it
  91  *
  92  * This function searchs for the first bit in the TrackBits,
  93  * remove this bit from the parameter and returns the found
  94  * bit as Track value. It returns INVALID_TRACK if the
  95  * parameter was TRACK_BIT_NONE or INVALID_TRACK_BIT. This
  96  * is basically used in while-loops to get up to 6 possible
  97  * tracks on a tile until the parameter becomes TRACK_BIT_NONE.
  98  *
  99  * @param tracks The value with the TrackBits
 100  * @return The first Track from the TrackBits value
 101  * @see FindFirstTrack
 102  */
 103 static inline Track RemoveFirstTrack(TrackBits *tracks)
 104 {
 105         if (*tracks != TRACK_BIT_NONE && *tracks != INVALID_TRACK_BIT) {
 106                 Track first = (Track)FIND_FIRST_BIT(*tracks);
 107                 ClrBit(*tracks, first);
 108                 return first;
 109         }
 110         return INVALID_TRACK;
 111 }
 112
 113 /**
 114  * Removes first Trackdir from TrackdirBits and returns it
 115  *
 116  * This function searchs for the first bit in the TrackdirBits parameter,
 117  * remove this bit from the parameter and returns the fnound bit as
 118  * Trackdir value. It returns INVALID_TRACKDIR if the trackdirs is
 119  * TRACKDIR_BIT_NONE or INVALID_TRACKDIR_BIT. This is basically used in a
 120  * while-loop to get all track-directions step by step until the value
 121  * reaches TRACKDIR_BIT_NONE.
 122  *
 123  * @param trackdirs The value with the TrackdirBits
 124  * @return The first Trackdir from the TrackdirBits value
 125  * @see FindFirstTrackdir
 126  */
 127 static inline Trackdir RemoveFirstTrackdir(TrackdirBits *trackdirs)
 128 {
 129         if (*trackdirs != TRACKDIR_BIT_NONE && *trackdirs != INVALID_TRACKDIR_BIT) {
 130                 Trackdir first = (Trackdir)FindFirstBit2x64(*trackdirs);
 131                 ClrBit(*trackdirs, first);
 132                 return first;
 133         }
 134         return INVALID_TRACKDIR;
 135 }
 136
 137 /**
 138  * Returns first Track from TrackBits or INVALID_TRACK
 139  *
 140  * This function returns the first Track found in the TrackBits value as Track-value.
 141  * It returns INVALID_TRACK if the parameter is TRACK_BIT_NONE or INVALID_TRACK_BIT.
 142  *
 143  * @param tracks The TrackBits value
 144  * @return The first Track found or INVALID_TRACK
 145  * @see RemoveFirstTrack
 146  */
 147 static inline Track FindFirstTrack(TrackBits tracks)
 148 {
 149         return (tracks != TRACK_BIT_NONE && tracks != INVALID_TRACK_BIT) ? (Track)FIND_FIRST_BIT(tracks) : INVALID_TRACK;
 150 }
 151
 152 /**
 153  * Converts TrackBits to Track.
 154  *
 155  * This function converts a TrackBits value to a Track value. As it
 156  * is not possible to convert two or more tracks to one track the
 157  * parameter must contain only one track or be the INVALID_TRACK_BIT value.
 158  *
 159  * @param tracks The TrackBits value to convert
 160  * @return The Track from the value or INVALID_TRACK
 161  * @pre tracks must contains only one Track or be INVALID_TRACK_BIT
 162  */
 163 static inline Track TrackBitsToTrack(TrackBits tracks)
 164 {
 165         assert(tracks == INVALID_TRACK_BIT || (tracks != TRACK_BIT_NONE && KillFirstBit(tracks & TRACK_BIT_MASK) == TRACK_BIT_NONE));
 166         return tracks != INVALID_TRACK_BIT ? (Track)FIND_FIRST_BIT(tracks & TRACK_BIT_MASK) : INVALID_TRACK;
 167 }
 168
 169 /**
 170  * Returns first Trackdir from TrackdirBits or INVALID_TRACKDIR
 171  *
 172  * This function returns the first Trackdir in the given TrackdirBits value or
 173  * INVALID_TRACKDIR if the value is TRACKDIR_BIT_NONE. The TrackdirBits must
 174  * not be INVALID_TRACKDIR_BIT.
