2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2011, Dave Pare, Jeff Bailey, Thomas Ruschak,
4 * Ken Stevens, Steve McClure, Markus Armbruster
6 * Empire is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
21 * See files README, COPYING and CREDITS in the root of the source
22 * tree for related information and legal notices. It is expected
23 * that future projects/authors will amend these files as needed.
27 * path.c: Empire/A* Interface code.
29 * Known contributors to this file:
32 * Thomas Ruschak, 1993
37 * Define AS_STATS for A* statistics on stderr.
39 * Define AS_NO_PATH_CACHE to disable the path cache. The path cache
40 * saves a lot of work, but uses lots of memory. It should be a
41 * significant net win, unless you run out of memory.
43 * Define AS_NO_NEIGHBOR_CACHE to disable the neighbor cache. The
44 * neighbor cache trades a modest amount of memory to save a bit of
45 * work. In its current form, it doesn't really make a difference.
56 #include "prototypes.h"
60 #define BP_ASHASHSIZE 128 /* A* queue hash table size */
61 #define BP_NEIGHBORS 6 /* max number of neighbors */
68 static int bp_path(struct as_path *pp, char *buf);
69 static int bp_neighbors(struct as_coord c, struct as_coord *cp, void *);
70 static double bp_lbcost(struct as_coord from, struct as_coord to, void *);
71 static double bp_realcost(struct as_coord from, struct as_coord to, void *);
72 static double bp_seccost(struct as_coord from, struct as_coord to, void *);
73 static int bp_coord_hash(struct as_coord c);
75 /* We use this for caching neighbors. It never changes except
76 * at reboot time (maybe) so we never need to free it */
77 static struct sctstr **neighsects;
84 bp = malloc(sizeof(*bp));
85 memset(bp, 0, sizeof(*bp));
86 bp->adp = as_init(BP_NEIGHBORS, BP_ASHASHSIZE, bp_coord_hash,
87 bp_neighbors, bp_lbcost, bp_realcost,
93 #ifndef AS_NO_NEIGHBOR_CACHE
94 if (neighsects == NULL)
95 neighsects = calloc(WORLD_SZ() * 6, sizeof(struct sctstr *));
102 * Find the best path from sector to to sector, and put the Empire movement
103 * string in path. Return 0 on success, -1 on error.
104 * FIXME unsafe by design: assumes path[] has space; buffer overrun
105 * when path gets long!
108 best_path(struct sctstr *from, struct sctstr *to, char *path, int mob_type)
110 static struct bestp *mybestpath;
116 mybestpath = bp_init();
117 adp = mybestpath->adp;
118 #ifdef AS_NO_PATH_CACHE
121 ap = as_find_cachepath(from->sct_x, from->sct_y, to->sct_x, to->sct_y);
124 adp->from.x = from->sct_x;
125 adp->from.y = from->sct_y;
126 adp->to.x = to->sct_x;
127 adp->to.y = to->sct_y;
128 mybestpath->bp_mobtype = mob_type;
130 res = as_search(adp);
132 as_stats(adp, stderr);
133 #ifndef AS_NO_NEIGHBOR_CACHE
134 fprintf(stderr, "neighbor cache %zu bytes\n",
135 WORLD_SZ() * 6 * sizeof(struct sctstr *));
143 if (bp_path(ap, path) < 0)
149 * Translate an A* path into an empire movement string. Return 0 on
150 * success, -1 on failure.
153 bp_path(struct as_path *pp, char *buf)
162 dx = np->c.x - pp->c.x;
163 /* deal with wraparound from non-neg coords */
168 dy = np->c.y - pp->c.y;
173 for (n = 1; n <= 6; n++)
174 if (dx == diroff[n][0] && dy == diroff[n][1])
188 * Find coords neighboring this sector; return number of such
189 * coords, and coordinartes themselves in an array pointed
191 * XXX need to check ownership, sector types, etc.
194 bp_neighbors(struct as_coord c, struct as_coord *cp, void *pp)
196 struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
197 struct bestp *bp = pp;
201 struct sctstr *sp, *from, **ssp;
202 /* Six pointers, just in case our cache isn't there */
203 struct sctstr *tsp[] = { NULL, NULL, NULL, NULL, NULL, NULL };
210 offset = XYOFFSET(sx, sy);
211 from = §p[offset];
213 if (neighsects == NULL)
214 ssp = (struct sctstr **)&tsp[0];
216 ssp = (struct sctstr **)&neighsects[offset * 6];
217 for (i = 1; i <= 6; i++, ssp++) {
219 /* We haven't cached this neighbor yet */
220 nx = x + diroff[i][0];
221 ny = y + diroff[i][1];
224 offset = XYOFFSET(sx, sy);
232 /* No need to calculate cost each time, just make sure we can
233 move through it. We calculate it later. */
234 if (dchr[sp->sct_type].d_mob0 < 0)
236 if (bp->bp_mobtype == MOB_RAIL && !SCT_HAS_RAIL(sp))
238 if (sp->sct_own != from->sct_own)
248 * Compute a lower-bound on the cost from "from" to "to".
252 bp_lbcost(struct as_coord from, struct as_coord to, void *pp)
254 struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
255 struct bestp *bp = pp;
256 int x, y, sx, sy, offset;
262 offset = XYOFFSET(sx, sy);
263 return sector_mcost(§p[offset], bp->bp_mobtype);
267 * Compute the real cost to move from "from" to "to".
270 bp_realcost(struct as_coord from, struct as_coord to, void *pp)
272 return bp_lbcost(from, to, pp);
276 * Tie breaker secondary metric (only used when lower bound costs
281 bp_seccost(struct as_coord from, struct as_coord to, void *pp)
283 return mapdist((coord)from.x, (coord)from.y,
284 (coord)to.x, (coord)to.y);
288 * Hash a coordinate into an integer.
291 bp_coord_hash(struct as_coord c)
293 return ((abs(c.x) + 1) << 3) ^ abs(c.y);
297 bp_enable_cachepath(void)
299 #ifndef AS_NO_PATH_CACHE
300 as_enable_cachepath();
305 bp_disable_cachepath(void)
307 #ifndef AS_NO_PATH_CACHE
308 as_disable_cachepath();
313 bp_clear_cachepath(void)
315 #ifndef AS_NO_PATH_CACHE
316 as_clear_cachepath();
321 pathcost(struct sctstr *start, char *path, int mob_type)
323 struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
340 if (CANT_HAPPEN(i >= sizeof(dirindex) / sizeof(*dirindex)))
343 if (CANT_HAPPEN(o < 0))
349 offset = XYOFFSET(sx, sy);
351 cost += sector_mcost(sp, mob_type);
359 BestDistPath(char *path,
361 struct sctstr *to, double *cost)
363 return BestLandPath(path, from, to, cost, MOB_MOVE);
367 BestLandPath(char *path,
369 struct sctstr *to, double *cost, int mob_type)
375 if (best_path(from, to, path, mob_type) < 0)
377 *cost = pathcost(from, path, mob_type);
378 length = strlen(path);
380 path[length + 1] = '\0';
385 BestShipPath(char *path, int fx, int fy, int tx, int ty, int owner)
389 map = ef_ptr(EF_BMAP, owner);
392 return bestownedpath(path, map, fx, fy, tx, ty, owner);
396 BestAirPath(char *path, int fx, int fy, int tx, int ty)
398 return bestownedpath(path, NULL, fx, fy, tx, ty, -1);