pathfind.cpp

Go to the documentation of this file.
00001 /* $Id: pathfind.cpp 17346 2009-09-01 13:16:53Z rubidium $ */
00002 
00005 #include "stdafx.h"
00006 #include "station_map.h"
00007 #include "settings_type.h"
00008 #include "pathfind.h"
00009 #include "debug.h"
00010 #include "tunnelbridge_map.h"
00011 #include "core/random_func.hpp"
00012 #include "core/alloc_type.hpp"
00013 #include "tunnelbridge.h"
00014 
00015 /* remember which tiles we have already visited so we don't visit them again. */
00016 static bool TPFSetTileBit(TrackPathFinder *tpf, TileIndex tile, int dir)
00017 {
00018   uint hash, val, offs;
00019   TrackPathFinderLink *link, *new_link;
00020   uint bits = 1 << dir;
00021 
00022   if (tpf->disable_tile_hash)
00023     return true;
00024 
00025   hash = PATHFIND_HASH_TILE(tile);
00026 
00027   val = tpf->hash_head[hash];
00028 
00029   if (val == 0) {
00030     /* unused hash entry, set the appropriate bit in it and return true
00031      * to indicate that a bit was set. */
00032     tpf->hash_head[hash] = bits;
00033     tpf->hash_tile[hash] = tile;
00034     return true;
00035   } else if (!(val & 0x8000)) {
00036     /* single tile */
00037 
00038     if (tile == tpf->hash_tile[hash]) {
00039       /* found another bit for the same tile,
00040        * check if this bit is already set, if so, return false */
00041       if (val & bits)
00042         return false;
00043 
00044       /* otherwise set the bit and return true to indicate that the bit
00045        * was set */
00046       tpf->hash_head[hash] = val | bits;
00047       return true;
00048     } else {
00049       /* two tiles with the same hash, need to make a link */
00050 
00051       /* allocate a link. if out of links, handle this by returning
00052        * that a tile was already visisted. */
00053       if (tpf->num_links_left == 0) {
00054         return false;
00055       }
00056       tpf->num_links_left--;
00057       link = tpf->new_link++;
00058 
00059       /* move the data that was previously in the hash_??? variables
00060        * to the link struct, and let the hash variables point to the link */
00061       link->tile = tpf->hash_tile[hash];
00062       tpf->hash_tile[hash] = PATHFIND_GET_LINK_OFFS(tpf, link);
00063 
00064       link->flags = tpf->hash_head[hash];
00065       tpf->hash_head[hash] = 0xFFFF; // multi link
00066 
00067       link->next = 0xFFFF;
00068     }
00069   } else {
00070     /* a linked list of many tiles,
00071      * find the one corresponding to the tile, if it exists.
00072      * otherwise make a new link */
00073 
00074     offs = tpf->hash_tile[hash];
00075     do {
00076       link = PATHFIND_GET_LINK_PTR(tpf, offs);
00077       if (tile == link->tile) {
00078         /* found the tile in the link list,
00079          * check if the bit was alrady set, if so return false to indicate that the
00080          * bit was already set */
00081         if (link->flags & bits)
00082           return false;
00083         link->flags |= bits;
00084         return true;
00085       }
00086     } while ((offs=link->next) != 0xFFFF);
00087   }
00088 
00089   /* get here if we need to add a new link to link,
00090    * first, allocate a new link, in the same way as before */
00091   if (tpf->num_links_left == 0) {
00092       return false;
00093   }
00094   tpf->num_links_left--;
00095   new_link = tpf->new_link++;
00096 
00097   /* then fill the link with the new info, and establish a ptr from the old
00098    * link to the new one */
00099   new_link->tile = tile;
00100   new_link->flags = bits;
00101   new_link->next = 0xFFFF;
00102 
00103   link->next = PATHFIND_GET_LINK_OFFS(tpf, new_link);
00104   return true;
00105 }
00106 
00107 static void TPFModeShip(TrackPathFinder *tpf, TileIndex tile, DiagDirection direction)
00108 {
00109   assert(tpf->tracktype == TRANSPORT_WATER);
00110 
00111   if (IsTileType(tile, MP_TUNNELBRIDGE)) {
00112     /* wrong track type */
00113     if (GetTunnelBridgeTransportType(tile) != tpf->tracktype) return;
00114 
00115     DiagDirection dir = GetTunnelBridgeDirection(tile);
00116     /* entering tunnel / bridge? */
00117     if (dir == direction) {
00118       TileIndex endtile = GetOtherTunnelBridgeEnd(tile);
00119 
00120       tpf->rd.cur_length += GetTunnelBridgeLength(tile, endtile) + 1;
00121 
00122       TPFSetTileBit(tpf, tile, 14);
00123       TPFSetTileBit(tpf, endtile, 14);
00124 
00125       tile = endtile;
00126     } else {
00127       /* leaving tunnel / bridge? */
00128       if (ReverseDiagDir(dir) != direction) return;
00129     }
00130   }
00131 
00132   /* This addition will sometimes overflow by a single tile.