 175  *
 176  * @param trackdirs The TrackdirBits value
 177  * @return The first Trackdir from the TrackdirBits or INVALID_TRACKDIR on TRACKDIR_BIT_NONE.
 178  * @pre trackdirs must not be INVALID_TRACKDIR_BIT
 179  * @see RemoveFirstTrackdir
 180  */
 181 static inline Trackdir FindFirstTrackdir(TrackdirBits trackdirs)
 182 {
 183         assert((trackdirs & ~TRACKDIR_BIT_MASK) == TRACKDIR_BIT_NONE);
 184         return (trackdirs != TRACKDIR_BIT_NONE) ? (Trackdir)FindFirstBit2x64(trackdirs) : INVALID_TRACKDIR;
 185 }
 186
 187 /**
 188  * Checks if a Track is valid.
 189  *
 190  * @param track The value to check
 191  * @return true if the given value is a valid track.
 192  * @note Use this in an assert()
 193  */
 194 static inline bool IsValidTrack(Track track)
 195 {
 196         return track < TRACK_END;
 197 }
 198
 199 /**
 200  * Checks if a Trackdir is valid.
 201  *
 202  * @param trackdir The value to check
 203  * @return true if the given valie is a valid Trackdir
 204  * @note Use this in an assert()
 205  */
 206 static inline bool IsValidTrackdir(Trackdir trackdir)
 207 {
 208         return (TrackdirToTrackdirBits(trackdir) & TRACKDIR_BIT_MASK) != 0;
 209 }
 210
 211
 212 /*
 213  * Functions describing logical relations between Tracks, TrackBits, Trackdirs
 214  * TrackdirBits, Direction and DiagDirections.
 215  */
 216
 217 /**
 218  * Find the opposite track to a given track.
 219  *
 220  * TRACK_LOWER -> TRACK_UPPER and vice versa, likewise for left/right.
 221  * TRACK_X is mapped to TRACK_Y and reversed.
 222  *
 223  * @param t the track to convert
 224  * @return the opposite track
 225  */
 226 static inline Track TrackToOppositeTrack(Track t)
 227 {
 228         assert(t != INVALID_TRACK);
 229         return (Track)(t ^ 1);
 230 }
 231
 232 /**
 233  * Maps a trackdir to the reverse trackdir.
 234  *
 235  * Returns the reverse trackdir of a Trackdir value. The reverse trackdir
 236  * is the same track with the other direction on it.
 237  *
 238  * @param trackdir The Trackdir value
 239  * @return The reverse trackdir
 240  * @pre trackdir must not be INVALID_TRACKDIR
 241  */
 242 static inline Trackdir ReverseTrackdir(Trackdir trackdir)
 243 {
 244         assert(trackdir != INVALID_TRACKDIR);
 245         return (Trackdir)(trackdir ^ 8);
 246 }
 247
 248 /**
 249  * Returns the Track that a given Trackdir represents
 250  *
 251  * This function filters the Track which is used in the Trackdir value and
 252  * returns it as a Track value.
 253  *
 254  * @param trackdir The trackdir value
 255  * @return The Track which is used in the value
 256  */
 257 static inline Track TrackdirToTrack(Trackdir trackdir)
 258 {
 259         return (Track)(trackdir & 0x7);
 260 }
 261
 262 /**
 263  * Returns a Trackdir for the given Track
 264  *
 265  * Since every Track corresponds to two Trackdirs, we choose the
 266  * one which points between NE and S. Note that the actual
 267  * implementation is quite futile, but this might change
 268  * in the future.
