Source:NetHack 3.6.0/src/ball.c

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 /* NetHack 3.6	ball.c	$NHDT-Date: 1446808438 2015/11/06 11:13:58 $  $NHDT-Branch: master $:$NHDT-Revision: 1.28 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
 /* Ball & Chain
  * =============================================================*/
 
 #include "hack.h"
 
 STATIC_DCL int NDECL(bc_order);
 STATIC_DCL void NDECL(litter);
 

ballrelease

 void
 ballrelease(showmsg)
 boolean showmsg;
 {
     if (carried(uball)) {
         if (showmsg)
             pline("Startled, you drop the iron ball.");
         if (uwep == uball)
             setuwep((struct obj *) 0);
         if (uswapwep == uball)
             setuswapwep((struct obj *) 0);
         if (uquiver == uball)
             setuqwep((struct obj *) 0);
         ;
         if (uwep != uball)
             freeinv(uball);
     }
 }
 

ballfall

 void
 ballfall()
 {
     boolean gets_hit;
 
     gets_hit = (((uball->ox != u.ux) || (uball->oy != u.uy))
                 && ((uwep == uball) ? FALSE : (boolean) rn2(5)));
     ballrelease(TRUE);
     if (gets_hit) {
         int dmg = rn1(7, 25);
         pline_The("iron ball falls on your %s.", body_part(HEAD));
         if (uarmh) {
             if (is_metallic(uarmh)) {
                 pline("Fortunately, you are wearing a hard helmet.");
                 dmg = 3;
             } else if (flags.verbose)
                 pline("%s does not protect you.", Yname2(uarmh));
         }
         losehp(Maybe_Half_Phys(dmg), "crunched in the head by an iron ball",
                NO_KILLER_PREFIX);
     }
 }
 

placebc

 /*
  *  To make this work, we have to mess with the hero's mind.  The rules for
  *  ball&chain are:
  *
  *      1. If the hero can see them, fine.
  *      2. If the hero can't see either, it isn't seen.
  *      3. If either is felt it is seen.
  *      4. If either is felt and moved, it disappears.
  *
  *  If the hero can see, then when a move is done, the ball and chain are
  *  first picked up, the positions under them are corrected, then they
  *  are moved after the hero moves.  Not too bad.
  *
  *  If the hero is blind, then she can "feel" the ball and/or chain at any
  *  time.  However, when the hero moves, the felt ball and/or chain become
  *  unfelt and whatever was felt "under" the ball&chain appears.  Pretty
  *  nifty, but it requires that the ball&chain "remember" what was under
  *  them --- i.e. they pick-up glyphs when they are felt and drop them when
  *  moved (and felt).  When swallowed, the ball&chain are pulled completely
  *  off of the dungeon, but are still on the object chain.  They are placed
  *  under the hero when she is expelled.
  */
 
 /*
  * from you.h
  *      int u.bglyph            glyph under the ball
  *      int u.cglyph            glyph under the chain
  *      int u.bc_felt           mask for ball/chain being felt
  *      #define BC_BALL  0x01   bit mask in u.bc_felt for ball
  *      #define BC_CHAIN 0x02   bit mask in u.bc_felt for chain
  *      int u.bc_order          ball & chain order
  *
  * u.bc_felt is also manipulated in display.c and read.c, the others only
  * in this file.  None of these variables are valid unless the player is
  * Blind.
  */
 
 /* values for u.bc_order */
 #define BCPOS_DIFFER 0 /* ball & chain at different positions */
 #define BCPOS_CHAIN 1  /* chain on top of ball */
 #define BCPOS_BALL 2   /* ball on top of chain */
 
 /*
  *  Place the ball & chain under the hero.  Make sure that the ball & chain
  *  variables are set (actually only needed when blind, but what the heck).
  *  It is assumed that when this is called, the ball and chain are NOT
  *  attached to the object list.
  *
  *  Should not be called while swallowed except on waterlevel.
  */
 void
 placebc()
 {
     if (!uchain || !uball) {
         impossible("Where are your ball and chain?");
         return;
     }
 
