2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2010, Dave Pare, Jeff Bailey, Thomas Ruschak,
4 * Ken Stevens, Steve McClure
6 * This program 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 2 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, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 * See files README, COPYING and CREDITS in the root of the source
23 * tree for related information and legal notices. It is expected
24 * that future projects/authors will amend these files as needed.
28 * path.c: Empire/A* Interface code.
29 * Define AS_STATS for A* statistics.
31 * Known contributors to this file:
34 * Thomas Ruschak, 1993
46 #include "prototypes.h"
50 #define BP_ASHASHSIZE 128 /* A* queue hash table size */
51 #define BP_NEIGHBORS 6 /* max number of neighbors */
58 static int bp_path(struct as_path *pp, char *buf);
59 static int bp_neighbors(struct as_coord c, struct as_coord *cp, void *);
60 static double bp_lbcost(struct as_coord from, struct as_coord to, void *);
61 static double bp_realcost(struct as_coord from, struct as_coord to, void *);
62 static double bp_seccost(struct as_coord from, struct as_coord to, void *);
63 static int bp_coord_hash(struct as_coord c);
65 /* We use this for caching neighbors. It never changes except
66 * at reboot time (maybe) so we never need to free it */
67 static struct sctstr **neighsects;
74 bp = malloc(sizeof(*bp));
75 memset(bp, 0, sizeof(*bp));
76 bp->adp = as_init(BP_NEIGHBORS, BP_ASHASHSIZE, bp_coord_hash,
77 bp_neighbors, bp_lbcost, bp_realcost,
83 if (neighsects == NULL)
84 neighsects = calloc(WORLD_SZ() * 6, sizeof(struct sctstr *));
90 * Find the best path from sector to to sector, and put the Empire movement
91 * string in path. Return 0 on success, -1 on error.
92 * FIXME unsafe by design: assumes path[] has space; buffer overrun
93 * when path gets long!
96 best_path(struct sctstr *from, struct sctstr *to, char *path, int mob_type)
98 static struct bestp *mybestpath;
103 mybestpath = bp_init();
104 adp = mybestpath->adp;
105 ap = as_find_cachepath(from->sct_x, from->sct_y, to->sct_x, to->sct_y);
107 adp->from.x = from->sct_x;
108 adp->from.y = from->sct_y;
109 adp->to.x = to->sct_x;
110 adp->to.y = to->sct_y;
111 mybestpath->bp_mobtype = mob_type;
113 if (as_search(adp) < 0)
118 if (bp_path(ap, path) < 0)
122 as_stats(adp, stderr);
123 fprintf(stderr, "neighbor cache %zu bytes\n",
124 WORLD_SZ() * 6 * sizeof(struct sctstr *));
125 #endif /* AS_STATS */
130 * Translate an A* path into an empire movement string. Return 0 on
131 * success, -1 on failure.
134 bp_path(struct as_path *pp, char *buf)
143 dx = np->c.x - pp->c.x;
144 /* deal with wraparound from non-neg coords */
149 dy = np->c.y - pp->c.y;
154 for (n = 1; n <= 6; n++)
155 if (dx == diroff[n][0] && dy == diroff[n][1])
169 * Find coords neighboring this sector; return number of such
170 * coords, and coordinartes themselves in an array pointed
172 * XXX need to check ownership, sector types, etc.
175 bp_neighbors(struct as_coord c, struct as_coord *cp, void *pp)
177 struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
178 struct bestp *bp = pp;
182 struct sctstr *sp, *from, **ssp;
183 /* Six pointers, just in case our cache isn't there */
184 struct sctstr *tsp[] = { NULL, NULL, NULL, NULL, NULL, NULL };
191 offset = XYOFFSET(sx, sy);
192 from = §p[offset];
194 if (neighsects == NULL)
195 ssp = (struct sctstr **)&tsp[0];
197 ssp = (struct sctstr **)&neighsects[offset * 6];
198 for (i = 1; i <= 6; i++, ssp++) {
200 /* We haven't cached this neighbor yet */
201 nx = x + diroff[i][0];
202 ny = y + diroff[i][1];
205 offset = XYOFFSET(sx, sy);
210 sx = XNORM(sp->sct_x);
211 sy = YNORM(sp->sct_y);
213 /* No need to calculate cost each time, just make sure we can
214 move through it. We calculate it later. */
215 if (dchr[sp->sct_type].d_mob0 < 0)
217 if (bp->bp_mobtype == MOB_RAIL && !SCT_HAS_RAIL(sp))
219 if (sp->sct_own != from->sct_own)
229 * Compute a lower-bound on the cost from "from" to "to".
233 bp_lbcost(struct as_coord from, struct as_coord to, void *pp)
235 struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
236 struct bestp *bp = pp;
237 int x, y, sx, sy, offset;
243 offset = XYOFFSET(sx, sy);
244 return sector_mcost(§p[offset], bp->bp_mobtype);
248 * Compute the real cost to move from "from" to "to".
251 bp_realcost(struct as_coord from, struct as_coord to, void *pp)
253 return bp_lbcost(from, to, pp);
257 * Tie breaker secondary metric (only used when lower bound costs
262 bp_seccost(struct as_coord from, struct as_coord to, void *pp)
264 return mapdist((coord)from.x, (coord)from.y,
265 (coord)to.x, (coord)to.y);
269 * Hash a coordinate into an integer.
272 bp_coord_hash(struct as_coord c)
274 return ((abs(c.x) + 1) << 3) ^ abs(c.y);
278 bp_enable_cachepath(void)
280 as_enable_cachepath();
284 bp_disable_cachepath(void)
286 as_disable_cachepath();
290 bp_clear_cachepath(void)
292 as_clear_cachepath();
296 pathcost(struct sctstr *start, char *path, int mob_type)
298 struct sctstr *sectp = (void *)empfile[EF_SECTOR].cache;
315 if (CANT_HAPPEN(i >= sizeof(dirindex) / sizeof(*dirindex)))
318 if (CANT_HAPPEN(o < 0))
324 offset = XYOFFSET(sx, sy);
326 cost += sector_mcost(sp, mob_type);
334 BestDistPath(char *path,
336 struct sctstr *to, double *cost)
338 return BestLandPath(path, from, to, cost, MOB_MOVE);
342 BestLandPath(char *path,
344 struct sctstr *to, double *cost, int mob_type)
350 if (best_path(from, to, path, mob_type) < 0)
352 *cost = pathcost(from, path, mob_type);
353 length = strlen(path);
355 path[length + 1] = '\0';
360 BestShipPath(char *path, int fx, int fy, int tx, int ty, int owner)
364 map = ef_ptr(EF_BMAP, owner);
367 return bestownedpath(path, map, fx, fy, tx, ty, owner);
371 BestAirPath(char *path, int fx, int fy, int tx, int ty)
373 return bestownedpath(path, NULL, fx, fy, tx, ty, -1);