src/lib/subs/shpsub.c

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/*
 *  Empire - A multi-player, client/server Internet based war game.
 *  Copyright (C) 1986-2007, Dave Pare, Jeff Bailey, Thomas Ruschak,
 *                           Ken Stevens, Steve McClure
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  ---
 *
 *  See files README, COPYING and CREDITS in the root of the source
 *  tree for related information and legal notices.  It is expected
 *  that future projects/authors will amend these files as needed.
 *
 *  ---
 *
 *  shpsub.c: Ship subroutine stuff
 * 
 *  Known contributors to this file:
 *     Ken Stevens, 1995
 *     Steve McClure, 1996-2000
 *     Markus Armbruster, 2006
 */

#include <config.h>

#include <math.h>
#include <stdlib.h>
#include "damage.h"
#include "file.h"
#include "map.h"
#include "misc.h"
#include "mission.h"
#include "nsc.h"
#include "optlist.h"
#include "path.h"
#include "player.h"
#include "prototypes.h"
#include "queue.h"
#include "server.h"
#include "xy.h"
#include "empobj.h"
#include "unit.h"

static int shp_check_one_mines(struct ulist *);
static int shp_hit_mine(struct shpstr *, struct mchrstr *);
static void shp_mess(char *, struct ulist *);

void
shp_sel(struct nstr_item *ni, struct emp_qelem *list)


    /*  int     wantflags;
       int      nowantflags;
     */
{
    struct shpstr ship;
    struct mchrstr *mcp;
    struct ulist *mlp;

    emp_initque(list);
    while (nxtitem(ni, &ship)) {
        if (!player->owner)
            continue;
        mcp = &mchr[(int)ship.shp_type];
        /* if (wantflags && (mcp->m_flags & wantflags) != wantflags)
           continue;
           if (nowantflags && mcp->m_flags & nowantflags)
           continue;
         */
        if (opt_MARKET) {
            if (ontradingblock(EF_SHIP, &ship)) {
                pr("ship #%d inelligible - it's for sale.\n",
                   ship.shp_uid);
                continue;
            }
        }
        /* This abuse is better fixed by building a ship with the normal negative
           mobility that everything else is built with */
/*
        if (opt_MOB_ACCESS) {
          if (ship.shp_effic < 21 &&
            ship.shp_mobil < etu_per_update) {
            pr("%s needs at least %d mob to navigate.\n",
               prship(&ship), etu_per_update);
            continue;
          }
        }
*/
        ship.shp_mission = 0;
        ship.shp_rflags = 0;
        memset(ship.shp_rpath, 0, sizeof(ship.shp_rpath));
        putship(ship.shp_uid, &ship);
        mlp = malloc(sizeof(struct ulist));
        mlp->chrp = (struct empobj_chr *)mcp;
        mlp->unit.ship = ship;
        mlp->mobil = ship.shp_mobil;
        emp_insque(&mlp->queue, list);
    }
}

/* This function assumes that the list was created by shp_sel */
void
shp_nav(struct emp_qelem *list, double *minmobp, double *maxmobp,
        int *togetherp, natid actor)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    struct sctstr sect;
    struct shpstr ship;
    coord allx;
    coord ally;
    int first = 1;