     (void) flooreffects(uchain, u.ux, u.uy, ""); /* chain might rust */
 
     if (carried(uball)) /* the ball is carried */
         u.bc_order = BCPOS_DIFFER;
     else {
         /* ball might rust -- already checked when carried */
         (void) flooreffects(uball, u.ux, u.uy, "");
         place_object(uball, u.ux, u.uy);
         u.bc_order = BCPOS_CHAIN;
     }
 
     place_object(uchain, u.ux, u.uy);
 
     u.bglyph = u.cglyph = levl[u.ux][u.uy].glyph; /* pick up glyph */
 
     newsym(u.ux, u.uy);
 }
 

unplacebc

 void
 unplacebc()
 {
     if (u.uswallow) {
         if (Is_waterlevel(&u.uz)) {
             /* we need to proceed with the removal from the floor
              * so that movebubbles() processing will disregard it as
              * intended. Ignore all the vision stuff.
              */
             if (!carried(uball))
                 obj_extract_self(uball);
             obj_extract_self(uchain);
         }
         /* ball&chain not unplaced while swallowed */
         return;
     }
 
     if (!carried(uball)) {
         obj_extract_self(uball);
         if (Blind && (u.bc_felt & BC_BALL)) /* drop glyph */
             levl[uball->ox][uball->oy].glyph = u.bglyph;
 
         newsym(uball->ox, uball->oy);
     }
     obj_extract_self(uchain);
     if (Blind && (u.bc_felt & BC_CHAIN)) /* drop glyph */
         levl[uchain->ox][uchain->oy].glyph = u.cglyph;
 
     newsym(uchain->ox, uchain->oy);
     u.bc_felt = 0; /* feel nothing */
 }
 

bc_order

 /*
  *  Return the stacking of the hero's ball & chain.  This assumes that the
  *  hero is being punished.
  */
 STATIC_OVL int
 bc_order()
 {
     struct obj *obj;
 
     if (uchain->ox != uball->ox || uchain->oy != uball->oy || carried(uball)
         || u.uswallow)
         return BCPOS_DIFFER;
 
     for (obj = level.objects[uball->ox][uball->oy]; obj;
          obj = obj->nexthere) {
         if (obj == uchain)
             return BCPOS_CHAIN;
         if (obj == uball)
             return BCPOS_BALL;
     }
     impossible("bc_order:  ball&chain not in same location!");
     return BCPOS_DIFFER;
 }
 

set_bc

 /*
  *  set_bc()
  *
  *  The hero is either about to go blind or already blind and just punished.
  *  Set up the ball and chain variables so that the ball and chain are "felt".
  */
 void
 set_bc(already_blind)
 int already_blind;
 {
     int ball_on_floor = !carried(uball);
 
     u.bc_order = bc_order(); /* get the order */
     u.bc_felt = ball_on_floor ? BC_BALL | BC_CHAIN : BC_CHAIN; /* felt */
 
     if (already_blind || u.uswallow) {
         u.cglyph = u.bglyph = levl[u.ux][u.uy].glyph;
         return;
     }
 
     /*
      *  Since we can still see, remove the ball&chain and get the glyph that
      *  would be beneath them.  Then put the ball&chain back.  This is pretty
      *  disgusting, but it will work.
      */
     remove_object(uchain);
     if (ball_on_floor)
         remove_object(uball);
 
     newsym(uchain->ox, uchain->oy);
     u.cglyph = levl[uchain->ox][uchain->oy].glyph;
 
     if (u.bc_order == BCPOS_DIFFER) { /* different locations */
         place_object(uchain, uchain->ox, uchain->oy);
         newsym(uchain->ox, uchain->oy);
         if (ball_on_floor) {
             newsym(uball->ox, uball->oy); /* see under ball */
             u.bglyph = levl[uball->ox][uball->oy].glyph;
             place_object(uball, uball->ox, uball->oy);
             newsym(uball->ox, uball->oy); /* restore ball */
         }
     } else {
         u.bglyph = u.cglyph;
         if (u.bc_order == BCPOS_CHAIN) {
             place_object(uball, uball->ox, uball->oy);
             place_object(uchain, uchain->ox, uchain->oy);
         } else {
             place_object(uchain, uchain->ox, uchain->oy);
             place_object(uball, uball->ox, uball->oy);
         }
         newsym(uball->ox, uball->oy);
     }
 }
 

