/*      $OpenBSD: pickmove.c,v 1.16 2016/01/08 21:38:33 mestre Exp $    */
/*
 * Copyright (c) 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Ralph Campbell.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <curses.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>

#include "gomoku.h"

#define BITS_PER_INT    (sizeof(int) * CHAR_BIT)
#define MAPSZ           (BAREA / BITS_PER_INT)

#define BIT_SET(a, b)   ((a)[(b)/BITS_PER_INT] |= (1 << ((b) % BITS_PER_INT)))
#define BIT_CLR(a, b)   ((a)[(b)/BITS_PER_INT] &= ~(1 << ((b) % BITS_PER_INT)))
#define BIT_TEST(a, b)  ((a)[(b)/BITS_PER_INT] & (1 << ((b) % BITS_PER_INT)))

struct  combostr *hashcombos[FAREA];    /* hash list for finding duplicates */
struct  combostr *sortcombos;           /* combos at higher levels */
int     combolen;                       /* number of combos in sortcombos */
int     nextcolor;                      /* color of next move */
int     elistcnt;                       /* count of struct elist allocated */
int     combocnt;                       /* count of struct combostr allocated */
int     forcemap[MAPSZ];                /* map for blocking <1,x> combos */
int     tmpmap[MAPSZ];                  /* map for blocking <1,x> combos */
int     nforce;                         /* count of opponent <1,x> combos */

int
pickmove(int us)
{
        struct spotstr *sp, *sp1, *sp2;
        union comboval *Ocp, *Tcp;
        int m;

        /* first move is easy */
        if (movenum == 1)
                return (PT(K,10));

        /* initialize all the board values */
        for (sp = &board[PT(T,20)]; --sp >= &board[PT(A,1)]; ) {
                sp->s_combo[BLACK].s = MAXCOMBO + 1;
                sp->s_combo[WHITE].s = MAXCOMBO + 1;
                sp->s_level[BLACK] = 255;
                sp->s_level[WHITE] = 255;
                sp->s_nforce[BLACK] = 0;
                sp->s_nforce[WHITE] = 0;
                sp->s_flg &= ~(FFLAGALL | MFLAGALL);
        }
        nforce = 0;
        memset(forcemap, 0, sizeof(forcemap));

        /* compute new values */
        nextcolor = us;
        scanframes(BLACK);
        scanframes(WHITE);

        /* find the spot with the highest value */
        for (sp = sp1 = sp2 = &board[PT(T,19)]; --sp >= &board[PT(A,1)]; ) {
                if (sp->s_occ != EMPTY)
                        continue;
                if (debug && (sp->s_combo[BLACK].c.a == 1 ||
                    sp->s_combo[WHITE].c.a == 1)) {
                        snprintf(fmtbuf, sizeof fmtbuf,
                                "- %s %x/%d %d %x/%d %d %d", stoc(sp - board),
                                sp->s_combo[BLACK].s, sp->s_level[BLACK],
                                sp->s_nforce[BLACK],
                                sp->s_combo[WHITE].s, sp->s_level[WHITE],
                                sp->s_nforce[WHITE],
                                sp->s_wval);
                        dlog(fmtbuf);
                }
                /* pick the best black move */
                if (better(sp, sp1, BLACK))
                        sp1 = sp;
                /* pick the best white move */
                if (better(sp, sp2, WHITE))
                        sp2 = sp;
        }

        if (debug) {
                snprintf(fmtbuf, sizeof fmtbuf,
                        "B %s %x/%d %d %x/%d %d %d",
                        stoc(sp1 - board),
                        sp1->s_combo[BLACK].s, sp1->s_level[BLACK],
                        sp1->s_nforce[BLACK],
                        sp1->s_combo[WHITE].s, sp1->s_level[WHITE],
                        sp1->s_nforce[WHITE], sp1->s_wval);
                dlog(fmtbuf);
                snprintf(fmtbuf, sizeof fmtbuf,
                        "W %s %x/%d %d %x/%d %d %d",
                        stoc(sp2 - board),
                        sp2->s_combo[WHITE].s, sp2->s_level[WHITE],
                        sp2->s_nforce[WHITE],
                        sp2->s_combo[BLACK].s, sp2->s_level[BLACK],
                        sp2->s_nforce[BLACK], sp2->s_wval);
                dlog(fmtbuf);
                /*
                 * Check for more than one force that can't
                 * all be blocked with one move.
                 */
                sp = (us == BLACK) ? sp2 : sp1;
                m = sp - board;
                if (sp->s_combo[!us].c.a == 1 && !BIT_TEST(forcemap, m))
                        dlog("*** Can't be blocked");
        }
        if (us == BLACK) {
                Ocp = &sp1->s_combo[BLACK];
                Tcp = &sp2->s_combo[WHITE];
        } else {
                Tcp = &sp1->s_combo[BLACK];
                Ocp = &sp2->s_combo[WHITE];
                sp = sp1;
                sp1 = sp2;
                sp2 = sp;
        }
        /*
         * Block their combo only if we have to (i.e., if they are one move
         * away from completing a force and we don't have a force that
         * we can complete which takes fewer moves to win).
         */
        if (Tcp->c.a <= 1 && (Ocp->c.a > 1 ||
            Tcp->c.a + Tcp->c.b < Ocp->c.a + Ocp->c.b))
                return (sp2 - board);
        return (sp1 - board);
}