    *minmobp = 9876.0;
    *maxmobp = -9876.0;
    *togetherp = 1;
    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        getship(mlp->unit.ship.shp_uid, &ship);
        if (ship.shp_own != actor) {
            mpr(actor, "%s was sunk at %s\n",
                prship(&ship), xyas(ship.shp_x, ship.shp_y, actor));
            emp_remque((struct emp_qelem *)mlp);
            free(mlp);
            continue;
        }
        if (opt_SAIL) {
            if (*ship.shp_path && !update_running) {
                shp_mess("has a sail path", mlp);
                mpr(actor, "Use `sail <#> -' to reset\n");
                continue;
            }
        }
        /* check crew - uws don't count */
        if (ship.shp_item[I_MILIT] == 0 && ship.shp_item[I_CIVIL] == 0) {
            shp_mess("is crewless", mlp);
            continue;
        }
        if (!getsect(ship.shp_x, ship.shp_y, &sect)) {
            shp_mess("was sucked into the sky by a strange looking spaceship", mlp);    /* heh -KHS */
            continue;
        }
        switch (shp_check_nav(&sect, &ship)) {
        case CN_CONSTRUCTION:
            shp_mess("is caught in a construction zone", mlp);
            continue;
        case CN_LANDLOCKED:
            shp_mess("is landlocked", mlp);
            continue;
        case CN_NAVIGABLE:
            break;
        case CN_ERROR:
        default:
            shp_mess("was just swallowed by a big green worm", mlp);
            continue;
        }
        if (first) {
            allx = ship.shp_x;
            ally = ship.shp_y;
            first = 0;
        }
        if (ship.shp_x != allx || ship.shp_y != ally)
            *togetherp = 0;
        if (ship.shp_mobil + 1 < (int)mlp->mobil) {
            mlp->mobil = ship.shp_mobil;
        }
        if (mlp->mobil < *minmobp)
            *minmobp = mlp->mobil;
        if (mlp->mobil > *maxmobp)
            *maxmobp = mlp->mobil;
        mlp->unit.ship = ship;
    }
}

int
shp_sweep(struct emp_qelem *ship_list, int verbose, int takemob, natid actor)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    struct sctstr sect;
    int mines, m, max, shells;
    int changed = 0;
    int stopping = 0;

    for (qp = ship_list->q_back; qp != ship_list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (!(((struct mchrstr *)mlp->chrp)->m_flags & M_SWEEP)) {
            if (verbose)
                mpr(actor, "%s doesn't have minesweeping capability!\n",
                    prship(&mlp->unit.ship));
            continue;
        }
        if (takemob && mlp->mobil <= 0.0) {
            if (verbose)
                mpr(actor, "%s is out of mobility!\n",
                    prship(&mlp->unit.ship));
            continue;
        }
        getsect(mlp->unit.ship.shp_x, mlp->unit.ship.shp_y, &sect);
        if (sect.sct_type != SCT_WATER) {
            if (verbose)
                mpr(actor, "%s is not at sea.  No mines there!\n",
                    prship(&mlp->unit.ship));
            continue;
        }
        if (takemob) {
            mlp->mobil -= shp_mobcost(&mlp->unit.ship);
            mlp->unit.ship.shp_mobil = (int)mlp->mobil;
        }
        putship(mlp->unit.ship.shp_uid, &mlp->unit.ship);
        if (!(mines = sect.sct_mines))
            continue;
        max = ((struct mchrstr *)mlp->chrp)->m_item[I_SHELL];
        shells = mlp->unit.ship.shp_item[I_SHELL];
        for (m = 0; mines > 0 && m < 5; m++) {
            if (chance(0.66)) {
                mpr(actor, "Sweep...\n");
                mines--;
                shells = MIN(max, shells + 1);
                changed |= map_set(actor, sect.sct_x, sect.sct_y, 'X', 0);
            }
        }
        sect.sct_mines = mines;
        mlp->unit.ship.shp_item[I_SHELL] = shells;
        if (shp_check_one_mines(mlp)) {
            stopping = 1;
            emp_remque(qp);
            free(qp);
        }
        putship(mlp->unit.ship.shp_uid, &mlp->unit.ship);
        putsect(&sect);
    }
    if (changed)
        writemap(actor);
    return stopping;
}

static int
shp_check_one_mines(struct ulist *mlp)
{
    struct sctstr sect;
    int actor;