00133    * The use of TILE_MASK here makes sure that we still point at a valid
00134    * tile, and then this tile will be in the sentinel row/col, so GetTileTrackStatus will fail. */
00135   tile = TILE_MASK(tile + TileOffsByDiagDir(direction));
00136 
00137   if (++tpf->rd.cur_length > 50)
00138     return;
00139 
00140   TrackBits bits = TrackStatusToTrackBits(GetTileTrackStatus(tile, tpf->tracktype, tpf->sub_type)) & DiagdirReachesTracks(direction);
00141   if (bits == TRACK_BIT_NONE) return;
00142 
00143   assert(TileX(tile) != MapMaxX() && TileY(tile) != MapMaxY());
00144 
00145   bool only_one_track = true;
00146   do {
00147     Track track = RemoveFirstTrack(&bits);
00148     if (bits != TRACK_BIT_NONE) only_one_track = false;
00149     RememberData rd = tpf->rd;
00150 
00151     /* Change direction 4 times only */
00152     if (!only_one_track && track != tpf->rd.last_choosen_track) {
00153       if (++tpf->rd.depth > 4) {
00154         tpf->rd = rd;
00155         return;
00156       }
00157       tpf->rd.last_choosen_track = track;
00158     }
00159 
00160     tpf->the_dir = TrackEnterdirToTrackdir(track, direction);
00161 
00162     if (!tpf->enum_proc(tile, tpf->userdata, tpf->the_dir, tpf->rd.cur_length)) {
00163       TPFModeShip(tpf, tile, TrackdirToExitdir(tpf->the_dir));
00164     }
00165 
00166     tpf->rd = rd;
00167   } while (bits != TRACK_BIT_NONE);
00168 
00169 }
00170 
00180 static inline bool CanAccessTileInDir(TileIndex tile, DiagDirection side, TransportType tracktype)
00181 {
00182   if (tracktype == TRANSPORT_RAIL) {
00183     /* depot from wrong side */
00184     if (IsRailDepotTile(tile) && GetRailDepotDirection(tile) != side) return false;
00185   } else if (tracktype == TRANSPORT_ROAD) {
00186     /* depot from wrong side */
00187     if (IsRoadDepotTile(tile) && GetRoadDepotDirection(tile) != side) return false;
00188     /* non-driverthrough road station from wrong side */
00189     if (IsStandardRoadStopTile(tile) && GetRoadStopDir(tile) != side) return false;
00190   }
00191 
00192   return true;
00193 }
00194 
00195 static void TPFModeNormal(TrackPathFinder *tpf, TileIndex tile, DiagDirection direction)
00196 {
00197   const TileIndex tile_org = tile;
00198 
00199   if (IsTileType(tile, MP_TUNNELBRIDGE)) {
00200     /* wrong track type */
00201     if (GetTunnelBridgeTransportType(tile) != tpf->tracktype) return;
00202 
00203     DiagDirection dir = GetTunnelBridgeDirection(tile);
00204     /* entering tunnel / bridge? */
00205     if (dir == direction) {
00206       TileIndex endtile = GetOtherTunnelBridgeEnd(tile);
00207 
00208       tpf->rd.cur_length += GetTunnelBridgeLength(tile, endtile) + 1;
00209 
00210       TPFSetTileBit(tpf, tile, 14);
00211       TPFSetTileBit(tpf, endtile, 14);
00212 
00213       tile = endtile;
00214     } else {