 269  *
 270  * @param track The given Track
 271  * @return The Trackdir from the given Track
 272  */
 273 static inline Trackdir TrackToTrackdir(Track track)
 274 {
 275         return (Trackdir)track;
 276 }
 277
 278 /**
 279  * Returns a TrackdirBit mask from a given Track
 280  *
 281  * The TrackdirBit mask contains the two TrackdirBits that
 282  * correspond with the given Track (one for each direction).
 283  *
 284  * @param track The track to get the TrackdirBits from
 285  * @return The TrackdirBits which the selected tracks
 286  */
 287 static inline TrackdirBits TrackToTrackdirBits(Track track)
 288 {
 289         Trackdir td = TrackToTrackdir(track);
 290         return (TrackdirBits)(TrackdirToTrackdirBits(td) | TrackdirToTrackdirBits(ReverseTrackdir(td)));
 291 }
 292
 293 /**
 294  * Discards all directional information from a TrackdirBits value
 295  *
 296  * Any Track which is present in either direction will be present in the result.
 297  *
 298  * @param bits The TrackdirBits to get the TrackBits from
 299  * @return The TrackBits
 300  */
 301 static inline TrackBits TrackdirBitsToTrackBits(TrackdirBits bits)
 302 {
 303         return (TrackBits)((bits | (bits >> 8)) & TRACK_BIT_MASK);
 304 }
 305
 306 /**
 307  * Converts TrackBits to TrackdirBits while allowing both directions.
 308  *
 309  * @param bits The TrackBits
 310  * @return The TrackdirBits containing of bits in both directions.
 311  */
 312 static inline TrackdirBits TrackBitsToTrackdirBits(TrackBits bits)
 313 {
 314         return (TrackdirBits)(bits * 0x101);
 315 }
 316
 317 /**
 318  * Returns the present-trackdir-information of a TrackStatus.
 319  *
 320  * @param ts The TrackStatus returned by GetTileTrackStatus()
 321  * @return the present trackdirs
 322  */
 323 static inline TrackdirBits TrackStatusToTrackdirBits(TrackStatus ts)
 324 {
 325         return (TrackdirBits)(ts & TRACKDIR_BIT_MASK);
 326 }
 327
 328 /**
 329  * Returns the present-track-information of a TrackStatus.
 330  *
 331  * @param ts The TrackStatus returned by GetTileTrackStatus()
 332  * @return the present tracks
 333  */
 334 static inline TrackBits TrackStatusToTrackBits(TrackStatus ts)
 335 {
 336         return TrackdirBitsToTrackBits(TrackStatusToTrackdirBits(ts));
 337 }
 338
 339 /**
 340  * Returns the red-signal-information of a TrackStatus.
 341  *
 342  * Note: The result may contain red signals for non-present tracks.
 343  *
 344  * @param ts The TrackStatus returned by GetTileTrackStatus()
 345  * @return the The trackdirs that are blocked by red-signals
 346  */
 347 static inline TrackdirBits TrackStatusToRedSignals(TrackStatus ts)
 348 {
 349         return (TrackdirBits)((ts >> 16) & TRACKDIR_BIT_MASK);
 350 }
 351
 352 /**
 353  * Builds a TrackStatus
 354  *
 355  * @param trackdirbits present trackdirs
 356  * @param red_signals red signals
 357  * @return the TrackStatus representing the given information
 358  */
 359 static inline TrackStatus CombineTrackStatus(TrackdirBits trackdirbits, TrackdirBits red_signals)
 360 {
 361         return (TrackStatus)(trackdirbits | (red_signals << 16));
 362 }
 363
 364 /**
 365  * Maps a trackdir to the trackdir that you will end up on if you go straight
 366  * ahead.
 367  *
 368  * This will be the same trackdir for diagonal trackdirs, but a
 369  * different (alternating) one for straight trackdirs
 370  *
 371  * @param trackdir The given trackdir
 372  * @return The next Trackdir value of the next tile.