    getsect(mlp->unit.ship.shp_x, mlp->unit.ship.shp_y, &sect);
    if (sect.sct_type != SCT_WATER)
        return 0;
    if (!sect.sct_mines)
        return 0;
    if (chance(DMINE_HITCHANCE(sect.sct_mines))) {
        actor = mlp->unit.ship.shp_own;
        shp_hit_mine(&mlp->unit.ship, ((struct mchrstr *)mlp->chrp));
        sect.sct_mines--;
        if (map_set(actor, sect.sct_x, sect.sct_y, 'X', 0))
            writemap(actor);
        putsect(&sect);
        putship(mlp->unit.ship.shp_uid, &mlp->unit.ship);
        if (!mlp->unit.ship.shp_own)
            return 1;
    }
    return 0;
}

static int
shp_check_mines(struct emp_qelem *ship_list)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    int stopping = 0;

    for (qp = ship_list->q_back; qp != ship_list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (shp_check_one_mines(mlp)) {
            stopping = 1;
            emp_remque(qp);
            free(qp);
        }
    }
    return stopping;
}


static void
shp_mess(char *str, struct ulist *mlp)
{
    mpr(mlp->unit.ship.shp_own, "%s %s & stays in %s\n",
        prship(&mlp->unit.ship),
        str, xyas(mlp->unit.ship.shp_x, mlp->unit.ship.shp_y,
                  mlp->unit.ship.shp_own));
    mlp->unit.ship.shp_mobil = (int)mlp->mobil;
    putship(mlp->unit.ship.shp_uid, &mlp->unit.ship);
    emp_remque((struct emp_qelem *)mlp);
    free(mlp);
}

int
shp_check_nav(struct sctstr *sect, struct shpstr *shp)
{
    switch (dchr[sect->sct_type].d_nav) {
    case NAVOK:
        break;
    case NAV_CANAL:
        if (mchr[(int)shp->shp_type].m_flags & M_CANAL) {
            if (sect->sct_effic < 2)
                return CN_CONSTRUCTION;
        } else
            return CN_LANDLOCKED;
        break;
    case NAV_02:
        if (sect->sct_effic < 2)
            return CN_CONSTRUCTION;
        break;
    case NAV_60:
        if (sect->sct_effic < 60)
            return CN_CONSTRUCTION;
        break;
    default:
        return CN_LANDLOCKED;
    }
    return CN_NAVIGABLE;
}

int
sect_has_dock(struct sctstr *sect)
{
    switch (dchr[sect->sct_type].d_nav) {
    case NAV_02:
    case NAV_CANAL:
        return 1;
    default:
        return 0;
    }
}

static int
shp_count(struct emp_qelem *list, int wantflags, int nowantflags,
          int x, int y)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    int count = 0;

    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (mlp->unit.ship.shp_x != x || mlp->unit.ship.shp_y != y)
            continue;
        if (wantflags &&
            (((struct mchrstr *)mlp->chrp)->m_flags & wantflags) != wantflags)
            continue;
        if (nowantflags &&
            ((struct mchrstr *)mlp->chrp)->m_flags & nowantflags)
            continue;
        ++count;
    }
    return count;
}

static void
shp_damage_one(struct ulist *mlp, int dam)
{
    shipdamage(&mlp->unit.ship, dam);
    putship(mlp->unit.ship.shp_uid, &mlp->unit.ship);
    if (!mlp->unit.ship.shp_own) {
        emp_remque((struct emp_qelem *)mlp);
        free(mlp);
    }
}

static int
shp_damage(struct emp_qelem *list, int totdam, int wantflags,
           int nowantflags, int x, int y)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    int dam;
    int count;

    if (!totdam
        || !(count = shp_count(list, wantflags, nowantflags, x, y)))
        return 0;
    dam = ldround((double)totdam / count, 1);
    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (mlp->unit.ship.shp_x != x || mlp->unit.ship.shp_y != y)
            continue;
        if (wantflags &&
            (((struct mchrstr *)mlp->chrp)->m_flags & wantflags) != wantflags)
            continue;
        if (nowantflags &&
            ((struct mchrstr *)mlp->chrp)->m_flags & nowantflags)
            continue;
        shp_damage_one(mlp, dam);
    }
    return dam;
}

static int
shp_contains(struct emp_qelem *list, int newx, int newy, int wantflags,
             int nowantflags)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;