00215       /* leaving tunnel / bridge? */
00216       if (ReverseDiagDir(dir) != direction) return;
00217     }
00218   } else {
00219     /* can we leave tile in this dir? */
00220     if (!CanAccessTileInDir(tile, direction, tpf->tracktype)) return;
00221   }
00222 
00223   tile += TileOffsByDiagDir(direction);
00224 
00225   /* can we enter tile in this dir? */
00226   if (!CanAccessTileInDir(tile, ReverseDiagDir(direction), tpf->tracktype)) return;
00227 
00228   /* Check if the new tile is a tunnel or bridge head and that the direction
00229    * and transport type match */
00230   if (IsTileType(tile, MP_TUNNELBRIDGE)) {
00231     if (GetTunnelBridgeDirection(tile) != direction ||
00232         GetTunnelBridgeTransportType(tile) != tpf->tracktype) {
00233       return;
00234     }
00235   }
00236 
00237   TrackdirBits trackdirbits = TrackStatusToTrackdirBits(GetTileTrackStatus(tile, tpf->tracktype, tpf->sub_type));
00238 
00239   /* Check in case of rail if the owner is the same */
00240   if (tpf->tracktype == TRANSPORT_RAIL) {
00241     if (trackdirbits != TRACKDIR_BIT_NONE && TrackStatusToTrackdirBits(GetTileTrackStatus(tile_org, TRANSPORT_RAIL, 0)) != TRACKDIR_BIT_NONE) {
00242       if (GetTileOwner(tile_org) != GetTileOwner(tile)) return;
00243     }
00244   }
00245 
00246   tpf->rd.cur_length++;
00247 
00248   trackdirbits &= DiagdirReachesTrackdirs(direction);
00249   TrackBits bits = TrackdirBitsToTrackBits(trackdirbits);
00250 
00251   if (bits != TRACK_BIT_NONE) {
00252     if (!tpf->disable_tile_hash || (tpf->rd.cur_length <= 64 && (KillFirstBit(bits) == 0 || ++tpf->rd.depth <= 7))) {
00253       do {
00254         Track track = RemoveFirstTrack(&bits);
00255 
00256         tpf->the_dir = TrackEnterdirToTrackdir(track, direction);
00257         RememberData rd = tpf->rd;
00258 
00259         /* make sure we are not leaving from invalid side */
00260         if (TPFSetTileBit(tpf, tile, tpf->the_dir) && CanAccessTileInDir(tile, TrackdirToExitdir(tpf->the_dir), tpf->tracktype) &&
00261             !tpf->enum_proc(tile, tpf->userdata, tpf->the_dir, tpf->rd.cur_length) ) {
00262           TPFModeNormal(tpf, tile, TrackdirToExitdir(tpf->the_dir));
00263         }
00264         tpf->rd = rd;
00265       } while (bits != TRACK_BIT_NONE);
00266     }
00267   }
00268 }
00269 
00270 void FollowTrack(TileIndex tile, PathfindFlags flags, TransportType tt, uint sub_type, DiagDirection direction, TPFEnumProc *enum_proc, TPFAfterProc *after_proc, void *data)
00271 {
00272   assert(IsValidDiagDirection(direction));
00273 
00274   SmallStackSafeStackAlloc<TrackPathFinder, 1> tpf;
00275 
00276   /* initialize path finder variables */
00277   tpf->userdata = data;
00278   tpf->enum_proc = enum_proc;
00279   tpf->new_link = tpf->links;
00280   tpf->num_links_left = lengthof(tpf->links);
00281 
00282   tpf->rd.cur_length = 0;