move_bc

 /*
  *  move_bc()
  *
  *  Move the ball and chain.  This is called twice for every move.  The first
  *  time to pick up the ball and chain before the move, the second time to
  *  place the ball and chain after the move.  If the ball is carried, this
  *  function should never have BC_BALL as part of its control.
  *
  *  Should not be called while swallowed.
  */
 void
 move_bc(before, control, ballx, bally, chainx, chainy)
 int before, control;
 xchar ballx, bally, chainx, chainy; /* only matter !before */
 {
     if (Blind) {
         /*
          *  The hero is blind.  Time to work hard.  The ball and chain that
          *  are attached to the hero are very special.  The hero knows that
          *  they are attached, so when they move, the hero knows that they
          *  aren't at the last position remembered.  This is complicated
          *  by the fact that the hero can "feel" the surrounding locations
          *  at any time, hence, making one or both of them show up again.
          *  So, we have to keep track of which is felt at any one time and
          *  act accordingly.
          */
         if (!before) {
             if ((control & BC_CHAIN) && (control & BC_BALL)) {
                 /*
                  *  Both ball and chain moved.  If felt, drop glyph.
                  */
                 if (u.bc_felt & BC_BALL)
                     levl[uball->ox][uball->oy].glyph = u.bglyph;
                 if (u.bc_felt & BC_CHAIN)
                     levl[uchain->ox][uchain->oy].glyph = u.cglyph;
                 u.bc_felt = 0;
 
                 /* Pick up glyph at new location. */
                 u.bglyph = levl[ballx][bally].glyph;
                 u.cglyph = levl[chainx][chainy].glyph;
 
                 movobj(uball, ballx, bally);
                 movobj(uchain, chainx, chainy);
             } else if (control & BC_BALL) {
                 if (u.bc_felt & BC_BALL) {
                     if (u.bc_order == BCPOS_DIFFER) { /* ball by itself */
                         levl[uball->ox][uball->oy].glyph = u.bglyph;
                     } else if (u.bc_order == BCPOS_BALL) {
                         if (u.bc_felt & BC_CHAIN) { /* know chain is there */
                             map_object(uchain, 0);
                         } else {
                             levl[uball->ox][uball->oy].glyph = u.bglyph;
                         }
                     }
                     u.bc_felt &= ~BC_BALL; /* no longer feel the ball */
                 }
 
                 /* Pick up glyph at new position. */
                 u.bglyph = (ballx != chainx || bally != chainy)
                                ? levl[ballx][bally].glyph
                                : u.cglyph;
 
                 movobj(uball, ballx, bally);
             } else if (control & BC_CHAIN) {
                 if (u.bc_felt & BC_CHAIN) {
                     if (u.bc_order == BCPOS_DIFFER) {
                         levl[uchain->ox][uchain->oy].glyph = u.cglyph;
                     } else if (u.bc_order == BCPOS_CHAIN) {
                         if (u.bc_felt & BC_BALL) {
                             map_object(uball, 0);
                         } else {
                             levl[uchain->ox][uchain->oy].glyph = u.cglyph;
                         }
                     }
                     u.bc_felt &= ~BC_CHAIN;
                 }
                 /* Pick up glyph at new position. */
                 u.cglyph = (ballx != chainx || bally != chainy)
                                ? levl[chainx][chainy].glyph
                                : u.bglyph;
 
                 movobj(uchain, chainx, chainy);
             }
 
             u.bc_order = bc_order(); /* reset the order */
         }
 
     } else {
         /*
          *  The hero is not blind.  To make this work correctly, we need to
          *  pick up the ball and chain before the hero moves, then put them
          *  in their new positions after the hero moves.
          */
         if (before) {
             if (!control) {
                 /*
                  * Neither ball nor chain is moving, so remember which was
                  * on top until !before.  Use the variable u.bc_order
                  * since it is only valid when blind.
                  */
                 u.bc_order = bc_order();
             }
 
             remove_object(uchain);
             newsym(uchain->ox, uchain->oy);
             if (!carried(uball)) {
                 remove_object(uball);
                 newsym(uball->ox, uball->oy);
             }
         } else {
             int on_floor = !carried(uball);
 
             if ((control & BC_CHAIN)
                 || (!control && u.bc_order == BCPOS_CHAIN)) {
                 /* If the chain moved or nothing moved & chain on top. */
                 if (on_floor)
                     place_object(uball, ballx, bally);
                 place_object(uchain, chainx, chainy); /* chain on top */
             } else {
                 place_object(uchain, chainx, chainy);
                 if (on_floor)
                     place_object(uball, ballx, bally);
                 /* ball on top */
             }
             newsym(chainx, chainy);
             if (on_floor)
                 newsym(ballx, bally);
         }
     }
 }
 