 373  */
 374 static inline Trackdir NextTrackdir(Trackdir trackdir)
 375 {
 376         extern const Trackdir _next_trackdir[TRACKDIR_END];
 377         return _next_trackdir[trackdir];
 378 }
 379
 380 /**
 381  * Maps a track to all tracks that make 90 deg turns with it.
 382  *
 383  * For the diagonal directions these are the complement of the
 384  * direction, for the straight directions these are the
 385  * two vertical or horizontal tracks, depend on the given direction
 386  *
 387  * @param track The given track
 388  * @return The TrackBits with the tracks marked which cross the given track by 90 deg.
 389  */
 390 static inline TrackBits TrackCrossesTracks(Track track)
 391 {
 392         extern const TrackBits _track_crosses_tracks[TRACK_END];
 393         return _track_crosses_tracks[track];
 394 }
 395
 396 /**
 397  * Maps a trackdir to the (4-way) direction the tile is exited when following
 398  * that trackdir.
 399  *
 400  * For the diagonal directions these are the same directions. For
 401  * the straight directions these are the directions from the imagined
 402  * base-tile to the bordering tile which will be joined if the given
 403  * straight direction is leaved from the base-tile.
 404  *
 405  * @param trackdir The given track direction
 406  * @return The direction which points to the resulting tile if following the Trackdir
 407  */
 408 static inline DiagDirection TrackdirToExitdir(Trackdir trackdir)
 409 {
 410         extern const DiagDirection _trackdir_to_exitdir[TRACKDIR_END];
 411         return _trackdir_to_exitdir[trackdir];
 412 }
 413
 414 /**
 415  * Maps a track and an (4-way) dir to the trackdir that represents the track
 416  * with the exit in the given direction.
 417  *
 418  * For the diagonal tracks the resulting track direction are clear for a given
 419  * DiagDirection. It either matches the direction or it returns INVALID_TRACKDIR,
 420  * as a TRACK_X cannot be applied with DIAG_SE.
 421  * For the straight tracks the resulting track direction will be the
 422  * direction which the DiagDirection is pointing. But this will be INVALID_TRACKDIR
 423  * if the DiagDirection is pointing 'away' the track.
 424  *
 425  * @param track The track to applie an direction on
 426  * @param diagdir The DiagDirection to applie on
 427  * @return The resulting track direction or INVALID_TRACKDIR if not possible.
 428  */
 429 static inline Trackdir TrackExitdirToTrackdir(Track track, DiagDirection diagdir)
 430 {
 431         extern const Trackdir _track_exitdir_to_trackdir[TRACK_END][DIAGDIR_END];
 432         return _track_exitdir_to_trackdir[track][diagdir];
 433 }
 434
 435 /**
 436  * Maps a track and an (4-way) dir to the trackdir that represents the track
 437  * with the entry in the given direction.
 438  *
 439  * For the diagonal tracks the return value is clear, its either the matching
 440  * track direction or INVALID_TRACKDIR.
 441  * For the straight tracks this returns the track direction which results if
 442  * you follow the DiagDirection and then turn by 45 deg left or right on the
 443  * next tile. The new direction on the new track will be the returning Trackdir
 444  * value. If the parameters makes no sense like the track TRACK_UPPER and the
 445  * diraction DIAGDIR_NE (target track cannot be reached) this function returns
 446  * INVALID_TRACKDIR.
 447  *
 448  * @param track The target track
 449  * @param diagdir The direction to "come from"
 450  * @return the resulting Trackdir or INVALID_TRACKDIR if not possible.
 451  */
 452 static inline Trackdir TrackEnterdirToTrackdir(Track track, DiagDirection diagdir)
 453 {
 454         extern const Trackdir _track_enterdir_to_trackdir[TRACK_END][DIAGDIR_END];
 455         return _track_enterdir_to_trackdir[track][diagdir];
 456 }
 457
 458 /**
 459  * Maps a track and a full (8-way) direction to the trackdir that represents
 460  * the track running in the given direction.