00283   tpf->rd.depth = 0;
00284   tpf->rd.last_choosen_track = INVALID_TRACK;
00285 
00286   tpf->disable_tile_hash = (flags & PATHFIND_FLAGS_DISABLE_TILE_HASH) != 0;
00287 
00288   tpf->tracktype = tt;
00289   tpf->sub_type = sub_type;
00290 
00291   if ((flags & PATHFIND_FLAGS_SHIP_MODE) != 0) {
00292     tpf->enum_proc(tile, data, INVALID_TRACKDIR, 0);
00293     TPFModeShip(tpf, tile, direction);
00294   } else {
00295     /* clear the hash_heads */
00296     memset(tpf->hash_head, 0, sizeof(tpf->hash_head));
00297     TPFModeNormal(tpf, tile, direction);
00298   }
00299 
00300   if (after_proc != NULL) after_proc(tpf);
00301 }
00302 
00303 struct StackedItem {
00304   TileIndex tile;
00305   uint16 cur_length; 
00306   uint16 priority;   
00307   TrackdirByte track;
00308   byte depth;
00309   byte state;
00310   byte first_track;
00311 };
00312 
00313 struct HashLink {
00314   TileIndex tile;
00315   uint16 typelength;
00316   uint16 next;
00317 };
00318 
00319 struct NewTrackPathFinder {
00320   NTPEnumProc *enum_proc;
00321   void *userdata;
00322   TileIndex dest;
00323 
00324   TransportType tracktype;
00325   RailTypes railtypes;
00326   uint maxlength;
00327 
00328   HashLink *new_link;
00329   uint num_links_left;
00330 
00331   uint nstack;
00332   StackedItem stack[256];     
00333 
00334   uint16 hash_head[0x400];    
00335   TileIndex hash_tile[0x400]; 
00336 
00337   HashLink links[0x400];      
00338 
00339 };
00340 #define NTP_GET_LINK_OFFS(tpf, link) ((byte*)(link) - (byte*)tpf->links)
00341 #define NTP_GET_LINK_PTR(tpf, link_offs) (HashLink*)((byte*)tpf->links + (link_offs))
00342 
00343 #define ARR(i) tpf->stack[(i)-1]
00344 
00347 static inline void HeapifyUp(NewTrackPathFinder *tpf)
00348 {
00349   StackedItem si;
00350   int i = ++tpf->nstack;
00351 
00352   while (i != 1 && ARR(i).priority < ARR(i>>1).priority) {
00353     /* the child element is larger than the parent item.
00354      * swap the child item and the parent item. */
00355     si = ARR(i); ARR(i) = ARR(i >> 1); ARR(i >> 1) = si;
00356     i >>= 1;
00357   }
00358 }
00359 
00361 static inline void HeapifyDown(NewTrackPathFinder *tpf)
00362 {
00363   StackedItem si;
00364   int i = 1, j;
00365   int n;
00366 
00367   assert(tpf->nstack > 0);
00368   n = --tpf->nstack;
00369 
00370   if (n == 0) return; // heap is empty so nothing to do?
00371 
00372   /* copy the last item to index 0. we use it as base for heapify. */
00373   ARR(1) = ARR(n + 1);
00374 
00375   while ((j = i * 2) <= n) {
00376     /* figure out which is smaller of the children. */
00377     if (j != n && ARR(j).priority > ARR(j + 1).priority)
00378       j++; // right item is smaller
00379 
00380     assert(i <= n && j <= n);
00381     if (ARR(i).priority <= ARR(j).priority)
00382       break; // base elem smaller than smallest, done!
