/*
* This file has the core function for AyStar
* AyStar is a fast pathfinding routine and is used for things like
* AI_pathfinding and Train_pathfinding.
* For more information about AyStar (A* Algorithm), you can look at
* http://en.wikipedia.org/wiki/A-star_search_algorithm
*/
/*
* Friendly reminder:
* Call (AyStar).free() when you are done with Aystar. It reserves a lot of memory
* And when not free'd, it can cause system-crashes.
* Also remember that when you stop an algorithm before it is finished, your
* should call clear() yourself!
*/
#include "stdafx.h"
#include "ttd.h"
#include "aystar.h"
// This looks in the Hash if a node exists in ClosedList
// If so, it returns the PathNode, else NULL
static PathNode *AyStarMain_ClosedList_IsInList(AyStar *aystar, AyStarNode *node)
{
return (PathNode*)Hash_Get(&aystar->ClosedListHash, node->tile, node->direction);
}
// This adds a node to the ClosedList
// It makes a copy of the data
static void AyStarMain_ClosedList_Add(AyStar *aystar, PathNode *node)
{
// Add a node to the ClosedList
PathNode *new_node = malloc(sizeof(PathNode));
*new_node = *node;
Hash_Set(&aystar->ClosedListHash, node->node.tile, node->node.direction, new_node);
}
// Checks if a node is in the OpenList
// If so, it returns the OpenListNode, else NULL
static OpenListNode *AyStarMain_OpenList_IsInList(AyStar *aystar, AyStarNode *node)
{
return (OpenListNode*)Hash_Get(&aystar->OpenListHash, node->tile, node->direction);
}
// Gets the best node from OpenList
// returns the best node, or NULL of none is found
// Also it deletes the node from the OpenList
static OpenListNode *AyStarMain_OpenList_Pop(AyStar *aystar)
{
// Return the item the Queue returns.. the best next OpenList item.
OpenListNode* res = (OpenListNode*)aystar->OpenListQueue.pop(&aystar->OpenListQueue);
if (res != NULL)
Hash_Delete(&aystar->OpenListHash, res->path.node.tile, res->path.node.direction);
return res;
}
// Adds a node to the OpenList
// It makes a copy of node, and puts the pointer of parent in the struct
static void AyStarMain_OpenList_Add(AyStar *aystar, PathNode *parent, AyStarNode *node, int f, int g, int userdata)
{
// Add a new Node to the OpenList
OpenListNode* new_node = malloc(sizeof(OpenListNode));
new_node->g = g;
new_node->path.parent = parent;
new_node->path.node = *node;
Hash_Set(&aystar->OpenListHash, node->tile, node->direction, new_node);
// Add it to the queue
aystar->OpenListQueue.push(&aystar->OpenListQueue, new_node, f);
}
/*
* Checks one tile and calculate his f-value
* return values:
* AYSTAR_DONE : indicates we are done
*/
int AyStarMain_CheckTile(AyStar *aystar, AyStarNode *current, OpenListNode *parent) {
int new_f, new_g, new_h;
PathNode *closedlist_parent;
OpenListNode *check;
// Check the new node against the ClosedList
if (AyStarMain_ClosedList_IsInList(aystar, current) != NULL) return AYSTAR_DONE;
// Calculate the G-value for this node
new_g = aystar->CalculateG(aystar, current, parent);
// If the value was INVALID_NODE, we don't do anything with this node
if (new_g == AYSTAR_INVALID_NODE) return AYSTAR_DONE;
// There should not be given any other error-code..
assert(new_g >= 0);
// Add the parent g-value to the new g-value
new_g += parent->g;
if (aystar->max_path_cost != 0 && (uint)new_g > aystar->max_path_cost) return AYSTAR_DONE;
// Calculate the h-value
new_h = aystar->CalculateH(aystar, current, parent);
// There should not be given any error-code..
assert(new_h >= 0);
// The f-value if g + h
new_f = new_g + new_h;
// Get the pointer to the parent in the ClosedList (the currentone is to a copy of the one in the OpenList)
closedlist_parent = AyStarMain_ClosedList_IsInList(aystar, &parent->path.node);
// Check if this item is already in the OpenList
if ((check = AyStarMain_OpenList_IsInList(aystar, current)) != NULL) {
uint i;
// Yes, check if this g value is lower..
if (new_g > check->g) return AYSTAR_DONE;
aystar->OpenListQueue.del(&aystar->OpenListQueue, check, 0);
// It is lower, so change it to this item
check->g = new_g;
check->path.parent = closedlist_parent;
/* Copy user data, will probably have changed */
for (i=0;i<lengthof(current->user_data);i++)
check->path.node.user_data[i] = current->user_data[i];
// Readd him in the OpenListQueue
aystar->OpenListQueue.push(&aystar->OpenListQueue, check, new_f);
} else {
// A new node, add him to the OpenList
AyStarMain_OpenList_Add(aystar, closedlist_parent, current, new_f, new_g, 0);
}
return AYSTAR_DONE;
}
/*
* This function is the core of AyStar. It handles one item and checks
* his neighbour items. If they are valid, they are added to be checked too.
* return values:
* AYSTAR_EMPTY_OPENLIST : indicates all items are tested, and no path
* has been found.
* AYSTAR_LIMIT_REACHED : Indicates that the max_nodes limit has been
* reached.
* AYSTAR_FOUND_END_NODE : indicates we found the end. Path_found now is true, and in path is the path found.
* AYSTAR_STILL_BUSY : indicates we have done this tile, did not found the path yet, and have items left to try.
