226 lines
6.3 KiB
C
226 lines
6.3 KiB
C
/*
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* Empire - A multi-player, client/server Internet based war game.
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* Copyright (C) 1986-2008, Dave Pare, Jeff Bailey, Thomas Ruschak,
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* Ken Stevens, Steve McClure
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* ---
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*
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* See files README, COPYING and CREDITS in the root of the source
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* tree for related information and legal notices. It is expected
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* that future projects/authors will amend these files as needed.
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*
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* ---
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*
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* bestpath.c: Find the best path between sectors
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*
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* Known contributors to this file:
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* Steve McClure, 1998-2000
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* Markus Armbruster, 2006
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*/
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/*
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* IMPORTANT: These routines are very selectively used in the server.
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*
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* "bestownedpath" is only used to determine paths for ships and planes.
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*
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* Callers should not be calling these directly anymore. They should use
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* the "BestShipPath", "BestAirPath", "BestLandPath" and "BestDistPath"
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* functions. Note that those last two use the A* algorithms to find
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* information.
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*/
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#include <config.h>
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#include "file.h"
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#include "misc.h"
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#include "nat.h"
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#include "optlist.h"
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#include "path.h"
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#include "prototypes.h"
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#include "sect.h"
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#include "xy.h"
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static int owned_and_navigable(char *, int, int, int);
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#define MAXROUTE 100
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#define valid(x,y) ((((x) ^ (y)) & 1) == 0)
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/*
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* Ok, note that here we malloc some buffers. BUT, we never
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* free them. Why, you may ask? Because we want to allocate
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* them based on world size which is now (or soon to be) dynamic,
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* but we don't want to allocate each and every time, since that
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* would be slow. And, since world size only changes at init
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* time, we can do this safely.
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*/
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static unsigned short *mapbuf;
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static unsigned short **mapindex;
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/*
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* Find passable path from X, Y to EX, EY for nation OWN.
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* BPATH is a buffer capable of holding at least MAXROUTE characters.
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* If BIGMAP is null, all sectors are passable (useful for flying).
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* Else it is taken to be a bmap.
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* Sectors owned by or allied to OWN are then passable according to
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* the usual rules.
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* Other sectors are assumed to be passable when BIGMAP shows '.' or
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* nothing.
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* Return a path if found, else a null pointer.
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* Wart: the path isn't terminated with 'h', except when if X,Y equals
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* EX,EY.
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*/
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char *
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bestownedpath(char *bpath, char *bigmap,
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int x, int y, int ex, int ey, int own)
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{
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int i, j, tx, ty, markedsectors;
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int minx, maxx, miny, maxy, scanx, scany;
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unsigned routelen;
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if (!mapbuf)
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mapbuf = malloc(WORLD_X * WORLD_Y * sizeof(*mapbuf));
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if (!mapbuf)
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return NULL;
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if (!mapindex) {
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mapindex = malloc(WORLD_X * sizeof(*mapindex));
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if (mapindex) {
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/* Setup the map pointers */
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for (i = 0; i < WORLD_X; i++)
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mapindex[i] = &mapbuf[WORLD_Y * i];
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}
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}
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if (!mapindex)
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return NULL;
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x = XNORM(x);
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y = YNORM(y);
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ex = XNORM(ex);
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ey = YNORM(ey);
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if (x == ex && y == ey)
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return "h";
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if (!valid(x, y) || !valid(ex, ey))
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return NULL;
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if (!owned_and_navigable(bigmap, ex, ey, own))
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return NULL;
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for (i = 0; i < WORLD_X; i++)
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for (j = 0; j < WORLD_Y; j++)
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mapindex[i][j] = 0xFFFF; /* clear the workspace */
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routelen = 0; /* path length is now 0 */
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mapindex[x][y] = 0; /* mark starting spot */
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markedsectors = 1; /* source sector marked */
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minx = x - 2; /* set X scan bounds */
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maxx = x + 2;
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miny = y - 1; /* set Y scan bounds */
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maxy = y + 1;
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do {
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if (++routelen == MAXROUTE)
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return NULL;
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markedsectors = 0;
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for (scanx = minx; scanx <= maxx; scanx++) {
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x = XNORM(scanx);
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for (scany = miny; scany <= maxy; scany++) {
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y = YNORM(scany);
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if (!valid(x, y))
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continue;
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if (((mapindex[x][y] & 0x1FFF) == routelen - 1)) {
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for (i = DIR_FIRST; i <= DIR_LAST; i++) {
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tx = x + diroff[i][0];
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ty = y + diroff[i][1];
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tx = XNORM(tx);
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ty = YNORM(ty);
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if (mapindex[tx][ty] == 0xFFFF) {
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if (owned_and_navigable(bigmap, tx, ty, own)) {
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if (CANT_HAPPEN(i < DIR_FIRST || i > DIR_LAST))
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i = DIR_STOP;
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mapindex[tx][ty] =
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((i - DIR_FIRST + 1) << 13) + routelen;
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markedsectors++;
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}
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}
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if (tx == ex && ty == ey) {
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bpath[routelen] = 0;
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while (routelen--) {
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i = (mapindex[tx][ty] >> 13)
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- 1 + DIR_FIRST;
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bpath[routelen] = dirch[i];
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tx = tx - diroff[i][0];
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ty = ty - diroff[i][1];
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tx = XNORM(tx);
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ty = YNORM(ty);
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}
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return bpath;
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}
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}
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}
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}
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}
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miny--;
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maxy++;
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minx -= 2;
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maxx += 2;
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} while (markedsectors);
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return NULL; /* no route possible */
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}
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/*
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* Return non-zero if sector X, Y is passable.
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* If BIGMAP is null, all sectors are passable (useful for flying).
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* Else it is taken to be a bmap.
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* Sectors owned by or allied to OWN are checked according to the
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* usual rules, and the result is correct.
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* Other sectors are assumed to be passable when BIGMAP shows '.' or
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* nothing.
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*/
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static int
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owned_and_navigable(char *bigmap, int x, int y, int own)
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{
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char mapspot;
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struct sctstr sect;
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if (!bigmap)
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return 1;
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/* Owned or allied sector? Check the real sector. */
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getsect(x, y, §);
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if (sect.sct_own == own
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|| (sect.sct_own && getrel(getnatp(sect.sct_own), own) == ALLIED)) {
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/* FIXME duplicates shp_check_nav() logic */
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switch (dchr[sect.sct_type].d_nav) {
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case NAVOK:
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return 1;
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case NAV_CANAL:
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/* FIXME return 1 when all ships have M_CANAL */
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return 0;
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case NAV_02:
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return sect.sct_effic >= 2;
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case NAV_60:
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return sect.sct_effic >= 60;
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default:
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return 0;
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}
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}
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/* Can only check bigmap */
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mapspot = bigmap[sctoff(x, y)];
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return mapspot == '.' || mapspot == ' ' || mapspot == 0;
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}
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