00383 
00384     /* swap parent with the child */
00385     si = ARR(i); ARR(i) = ARR(j); ARR(j) = si;
00386     i = j;
00387   }
00388 }
00389 
00393 static bool NtpVisit(NewTrackPathFinder *tpf, TileIndex tile, DiagDirection dir, uint length)
00394 {
00395   uint hash,head;
00396   HashLink *link, *new_link;
00397 
00398   assert(length < 16384-1);
00399 
00400   hash = PATHFIND_HASH_TILE(tile);
00401 
00402   /* never visited before? */
00403   if ((head=tpf->hash_head[hash]) == 0) {
00404     tpf->hash_tile[hash] = tile;
00405     tpf->hash_head[hash] = dir | (length << 2);
00406     return true;
00407   }
00408 
00409   if (head != 0xffff) {
00410     if (tile == tpf->hash_tile[hash] && (head & 0x3) == (uint)dir) {
00411 
00412       /* longer length */
00413       if (length >= (head >> 2)) return false;
00414 
00415       tpf->hash_head[hash] = dir | (length << 2);
00416       return true;
00417     }
00418     /* two tiles with the same hash, need to make a link
00419      * allocate a link. if out of links, handle this by returning
00420      * that a tile was already visisted. */
00421     if (tpf->num_links_left == 0) {
00422       DEBUG(ntp, 1, "No links left");
00423       return false;
00424     }
00425 
00426     tpf->num_links_left--;
00427     link = tpf->new_link++;
00428 
00429     /* move the data that was previously in the hash_??? variables
00430      * to the link struct, and let the hash variables point to the link */
00431     link->tile = tpf->hash_tile[hash];
00432     tpf->hash_tile[hash] = NTP_GET_LINK_OFFS(tpf, link);
00433 
00434     link->typelength = tpf->hash_head[hash];
00435     tpf->hash_head[hash] = 0xFFFF; // multi link
00436     link->next = 0xFFFF;
00437   } else {
00438     /* a linked list of many tiles,
00439      * find the one corresponding to the tile, if it exists.
00440      * otherwise make a new link */
00441 
00442     uint offs = tpf->hash_tile[hash];
00443     do {
00444       link = NTP_GET_LINK_PTR(tpf, offs);
00445       if (tile == link->tile && (link->typelength & 0x3U) == (uint)dir) {
00446         if (length >= (uint)(link->typelength >> 2)) return false;
00447         link->typelength = dir | (length << 2);
00448         return true;
00449       }
00450     } while ((offs = link->next) != 0xFFFF);
00451   }
00452 
00453   /* get here if we need to add a new link to link,
00454    * first, allocate a new link, in the same way as before */
00455   if (tpf->num_links_left == 0) {
00456     DEBUG(ntp, 1, "No links left");
00457     return false;
00458   }
00459   tpf->num_links_left--;
00460   new_link = tpf->new_link++;
00461 
00462   /* then fill the link with the new info, and establish a ptr from the old
00463    * link to the new one */
00464   new_link->tile = tile;
00465   new_link->typelength = dir | (length << 2);
00466   new_link->next = 0xFFFF;
00467 
00468   link->next = NTP_GET_LINK_OFFS(tpf, new_link);
00469   return true;
00470 }
00471 
00479 static bool NtpCheck(NewTrackPathFinder *tpf, TileIndex tile, uint dir, uint length)
00480 {
00481   uint hash,head,offs;
00482   HashLink *link;
00483 
00484   hash = PATHFIND_HASH_TILE(tile);
00485   head=tpf->hash_head[hash];
00486   assert(head);
00487 
00488   if (head != 0xffff) {
00489     assert( tpf->hash_tile[hash] == tile && (head & 3) == dir);
00490     assert( (head >> 2) <= length);
00491     return length == (head >> 2);
00492   }
00493 
00494   /* else it's a linked list of many tiles */
00495   offs = tpf->hash_tile[hash];
00496   for (;;) {
00497     link = NTP_GET_LINK_PTR(tpf, offs);
00498     if (tile == link->tile && (link->typelength & 0x3U) == dir) {
00499       assert((uint)(link->typelength >> 2) <= length);
00500       return length == (uint)(link->typelength >> 2);
00501     }
00502     offs = link->next;
00503     assert(offs != 0xffff);
00504   }
00505 }
00506 
00507 
00508 static uint DistanceMoo(TileIndex t0, TileIndex t1)
00509 {
00510   const uint dx = Delta(TileX(t0), TileX(t1));
00511   const uint dy = Delta(TileY(t0), TileY(t1));
00512 
00513   const uint straightTracks = 2 * min(dx, dy); // The number of straight (not full length) tracks
00514   /* OPTIMISATION:
00515    * Original: diagTracks = max(dx, dy) - min(dx,dy);
00516    * Proof:
00517    * (dx-dy) - straightTracks  == (min + max) - straightTracks = min + // max - 2 * min = max - min */
00518   const uint diagTracks = dx + dy - straightTracks; // The number of diagonal (full tile length) tracks.