/*
 * Return true if spot 'sp' is better than spot 'sp1' for color 'us'.
 */
int
better(struct spotstr *sp, struct spotstr *sp1, int us)
{
        int them, s, s1;

        if (sp->s_combo[us].s < sp1->s_combo[us].s)
                return (1);
        if (sp->s_combo[us].s != sp1->s_combo[us].s)
                return (0);
        if (sp->s_level[us] < sp1->s_level[us])
                return (1);
        if (sp->s_level[us] != sp1->s_level[us])
                return (0);
        if (sp->s_nforce[us] > sp1->s_nforce[us])
                return (1);
        if (sp->s_nforce[us] != sp1->s_nforce[us])
                return (0);

        them = !us;
        s = sp - board;
        s1 = sp1 - board;
        if (BIT_TEST(forcemap, s) && !BIT_TEST(forcemap, s1))
                return (1);
        if (!BIT_TEST(forcemap, s) && BIT_TEST(forcemap, s1))
                return (0);
        if (sp->s_combo[them].s < sp1->s_combo[them].s)
                return (1);
        if (sp->s_combo[them].s != sp1->s_combo[them].s)
                return (0);
        if (sp->s_level[them] < sp1->s_level[them])
                return (1);
        if (sp->s_level[them] != sp1->s_level[them])
                return (0);
        if (sp->s_nforce[them] > sp1->s_nforce[them])
                return (1);
        if (sp->s_nforce[them] != sp1->s_nforce[them])
                return (0);

        if (sp->s_wval > sp1->s_wval)
                return (1);
        if (sp->s_wval != sp1->s_wval)
                return (0);

        return (arc4random() & 1);
}

int     curcolor;       /* implicit parameter to makecombo() */
int     curlevel;       /* implicit parameter to makecombo() */

/*
 * Scan the sorted list of non-empty frames and
 * update the minimum combo values for each empty spot.
 * Also, try to combine frames to find more complex (chained) moves.
 */
void
scanframes(int color)
{
        struct combostr *cbp, *ecbp;
        struct spotstr *sp;
        union comboval *cp;
        struct elist *ep, *nep;
        int i, r, d, n;
        union comboval cb;

        curcolor = color;

        /* check for empty list of frames */
        cbp = sortframes[color];
        if (cbp == (struct combostr *)0)
                return;

        /* quick check for four in a row */
        sp = &board[cbp->c_vertex];
        cb.s = sp->s_fval[color][d = cbp->c_dir].s;
        if (cb.s < 0x101) {
                d = dd[d];
                for (i = 5 + cb.c.b; --i >= 0; sp += d) {
                        if (sp->s_occ != EMPTY)
                                continue;
                        sp->s_combo[color].s = cb.s;
                        sp->s_level[color] = 1;
                }
                return;
        }