    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
/* If the ship isn't in the requested sector, then continue */
        if (newx != mlp->unit.ship.shp_x || newy != mlp->unit.ship.shp_y)
            continue;
        if (wantflags &&
            (((struct mchrstr *)mlp->chrp)->m_flags & wantflags) != wantflags)
            continue;
        if (nowantflags &&
            ((struct mchrstr *)mlp->chrp)->m_flags & nowantflags)
            continue;
        return 1;
    }
    return 0;
}

static struct ulist *
most_valuable_ship(struct emp_qelem *list)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    struct ulist *mvs = 0;

    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (((struct mchrstr *)mlp->chrp)->m_flags & M_SUB)
            continue;
        if (!((struct mchrstr *)mlp->chrp)->m_nxlight &&
            !((struct mchrstr *)mlp->chrp)->m_nchoppers &&
            ((struct mchrstr *)mlp->chrp)->m_cost < 1000 &&
            !((struct mchrstr *)mlp->chrp)->m_nplanes &&
            !((struct mchrstr *)mlp->chrp)->m_nland)
            continue;
        if (!mvs) {
            mvs = mlp;
            continue;
        }
        if (((struct mchrstr *)mlp->chrp)->m_cost * mlp->unit.ship.shp_effic >
            ((struct mchrstr *)mlp->chrp)->m_cost * mvs->unit.ship.shp_effic)
            mvs = mlp;
    }
    return mvs;
}

static int
shp_easiest_target(struct emp_qelem *list, int wantflags, int nowantflags)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    int hard;
    int easiest = 9876;         /* things start great for victim */
    int count = 0;

    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (wantflags &&
            (((struct mchrstr *)mlp->chrp)->m_flags & wantflags) != wantflags)
            continue;
        if (nowantflags &&
            ((struct mchrstr *)mlp->chrp)->m_flags & nowantflags)
            continue;
        hard = shp_hardtarget(&mlp->unit.ship);
        if (hard < easiest)
            easiest = hard;     /* things get worse for victim */
        ++count;
    }
    return easiest - count;
}

static int
shp_missile_interdiction(struct emp_qelem *list, coord newx, coord newy,
                         natid victim)
{
    int dam;
    int twotries;
    int stopping = 0;
    struct emp_qelem msl_list, *qp, *newqp;
    struct ulist *mvs;
    char what[512];

    msl_sel(&msl_list, newx, newy, victim, P_T | P_MAR, 0, MI_INTERDICT);

    twotries = 0;
    while (!QEMPTY(&msl_list) && (mvs = most_valuable_ship(list))) {
        sprintf(what, "%s", prship(&mvs->unit.ship));
        dam = msl_launch_mindam(&msl_list, newx, newy,
                                shp_hardtarget(&mvs->unit.ship),
                                EF_SHIP, 1, what, victim, MI_INTERDICT);
        if (dam) {
            mpr(victim,
                "missile interdiction mission does %d damage to %s!\n",
                dam, what);
            shp_damage_one(mvs, dam);
            twotries = 0;
            stopping |= 1;
        } else if (++twotries >= 2) {
            break;
        }
    }
    qp = msl_list.q_forw;
    while (qp != msl_list.q_forw) {
        newqp = qp->q_forw;
        emp_remque(qp);
        free(qp);
        qp = newqp;
    }

    return stopping;
}

/* Note that this function has a side effect - it uses coastwatch
 * ranges to see if it should fire upon a ship.  So, this function
 * is expected to return positive if a ship is in range, and 0 if a
 * ship is not in range. */
static int
notify_coastguard(struct emp_qelem *list, int trange, struct sctstr *sectp)
{
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    struct natstr *natp;
    int vrange;

    natp = getnatp(sectp->sct_own);

    vrange = sectp->sct_type == SCT_RADAR ? 14 : 4;
    vrange *= tfact(sectp->sct_own, 1.0) * sectp->sct_effic / 100.0;

    if (vrange < 1)
        vrange = 1;

    if (vrange < trange)
        return 0;