drag_ball

 /* return TRUE if the caller needs to place the ball and chain down again
  *
  *  Should not be called while swallowed.  Should be called before movement,
  *  because we might want to move the ball or chain to the hero's old
  * position.
  *
  * It is called if we are moving.  It is also called if we are teleporting
  * *if* the ball doesn't move and we thus must drag the chain.  It is not
  * called for ordinary teleportation.
  *
  * allow_drag is only used in the ugly special case where teleporting must
  * drag the chain, while an identical-looking movement must drag both the ball
  * and chain.
  */
 boolean
 drag_ball(x, y, bc_control, ballx, bally, chainx, chainy, cause_delay,
           allow_drag)
 xchar x, y;
 int *bc_control;
 xchar *ballx, *bally, *chainx, *chainy;
 boolean *cause_delay;
 boolean allow_drag;
 {
     struct trap *t = (struct trap *) 0;
     boolean already_in_rock;
 
     *ballx = uball->ox;
     *bally = uball->oy;
     *chainx = uchain->ox;
     *chainy = uchain->oy;
     *bc_control = 0;
     *cause_delay = FALSE;
 
     if (dist2(x, y, uchain->ox, uchain->oy) <= 2) { /* nothing moved */
         move_bc(1, *bc_control, *ballx, *bally, *chainx, *chainy);
         return TRUE;
     }
 
     /* only need to move the chain? */
     if (carried(uball) || distmin(x, y, uball->ox, uball->oy) <= 2) {
         xchar oldchainx = uchain->ox, oldchainy = uchain->oy;
         *bc_control = BC_CHAIN;
         move_bc(1, *bc_control, *ballx, *bally, *chainx, *chainy);
         if (carried(uball)) {
             /* move chain only if necessary */
             if (distmin(x, y, uchain->ox, uchain->oy) > 1) {
                 *chainx = u.ux;
                 *chainy = u.uy;
             }
             return TRUE;
         }
 #define CHAIN_IN_MIDDLE(chx, chy) \
     (distmin(x, y, chx, chy) <= 1 \
      && distmin(chx, chy, uball->ox, uball->oy) <= 1)
 #define IS_CHAIN_ROCK(x, y)      \
     (IS_ROCK(levl[x][y].typ)     \
      || (IS_DOOR(levl[x][y].typ) \
          && (levl[x][y].doormask & (D_CLOSED | D_LOCKED))))
 /* Don't ever move the chain into solid rock.  If we have to, then instead
  * undo the move_bc() and jump to the drag ball code.  Note that this also
  * means the "cannot carry and drag" message will not appear, since unless we
  * moved at least two squares there is no possibility of the chain position
  * being in solid rock.
  */
 #define SKIP_TO_DRAG                                               \
     {                                                              \
         *chainx = oldchainx;                                       \
         *chainy = oldchainy;                                       \
         move_bc(0, *bc_control, *ballx, *bally, *chainx, *chainy); \
         goto drag;                                                 \
     }
         if (IS_CHAIN_ROCK(u.ux, u.uy) || IS_CHAIN_ROCK(*chainx, *chainy)
             || IS_CHAIN_ROCK(uball->ox, uball->oy))
             already_in_rock = TRUE;
         else
             already_in_rock = FALSE;
 
         switch (dist2(x, y, uball->ox, uball->oy)) {
         /* two spaces diagonal from ball, move chain inbetween */
         case 8:
             *chainx = (uball->ox + x) / 2;
             *chainy = (uball->oy + y) / 2;
             if (IS_CHAIN_ROCK(*chainx, *chainy) && !already_in_rock)
                 SKIP_TO_DRAG;
             break;
 
         /* player is distance 2/1 from ball; move chain to one of the
          * two spaces between
          *   @
          *   __
          *    0
          */
         case 5: {
             xchar tempx, tempy, tempx2, tempy2;
 
