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openttd/pathfind.c

916 lines
25 KiB
C
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/* $Id$ */
#include "stdafx.h"
#include "openttd.h"
#include "functions.h"
#include "map.h"
#include "tile.h"
#include "pathfind.h"
#include "rail.h"
#include "debug.h"
#include "variables.h"
// remember which tiles we have already visited so we don't visit them again.
static bool TPFSetTileBit(TrackPathFinder *tpf, TileIndex tile, int dir)
{
uint hash, val, offs;
TrackPathFinderLink *link, *new_link;
uint bits = 1 << dir;
if (tpf->disable_tile_hash)
return true;
hash = PATHFIND_HASH_TILE(tile);
val = tpf->hash_head[hash];
if (val == 0) {
/* unused hash entry, set the appropriate bit in it and return true
* to indicate that a bit was set. */
tpf->hash_head[hash] = bits;
tpf->hash_tile[hash] = tile;
return true;
} else if (!(val & 0x8000)) {
/* single tile */
if (tile == tpf->hash_tile[hash]) {
/* found another bit for the same tile,
* check if this bit is already set, if so, return false */
if (val & bits)
return false;
/* otherwise set the bit and return true to indicate that the bit
* was set */
tpf->hash_head[hash] = val | bits;
return true;
} else {
/* two tiles with the same hash, need to make a link */
/* allocate a link. if out of links, handle this by returning
* that a tile was already visisted. */
if (tpf->num_links_left == 0) {
return false;
}
tpf->num_links_left--;
link = tpf->new_link++;
/* move the data that was previously in the hash_??? variables
* to the link struct, and let the hash variables point to the link */
link->tile = tpf->hash_tile[hash];
tpf->hash_tile[hash] = PATHFIND_GET_LINK_OFFS(tpf, link);
link->flags = tpf->hash_head[hash];
tpf->hash_head[hash] = 0xFFFF; /* multi link */
link->next = 0xFFFF;
}
} else {
/* a linked list of many tiles,
* find the one corresponding to the tile, if it exists.
* otherwise make a new link */
offs = tpf->hash_tile[hash];
do {
link = PATHFIND_GET_LINK_PTR(tpf, offs);
if (tile == link->tile) {
/* found the tile in the link list,
* check if the bit was alrady set, if so return false to indicate that the
* bit was already set */
if (link->flags & bits)
return false;
link->flags |= bits;
return true;
}
} while ((offs=link->next) != 0xFFFF);
}
/* get here if we need to add a new link to link,
* first, allocate a new link, in the same way as before */
if (tpf->num_links_left == 0) {
return false;
}
tpf->num_links_left--;
new_link = tpf->new_link++;
/* then fill the link with the new info, and establish a ptr from the old
* link to the new one */
new_link->tile = tile;
new_link->flags = bits;
new_link->next = 0xFFFF;
link->next = PATHFIND_GET_LINK_OFFS(tpf, new_link);
return true;
}
static const byte _bits_mask[4] = {
0x19,
0x16,
0x25,
0x2A,
};
static const byte _tpf_new_direction[14] = {
0,1,0,1,2,1, 0,0,
2,3,3,2,3,0,
};
static const byte _tpf_prev_direction[14] = {
0,1,1,0,1,2, 0,0,
2,3,2,3,0,3,
};
static const byte _otherdir_mask[4] = {
0x10,
0,
0x5,
0x2A,
};
static void TPFMode2(TrackPathFinder *tpf, TileIndex tile, int direction)
{
uint bits;
int i;
RememberData rd;
int owner = -1;
/* XXX: Mode 2 is currently only used for ships, why is this code here? */
if (tpf->tracktype == TRANSPORT_RAIL) {
if (IsTileType(tile, MP_RAILWAY) || IsTileType(tile, MP_STATION) || IsTileType(tile, MP_TUNNELBRIDGE)) {
owner = GetTileOwner(tile);
/* Check if we are on the middle of a bridge (has no owner) */
if (IsTileType(tile, MP_TUNNELBRIDGE) && (_m[tile].m5 & 0xC0) == 0xC0)
owner = -1;
}
}
// This addition will sometimes overflow by a single tile.