    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        if (((struct mchrstr *)mlp->chrp)->m_flags & M_SUB)
            continue;
        if (natp->nat_flags & NF_COASTWATCH)
            wu(0, sectp->sct_own,
               "%s %s sighted at %s\n",
               cname(mlp->unit.ship.shp_own),
               prship(&mlp->unit.ship),
               xyas(mlp->unit.ship.shp_x, mlp->unit.ship.shp_y,
                    sectp->sct_own));
        if (opt_HIDDEN)
            setcont(sectp->sct_own, mlp->unit.ship.shp_own, FOUND_COAST);
    }

    return 1;
}

static int
shp_fort_interdiction(struct emp_qelem *list, coord newx, coord newy,
                      natid victim)
{
    struct nstr_sect ns;
    struct sctstr fsect;
    int trange, range;
    double guneff;
    int shell, gun;
    int dam;
    int totdam = 0;
    signed char notified[MAXNOC];
    int i;

    /* Inform neutral and worse */
    for (i = 0; i < MAXNOC; ++i) {
        if (getrel(getnatp(i), victim) <= NEUTRAL)
            notified[i] = 0;
        else
            notified[i] = 1;
    }

    snxtsct_dist(&ns, newx, newy, fort_max_interdiction_range);
    while (nxtsct(&ns, &fsect)) {
        if (!fsect.sct_own)
            continue;
        if (fsect.sct_own == victim)
            continue;
        if (notified[fsect.sct_own])
            continue;
        trange = mapdist(newx, newy, fsect.sct_x, fsect.sct_y);
        if (notify_coastguard(list, trange, &fsect))
            notified[fsect.sct_own] = 1;
    }
    if (opt_NO_FORT_FIRE)
        return 0;               /* Only coastwatch notify in nofortfire */
    /* Only fire at Hostile ships */
    for (i = 0; i < MAXNOC; ++i) {
        if (getrel(getnatp(i), victim) >= NEUTRAL)
            notified[i] = 0;
    }
    snxtsct_dist(&ns, newx, newy, fort_max_interdiction_range);
    while (nxtsct(&ns, &fsect)) {
        if (!notified[fsect.sct_own])
            continue;
        gun = fsect.sct_item[I_GUN];
        if (gun < 1)
            continue;
        range = roundrange(fortrange(&fsect));
        trange = mapdist(newx, newy, fsect.sct_x, fsect.sct_y);
        if (trange > range)
            continue;
        if (fsect.sct_item[I_MILIT] < 5)
            continue;
        shell = fsect.sct_item[I_SHELL];
        if (shell < 1)
            shell += supply_commod(fsect.sct_own, fsect.sct_x, fsect.sct_y,
                                   I_SHELL, 1);
        if (shell < 1)
            continue;
        shell--;
        fsect.sct_item[I_SHELL] = shell;
        putsect(&fsect);
        if (gun > 7)
            gun = 7;
        guneff = landgun((int)fsect.sct_effic, gun);
        dam = (int)guneff;
        totdam += dam;
        mpr(victim, "Incoming fire does %d damage!\n", dam);
/*
  mpr(victim, "%s fires at you for %d!\n",
  xyas(fsect.sct_x,fsect.sct_y,victim),
  dam);
*/
        wu(0, fsect.sct_own,
           "%s fires at %s ships in %s for %d!\n",
           xyas(fsect.sct_x, fsect.sct_y,
                fsect.sct_own),
           cname(victim), xyas(newx, newy, fsect.sct_own), dam);
        nreport(fsect.sct_own, N_SHP_SHELL, victim, 1);
    }
    if (totdam > 0)
        return shp_damage(list, totdam, 0, M_SUB, newx, newy);
    return 0;
}