             /* find position closest to current position of chain */
             /* no effect if current position is already OK */
             if (abs(x - uball->ox) == 1) {
                 tempx = x;
                 tempx2 = uball->ox;
                 tempy = tempy2 = (uball->oy + y) / 2;
             } else {
                 tempx = tempx2 = (uball->ox + x) / 2;
                 tempy = y;
                 tempy2 = uball->oy;
             }
             if (IS_CHAIN_ROCK(tempx, tempy) && !IS_CHAIN_ROCK(tempx2, tempy2)
                 && !already_in_rock) {
                 if (allow_drag) {
                     /* Avoid pathological case *if* not teleporting:
                      *   0                          0_
                      *   _X  move northeast  ----->  X@
                      *    @
                      */
                     if (dist2(u.ux, u.uy, uball->ox, uball->oy) == 5
                         && dist2(x, y, tempx, tempy) == 1)
                         SKIP_TO_DRAG;
                     /* Avoid pathological case *if* not teleporting:
                      *    0                          0
                      *   _X  move east       ----->  X_
                      *    @                           @
                      */
                     if (dist2(u.ux, u.uy, uball->ox, uball->oy) == 4
                         && dist2(x, y, tempx, tempy) == 2)
                         SKIP_TO_DRAG;
                 }
                 *chainx = tempx2;
                 *chainy = tempy2;
             } else if (!IS_CHAIN_ROCK(tempx, tempy)
                        && IS_CHAIN_ROCK(tempx2, tempy2) && !already_in_rock) {
                 if (allow_drag) {
                     if (dist2(u.ux, u.uy, uball->ox, uball->oy) == 5
                         && dist2(x, y, tempx2, tempy2) == 1)
                         SKIP_TO_DRAG;
                     if (dist2(u.ux, u.uy, uball->ox, uball->oy) == 4
                         && dist2(x, y, tempx2, tempy2) == 2)
                         SKIP_TO_DRAG;
                 }
                 *chainx = tempx;
                 *chainy = tempy;
             } else if (IS_CHAIN_ROCK(tempx, tempy)
                        && IS_CHAIN_ROCK(tempx2, tempy2) && !already_in_rock) {
                 SKIP_TO_DRAG;
             } else if (dist2(tempx, tempy, uchain->ox, uchain->oy)
                            < dist2(tempx2, tempy2, uchain->ox, uchain->oy)
                        || ((dist2(tempx, tempy, uchain->ox, uchain->oy)
                             == dist2(tempx2, tempy2, uchain->ox, uchain->oy))
                            && rn2(2))) {
                 *chainx = tempx;
                 *chainy = tempy;
             } else {
                 *chainx = tempx2;
                 *chainy = tempy2;
             }
             break;
         }
 
         /* ball is two spaces horizontal or vertical from player; move*/
         /* chain inbetween *unless* current chain position is OK */
         case 4:
             if (CHAIN_IN_MIDDLE(uchain->ox, uchain->oy))
                 break;
             *chainx = (x + uball->ox) / 2;
             *chainy = (y + uball->oy) / 2;
             if (IS_CHAIN_ROCK(*chainx, *chainy) && !already_in_rock)
                 SKIP_TO_DRAG;
             break;
 
         /* ball is one space diagonal from player.  Check for the
          * following special case:
          *   @
          *    _    moving southwest becomes  @_
          *   0                                0
          * (This will also catch teleporting that happens to resemble
          * this case, but oh well.)  Otherwise fall through.
          */
         case 2:
             if (dist2(x, y, uball->ox, uball->oy) == 2
                 && dist2(x, y, uchain->ox, uchain->oy) == 4) {
                 if (uchain->oy == y)
                     *chainx = uball->ox;
                 else
                     *chainy = uball->oy;
                 if (IS_CHAIN_ROCK(*chainx, *chainy) && !already_in_rock)
                     SKIP_TO_DRAG;
                 break;
             }
         /* fall through */
         case 1:
         case 0:
             /* do nothing if possible */
             if (CHAIN_IN_MIDDLE(uchain->ox, uchain->oy))
                 break;
             /* otherwise try to drag chain to player's old position */
             if (CHAIN_IN_MIDDLE(u.ux, u.uy)) {
                 *chainx = u.ux;
                 *chainy = u.uy;
                 break;
             }
             /* otherwise use player's new position (they must have
                teleported, for this to happen) */
             *chainx = x;
             *chainy = y;
             break;
 
         default:
             impossible("bad chain movement");
             break;
         }
 #undef SKIP_TO_DRAG
 #undef CHAIN_IN_MIDDLE
         return TRUE;
     }
 
 drag:
 