        /*
         * Update the minimum combo value for each spot in the frame
         * and try making all combinations of two frames intersecting at
         * an empty spot.
         */
        n = combolen;
        ecbp = cbp;
        do {
                sp = &board[cbp->c_vertex];
                cp = &sp->s_fval[color][r = cbp->c_dir];
                d = dd[r];
                if (cp->c.b) {
                        /*
                         * Since this is the first spot of an open ended
                         * frame, we treat it as a closed frame.
                         */
                        cb.c.a = cp->c.a + 1;
                        cb.c.b = 0;
                        if (cb.s < sp->s_combo[color].s) {
                                sp->s_combo[color].s = cb.s;
                                sp->s_level[color] = 1;
                        }
                        /*
                         * Try combining other frames that intersect
                         * at this spot.
                         */
                        makecombo2(cbp, sp, 0, cb.s);
                        if (cp->s != 0x101)
                                cb.s = cp->s;
                        else if (color != nextcolor)
                                memset(tmpmap, 0, sizeof(tmpmap));
                        sp += d;
                        i = 1;
                } else {
                        cb.s = cp->s;
                        i = 0;
                }
                for (; i < 5; i++, sp += d) {   /* for each spot */
                        if (sp->s_occ != EMPTY)
                                continue;
                        if (cp->s < sp->s_combo[color].s) {
                                sp->s_combo[color].s = cp->s;
                                sp->s_level[color] = 1;
                        }
                        if (cp->s == 0x101) {
                                sp->s_nforce[color]++;
                                if (color != nextcolor) {
                                        n = sp - board;
                                        BIT_SET(tmpmap, n);
                                }
                        }
                        /*
                         * Try combining other frames that intersect
                         * at this spot.
                         */
                        makecombo2(cbp, sp, i, cb.s);
                }
                if (cp->s == 0x101 && color != nextcolor) {
                        if (nforce == 0)
                                memcpy(forcemap, tmpmap, sizeof(tmpmap));
                        else {
                                for (i = 0; i < MAPSZ; i++)
                                        forcemap[i] &= tmpmap[i];
                        }
                }
                /* mark frame as having been processed */
                board[cbp->c_vertex].s_flg |= MFLAG << r;
        } while ((cbp = cbp->c_next) != ecbp);

        /*
         * Try to make new 3rd level combos, 4th level, etc.
         * Limit the search depth early in the game.
         */
        d = 2;
        while (d <= ((unsigned)(movenum + 1) >> 1) && combolen > n) {
                if (debug) {
                        snprintf(fmtbuf, sizeof fmtbuf,
                                "%cL%d %d %d %d", "BW"[color],
                                d, combolen - n, combocnt, elistcnt);
                        dlog(fmtbuf);
                        refresh();
                }
                n = combolen;
                addframes(d);
                d++;
        }

        /* scan for combos at empty spots */
        for (sp = &board[PT(T,20)]; --sp >= &board[PT(A,1)]; ) {
                for (ep = sp->s_empty; ep; ep = nep) {
                        cbp = ep->e_combo;
                        if (cbp->c_combo.s <= sp->s_combo[color].s) {
                                if (cbp->c_combo.s != sp->s_combo[color].s) {
                                        sp->s_combo[color].s = cbp->c_combo.s;
                                        sp->s_level[color] = cbp->c_nframes;
                                } else if (cbp->c_nframes < sp->s_level[color])
                                        sp->s_level[color] = cbp->c_nframes;
                        }
                        nep = ep->e_next;
                        free(ep);
                        elistcnt--;
                }
                sp->s_empty = (struct elist *)0;
                for (ep = sp->s_nempty; ep; ep = nep) {
                        cbp = ep->e_combo;
                        if (cbp->c_combo.s <= sp->s_combo[color].s) {
                                if (cbp->c_combo.s != sp->s_combo[color].s) {
                                        sp->s_combo[color].s = cbp->c_combo.s;
                                        sp->s_level[color] = cbp->c_nframes;
                                } else if (cbp->c_nframes < sp->s_level[color])
                                        sp->s_level[color] = cbp->c_nframes;
                        }
                        nep = ep->e_next;
                        free(ep);
                        elistcnt--;
                }
                sp->s_nempty = (struct elist *)0;
        }

        /* remove old combos */
        if ((cbp = sortcombos) != (struct combostr *)0) {
                struct combostr *ncbp;

                /* scan the list */
                ecbp = cbp;
                do {
                        ncbp = cbp->c_next;
                        free(cbp);
                        combocnt--;
                } while ((cbp = ncbp) != ecbp);
                sortcombos = (struct combostr *)0;
        }
        combolen = 0;

#ifdef DEBUG
        if (combocnt) {
                snprintf(fmtbuf, sizeof fmtbuf,
                        "scanframes: %c combocnt %d", "BW"[color],
                        combocnt);
                dlog(fmtbuf);
                whatsup(0);
        }
        if (elistcnt) {
                snprintf(fmtbuf, sizeof fmtbuf,
                        "scanframes: %c elistcnt %d", "BW"[color],
                        elistcnt);
                dlog(fmtbuf);
                whatsup(0);
        }
#endif
}