static int
shp_interdict(struct emp_qelem *list, coord newx, coord newy, natid victim)
{
    int stopping = 0;

    if (shp_contains(list, newx, newy, 0, M_SUB)) {
        stopping |= shp_fort_interdiction(list, newx, newy, victim);

        if (shp_contains(list, newx, newy, 0, M_SUB)) {
            stopping |=
                shp_damage(list,
                           unit_interdict(newx, newy, victim, "ships",
                                          shp_easiest_target(list, 0, M_SUB),
                                          MI_INTERDICT),
                           0, M_SUB, newx, newy);
            if (most_valuable_ship(list)) {
                stopping |=
                    shp_missile_interdiction(list, newx, newy, victim);
            }
        }
    }
    if (shp_contains(list, newx, newy, M_SUB, 0)) {
        stopping |=
            shp_damage(list,
                       unit_interdict(newx, newy, victim, "subs",
                                      shp_easiest_target(list, M_SUB, 0),
                                      MI_SINTERDICT),
                       M_SUB, 0, newx, newy);
    }
    return stopping;
}

/* high value of hardtarget is harder to hit */
int
shp_hardtarget(struct shpstr *sp)
{
    struct sctstr sect;
    int vis, onsea;
    struct mchrstr *mcp = mchr + sp->shp_type;

    vis = sp->shp_visib;
    getsect(sp->shp_x, sp->shp_y, &sect);
    onsea = sect.sct_type == SCT_WATER;
    if (mcp->m_flags & M_SUB)
        vis *= 4;
    return (int)((sp->shp_effic / 100.0) *
                 (20 + sp->shp_speed * onsea / 2.0 - vis));
}

static int
shp_hit_mine(struct shpstr *sp, struct mchrstr *mcp)
{
    double m;

    mpr(sp->shp_own, "Kawhomp! Mine detected in %s!\n",
        xyas(sp->shp_x, sp->shp_y, sp->shp_own));

    nreport(sp->shp_own, N_HIT_MINE, 0, 1);

    m = MINE_DAMAGE();
    if (mcp->m_flags & M_SWEEP)
        m /= 2.0;

    shipdamage(sp, ldround(m, 1));

    return (int)m;
}

int
shp_nav_one_sector(struct emp_qelem *list, int dir, natid actor,
                   int together)
{
    struct sctstr sect;
    struct emp_qelem *qp;
    struct emp_qelem *next;
    struct ulist *mlp;
    struct emp_qelem done;
    coord dx;
    coord dy;
    coord newx;
    coord newy;
    int stopping = 0;
    double mobcost;
    double tech;                /* for mapping */
    double tf;                  /* for mapping */
    char dp[80];
    int navigate;

    if (dir <= DIR_STOP || dir >= DIR_VIEW) {
        unit_put(list, actor);
        return 1;
    }
    dx = diroff[dir][0];
    dy = diroff[dir][1];
    for (qp = list->q_back; qp != list; qp = next) {
        next = qp->q_back;
        mlp = (struct ulist *)qp;
        newx = xnorm(mlp->unit.ship.shp_x + dx);
        newy = ynorm(mlp->unit.ship.shp_y + dy);
        getsect(newx, newy, &sect);
        navigate = shp_check_nav(&sect, &mlp->unit.ship);
        if (navigate != CN_NAVIGABLE ||
            (sect.sct_own && actor != sect.sct_own &&
             getrel(getnatp(sect.sct_own), actor) < FRIENDLY)) {
            if (dchr[sect.sct_type].d_nav == NAV_CANAL &&
                !(((struct mchrstr *)mlp->chrp)->m_flags & M_CANAL) &&
                navigate == CN_LANDLOCKED)
                sprintf(dp,
                        "is too large to fit into the canal system at %s",
                        xyas(newx, newy, actor));
            else
                sprintf(dp, "can't go to %s", xyas(newx, newy, actor));
            if (together) {
                mpr(actor, "%s\n", dp);
                return 2;
            } else {
                shp_mess(dp, mlp);
                continue;
            }
        }

