moved pathfinding to separate file

diff --git a/astar.c b/astar.c
new file mode 100644 (file)
index 0000000..37bc404
--- /dev/null
+++ b/astar.c
@@ -0,0 +1,161 @@
+#include "hexmap.h"
+
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+struct astar_hex {
+       int hex;
+       int f, g, h;
+       int parent;
+};
+
+struct astar {
+       int open, closed; /* how many in open or closed */
+       int closedroom, openroom; /* how much is malloced */
+       struct astar_hex *openlist;
+       struct astar_hex *closedlist;
+       int known, index;
+       int error;
+};
+
+static void astar_init(struct astar *state) {
+       state->open = 0;
+       state->closed = 0;
+       state->closedroom = 0;
+       state->openroom = 0;
+       state->openlist = 0;
+       state->closedlist = 0;
+       state->error = 0;
+       state->known = 0;
+       state->index = 0;
+
+       return;
+}
+
+static void removeopen(struct astar *s, int hex) {
+       int index;
+
+       if (s->error) return;
+       if (s->open == 0) return;
+
+       if (s->known != hex) {
+               for (index = 0; index < s->open; index++) {
+                       if (s->openlist[index].hex == hex) break;
+               }
+       } else {
+               index = s->index;
+               s->known = 0; s->index = 0;
+       }
+       s->openlist[index] = s->openlist[open];
+       s->open--;
+}
+
+static void addopen(struct astar *s, int hex) {
+       struct astar_hex *mem;
+       if (s->error) return;
+
+       if (s->open + 1 > s->openroom) {
+               mem = realloc(s->openlist, s->openroom * 2 * sizeof *mem);
+               if (mem == NULL) {
+                       s->error = errno;
+                       return;
+               }
+               state->openlist = mem;
+               s->openroom = s->openroom * 2;
+       }
+
+       s->openlist[s->open].hex = hex;
+       s->openlist[s->open].f = 0;
+       s->openlist[s->open].g = 0;
+       s->openlist[s->open].h = 0;
+       s->known = hex;
+       s->index = s->open;
+       s->open = s->open + 1;
+}
+
+int lowrank(struct astar *s) {
+       int f;
+       int hex;
+       int i;
+
+       if (!s || s->open = 0) return 0;
+
+       hex = s->openlist[0].hex;
+       f = s->openlist[0].f;
+
+       for(i=1; i < s->open; i++) {
+               if (s->openlist[i].f < f) {
+                       hex = s->openlist[i].hex;
+                       f = s->openlist[i].f;
+               }
+               /* TODO check s->openlist[i].tiebreak */
+       }
+
+       return hex;
+}
+
+static int default_metric(int a, int b) {
+       return 1;
+}
+
+/*
+ * find a path from start to end.  we use A*
+ */
+int HL_findpath(int start, int end, int psize, int *path,
+               double (*metric)(int,int)) {
+       int neighbors[6];
+       int count;
+       int cur = 0;
+       struct astar state;
+       int neighbor;
+
+       if (start == end) return 0;
+       if (!metric) metric = default_metric;
+
+       astar_init(&state);
+       addopen(&state, start);
+
+       while (1) {
+               cur = lowrank(&state);
+               if (cur == end) {
+                       break;
+               }
+               addclosed(&state, cur);
+               count = HL_hexes_at_range(cur->hex, 1, neighbors, 6);
+               for (i=0;i<count;i++) {
+                       neighbor = neighbors[i];
+                       cost = g(&state, current) + metric(current, neighbor);
+                       if (inopen(&state, neighbor) && cost < g(&state, neighbor)) {
+                               removeopen(&state, neighbor);
+                       } else
+                       if (inclosed(&state, neighbor) && cost < g(&state, neighbor)) {
+                               /* should never happen with
+                                * admissible heuristic
+                                */
+                               removeclosed(&state, neighbor);
+                       } else
+                       if (!inopen(&state, neighbor) && !inclosed(&state, neighbor)) {
+                               addopen(&state, neighbor);
+                               setg(&state, neighbor, cost);
+                               setrank(&state, neighbor, cost + h(neighbor,end));
+                               setparent(&state, neighbor, current);
+                       } else {
+                               abort();
+                       }
+               }
+       }
+
+       count = 0;
+       while (parent(&state, cur) != start) {
+               count++;
+               cur = parent(&state, cur);
+       }
+       cur = end;
+       while (parent(&state, cur) != start) {
+               path[count--] = cur;
+               cur = parent(&state, cur);
+       }
+
+}