// The use of TILE_MASK here makes sure that we still point at a valid
// tile, and then this tile will be in the sentinel row/col, so GetTileTrackStatus will fail.
tile = TILE_MASK(tile + TileOffsByDir(direction));
/* Check in case of rail if the owner is the same */
if (tpf->tracktype == TRANSPORT_RAIL) {
if (IsTileType(tile, MP_RAILWAY) || IsTileType(tile, MP_STATION) || IsTileType(tile, MP_TUNNELBRIDGE))
/* Check if we are on the middle of a bridge (has no owner) */
if (!IsTileType(tile, MP_TUNNELBRIDGE) || (_m[tile].m5 & 0xC0) != 0xC0)
if (owner != -1 && !IsTileOwner(tile, owner))
return;
}
if (++tpf->rd.cur_length > 50)
return;
bits = GetTileTrackStatus(tile, tpf->tracktype);
bits = (byte)((bits | (bits >> 8)) & _bits_mask[direction]);
if (bits == 0)
return;
assert(TileX(tile) != MapMaxX() && TileY(tile) != MapMaxY());
if ( (bits & (bits - 1)) == 0 ) {
/* only one direction */
i = 0;
while (!(bits&1))
i++, bits>>=1;
rd = tpf->rd;
goto continue_here;
}
/* several directions */
i=0;
do {
if (!(bits & 1)) continue;
rd = tpf->rd;
// Change direction 4 times only
if ((byte)i != tpf->rd.pft_var6) {
if(++tpf->rd.depth > 4) {
tpf->rd = rd;
return;
}
tpf->rd.pft_var6 = (byte)i;
}
continue_here:;
tpf->the_dir = HASBIT(_otherdir_mask[direction],i) ? (i+8) : i;
if (!tpf->enum_proc(tile, tpf->userdata, tpf->the_dir, tpf->rd.cur_length, NULL)) {
TPFMode2(tpf, tile, _tpf_new_direction[tpf->the_dir]);
}
tpf->rd = rd;
} while (++i, bits>>=1);
}
static const int8 _get_tunlen_inc[5] = { -16, 0, 16, 0, -16 };
/* Returns the end tile and the length of a tunnel. The length does not
* include the starting tile (entry), it does include the end tile (exit).
*/
FindLengthOfTunnelResult FindLengthOfTunnel(TileIndex tile, int direction)
{
FindLengthOfTunnelResult flotr;
int x,y;
byte z;
flotr.length = 0;
x = TileX(tile) * 16;
y = TileY(tile) * 16;
z = GetSlopeZ(x+8, y+8);
for(;;) {
flotr.length++;
x += _get_tunlen_inc[direction];
y += _get_tunlen_inc[direction+1];
tile = TileVirtXY(x, y);
if (IsTileType(tile, MP_TUNNELBRIDGE) &&
(_m[tile].m5 & 0xF0) == 0 && // tunnel entrance/exit
//((_m[tile].m5>>2)&3) == type && // rail/road-tunnel <-- This is not necesary to check, right?
((_m[tile].m5 & 3)^2) == direction && // entrance towards: 0 = NE, 1 = SE, 2 = SW, 3 = NW
GetSlopeZ(x+8, y+8) == z)
break;
}
flotr.tile = tile;
return flotr;
}
static const uint16 _tpfmode1_and[4] = { 0x1009, 0x16, 0x520, 0x2A00 };
static uint SkipToEndOfTunnel(TrackPathFinder *tpf, TileIndex tile, int direction)
{
FindLengthOfTunnelResult flotr;
TPFSetTileBit(tpf, tile, 14);
flotr = FindLengthOfTunnel(tile, direction);
tpf->rd.cur_length += flotr.length;
TPFSetTileBit(tpf, flotr.tile, 14);
return flotr.tile;
}
const byte _ffb_64[128] = {
0,0,1,0,2,0,1,0,
3,0,1,0,2,0,1,0,
4,0,1,0,2,0,1,0,
3,0,1,0,2,0,1,0,
5,0,1,0,2,0,1,0,
3,0,1,0,2,0,1,0,
4,0,1,0,2,0,1,0,
3,0,1,0,2,0,1,0,
0,0,0,2,0,4,4,6,
0,8,8,10,8,12,12,14,
0,16,16,18,16,20,20,22,
16,24,24,26,24,28,28,30,
0,32,32,34,32,36,36,38,
32,40,40,42,40,44,44,46,
32,48,48,50,48,52,52,54,
48,56,56,58,56,60,60,62,
};
static void TPFMode1(TrackPathFinder *tpf, TileIndex tile, int direction)
{
uint bits;
int i;
RememberData rd;
TileIndex tile_org = tile;
if (IsTileType(tile, MP_TUNNELBRIDGE) && (_m[tile].m5 & 0xF0) == 0) {
if ((_m[tile].m5 & 3) != direction || ((_m[tile].m5>>2)&3) != tpf->tracktype)
return;