 461  */
 462 static inline Trackdir TrackDirectionToTrackdir(Track track, Direction dir)
 463 {
 464         extern const Trackdir _track_direction_to_trackdir[TRACK_END][DIR_END];
 465         return _track_direction_to_trackdir[track][dir];
 466 }
 467
 468 /**
 469  * Maps a (4-way) direction to the diagonal track incidating with that diagdir
 470  *
 471  * @param diagdir The direction
 472  * @return The resulting Track
 473  */
 474 static inline Track DiagDirToDiagTrack(DiagDirection diagdir)
 475 {
 476         return (Track)(diagdir & 1);
 477 }
 478
 479 /**
 480  * Maps a (4-way) direction to the diagonal track bits incidating with that diagdir
 481  *
 482  * @param diagdir The direction
 483  * @return The resulting TrackBits
 484  */
 485 static inline TrackBits DiagDirToDiagTrackBits(DiagDirection diagdir)
 486 {
 487         return TrackToTrackBits(DiagDirToDiagTrack(diagdir));
 488 }
 489
 490 /**
 491  * Maps a (4-way) direction to the diagonal trackdir that runs in that
 492  * direction.
 493  *
 494  * @param diagdir The direction
 495  * @return The resulting Trackdir direction
 496  */
 497 static inline Trackdir DiagDirToDiagTrackdir(DiagDirection diagdir)
 498 {
 499         extern const Trackdir _dir_to_diag_trackdir[DIAGDIR_END];
 500         return _dir_to_diag_trackdir[diagdir];
 501 }
 502
 503 /**
 504  * Returns all trackdirs that can be reached when entering a tile from a given
 505  * (diagonal) direction.
 506  *
 507  * This will obviously include 90 degree turns, since no information is available
 508  * about the exact angle of entering
 509  *
 510  * @param diagdir The joining direction
 511  * @return The TrackdirBits which can be used from the given direction
 512  * @see DiagdirReachesTracks
 513  */
 514 static inline TrackdirBits DiagdirReachesTrackdirs(DiagDirection diagdir)
 515 {
 516         extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
 517         return _exitdir_reaches_trackdirs[diagdir];
 518 }
 519
 520 /**
 521  * Returns all tracks that can be reached when entering a tile from a given
 522  * (diagonal) direction.
 523  *
 524  * This will obviously include 90 degree turns, since no
 525  * information is available about the exact angle of entering
 526  *
 527  * @param diagdir The joining irection
 528  * @return The tracks which can be used
 529  * @see DiagdirReachesTrackdirs
 530  */
 531 static inline TrackBits DiagdirReachesTracks(DiagDirection diagdir) { return TrackdirBitsToTrackBits(DiagdirReachesTrackdirs(diagdir)); }
 532
 533 /**
 534  * Maps a trackdir to the trackdirs that can be reached from it (ie, when
 535  * entering the next tile.
 536  *
 537  * This will include 90 degree turns!
 538  *
 539  * @param trackdir The track direction which will be leaved
 540  * @return The track directions which can be used from this direction (in the next tile)
 541  */
 542 static inline TrackdirBits TrackdirReachesTrackdirs(Trackdir trackdir)
 543 {
 544         extern const TrackdirBits _exitdir_reaches_trackdirs[DIAGDIR_END];
 545         return _exitdir_reaches_trackdirs[TrackdirToExitdir(trackdir)];
 546 }
 547 /* Note that there is no direct table for this function (there used to be),
 548  * but it uses two simpeler tables to achieve the result */
 549
 550 /**
 551  * Maps a trackdir to all trackdirs that make 90 deg turns with it.
 552  *
 553  * For the diagonal tracks this returns the track direction bits
 554  * of the other axis in both directions, which cannot be joined by
 555  * the given track direction.
 556  * For the straight tracks this returns all possible 90 deg turns
 557  * either on the current tile (which no train can joined) or on the
 558  * bordering tiles.