/*
 * Compute all level 2 combos of frames intersecting spot 'osp'
 * within the frame 'ocbp' and combo value 's'.
 */
void
makecombo2(struct combostr *ocbp, struct spotstr *osp, int off, int s)
{
        struct spotstr *fsp;
        struct combostr *ncbp;
        int f, r, d, c;
        int baseB, fcnt, emask, bmask, n;
        union comboval ocb, fcb;
        struct combostr **scbpp, *fcbp;

        /* try to combine a new frame with those found so far */
        ocb.s = s;
        baseB = ocb.c.a + ocb.c.b - 1;
        fcnt = ocb.c.a - 2;
        emask = fcnt ? ((ocb.c.b ? 0x1E : 0x1F) & ~(1 << off)) : 0;
        for (r = 4; --r >= 0; ) {                       /* for each direction */
            /* don't include frames that overlap in the same direction */
            if (r == ocbp->c_dir)
                continue;
            d = dd[r];
            /*
             * Frame A combined with B is the same value as B combined with A
             * so skip frames that have already been processed (MFLAG).
             * Also skip blocked frames (BFLAG) and frames that are <1,x>
             * since combining another frame with it isn't valid.
             */
            bmask = (BFLAG | FFLAG | MFLAG) << r;
            fsp = osp;
            for (f = 0; f < 5; f++, fsp -= d) {         /* for each frame */
                if (fsp->s_occ == BORDER)
                    break;
                if (fsp->s_flg & bmask)
                    continue;

                /* don't include frames of the wrong color */
                fcb.s = fsp->s_fval[curcolor][r].s;
                if (fcb.c.a >= MAXA)
                    continue;

                /*
                 * Get the combo value for this frame.
                 * If this is the end point of the frame,
                 * use the closed ended value for the frame.
                 */
                if (f == 0 && (fcb.c.b || fcb.s == 0x101)) {
                    fcb.c.a++;
                    fcb.c.b = 0;
                }

                /* compute combo value */
                c = fcb.c.a + ocb.c.a - 3;
                if (c > 4)
                    continue;
                n = fcb.c.a + fcb.c.b - 1;
                if (baseB < n)
                    n = baseB;

                /* make a new combo! */
                ncbp = reallocarray(NULL, 3, sizeof(struct combostr));
                if (ncbp == (struct combostr *)NULL)
                    qlog("Memory allocation failure.");
                scbpp = (struct combostr **)(ncbp + 1);
                fcbp = fsp->s_frame[r];
                if (ocbp < fcbp) {
                    scbpp[0] = ocbp;
                    scbpp[1] = fcbp;
                } else {
                    scbpp[0] = fcbp;
                    scbpp[1] = ocbp;
                }
                ncbp->c_combo.c.a = c;
                ncbp->c_combo.c.b = n;
                ncbp->c_link[0] = ocbp;
                ncbp->c_link[1] = fcbp;
                ncbp->c_linkv[0].s = ocb.s;
                ncbp->c_linkv[1].s = fcb.s;
                ncbp->c_voff[0] = off;
                ncbp->c_voff[1] = f;
                ncbp->c_vertex = osp - board;
                ncbp->c_nframes = 2;
                ncbp->c_dir = 0;
                ncbp->c_frameindex = 0;
                ncbp->c_flg = (ocb.c.b) ? C_OPEN_0 : 0;
                if (fcb.c.b)
                    ncbp->c_flg |= C_OPEN_1;
                ncbp->c_framecnt[0] = fcnt;
                ncbp->c_emask[0] = emask;
                ncbp->c_framecnt[1] = fcb.c.a - 2;
                ncbp->c_emask[1] = ncbp->c_framecnt[1] ?
                    ((fcb.c.b ? 0x1E : 0x1F) & ~(1 << f)) : 0;
                combocnt++;

                if (c == 1 && debug > 1) {
                    snprintf(fmtbuf, sizeof fmtbuf,
                        "%c c %d %d m %x %x o %d %d",
                        "bw"[curcolor],
                        ncbp->c_framecnt[0], ncbp->c_framecnt[1],
                        ncbp->c_emask[0], ncbp->c_emask[1],
                        ncbp->c_voff[0], ncbp->c_voff[1]);
                    dlog(fmtbuf);
                    printcombo(ncbp, fmtbuf, sizeof fmtbuf);
                    dlog(fmtbuf);
                }
                if (c > 1) {
                    /* record the empty spots that will complete this combo */
                    makeempty(ncbp);