tile = SkipToEndOfTunnel(tpf, tile, direction);
}
tile += TileOffsByDir(direction);
/* Check in case of rail if the owner is the same */
if (tpf->tracktype == TRANSPORT_RAIL) {
if (IsTileType(tile_org, MP_RAILWAY) || IsTileType(tile_org, MP_STATION) || IsTileType(tile_org, MP_TUNNELBRIDGE))
if (IsTileType(tile, MP_RAILWAY) || IsTileType(tile, MP_STATION) || IsTileType(tile, MP_TUNNELBRIDGE))
/* Check if we are on a bridge (middle parts don't have an owner */
if (!IsTileType(tile, MP_TUNNELBRIDGE) || (_m[tile].m5 & 0xC0) != 0xC0)
if (!IsTileType(tile_org, MP_TUNNELBRIDGE) || (_m[tile_org].m5 & 0xC0) != 0xC0)
if (GetTileOwner(tile_org) != GetTileOwner(tile))
return;
}
tpf->rd.cur_length++;
bits = GetTileTrackStatus(tile, tpf->tracktype);
if ((byte)bits != tpf->var2) {
bits &= _tpfmode1_and[direction];
bits = bits | (bits>>8);
}
bits &= 0xBF;
if (bits != 0) {
if (!tpf->disable_tile_hash || (tpf->rd.cur_length <= 64 && (KILL_FIRST_BIT(bits) == 0 || ++tpf->rd.depth <= 7))) {
do {
i = FIND_FIRST_BIT(bits);
bits = KILL_FIRST_BIT(bits);
tpf->the_dir = (_otherdir_mask[direction] & (byte)(1 << i)) ? (i+8) : i;
rd = tpf->rd;
if (TPFSetTileBit(tpf, tile, tpf->the_dir) &&
!tpf->enum_proc(tile, tpf->userdata, tpf->the_dir, tpf->rd.cur_length, &tpf->rd.pft_var6) ) {
TPFMode1(tpf, tile, _tpf_new_direction[tpf->the_dir]);
}
tpf->rd = rd;
} while (bits != 0);
}
}
/* the next is only used when signals are checked.
* seems to go in 2 directions simultaneously */
/* if i can get rid of this, tail end recursion can be used to minimize
* stack space dramatically. */
/* If we are doing signal setting, we must reverse at evere tile, so we
* iterate all the tracks in a signal block, even when a normal train would
* not reach it (for example, when two lines merge */
if (tpf->hasbit_13)
return;
tile = tile_org;
direction ^= 2;
bits = GetTileTrackStatus(tile, tpf->tracktype);
bits |= (bits >> 8);
if ( (byte)bits != tpf->var2) {
bits &= _bits_mask[direction];
}
bits &= 0xBF;
if (bits == 0)
return;
do {
i = FIND_FIRST_BIT(bits);
bits = KILL_FIRST_BIT(bits);
tpf->the_dir = (_otherdir_mask[direction] & (byte)(1 << i)) ? (i+8) : i;
rd = tpf->rd;
if (TPFSetTileBit(tpf, tile, tpf->the_dir) &&
!tpf->enum_proc(tile, tpf->userdata, tpf->the_dir, tpf->rd.cur_length, &tpf->rd.pft_var6) ) {
TPFMode1(tpf, tile, _tpf_new_direction[tpf->the_dir]);
}
tpf->rd = rd;
} while (bits != 0);
}
void FollowTrack(TileIndex tile, uint16 flags, byte direction, TPFEnumProc *enum_proc, TPFAfterProc *after_proc, void *data)
{
TrackPathFinder tpf;
assert(direction < 4);
/* initialize path finder variables */
tpf.userdata = data;
tpf.enum_proc = enum_proc;
tpf.new_link = tpf.links;
tpf.num_links_left = lengthof(tpf.links);
tpf.rd.cur_length = 0;
tpf.rd.depth = 0;
tpf.rd.pft_var6 = 0;
tpf.var2 = HASBIT(flags, 15) ? 0x43 : 0xFF; /* 0x8000 */
tpf.disable_tile_hash = HASBIT(flags, 12) != 0; /* 0x1000 */
tpf.hasbit_13 = HASBIT(flags, 13) != 0; /* 0x2000 */
tpf.tracktype = (byte)flags;
if (HASBIT(flags, 11)) {
tpf.rd.pft_var6 = 0xFF;
tpf.enum_proc(tile, data, 0, 0, 0);
TPFMode2(&tpf, tile, direction);
} else {
/* clear the hash_heads */
memset(tpf.hash_head, 0, sizeof(tpf.hash_head));
TPFMode1(&tpf, tile, direction);
}
if (after_proc != NULL)
after_proc(&tpf);
}
typedef struct {
TileIndex tile;
uint16 cur_length; // This is the current length to this tile.