     if (near_capacity() > SLT_ENCUMBER && dist2(x, y, u.ux, u.uy) <= 2) {
         You("cannot %sdrag the heavy iron ball.",
             invent ? "carry all that and also " : "");
         nomul(0);
         return FALSE;
     }
 
     if ((is_pool(uchain->ox, uchain->oy)
          /* water not mere continuation of previous water */
          && (levl[uchain->ox][uchain->oy].typ == POOL
              || !is_pool(uball->ox, uball->oy)
              || levl[uball->ox][uball->oy].typ == POOL))
         || ((t = t_at(uchain->ox, uchain->oy))
             && (t->ttyp == PIT || t->ttyp == SPIKED_PIT || t->ttyp == HOLE
                 || t->ttyp == TRAPDOOR))) {
         if (Levitation) {
             You_feel("a tug from the iron ball.");
             if (t)
                 t->tseen = 1;
         } else {
             struct monst *victim;
 
             You("are jerked back by the iron ball!");
             if ((victim = m_at(uchain->ox, uchain->oy)) != 0) {
                 int tmp;
 
                 tmp = -2 + Luck + find_mac(victim);
                 tmp += omon_adj(victim, uball, TRUE);
                 if (tmp >= rnd(20))
                     (void) hmon(victim, uball, HMON_DRAGGED);
                 else
                     miss(xname(uball), victim);
 
             } /* now check again in case mon died */
             if (!m_at(uchain->ox, uchain->oy)) {
                 u.ux = uchain->ox;
                 u.uy = uchain->oy;
                 newsym(u.ux0, u.uy0);
             }
             nomul(0);
 
             *bc_control = BC_BALL;
             move_bc(1, *bc_control, *ballx, *bally, *chainx, *chainy);
             *ballx = uchain->ox;
             *bally = uchain->oy;
             move_bc(0, *bc_control, *ballx, *bally, *chainx, *chainy);
             spoteffects(TRUE);
             return FALSE;
         }
     }
 
     *bc_control = BC_BALL | BC_CHAIN;
 
     move_bc(1, *bc_control, *ballx, *bally, *chainx, *chainy);
     if (dist2(x, y, u.ux, u.uy) > 2) {
         /* Awful case: we're still in range of the ball, so we thought we
          * could only move the chain, but it turned out that the target
          * square for the chain was rock, so we had to drag it instead.
          * But we can't drag it either, because we teleported and are more
          * than one square from our old position.  Revert to the teleport
          * behavior.
          */
         *ballx = *chainx = x;
         *bally = *chainy = y;
     } else {
         xchar newchainx = u.ux, newchainy = u.uy;
 
         /*
          * Generally, chain moves to hero's previous location and ball
          * moves to chain's previous location, except that we try to
          * keep the chain directly between the hero and the ball.  But,
          * take the simple approach if the hero's previous location or
          * the potential between location is inaccessible.
          */
         if (dist2(x, y, uchain->ox, uchain->oy) == 4
             && !IS_CHAIN_ROCK(newchainx, newchainy)) {
             newchainx = (x + uchain->ox) / 2;
             newchainy = (y + uchain->oy) / 2;
             if (IS_CHAIN_ROCK(newchainx, newchainy)) {
                 /* don't let chain move to inaccessible location */
                 newchainx = u.ux;
                 newchainy = u.uy;
             }
         }
 
         *ballx = uchain->ox;
         *bally = uchain->oy;
         *chainx = newchainx;
         *chainy = newchainy;
     }
 #undef IS_CHAIN_ROCK
     *cause_delay = TRUE;
     return TRUE;
 }
 

drop_ball

 /*
  *  drop_ball()
  *
  *  The punished hero drops or throws her iron ball.  If the hero is
  *  blind, we must reset the order and glyph.  Check for side effects.
  *  This routine expects the ball to be already placed.
  *
  *  Should not be called while swallowed.
  */
 void
 drop_ball(x, y)
 xchar x, y;
 {
     if (Blind) {
         /* get the order */
         u.bc_order = bc_order();
         /* pick up glyph */
         u.bglyph = (u.bc_order) ? u.cglyph : levl[x][y].glyph;
     }
 
     if (x != u.ux || y != u.uy) {
         struct trap *t;
         const char *pullmsg = "The ball pulls you out of the %s!";
 