*/
int AyStarMain_Loop(AyStar *aystar) {
int i, r;
// Get the best node from OpenList
OpenListNode *current = AyStarMain_OpenList_Pop(aystar);
// If empty, drop an error
if (current == NULL) return AYSTAR_EMPTY_OPENLIST;
// Check for end node and if found, return that code
if (aystar->EndNodeCheck(aystar, ¤t->path.node) == AYSTAR_FOUND_END_NODE) {
if (aystar->FoundEndNode != NULL)
aystar->FoundEndNode(aystar, current);
free(current);
return AYSTAR_FOUND_END_NODE;
}
// Add the node to the ClosedList
AyStarMain_ClosedList_Add(aystar, ¤t->path);
// Load the neighbours
aystar->GetNeighbours(aystar, current);
// Go through all neighbours
for (i=0;i<aystar->num_neighbours;i++) {
// Check and add them to the OpenList if needed
r = aystar->checktile(aystar, &aystar->neighbours[i], current);
}
// Free the node
free(current);
if (aystar->max_search_nodes != 0 && Hash_Size(&aystar->ClosedListHash) >= aystar->max_search_nodes)
/* We've expanded enough nodes */
return AYSTAR_LIMIT_REACHED;
else
// Return that we are still busy
return AYSTAR_STILL_BUSY;
}
/*
* This function frees the memory it allocated
*/
void AyStarMain_Free(AyStar *aystar) {
aystar->OpenListQueue.free(&aystar->OpenListQueue, false);
/* 2nd argument above is false, below is true, to free the values only
* once */
delete_Hash(&aystar->OpenListHash, true);
delete_Hash(&aystar->ClosedListHash, true);
#ifdef AYSTAR_DEBUG
printf("[AyStar] Memory free'd\n");
#endif
}
/*
* This function make the memory go back to zero
* This function should be called when you are using the same instance again.
*/
void AyStarMain_Clear(AyStar *aystar) {
// Clean the Queue, but not the elements within. That will be done by
// the hash.
aystar->OpenListQueue.clear(&aystar->OpenListQueue, false);
// Clean the hashes
clear_Hash(&aystar->OpenListHash, true);
clear_Hash(&aystar->ClosedListHash, true);
#ifdef AYSTAR_DEBUG
printf("[AyStar] Cleared AyStar\n");
#endif
}
/*
* This is the function you call to run AyStar.
* return values:
* AYSTAR_FOUND_END_NODE : indicates we found an end node.
* AYSTAR_NO_PATH : indicates that there was no path found.
* AYSTAR_STILL_BUSY : indicates we have done some checked, that we did not found the path yet, and that we still have items left to try.
* When the algorithm is done (when the return value is not AYSTAR_STILL_BUSY)
* aystar->clear() is called. Note that when you stop the algorithm halfway,
* you should still call clear() yourself!
*/
int AyStarMain_Main(AyStar *aystar) {
int r, i = 0;
// Loop through the OpenList
// Quit if result is no AYSTAR_STILL_BUSY or is more than loops_per_tick
while ((r = aystar->loop(aystar)) == AYSTAR_STILL_BUSY && (aystar->loops_per_tick == 0 || ++i < aystar->loops_per_tick)) { }
#ifdef AYSTAR_DEBUG
if (r == AYSTAR_FOUND_END_NODE)
printf("[AyStar] Found path!\n");
else if (r == AYSTAR_EMPTY_OPENLIST)
printf("[AyStar] OpenList run dry, no path found\n");
else if (r == AYSTAR_LIMIT_REACHED)
printf("[AyStar] Exceeded search_nodes, no path found\n");
#endif
if (r != AYSTAR_STILL_BUSY)
/* We're done, clean up */
aystar->clear(aystar);
// Check result-value
if (r == AYSTAR_FOUND_END_NODE) return AYSTAR_FOUND_END_NODE;
// Check if we have some left in the OpenList
if (r == AYSTAR_EMPTY_OPENLIST || r == AYSTAR_LIMIT_REACHED) return AYSTAR_NO_PATH;
// Return we are still busy
return AYSTAR_STILL_BUSY;
}
/*
* Adds a node from where to start an algorithm. Multiple nodes can be added
* if wanted. You should make sure that clear() is called before adding nodes
* if the AyStar has been used before (though the normal main loop calls
* clear() automatically when the algorithm finishes
*/
void AyStarMain_AddStartNode(AyStar *aystar, AyStarNode *start_node) {
#ifdef AYSTAR_DEBUG
printf("[AyStar] Starting A* Algorithm from node (%d, %d, %d)\n",
TileX(start_node->tile), TileY(start_node->tile), start_node->direction);
#endif
AyStarMain_OpenList_Add(aystar, NULL, start_node, 0, 0, 0);
}
void init_AyStar(AyStar* aystar, Hash_HashProc hash, uint num_buckets) {
// Allocated the Hash for the OpenList and ClosedList
init_Hash(&aystar->OpenListHash, hash, num_buckets);
init_Hash(&aystar->ClosedListHash, hash, num_buckets);
// Set up our sorting queue
// BinaryHeap allocates a block of 1024 nodes
// When thatone gets full it reserves an otherone, till this number
// That is why it can stay this high
init_BinaryHeap(&aystar->OpenListQueue, 102400);
aystar->addstart = AyStarMain_AddStartNode;
aystar->main = AyStarMain_Main;
aystar->loop = AyStarMain_Loop;
aystar->free = AyStarMain_Free;
aystar->clear = AyStarMain_Clear;
aystar->checktile = AyStarMain_CheckTile;
}