uint16 priority; // This is the current length + estimated length to the goal.
byte track;
byte depth;
byte state;
byte first_track;
} StackedItem;
static const byte _new_track[6][4] = {
{0,0xff,8,0xff,},
{0xff,1,0xff,9,},
{0xff,2,10,0xff,},
{3,0xff,0xff,11,},
{12,4,0xff,0xff,},
{0xff,0xff,5,13,},
};
typedef struct HashLink {
TileIndex tile;
uint16 typelength;
uint16 next;
} HashLink;
typedef struct {
NTPEnumProc *enum_proc;
void *userdata;
TileIndex dest;
byte tracktype;
uint maxlength;
HashLink *new_link;
uint num_links_left;
uint nstack;
StackedItem stack[256]; // priority queue of stacked items
uint16 hash_head[0x400]; // hash heads. 0 means unused. 0xFFFC = length, 0x3 = dir
TileIndex hash_tile[0x400]; // tiles. or links.
HashLink links[0x400]; // hash links
} NewTrackPathFinder;
#define NTP_GET_LINK_OFFS(tpf, link) ((byte*)(link) - (byte*)tpf->links)
#define NTP_GET_LINK_PTR(tpf, link_offs) (HashLink*)((byte*)tpf->links + (link_offs))
#define ARR(i) tpf->stack[(i)-1]
// called after a new element was added in the queue at the last index.
// move it down to the proper position
static inline void HeapifyUp(NewTrackPathFinder *tpf)
{
StackedItem si;
int i = ++tpf->nstack;
while (i != 1 && ARR(i).priority < ARR(i>>1).priority) {
// the child element is larger than the parent item.
// swap the child item and the parent item.
si = ARR(i); ARR(i) = ARR(i>>1); ARR(i>>1) = si;
i>>=1;
}
}
// called after the element 0 was eaten. fill it with a new element
static inline void HeapifyDown(NewTrackPathFinder *tpf)
{
StackedItem si;
int i = 1, j;
int n;
assert(tpf->nstack > 0);
n = --tpf->nstack;
if (n == 0) return; // heap is empty so nothing to do?
// copy the last item to index 0. we use it as base for heapify.
ARR(1) = ARR(n+1);
while ((j=i*2) <= n) {
// figure out which is smaller of the children.
if (j != n && ARR(j).priority > ARR(j+1).priority)
j++; // right item is smaller
assert(i <= n && j <= n);
if (ARR(i).priority <= ARR(j).priority)
break; // base elem smaller than smallest, done!
// swap parent with the child
si = ARR(i); ARR(i) = ARR(j); ARR(j) = si;
i = j;
}
}
// mark a tile as visited and store the length of the path.
// if we already had a better path to this tile, return false.
// otherwise return true.
static bool NtpVisit(NewTrackPathFinder *tpf, TileIndex tile, uint dir, uint length)
{
uint hash,head;
HashLink *link, *new_link;
assert(length < 16384-1);
hash = PATHFIND_HASH_TILE(tile);
// never visited before?
if ((head=tpf->hash_head[hash]) == 0) {
tpf->hash_tile[hash] = tile;
tpf->hash_head[hash] = dir | (length << 2);
return true;
}
if (head != 0xffff) {
if (tile == tpf->hash_tile[hash] && (head & 0x3) == dir) {
// longer length
if (length >= (head >> 2)) return false;
tpf->hash_head[hash] = dir | (length << 2);
return true;
}
// two tiles with the same hash, need to make a link
// allocate a link. if out of links, handle this by returning
// that a tile was already visisted.