                    /* add the new combo to the end of the list */
                    appendcombo(ncbp);
                } else {
                    updatecombo(ncbp, curcolor);
                    free(ncbp);
                    combocnt--;
                }
#ifdef DEBUG
                if (c == 1 && debug > 1 || debug > 5) {
                    markcombo(ncbp);
                    bdisp();
                    whatsup(0);
                    clearcombo(ncbp, 0);
                }
#endif /* DEBUG */
            }
        }
}

/*
 * Scan the sorted list of frames and try to add a frame to
 * combinations of 'level' number of frames.
 */
void
addframes(int level)
{
        struct combostr *cbp, *ecbp;
        struct spotstr *sp, *fsp;
        struct elist *ep, *nep;
        int i, r, d;
        struct combostr **cbpp, *pcbp;
        union comboval fcb, cb;

        curlevel = level;

        /* scan for combos at empty spots */
        i = curcolor;
        for (sp = &board[PT(T,20)]; --sp >= &board[PT(A,1)]; ) {
                for (ep = sp->s_empty; ep; ep = nep) {
                        cbp = ep->e_combo;
                        if (cbp->c_combo.s <= sp->s_combo[i].s) {
                                if (cbp->c_combo.s != sp->s_combo[i].s) {
                                        sp->s_combo[i].s = cbp->c_combo.s;
                                        sp->s_level[i] = cbp->c_nframes;
                                } else if (cbp->c_nframes < sp->s_level[i])
                                        sp->s_level[i] = cbp->c_nframes;
                        }
                        nep = ep->e_next;
                        free(ep);
                        elistcnt--;
                }
                sp->s_empty = sp->s_nempty;
                sp->s_nempty = (struct elist *)0;
        }

        /* try to add frames to the uncompleted combos at level curlevel */
        cbp = ecbp = sortframes[curcolor];
        do {
                fsp = &board[cbp->c_vertex];
                r = cbp->c_dir;
                /* skip frames that are part of a <1,x> combo */
                if (fsp->s_flg & (FFLAG << r))
                        continue;

                /*
                 * Don't include <1,x> combo frames,
                 * treat it as a closed three in a row instead.
                 */
                fcb.s = fsp->s_fval[curcolor][r].s;
                if (fcb.s == 0x101)
                        fcb.s = 0x200;

                /*
                 * If this is an open ended frame, use
                 * the combo value with the end closed.
                 */
                if (fsp->s_occ == EMPTY) {
                        if (fcb.c.b) {
                                cb.c.a = fcb.c.a + 1;
                                cb.c.b = 0;
                        } else
                                cb.s = fcb.s;
                        makecombo(cbp, fsp, 0, cb.s);
                }

                /*
                 * The next four spots are handled the same for both
                 * open and closed ended frames.
                 */
                d = dd[r];
                sp = fsp + d;
                for (i = 1; i < 5; i++, sp += d) {
                        if (sp->s_occ != EMPTY)
                                continue;
                        makecombo(cbp, sp, i, fcb.s);
                }
        } while ((cbp = cbp->c_next) != ecbp);

        /* put all the combos in the hash list on the sorted list */
        cbpp = &hashcombos[FAREA];
        do {
                cbp = *--cbpp;
                if (cbp == (struct combostr *)0)
                        continue;
                *cbpp = (struct combostr *)0;
                ecbp = sortcombos;
                if (ecbp == (struct combostr *)0)
                        sortcombos = cbp;
                else {
                        /* append to sort list */
                        pcbp = ecbp->c_prev;
                        pcbp->c_next = cbp;
                        ecbp->c_prev = cbp->c_prev;
                        cbp->c_prev->c_next = ecbp;
                        cbp->c_prev = pcbp;
                }
        } while (cbpp != hashcombos);
}

/*
 * Compute all level N combos of frames intersecting spot 'osp'
 * within the frame 'ocbp' and combo value 's'.
 */
void
makecombo(struct combostr *ocbp, struct spotstr *osp, int off, int s)
{
        struct combostr *cbp, *ncbp;
        struct spotstr *sp;
        struct elist *ep;
        int n, c;
        struct elist *nep;
        struct combostr **scbpp;
        int baseB, fcnt, emask, verts;
        union comboval ocb;
        struct ovlp_info vertices[1];

        ocb.s = s;
        baseB = ocb.c.a + ocb.c.b - 1;
        fcnt = ocb.c.a - 2;
        emask = fcnt ? ((ocb.c.b ? 0x1E : 0x1F) & ~(1 << off)) : 0;
        for (ep = osp->s_empty; ep; ep = ep->e_next) {
            /* check for various kinds of overlap */
            cbp = ep->e_combo;
            verts = checkframes(cbp, ocbp, osp, s, vertices);
            if (verts < 0)
                continue;

