OpenTTD: src/pathfinder/npf/aystar.h File Reference

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aystar.h File Reference

This file has the header for AyStar. More...

`#include "queue.h"`
`#include "../../tile_type.h"`
`#include "../../track_type.h"`

Go to the source code of this file.

## Data Structures
struct | AyStarNode
| Node in the search. More...
struct | PathNode
| A path of nodes. More...
struct | OpenListNode
| Internal node. More...
struct | AyStar
| AyStar search algorithm struct. More...

## Typedefs
typedef int32 | AyStar_EndNodeCheck (AyStar *aystar, OpenListNode *current)
| Check whether the end-tile is found.
typedef int32 | AyStar_CalculateG (AyStar *aystar, AyStarNode *current, OpenListNode *parent)
| Calculate the G-value for the AyStar algorithm.
typedef int32 | AyStar_CalculateH (AyStar *aystar, AyStarNode *current, OpenListNode *parent)
| Calculate the H-value for the AyStar algorithm.
typedef void | AyStar_GetNeighbours (AyStar *aystar, OpenListNode *current)
| This function requests the tiles around the current tile and put them in #tiles_around.
typedef void | AyStar_FoundEndNode (AyStar *aystar, OpenListNode *current)
| If the End Node is found, this function is called.

## Enumerations
enum | AystarStatus { AYSTAR_FOUND_END_NODE, AYSTAR_EMPTY_OPENLIST, AYSTAR_STILL_BUSY, AYSTAR_NO_PATH, AYSTAR_LIMIT_REACHED, AYSTAR_DONE }
| Return status of AyStar methods. More...

## Variables
static const int | AYSTAR_INVALID_NODE = -1
| Item is not valid (for example, not walkable).

## Detailed Description

This file has the header for AyStar.

AyStar is a fast path finding routine and is used for things like AI path finding and Train path finding. For more information about AyStar (A* Algorithm), you can look at http://en.wikipedia.org/wiki/A-star_search_algorithm.

Definition in file aystar.h.

## Typedef Documentation

typedef int32 AyStar_CalculateG(AyStar *aystar, AyStarNode *current, OpenListNode *parent)

Calculate the G-value for the AyStar algorithm.

Returns
  G value of the node:
  - AYSTAR_INVALID_NODE : indicates an item is not valid (e.g.: unwalkable)
  - Any value >= 0 : the g-value for this tile

Definition at line 86 of file aystar.h.

typedef int32 AyStar_CalculateH(AyStar *aystar, AyStarNode *current, OpenListNode *parent)

Calculate the H-value for the AyStar algorithm.

Mostly, this must return the distance (Manhattan way) between the current point and the end point.

Returns
  The h-value for this tile (any value >= 0)

Definition at line 93 of file aystar.h.

typedef int32 AyStar_EndNodeCheck(AyStar *aystar, OpenListNode *current)

Check whether the end-tile is found.

Parameters

  aystar | AyStar search algorithm data.
  current | Node to exam one.

Note
  The 2nd parameter should be OpenListNode, and not AyStarNode. AyStarNode is part of OpenListNode and so it could be accessed without any problems. The good part about OpenListNode is, and how AIs use it, that you can access the parent of the current node, and so check if you, for example don't try to enter the file tile with a 90-degree curve. So please, leave this an OpenListNode, it works just fine.

Returns
  Status of the node:
  - AYSTAR_FOUND_END_NODE : indicates this is the end tile
  - AYSTAR_DONE : indicates this is not the end tile (or direction was wrong)

Definition at line 78 of file aystar.h.

typedef void AyStar_FoundEndNode(AyStar *aystar, OpenListNode *current)

If the End Node is found, this function is called.

It can do, for example, calculate the route and put that in an array.

Definition at line 106 of file aystar.h.

typedef void AyStar_GetNeighbours(AyStar *aystar, OpenListNode *current)

This function requests the tiles around the current tile and put them in #tiles_around.

#tiles_around is never reset, so if you are not using directions, just leave it alone.

Warning
  Never add more tiles_around than memory allocated for it.

Definition at line 100 of file aystar.h.

## Enumeration Type Documentation

enum AystarStatus

Return status of AyStar methods.

Enumerator:

  AYSTAR_FOUND_END_NODE | An end node was found.
  AYSTAR_EMPTY_OPENLIST | All items are tested, and no path has been found.
  AYSTAR_STILL_BUSY | Some checking was done, but no path found yet, and there are still items left to try.
  AYSTAR_NO_PATH | No path to the goal was found.
  AYSTAR_LIMIT_REACHED | The #max_nodes limit has been reached, aborting search.
  AYSTAR_DONE | Not an end-tile, or wrong direction.

Definition at line 28 of file aystar.h.