00519 
00520   return diagTracks*DIAG_FACTOR + straightTracks*STR_FACTOR;
00521 }
00522 
00523 /* These has to be small cause the max length of a track
00524  * is currently limited to 16384 */
00525 
00526 static const byte _length_of_track[16] = {
00527   DIAG_FACTOR, DIAG_FACTOR, STR_FACTOR, STR_FACTOR, STR_FACTOR, STR_FACTOR, 0, 0,
00528   DIAG_FACTOR, DIAG_FACTOR, STR_FACTOR, STR_FACTOR, STR_FACTOR, STR_FACTOR, 0, 0
00529 };
00530 
00531 /* new more optimized pathfinder for trains...
00532  * Tile is the tile the train is at.
00533  * direction is the tile the train is moving towards. */
00534 
00535 static void NTPEnum(NewTrackPathFinder *tpf, TileIndex tile, DiagDirection direction)
00536 {
00537   TrackBits bits, allbits;
00538   Trackdir track;
00539   TileIndex tile_org;
00540   StackedItem si;
00541   int estimation;
00542 
00543 
00544 
00545   /* Need to have a special case for the start.
00546    * We shouldn't call the callback for the current tile. */
00547   si.cur_length = 1; // Need to start at 1 cause 0 is a reserved value.
00548   si.depth = 0;
00549   si.state = 0;
00550   si.first_track = 0xFF;
00551   goto start_at;
00552 
00553   for (;;) {
00554     /* Get the next item to search from from the priority queue */
00555     do {
00556       if (tpf->nstack == 0)
00557         return; // nothing left? then we're done!
00558       si = tpf->stack[0];
00559       tile = si.tile;
00560 
00561       HeapifyDown(tpf);
00562       /* Make sure we havn't already visited this tile. */
00563     } while (!NtpCheck(tpf, tile, ReverseDiagDir(TrackdirToExitdir(ReverseTrackdir(si.track))), si.cur_length));
00564 
00565     /* Add the length of this track. */
00566     si.cur_length += _length_of_track[si.track];
00567 
00568 callback_and_continue:
00569     if (tpf->enum_proc(tile, tpf->userdata, si.first_track, si.cur_length))
00570       return;
00571 
00572     assert(si.track <= 13);
00573     direction = TrackdirToExitdir(si.track);
00574 
00575 start_at:
00576     /* If the tile is the entry tile of a tunnel, and we're not going out of the tunnel,
00577      *   need to find the exit of the tunnel. */
00578     if (IsTileType(tile, MP_TUNNELBRIDGE)) {
00579       if (GetTunnelBridgeDirection(tile) != ReverseDiagDir(direction)) {
00580         /* We are not just driving out of the tunnel/bridge */
00581         if (GetTunnelBridgeDirection(tile) != direction ||
00582             GetTunnelBridgeTransportType(tile) != tpf->tracktype) {
00583           /* We are not driving into the tunnel/bridge, or it is an invalid tunnel/bridge */
00584           continue;
00585         }
00586         if (!HasBit(tpf->railtypes, GetRailType(tile))) {
00587           bits = TRACK_BIT_NONE;
00588           break;
00589         }
00590 
00591         TileIndex endtile = GetOtherTunnelBridgeEnd(tile);
00592         si.cur_length += DIAG_FACTOR * (GetTunnelBridgeLength(tile, endtile) + 1);
00593         tile = endtile;
00594         /* tile now points to the exit tile of the tunnel/bridge */
00595       }
00596     }
00597 
00598     /* This is a special loop used to go through
00599      * a rail net and find the first intersection */
00600     tile_org = tile;
00601     for (;;) {
00602       assert(direction <= 3);
00603       tile += TileOffsByDiagDir(direction);
00604 
00605       /* too long search length? bail out. */
00606       if (si.cur_length >= tpf->maxlength) {
00607         DEBUG(ntp, 1, "Cur_length too big");
00608         bits = TRACK_BIT_NONE;
00609         break;
00610       }
00611 
00612       /* Not a regular rail tile?
00613        * Then we can't use the code below, but revert to more general code. */
00614       if (!IsPlainRailTile(tile)) {
00615         /* We found a tile which is not a normal railway tile.
