2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2006, 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 * bestpath.c: Find the best path between sectors
30 * Known contributors to this file:
31 * Steve McClure, 1998-2000
35 * IMPORTANT: These routines are very selectively used in the server.
37 * "bestownedpath" is only used to determine paths for ships and planes.
39 * Callers should not be calling these directly anymore. They should use
40 * the "BestShipPath", "BestAirPath", "BestLandPath" and "BestDistPath"
41 * functions. Note that those last two use the A* algorithms to find
55 static int owned_and_navigable(s_char *, int, int, s_char *, int);
57 #define MAXROUTE 100 /* return '?' if path longer than this */
58 #define valid(x,y) (((x^y)&1)==0)
60 /* ________________________________________________________________
62 ** bestpath(x1,y1,x2,y2,(s_char *)terrain);
64 ** Calculate routing string to get from sector [x1,y1] to sector [x2,y2]
65 ** via a specified type of terrain.
69 ** x1,y1 starting coordinates
71 ** x2,y2 destination coordinates
73 ** terrain ptr to string showing the types of sectors that
74 ** we're allowed to pass through:
76 ** A null string enables routing through any kind of
77 ** sector (useful for airplanes).
79 ** A string that begins with an 'R' ensures that
80 ** the source and destination sectors also match
81 ** the specified type of terrain.
83 ** A string that begins with a '~' (after the 'R',
84 ** if necessary) specifies that we can pass through
85 ** any kind of sector EXCEPT those in the remainder
90 ** "R~.^" all sectors along route must be
91 ** non-ocean, non-mountain
93 ** "+" all sectors between start and end
96 ** "h. " all sectors along route must be
97 ** harbor, water, or unmapped
99 ** 'bestpath' returns a pointer to a route string containing either:
101 ** yugjbn - string of normal routing characters if route possible
102 ** ? - if route is longer than MAXROUTE characters
103 ** \0 - (null string) if no route possible
104 ** h - if start and end points are the same sector
105 ** ________________________________________________________________
108 static char *dirchar = "juygbn";
109 int dx[6] = { 2, 1, -1, -2, -1, 1 };
110 int dy[6] = { 0, -1, -1, 0, 1, 1 };
113 * Ok, note that here we malloc some buffers. BUT, we never
114 * free them. Why, you may ask? Because we want to allocate
115 * them based on world size which is now (or soon to be) dynamic,
116 * but we don't want to allocate each and every time, since that
117 * would be slow. And, since world size only changes at init
118 * time, we can do this safely.
120 static unsigned int *mapbuf;
121 static unsigned int **mapindex;
124 bestownedpath(s_char *bpath,
126 int x, int y, int ex, int ey, s_char *terrain, int own)
128 int i, j, tx, ty, markedsectors, restr2;
129 int minx, maxx, miny, maxy, scanx, scany;
130 unsigned int routelen;
133 mapbuf = malloc((WORLD_X * WORLD_Y) *
134 sizeof(unsigned int));
138 mapindex = malloc(WORLD_X * sizeof(unsigned int *));
140 /* Setup the map pointers */
141 for (i = 0; i < WORLD_X; i++)
142 mapindex[i] = &mapbuf[WORLD_Y * i];
149 if (0 != (restr2 = (*terrain == 'R')))
157 if (x == ex && y == ey) {
163 if (!valid(x, y) || !valid(ex, ey))
166 if (restr2 && (!owned_and_navigable(bigmap, x, y, terrain, own) ||
167 !owned_and_navigable(bigmap, ex, ey, terrain, own)))
170 for (i = 0; i < WORLD_X; i++)
171 for (j = 0; j < WORLD_Y; j++)
172 mapindex[i][j] = 0xFFFF; /* clear the workspace */
174 routelen = 0; /* path length is now 0 */
175 mapindex[x][y] = 0; /* mark starting spot */
176 markedsectors = 1; /* source sector marked */
177 minx = x - 2; /* set X scan bounds */
179 miny = y - 1; /* set Y scan bounds */
183 if (++routelen == MAXROUTE) {
189 for (scanx = minx; scanx <= maxx; scanx++) {
191 for (scany = miny; scany <= maxy; scany++) {
194 if ((((mapindex[x][y]) & 0x1FFF) == (routelen - 1))) {
195 for (i = 0; i < 6; i++) {
200 if (mapindex[tx][ty] == 0xFFFF) {
201 if (owned_and_navigable(bigmap, tx, ty,
203 || (tx == ex && ty == ey && !restr2)) {
205 ((i + 1) << 13) + routelen;
209 if (tx == ex && ty == ey) {
212 i = ((mapindex[tx][ty]) >> 13) - 1;
213 bpath[routelen] = dirchar[i];
230 } while (markedsectors);
233 return NULL; /* no route possible */
236 /* return TRUE if sector is passable */
238 owned_and_navigable(s_char *map, int x, int y, s_char *terrain, int own)
241 s_char mapspot; /* What this spot on the bmap is */
244 /* No terrain to check? Everything is navigable! (this
245 probably means we are flying) */
249 /* Are we checking this map? */
251 /* Do we know what this sector is? If not, we assume it's ok,
252 since otherwise we'll never venture anywhere */
253 mapspot = map[sctoff(x, y)];
254 if (mapspot == ' ' || mapspot == 0)
257 /* Now, is it marked with a 'x' or 'X'? If so, avoid it! */
258 if (mapspot == 'x' || mapspot == 'X')
261 /* We don't know what it is since we have no map, so return ok! */
265 /* Now, check this bmap entry to see if it is one of the
280 /* We found it, so we say it's bad since we are negating */
282 } else if (!negate && !*t) {
283 /* We didn't find it, so we say it's bad since we aren't negating */
287 /* According to our bmap, this sector is ok. */