            /* check to see if this frame forms a valid loop */
            if (verts) {
                sp = &board[vertices[0].o_intersect];
#ifdef DEBUG
                if (sp->s_occ != EMPTY) {
                    snprintf(fmtbuf, sizeof fmtbuf,
                        "loop: %c %s", "BW"[curcolor],
                        stoc(sp - board));
                    dlog(fmtbuf);
                    whatsup(0);
                }
#endif
                /*
                 * It is a valid loop if the intersection spot
                 * of the frame we are trying to attach is one
                 * of the completion spots of the combostr
                 * we are trying to attach the frame to.
                 */
                for (nep = sp->s_empty; nep; nep = nep->e_next) {
                    if (nep->e_combo == cbp)
                        goto fnd;
                    if (nep->e_combo->c_nframes < cbp->c_nframes)
                        break;
                }
                /* frame overlaps but not at a valid spot */
                continue;
            fnd:
                ;
            }

            /* compute the first half of the combo value */
            c = cbp->c_combo.c.a + ocb.c.a - verts - 3;
            if (c > 4)
                continue;

            /* compute the second half of the combo value */
            n = ep->e_fval.c.a + ep->e_fval.c.b - 1;
            if (baseB < n)
                n = baseB;

            /* make a new combo! */
            ncbp = malloc(sizeof(struct combostr) +
                (cbp->c_nframes + 1) * sizeof(struct combostr *));
            if (ncbp == (struct combostr *)NULL)
                qlog("Memory allocation failure.");
            scbpp = (struct combostr **)(ncbp + 1);
            if (sortcombo(scbpp, (struct combostr **)(cbp + 1), ocbp)) {
                free(ncbp);
                continue;
            }
            combocnt++;

            ncbp->c_combo.c.a = c;
            ncbp->c_combo.c.b = n;
            ncbp->c_link[0] = cbp;
            ncbp->c_link[1] = ocbp;
            ncbp->c_linkv[1].s = ocb.s;
            ncbp->c_voff[1] = off;
            ncbp->c_vertex = osp - board;
            ncbp->c_nframes = cbp->c_nframes + 1;
            ncbp->c_flg = ocb.c.b ? C_OPEN_1 : 0;
            ncbp->c_frameindex = ep->e_frameindex;
            /*
             * Update the completion spot mask of the frame we
             * are attaching 'ocbp' to so the intersection isn't
             * listed twice.
             */
            ncbp->c_framecnt[0] = ep->e_framecnt;
            ncbp->c_emask[0] = ep->e_emask;
            if (verts) {
                ncbp->c_flg |= C_LOOP;
                ncbp->c_dir = vertices[0].o_frameindex;
                ncbp->c_framecnt[1] = fcnt - 1;
                if (ncbp->c_framecnt[1]) {
                    n = (vertices[0].o_intersect - ocbp->c_vertex) /
                        dd[ocbp->c_dir];
                    ncbp->c_emask[1] = emask & ~(1 << n);
                } else
                    ncbp->c_emask[1] = 0;
                ncbp->c_voff[0] = vertices[0].o_off;
            } else {
                ncbp->c_dir = 0;
                ncbp->c_framecnt[1] = fcnt;
                ncbp->c_emask[1] = emask;
                ncbp->c_voff[0] = ep->e_off;
            }

            if (c == 1 && debug > 1) {
                snprintf(fmtbuf, sizeof fmtbuf,
                    "%c v%d i%d d%d c %d %d m %x %x o %d %d",
                    "bw"[curcolor], verts, ncbp->c_frameindex, ncbp->c_dir,
                    ncbp->c_framecnt[0], ncbp->c_framecnt[1],
                    ncbp->c_emask[0], ncbp->c_emask[1],
                    ncbp->c_voff[0], ncbp->c_voff[1]);
                dlog(fmtbuf);
                printcombo(ncbp, fmtbuf, sizeof fmtbuf);
                dlog(fmtbuf);
            }
            if (c > 1) {
                /* record the empty spots that will complete this combo */
                makeempty(ncbp);
                combolen++;
            } else {
                /* update board values */
                updatecombo(ncbp, curcolor);
            }
#ifdef DEBUG
            if (c == 1 && debug > 1 || debug > 4) {
                markcombo(ncbp);
                bdisp();
                whatsup(0);
                clearcombo(ncbp, 0);
            }
#endif /* DEBUG */
        }
}