00616          * Determine which tracks that exist on this tile. */
00617         bits = TrackdirBitsToTrackBits(TrackStatusToTrackdirBits(GetTileTrackStatus(tile, TRANSPORT_RAIL, 0)) & DiagdirReachesTrackdirs(direction));
00618 
00619         /* Check that the tile contains exactly one track */
00620         if (bits == 0 || KillFirstBit(bits) != 0) break;
00621 
00622         if (!HasBit(tpf->railtypes, GetRailType(tile))) {
00623           bits = TRACK_BIT_NONE;
00624           break;
00625         }
00626 
00627         /*******************
00628          * If we reach here, the tile has exactly one track.
00629          *   tile - index to a tile that is not rail tile, but still straight (with optional signals)
00630          *   bits - bitmask of which track that exist on the tile (exactly one bit is set)
00631          *   direction - which direction are we moving in?
00632          *******************/
00633         si.track = TrackEnterdirToTrackdir(FindFirstTrack(bits), direction);
00634         si.cur_length += _length_of_track[si.track];
00635         goto callback_and_continue;
00636       }
00637 
00638       /* Regular rail tile, determine which tracks exist. */
00639       allbits = GetTrackBits(tile);
00640       /* Which tracks are reachable? */
00641       bits = allbits & DiagdirReachesTracks(direction);
00642 
00643       /* The tile has no reachable tracks => End of rail segment
00644        * or Intersection => End of rail segment. We check this agains all the
00645        * bits, not just reachable ones, to prevent infinite loops. */
00646       if (bits == TRACK_BIT_NONE || TracksOverlap(allbits)) break;
00647 
00648       if (!HasBit(tpf->railtypes, GetRailType(tile))) {
00649         bits = TRACK_BIT_NONE;
00650         break;
00651       }
00652 
00653       /* If we reach here, the tile has exactly one track, and this
00654        track is reachable = > Rail segment continues */
00655 
00656       track = TrackEnterdirToTrackdir(FindFirstTrack(bits), direction);
00657       assert(track != INVALID_TRACKDIR);
00658 
00659       si.cur_length += _length_of_track[track];
00660 
00661       /* Check if this rail is an upwards slope. If it is, then add a penalty. */
00662       if (IsDiagonalTrackdir(track) && IsUphillTrackdir(GetTileSlope(tile, NULL), track)) {
00663         /* upwards slope. add some penalty. */
00664         si.cur_length += 4 * DIAG_FACTOR;
00665       }
00666 
00667       /* railway tile with signals..? */
00668       if (HasSignals(tile)) {
00669         if (!HasSignalOnTrackdir(tile, track)) {
00670           /* if one way signal not pointing towards us, stop going in this direction => End of rail segment. */
00671           if (HasSignalOnTrackdir(tile, ReverseTrackdir(track)) && IsOnewaySignal(tile, TrackdirToTrack(track))) {
00672             bits = TRACK_BIT_NONE;
00673             break;
00674           }
00675         } else if (GetSignalStateByTrackdir(tile, track) == SIGNAL_STATE_GREEN) {
00676           /* green signal in our direction. either one way or two way. */
00677           si.state |= 3;
00678         } else {
00679           /* reached a red signal. */
00680           if (HasSignalOnTrackdir(tile, ReverseTrackdir(track))) {
00681             /* two way red signal. unless we passed another green signal on the way,
00682              * stop going in this direction => End of rail segment.
00683              * this is to prevent us from going into a full platform. */
00684             if (!(si.state & 1)) {
00685               bits = TRACK_BIT_NONE;
00686               break;
00687             }
00688           }
00689           if (!(si.state & 2)) {
00690             /* Is this the first signal we see? And it's red... add penalty */
00691             si.cur_length += 10 * DIAG_FACTOR;
00692             si.state += 2; // remember that we added penalty.
00693             /* Because we added a penalty, we can't just continue as usual.