if (tpf->num_links_left == 0) {
DEBUG(ntp, 1) ("[NTP] no links left");
return false;
}
tpf->num_links_left--;
link = tpf->new_link++;
/* move the data that was previously in the hash_??? variables
* to the link struct, and let the hash variables point to the link */
link->tile = tpf->hash_tile[hash];
tpf->hash_tile[hash] = NTP_GET_LINK_OFFS(tpf, link);
link->typelength = tpf->hash_head[hash];
tpf->hash_head[hash] = 0xFFFF; /* multi link */
link->next = 0xFFFF;
} else {
// a linked list of many tiles,
// find the one corresponding to the tile, if it exists.
// otherwise make a new link
uint offs = tpf->hash_tile[hash];
do {
link = NTP_GET_LINK_PTR(tpf, offs);
if (tile == link->tile && (uint)(link->typelength & 0x3) == dir) {
if (length >= (uint)(link->typelength >> 2)) return false;
link->typelength = dir | (length << 2);
return true;
}
} while ((offs=link->next) != 0xFFFF);
}
/* get here if we need to add a new link to link,
* first, allocate a new link, in the same way as before */
if (tpf->num_links_left == 0) {
DEBUG(ntp, 1) ("[NTP] no links left");
return false;
}
tpf->num_links_left--;
new_link = tpf->new_link++;
/* then fill the link with the new info, and establish a ptr from the old
* link to the new one */
new_link->tile = tile;
new_link->typelength = dir | (length << 2);
new_link->next = 0xFFFF;
link->next = NTP_GET_LINK_OFFS(tpf, new_link);
return true;
}
static bool NtpCheck(NewTrackPathFinder *tpf, TileIndex tile, uint dir, uint length)
{
uint hash,head,offs;
HashLink *link;
hash = PATHFIND_HASH_TILE(tile);
head=tpf->hash_head[hash];
assert(head);
if (head != 0xffff) {
assert( tpf->hash_tile[hash] == tile && (head & 3) == dir);
assert( (head >> 2) <= length);
return length == (head >> 2);
}
// else it's a linked list of many tiles
offs = tpf->hash_tile[hash];
for(;;) {
link = NTP_GET_LINK_PTR(tpf, offs);
if (tile == link->tile && (uint)(link->typelength & 0x3) == dir) {
assert( (uint)(link->typelength >> 2) <= length);
return length == (uint)(link->typelength >> 2);
}
offs = link->next;
assert(offs != 0xffff);
}
}
static const uint16 _is_upwards_slope[15] = {
0, // no tileh
(1 << TRACKDIR_DIAG1_SW) | (1 << TRACKDIR_DIAG2_NW), // 1
(1 << TRACKDIR_DIAG1_SW) | (1 << TRACKDIR_DIAG2_SE), // 2
(1 << TRACKDIR_DIAG1_SW), // 3
(1 << TRACKDIR_DIAG1_NE) | (1 << TRACKDIR_DIAG2_SE), // 4
0, // 5
(1 << TRACKDIR_DIAG2_SE), // 6
0, // 7
(1 << TRACKDIR_DIAG1_NE) | (1 << TRACKDIR_DIAG2_NW), // 8,
(1 << TRACKDIR_DIAG2_NW), // 9
0, //10
0, //11,
(1 << TRACKDIR_DIAG1_NE), //12
0, //13
0, //14
};
#define DIAG_FACTOR 3
#define STR_FACTOR 2
static uint DistanceMoo(TileIndex t0, TileIndex t1)
{
const uint dx = abs(TileX(t0) - TileX(t1));
const uint dy = abs(TileY(t0) - TileY(t1));
const uint straightTracks = 2 * min(dx, dy); /* The number of straight (not full length) tracks */
/* OPTIMISATION:
* Original: diagTracks = max(dx, dy) - min(dx,dy);
* Proof:
* (dx-dy) - straightTracks == (min + max) - straightTracks = min + // max - 2 * min = max - min */
const uint diagTracks = dx + dy - straightTracks; /* The number of diagonal (full tile length) tracks. */
return diagTracks*DIAG_FACTOR + straightTracks*STR_FACTOR;
}
// These has to be small cause the max length of a track
// is currently limited to 16384
static const byte _length_of_track[16] = {
DIAG_FACTOR,DIAG_FACTOR,STR_FACTOR,STR_FACTOR,STR_FACTOR,STR_FACTOR,0,0,
DIAG_FACTOR,DIAG_FACTOR,STR_FACTOR,STR_FACTOR,STR_FACTOR,STR_FACTOR,0,0
};
// new more optimized pathfinder for trains...