#define MAXDEPTH        100
struct elist    einfo[MAXDEPTH];
struct combostr *ecombo[MAXDEPTH];      /* separate from elist to save space */

/*
 * Add the combostr 'ocbp' to the empty spots list for each empty spot
 * in 'ocbp' that will complete the combo.
 */
void
makeempty(struct combostr *ocbp)
{
        struct combostr *cbp, **cbpp;
        struct elist *ep, *nep;
        struct spotstr *sp;
        int s, d, m, emask, i;
        int nframes;

        if (debug > 2) {
                snprintf(fmtbuf, sizeof fmtbuf, "E%c ", "bw"[curcolor]);
                printcombo(ocbp, fmtbuf + 3, sizeof fmtbuf - 3);
                dlog(fmtbuf);
        }

        /* should never happen but check anyway */
        if ((nframes = ocbp->c_nframes) >= MAXDEPTH)
                return;

        /*
         * The lower level combo can be pointed to by more than one
         * higher level 'struct combostr' so we can't modify the
         * lower level. Therefore, higher level combos store the
         * real mask of the lower level frame in c_emask[0] and the
         * frame number in c_frameindex.
         *
         * First we traverse the tree from top to bottom and save the
         * connection info. Then we traverse the tree from bottom to
         * top overwriting lower levels with the newer emask information.
         */
        ep = &einfo[nframes];
        cbpp = &ecombo[nframes];
        for (cbp = ocbp; cbp->c_link[1] != NULL; cbp = cbp->c_link[0]) {
                ep--;
                ep->e_combo = cbp;
                *--cbpp = cbp->c_link[1];
                ep->e_off = cbp->c_voff[1];
                ep->e_frameindex = cbp->c_frameindex;
                ep->e_fval.s = cbp->c_linkv[1].s;
                ep->e_framecnt = cbp->c_framecnt[1];
                ep->e_emask = cbp->c_emask[1];
        }
        cbp = ep->e_combo;
        ep--;
        ep->e_combo = cbp;
        *--cbpp = cbp->c_link[0];
        ep->e_off = cbp->c_voff[0];
        ep->e_frameindex = 0;
        ep->e_fval.s = cbp->c_linkv[0].s;
        ep->e_framecnt = cbp->c_framecnt[0];
        ep->e_emask = cbp->c_emask[0];

        /* now update the emask info */
        s = 0;
        for (i = 2, ep += 2; i < nframes; i++, ep++) {
                cbp = ep->e_combo;
                nep = &einfo[ep->e_frameindex];
                nep->e_framecnt = cbp->c_framecnt[0];
                nep->e_emask = cbp->c_emask[0];

                if (cbp->c_flg & C_LOOP) {
                        s++;
                        /*
                         * Account for the fact that this frame connects
                         * to a previous one (thus forming a loop).
                         */
                        nep = &einfo[cbp->c_dir];
                        if (--nep->e_framecnt)
                                nep->e_emask &= ~(1 << cbp->c_voff[0]);
                        else
                                nep->e_emask = 0;
                }
        }

        /*
         * We only need to update the emask values of "complete" loops
         * to include the intersection spots.
         */
        if (s && ocbp->c_combo.c.a == 2) {
                /* process loops from the top down */
                ep = &einfo[nframes];
                do {
                        ep--;
                        cbp = ep->e_combo;
                        if (!(cbp->c_flg & C_LOOP))
                                continue;

                        /*
                         * Update the emask values to include the
                         * intersection spots.
                         */
                        nep = &einfo[cbp->c_dir];
                        nep->e_framecnt = 1;
                        nep->e_emask = 1 << cbp->c_voff[0];
                        ep->e_framecnt = 1;
                        ep->e_emask = 1 << ep->e_off;
                        ep = &einfo[ep->e_frameindex];
                        do {
                                ep->e_framecnt = 1;
                                ep->e_emask = 1 << ep->e_off;
                                ep = &einfo[ep->e_frameindex];
                        } while (ep > nep);
                } while (ep != einfo);
        }