         if (u.utrap && u.utraptype != TT_INFLOOR
             && u.utraptype != TT_BURIEDBALL) {
             switch (u.utraptype) {
             case TT_PIT:
                 pline(pullmsg, "pit");
                 break;
             case TT_WEB:
                 pline(pullmsg, "web");
                 pline_The("web is destroyed!");
                 deltrap(t_at(u.ux, u.uy));
                 break;
             case TT_LAVA:
                 pline(pullmsg, "lava");
                 break;
             case TT_BEARTRAP: {
                 register long side = rn2(3) ? LEFT_SIDE : RIGHT_SIDE;
                 pline(pullmsg, "bear trap");
                 set_wounded_legs(side, rn1(1000, 500));
                 if (!u.usteed) {
                     Your("%s %s is severely damaged.",
                          (side == LEFT_SIDE) ? "left" : "right",
                          body_part(LEG));
                     losehp(Maybe_Half_Phys(2),
                            "leg damage from being pulled out of a bear trap",
                            KILLED_BY);
                 }
                 break;
             }
             }
             u.utrap = 0;
             fill_pit(u.ux, u.uy);
         }
 
         u.ux0 = u.ux;
         u.uy0 = u.uy;
         if (!Levitation && !MON_AT(x, y) && !u.utrap
             && (is_pool(x, y)
                 || ((t = t_at(x, y))
                     && (t->ttyp == PIT || t->ttyp == SPIKED_PIT
                         || t->ttyp == TRAPDOOR || t->ttyp == HOLE)))) {
             u.ux = x;
             u.uy = y;
         } else {
             u.ux = x - u.dx;
             u.uy = y - u.dy;
         }
         vision_full_recalc = 1; /* hero has moved, recalculate vision later */
 
         if (Blind) {
             /* drop glyph under the chain */
             if (u.bc_felt & BC_CHAIN)
                 levl[uchain->ox][uchain->oy].glyph = u.cglyph;
             u.bc_felt = 0; /* feel nothing */
             /* pick up new glyph */
             u.cglyph = (u.bc_order) ? u.bglyph : levl[u.ux][u.uy].glyph;
         }
         movobj(uchain, u.ux, u.uy); /* has a newsym */
         if (Blind) {
             u.bc_order = bc_order();
         }
         newsym(u.ux0, u.uy0); /* clean up old position */
         if (u.ux0 != u.ux || u.uy0 != u.uy) {
             spoteffects(TRUE);
             sokoban_guilt();
         }
     }
 }
 

litter

 STATIC_OVL void
 litter()
 {
     struct obj *otmp = invent, *nextobj;
     int capacity = weight_cap();
 
     while (otmp) {
         nextobj = otmp->nobj;
         if ((otmp != uball) && (rnd(capacity) <= (int) otmp->owt)) {
             if (canletgo(otmp, "")) {
                 pline("%s you down the stairs.", Yobjnam2(otmp, "follow"));
                 dropx(otmp);
             }
         }
         otmp = nextobj;
     }
 }
 

drag_down

 void
 drag_down()
 {
     boolean forward;
     uchar dragchance = 3;
 
     /*
      *  Assume that the ball falls forward if:
      *
      *  a) the character is wielding it, or
      *  b) the character has both hands available to hold it (i.e. is
      *     not wielding any weapon), or
      *  c) (perhaps) it falls forward out of his non-weapon hand
      */
     forward = carried(uball) && (uwep == uball || !uwep || !rn2(3));
 
     if (carried(uball))
         You("lose your grip on the iron ball.");
 
     if (forward) {
         if (rn2(6)) {
             pline_The("iron ball drags you downstairs!");
             losehp(Maybe_Half_Phys(rnd(6)),
                    "dragged downstairs by an iron ball", NO_KILLER_PREFIX);
             litter();
         }
     } else {
         if (rn2(2)) {
             pline_The("iron ball smacks into you!");
             losehp(Maybe_Half_Phys(rnd(20)), "iron ball collision",
                    KILLED_BY_AN);
             exercise(A_STR, FALSE);
             dragchance -= 2;
         }
         if ((int) dragchance >= rnd(6)) {
             pline_The("iron ball drags you downstairs!");
             losehp(Maybe_Half_Phys(rnd(3)),
                    "dragged downstairs by an iron ball", NO_KILLER_PREFIX);
             exercise(A_STR, FALSE);
             litter();
         }
     }
 }
 
 /*ball.c*/