// Tile is the tile the train is at.
// direction is the tile the train is moving towards.
static void NTPEnum(NewTrackPathFinder *tpf, TileIndex tile, uint direction)
{
uint bits, tile_org, track;
StackedItem si;
FindLengthOfTunnelResult flotr;
int estimation;
// Need to have a special case for the start.
// We shouldn't call the callback for the current tile.
si.cur_length = 1; // Need to start at 1 cause 0 is a reserved value.
si.depth = 0;
si.state = 0;
si.first_track = 0xFF;
goto start_at;
for(;;) {
// Get the next item to search from from the priority queue
do {
if (tpf->nstack == 0)
return; // nothing left? then we're done!
si = tpf->stack[0];
tile = si.tile;
HeapifyDown(tpf);
// Make sure we havn't already visited this tile.
} while (!NtpCheck(tpf, tile, _tpf_prev_direction[si.track], si.cur_length));
// Add the length of this track.
si.cur_length += _length_of_track[si.track];
callback_and_continue:
if (tpf->enum_proc(tile, tpf->userdata, si.first_track, si.cur_length))
return;
assert(si.track <= 13);
direction = _tpf_new_direction[si.track];
start_at:
// If the tile is the entry tile of a tunnel, and we're not going out of the tunnel,
// need to find the exit of the tunnel.
if (IsTileType(tile, MP_TUNNELBRIDGE)) {
if ((_m[tile].m5 & 0xF0) == 0 &&
(uint)(_m[tile].m5 & 3) != (direction ^ 2)) {
/* This is a tunnel tile */
/* We are not just driving out of the tunnel */
if ( (uint)(_m[tile].m5 & 3) != direction || ((_m[tile].m5>>1)&6) != tpf->tracktype)
/* We are not driving into the tunnel, or it
* is an invalid tunnel */
continue;
flotr = FindLengthOfTunnel(tile, direction);
si.cur_length += flotr.length * DIAG_FACTOR;
tile = flotr.tile;
// tile now points to the exit tile of the tunnel
}
}
// This is a special loop used to go through
// a rail net and find the first intersection
tile_org = tile;
for(;;) {
assert(direction <= 3);
tile += TileOffsByDir(direction);
// too long search length? bail out.
if (si.cur_length >= tpf->maxlength) {
DEBUG(ntp,1) ("[NTP] cur_length too big");
bits = 0;
break;
}
// Not a regular rail tile?
// Then we can't use the code below, but revert to more general code.
if (!IsTileType(tile, MP_RAILWAY) || !IsPlainRailTile(tile)) {
// We found a tile which is not a normal railway tile.
// Determine which tracks that exist on this tile.
bits = GetTileTrackStatus(tile, TRANSPORT_RAIL) & _tpfmode1_and[direction];
bits = (bits | (bits >> 8)) & 0x3F;
// Check that the tile contains exactly one track
if (bits == 0 || KILL_FIRST_BIT(bits) != 0)
break;
///////////////////
// If we reach here, the tile has exactly one track.
// tile - index to a tile that is not rail tile, but still straight (with optional signals)
// bits - bitmask of which track that exist on the tile (exactly one bit is set)
// direction - which direction are we moving in?
///////////////////
si.track = _new_track[FIND_FIRST_BIT(bits)][direction];
si.cur_length += _length_of_track[si.track];
goto callback_and_continue;
}
// Regular rail tile, determine which tracks exist.
bits = _m[tile].m5 & _bits_mask[direction];
// The tile has no reachable tracks, or
// does the tile contain more than one track?
if (bits == 0 || KILL_FIRST_BIT(_m[tile].m5 & 0x3F) != 0)
break;
// If we reach here, the tile has exactly one track, and this
// track is reachable.
track = _new_track[FIND_FIRST_BIT(bits)][direction];
assert(track != 0xff);
si.cur_length += _length_of_track[track];
// Check if this rail is an upwards slope. If it is, then add a penalty.