        if (mlp->mobil <= 0.0) {
            shp_mess("is out of mobility", mlp);
            continue;
        }
        mobcost = shp_mobcost(&mlp->unit.ship);
        mlp->unit.ship.shp_x = newx;
        mlp->unit.ship.shp_y = newy;
        if (mlp->mobil - mobcost < -127) {
            mlp->mobil = -127;
        } else {
            mlp->mobil -= mobcost;
        }
        mlp->unit.ship.shp_mobil = (int)mlp->mobil;
        putship(mlp->unit.ship.shp_uid, &mlp->unit.ship);

        /* Now update the map for this ship */
        tech = techfact(mlp->unit.ship.shp_tech,
                        ((struct mchrstr *)mlp->chrp)->m_vrnge);
        if (((struct mchrstr *)mlp->chrp)->m_flags & M_SONAR)
            tf = techfact(mlp->unit.ship.shp_tech, 1.0);
        else
            tf = 0.0;
        radmapupd(mlp->unit.ship.shp_own,
                  mlp->unit.ship.shp_x, mlp->unit.ship.shp_y,
                  (int)mlp->unit.ship.shp_effic, (int)tech, tf);
    }
    if (QEMPTY(list))
        return stopping;
    stopping |= shp_sweep(list, 0, 0, actor);
    if (QEMPTY(list))
        return stopping;
    stopping |= shp_check_mines(list);
    if (QEMPTY(list))
        return stopping;

    /* interdict ships sector by sector */
    emp_initque(&done);
    while (!QEMPTY(list)) {
        mlp = (struct ulist *)list->q_back;
        newx = mlp->unit.ship.shp_x;
        newy = mlp->unit.ship.shp_y;
        stopping |= shp_interdict(list, newx, newy, actor);
        /* move survivors in this sector to done */
        for (qp = list->q_back; qp != list; qp = next) {
            next = qp->q_back;
            mlp = (struct ulist *)qp;
            if (mlp->unit.ship.shp_x == newx &&
                mlp->unit.ship.shp_y == newy) {
                emp_remque(qp);
                emp_insque(qp, &done);
            }
        }
    }
    /* assign surviving ships back to list */
    emp_insque(list, &done);
    emp_remque(&done);

    return stopping;
}

/*
 * shp_miss_defence 
 * Check for incoming missiles with a P_MAR flag. 
 * Return True=1 if the missile was shotdown.
 * Or False=0
 * 
 * Chad Zabel, July 95
 */

int
shp_missile_defense(coord dx, coord dy, natid bombown, int hardtarget)
{
    struct nstr_item ni;
    struct shpstr ship;
    int hitchance;
    int shell;
    double gun, eff, teff;

    snxtitem_dist(&ni, EF_SHIP, dx, dy, 1);

    while (nxtitem(&ni, &ship)) {
        if (!ship.shp_own)
            continue;

        if (!(mchr[(int)ship.shp_type].m_flags & M_ANTIMISSILE))
            continue;

        if (getrel(getnatp(ship.shp_own), bombown) >= NEUTRAL)
            continue;

        if (ship.shp_effic < 60)
            continue;

        shell = ship.shp_item[I_SHELL];
        if (ship.shp_item[I_MILIT] < 1) /* do we have mil? */
            continue;
        if (shell < 2) {        /* do we need shells */
            shell += supply_commod(ship.shp_own, ship.shp_x, ship.shp_y,
                                   I_SHELL, 2);
            if (shell < 2)
                continue;
        }
        if (ship.shp_item[I_GUN] < 1)   /* we need at least 1 gun */
            continue;