 559  *
 560  * @param trackdir The track direction
 561  * @return The TrackdirBits which are (more or less) 90 deg turns.
 562  */
 563 static inline TrackdirBits TrackdirCrossesTrackdirs(Trackdir trackdir)
 564 {
 565         extern const TrackdirBits _track_crosses_trackdirs[TRACKDIR_END];
 566         return _track_crosses_trackdirs[TrackdirToTrack(trackdir)];
 567 }
 568
 569 /**
 570  * Checks if a given Track is diagonal
 571  *
 572  * @param track The given track to check
 573  * @return true if diagonal, else false
 574  */
 575 static inline bool IsDiagonalTrack(Track track)
 576 {
 577         return (track == TRACK_X) || (track == TRACK_Y);
 578 }
 579
 580 /**
 581  * Checks if a given Trackdir is diagonal.
 582  *
 583  * @param trackdir The given trackdir
 584  * @return true if the trackdir use a diagonal track
 585  */
 586 static inline bool IsDiagonalTrackdir(Trackdir trackdir)
 587 {
 588         return IsDiagonalTrack(TrackdirToTrack(trackdir));
 589 }
 590
 591
 592 /**
 593  * Checks if the given tracks overlap, ie form a crossing. Basically this
 594  * means when there is more than one track on the tile, exept when there are
 595  * two parallel tracks.
 596  * @param  bits The tracks present.
 597  * @return Whether the tracks present overlap in any way.
 598  */
 599 static inline bool TracksOverlap(TrackBits bits)
 600 {
 601         /* With no, or only one track, there is no overlap */
 602         if (bits == TRACK_BIT_NONE || KillFirstBit(bits) == TRACK_BIT_NONE) return false;
 603         /* We know that there are at least two tracks present. When there are more
 604          * than 2 tracks, they will surely overlap. When there are two, they will
 605          * always overlap unless they are lower & upper or right & left. */
 606         return bits != TRACK_BIT_HORZ && bits != TRACK_BIT_VERT;
 607 }
 608
 609 /**
 610  * Check if a given track is contained within or overlaps some other tracks.
 611  *
 612  * @param tracks Tracks to be testet against
 613  * @param track The track to test
 614  * @return true if the track is already in the tracks or overlaps the tracks.
 615  */
 616 static inline bool TrackOverlapsTracks(TrackBits tracks, Track track)
 617 {
 618         if (HasBit(tracks, track)) return true;
 619         return TracksOverlap(tracks | TrackToTrackBits(track));
 620 }
 621
 622 /**
 623  * Checks whether the trackdir means that we are reversing.
 624  * @param dir the trackdir to check
 625  * @return true if it is a reversing road trackdir
 626  */
 627 static inline bool IsReversingRoadTrackdir(Trackdir dir)
 628 {
 629         return (dir & 0x07) >= 6;
 630 }
 631
 632 /**
 633  * Checks whether the given trackdir is a straight road
 634  * @param dir the trackdir to check
 635  * @return true if it is a straight road trackdir
 636  */
 637 static inline bool IsStraightRoadTrackdir(Trackdir dir)
 638 {
 639         return (dir & 0x06) == 0;
 640 }
 641
 642 /**
 643  * Checks whether a trackdir on a specific slope is going uphill.
 644  *
 645  * Valid for rail and road tracks.
 646  * Valid for tile-slopes (under foundation) and foundation-slopes (on foundation).
 647  *
 648  * @param slope The slope of the tile.
 649  * @param dir The trackdir of interest.
 650  * @return true iff the track goes upwards.
 651  */
 652 static inline bool IsUphillTrackdir(Slope slope, Trackdir dir)
 653 {
 654         extern const TrackdirBits _uphill_trackdirs[];
 655         return HasBit(_uphill_trackdirs[RemoveHalftileSlope(slope)], dir);
 656 }
 657
 658 #endif /* TRACK_FUNC_H */