00694              * Need to get out and let A* do it's job with
00695              * possibly finding an even shorter path. */
00696             break;
00697           }
00698         }
00699 
00700         if (tpf->enum_proc(tile, tpf->userdata, si.first_track, si.cur_length))
00701           return; // Don't process this tile any further
00702       }
00703 
00704       /* continue with the next track */
00705       direction = TrackdirToExitdir(track);
00706 
00707       /* safety check if we're running around chasing our tail... (infinite loop) */
00708       if (tile == tile_org) {
00709         bits = TRACK_BIT_NONE;
00710         break;
00711       }
00712     }
00713 
00714     /* There are no tracks to choose between.
00715      * Stop searching in this direction */
00716     if (bits == TRACK_BIT_NONE)
00717       continue;
00718 
00719     /****************
00720      * We got multiple tracks to choose between (intersection).
00721      * Branch the search space into several branches.
00722      ****************/
00723 
00724     /* Check if we've already visited this intersection.
00725      * If we've already visited it with a better length, then
00726      * there's no point in visiting it again. */
00727     if (!NtpVisit(tpf, tile, direction, si.cur_length))
00728       continue;
00729 
00730     /* Push all possible alternatives that we can reach from here
00731      * onto the priority heap.
00732      * 'bits' contains the tracks that we can choose between. */
00733 
00734     /* First compute the estimated distance to the target.
00735      * This is used to implement A* */
00736     estimation = 0;
00737     if (tpf->dest != 0)
00738       estimation = DistanceMoo(tile, tpf->dest);
00739 
00740     si.depth++;
00741     if (si.depth == 0)
00742       continue; // We overflowed our depth. No more searching in this direction.
00743     si.tile = tile;
00744     while (bits != TRACK_BIT_NONE) {
00745       Track track = RemoveFirstTrack(&bits);
00746       si.track = TrackEnterdirToTrackdir(track, direction);
00747       assert(si.track != 0xFF);
00748       si.priority = si.cur_length + estimation;
00749 
00750       /* out of stack items, bail out? */
00751       if (tpf->nstack >= lengthof(tpf->stack)) {
00752         DEBUG(ntp, 1, "Out of stack");
00753         break;
00754       }
00755 
00756       tpf->stack[tpf->nstack] = si;
00757       HeapifyUp(tpf);
00758     };
00759 
00760     /* If this is the first intersection, we need to fill the first_track member.
00761      * so the code outside knows which path is better.
00762      * also randomize the order in which we search through them. */
00763     if (si.depth == 1) {
00764       assert(tpf->nstack == 1 || tpf->nstack == 2 || tpf->nstack == 3);
00765       if (tpf->nstack != 1) {
00766         uint32 r = Random();
00767         if (r & 1) Swap(tpf->stack[0].track, tpf->stack[1].track);
00768         if (tpf->nstack != 2) {
00769           TrackdirByte t = tpf->stack[2].track;
00770           if (r & 2) Swap(tpf->stack[0].track, t);
00771           if (r & 4) Swap(tpf->stack[1].track, t);
00772           tpf->stack[2].first_track = tpf->stack[2].track = t;
00773         }
00774         tpf->stack[0].first_track = tpf->stack[0].track;
00775         tpf->stack[1].first_track = tpf->stack[1].track;
00776       }
00777     }
00778 
00779     /* Continue with the next from the queue... */
00780   }
00781 }
00782 
00783 
00785 void NewTrainPathfind(TileIndex tile, TileIndex dest, RailTypes railtypes, DiagDirection direction, NTPEnumProc *enum_proc, void *data)
00786 {
00787   SmallStackSafeStackAlloc<NewTrackPathFinder, 1> tpf;
00788 
00789   tpf->dest = dest;
00790   tpf->userdata = data;
00791   tpf->enum_proc = enum_proc;
00792   tpf->tracktype = TRANSPORT_RAIL;
00793   tpf->railtypes = railtypes;
00794   tpf->maxlength = min(_settings_game.pf.opf.pf_maxlength * 3, 10000);
00795   tpf->nstack = 0;
00796   tpf->new_link = tpf->links;
00797   tpf->num_links_left = lengthof(tpf->links);
00798   memset(tpf->hash_head, 0, sizeof(tpf->hash_head));
00799 
00800   NTPEnum(tpf, tile, direction);
00801 }

Generated on Sun Nov 15 15:40:13 2009 for OpenTTD by  doxygen 1.5.6