        /* now calculate the odds */
        gun = MIN(ship.shp_item[I_GUN], ship.shp_glim);
        eff = ship.shp_effic / 100.0;
        teff = ship.shp_tech / (ship.shp_tech + 200.0);
        /* raise 4.5 for better interception -KHS */
        hitchance = (int)(gun * eff * teff * 4.5) - hardtarget;
        if (hitchance < 0)
            hitchance = 0;
        if (hitchance > 100)
            hitchance = 100;

        mpr(bombown, "%s anti-missile system activated...",
            cname(ship.shp_own));
        mpr(ship.shp_own, "Ship #%i anti-missile system activated!\n",
            ship.shp_uid);
        mpr(ship.shp_own, "%d%% hitchance...", hitchance);
        /* use ammo */
        ship.shp_item[I_SHELL] = shell - 2;
        putship(ship.shp_uid, &ship);

        if (roll(100) <= hitchance) {
            mpr(bombown, "KABOOOM!! Missile destroyed\n\n");
            mpr(ship.shp_own,
                "KABOOOM!!  Incoming missile destroyed!\n\n");
            return 1;
        } else {
            mpr(bombown, "SWOOSH!!  anti-missile system failed!!\n");
            mpr(ship.shp_own,
                "SWOOSH!!  Missile evades anti-missile systems\n\n");
        }
    }
    return 0;                   /* all attempts failed */
}


/* Fire missiles at a ship which has fired shells */
void
shp_missdef(struct shpstr *sp, natid victim)
{
    struct emp_qelem list;
    struct ulist *mlp;
    int eff;
    char buf[512];

    emp_initque(&list);

    mlp = malloc(sizeof(struct ulist));
    mlp->chrp = (struct empobj_chr *)&mchr[(int)sp->shp_type];
    mlp->unit.ship = *sp;
    mlp->mobil = sp->shp_mobil;
    emp_insque(&mlp->queue, &list);
    sprintf(buf, "%s", prship(&mlp->unit.ship));

    eff = sp->shp_effic;
    if (most_valuable_ship(&list)) {
        shp_missile_interdiction(&list, sp->shp_x, sp->shp_y, sp->shp_own);
        getship(sp->shp_uid, sp);

        if (!sp->shp_own) {
            wu(0, victim,
               "missiles launched in defense did 100%% damage to %s\n",
               buf);
            wu(0, victim, "%s sunk!\n", buf);
        } else if (eff > 0 && sp->shp_effic < eff) {
            wu(0, victim,
               "missiles launched in defense did %d%% damage to %s\n",
               100 * (eff - sp->shp_effic) / eff, buf);
        }
    }
    if (!QEMPTY(&list))
        free(mlp);
}

double
shp_mobcost(struct shpstr *sp)
{
    return speed_factor(sp->shp_effic * 0.01 * sp->shp_speed,
                        sp->shp_tech);
}

/*
 * Set SP's tech to TLEV along with everything else that depends on it.
 */
void
shp_set_tech(struct shpstr *sp, int tlev)
{
    struct mchrstr *mcp = mchr + sp->shp_type;
    int tech_diff = tlev - mcp->m_tech;

    if (CANT_HAPPEN(tech_diff < 0)) {
      tlev -= tech_diff;
      tech_diff = 0;
    }

    sp->shp_tech = tlev;
    sp->shp_armor = (short)SHP_DEF(mcp->m_armor, tech_diff);
    sp->shp_speed = (short)SHP_SPD(mcp->m_speed, tech_diff);
    sp->shp_visib = (short)SHP_VIS(mcp->m_visib, tech_diff);
    sp->shp_frnge = (short)SHP_RNG(mcp->m_frnge, tech_diff);
    sp->shp_glim  = (short)SHP_FIR(mcp->m_glim, tech_diff);
}

---