// Small optimization here.. if (track&7)>1 then it can't be a slope so we avoid calling GetTileSlope
if ((track & 7) <= 1 && (_is_upwards_slope[GetTileSlope(tile, NULL)] & (1 << track)) ) {
// upwards slope. add some penalty.
si.cur_length += 4*DIAG_FACTOR;
}
// railway tile with signals..?
if (HasSignals(tile)) {
byte m3;
m3 = _m[tile].m3;
if (!(m3 & SignalAlongTrackdir(track))) {
// if one way signal not pointing towards us, stop going in this direction.
if (m3 & SignalAgainstTrackdir(track)) {
bits = 0;
break;
}
} else if (_m[tile].m2 & SignalAlongTrackdir(track)) {
// green signal in our direction. either one way or two way.
si.state |= 3;
} else {
// reached a red signal.
if (m3 & SignalAgainstTrackdir(track)) {
// two way red signal. unless we passed another green signal on the way,
// stop going in this direction.
// this is to prevent us from going into a full platform.
if (!(si.state&1)) {
bits = 0;
break;
}
}
if (!(si.state & 2)) {
// Is this the first signal we see? And it's red... add penalty
si.cur_length += 10*DIAG_FACTOR;
si.state += 2; // remember that we added penalty.
// Because we added a penalty, we can't just continue as usual.
// Need to get out and let A* do it's job with
// possibly finding an even shorter path.
break;
}
}
if (tpf->enum_proc(tile, tpf->userdata, si.first_track, si.cur_length))
return;
}
// continue with the next track
direction = _tpf_new_direction[track];
// safety check if we're running around chasing our tail... (infinite loop)
if (tile == tile_org) {
bits = 0;
break;
}
}
// There are no tracks to choose between.
// Stop searching in this direction
if (bits == 0)
continue;
////////////////
// We got multiple tracks to choose between (intersection).
// Branch the search space into several branches.
////////////////
// Check if we've already visited this intersection.
// If we've already visited it with a better length, then
// there's no point in visiting it again.
if (!NtpVisit(tpf, tile, direction, si.cur_length))
continue;
// Push all possible alternatives that we can reach from here
// onto the priority heap.
// 'bits' contains the tracks that we can choose between.
// First compute the estimated distance to the target.
// This is used to implement A*
estimation = 0;
if (tpf->dest != 0)
estimation = DistanceMoo(tile, tpf->dest);
si.depth++;
si.tile = tile;
do {
si.track = _new_track[FIND_FIRST_BIT(bits)][direction];
si.priority = si.cur_length + estimation;
// out of stack items, bail out?
if (tpf->nstack >= lengthof(tpf->stack)) {
DEBUG(ntp, 1) ("[NTP] out of stack");
break;
}
tpf->stack[tpf->nstack] = si;
HeapifyUp(tpf);
} while ((bits = KILL_FIRST_BIT(bits)) != 0);
// If this is the first intersection, we need to fill the first_track member.
// so the code outside knows which path is better.
// also randomize the order in which we search through them.
if (si.depth == 1) {
assert(tpf->nstack == 1 || tpf->nstack == 2 || tpf->nstack == 3);
if (tpf->nstack != 1) {
uint32 r = Random();
if (r&1) swap_byte(&tpf->stack[0].track, &tpf->stack[1].track);
if (tpf->nstack != 2) {
byte t = tpf->stack[2].track;
if (r&2) swap_byte(&tpf->stack[0].track, &t);
if (r&4) swap_byte(&tpf->stack[1].track, &t);
tpf->stack[2].first_track = tpf->stack[2].track = t;
}
tpf->stack[0].first_track = tpf->stack[0].track;
tpf->stack[1].first_track = tpf->stack[1].track;
}
}
// Continue with the next from the queue...
}
}
// new pathfinder for trains. better and faster.
void NewTrainPathfind(TileIndex tile, TileIndex dest, byte direction, NTPEnumProc *enum_proc, void *data)
{
NewTrackPathFinder tpf;
tpf.dest = dest;
tpf.userdata = data;
tpf.enum_proc = enum_proc;
tpf.tracktype = 0;
tpf.maxlength = min(_patches.pf_maxlength * 3, 10000);
tpf.nstack = 0;
tpf.new_link = tpf.links;
tpf.num_links_left = lengthof(tpf.links);
memset(tpf.hash_head, 0, sizeof(tpf.hash_head));
NTPEnum(&tpf, tile, direction);
}
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