        /* check all the frames for completion spots */
        for (i = 0, ep = einfo, cbpp = ecombo; i < nframes; i++, ep++, cbpp++) {
                /* skip this frame if there are no incomplete spots in it */
                if ((emask = ep->e_emask) == 0)
                        continue;
                cbp = *cbpp;
                sp = &board[cbp->c_vertex];
                d = dd[cbp->c_dir];
                for (s = 0, m = 1; s < 5; s++, sp += d, m <<= 1) {
                        if (sp->s_occ != EMPTY || !(emask & m))
                                continue;

                        /* add the combo to the list of empty spots */
                        nep = malloc(sizeof(struct elist));
                        if (nep == (struct elist *)NULL)
                                qlog("Memory allocation failure.");
                        nep->e_combo = ocbp;
                        nep->e_off = s;
                        nep->e_frameindex = i;
                        if (ep->e_framecnt > 1) {
                                nep->e_framecnt = ep->e_framecnt - 1;
                                nep->e_emask = emask & ~m;
                        } else {
                                nep->e_framecnt = 0;
                                nep->e_emask = 0;
                        }
                        nep->e_fval.s = ep->e_fval.s;
                        if (debug > 2) {
                                snprintf(fmtbuf, sizeof fmtbuf,
                                        "e %s o%d i%d c%d m%x %x",
                                        stoc(sp - board),
                                        nep->e_off,
                                        nep->e_frameindex,
                                        nep->e_framecnt,
                                        nep->e_emask,
                                        nep->e_fval.s);
                                dlog(fmtbuf);
                        }

                        /* sort by the number of frames in the combo */
                        nep->e_next = sp->s_nempty;
                        sp->s_nempty = nep;
                        elistcnt++;
                }
        }
}

/*
 * Update the board value based on the combostr.
 * This is called only if 'cbp' is a <1,x> combo.
 * We handle things differently depending on whether the next move
 * would be trying to "complete" the combo or trying to block it.
 */
void
updatecombo(struct combostr *cbp, int color)
{
        struct spotstr *sp;
        struct combostr *tcbp;
        int i, d;
        int nframes, s, flg = 0;
        union comboval cb;

        /* save the top level value for the whole combo */
        cb.c.a = cbp->c_combo.c.a;
        nframes = cbp->c_nframes;

        if (color != nextcolor)
                memset(tmpmap, 0, sizeof(tmpmap));

        for (; (tcbp = cbp->c_link[1]) != NULL; cbp = cbp->c_link[0]) {
                flg = cbp->c_flg;
                cb.c.b = cbp->c_combo.c.b;
                if (color == nextcolor) {
                        /* update the board value for the vertex */
                        sp = &board[cbp->c_vertex];
                        sp->s_nforce[color]++;
                        if (cb.s <= sp->s_combo[color].s) {
                                if (cb.s != sp->s_combo[color].s) {
                                        sp->s_combo[color].s = cb.s;
                                        sp->s_level[color] = nframes;
                                } else if (nframes < sp->s_level[color])
                                        sp->s_level[color] = nframes;
                        }
                } else {
                        /* update the board values for each spot in frame */
                        sp = &board[s = tcbp->c_vertex];
                        d = dd[tcbp->c_dir];
                        i = (flg & C_OPEN_1) ? 6 : 5;
                        for (; --i >= 0; sp += d, s += d) {
                                if (sp->s_occ != EMPTY)
                                        continue;
                                sp->s_nforce[color]++;
                                if (cb.s <= sp->s_combo[color].s) {
                                        if (cb.s != sp->s_combo[color].s) {
                                                sp->s_combo[color].s = cb.s;
                                                sp->s_level[color] = nframes;
                                        } else if (nframes < sp->s_level[color])
                                                sp->s_level[color] = nframes;
                                }
                                BIT_SET(tmpmap, s);
                        }
                }

                /* mark the frame as being part of a <1,x> combo */
                board[tcbp->c_vertex].s_flg |= FFLAG << tcbp->c_dir;
        }

        if (color != nextcolor) {
                /* update the board values for each spot in frame */
                sp = &board[s = cbp->c_vertex];
                d = dd[cbp->c_dir];
                i = (flg & C_OPEN_0) ? 6 : 5;
                for (; --i >= 0; sp += d, s += d) {
                        if (sp->s_occ != EMPTY)
                                continue;
                        sp->s_nforce[color]++;
                        if (cb.s <= sp->s_combo[color].s) {
                                if (cb.s != sp->s_combo[color].s) {
                                        sp->s_combo[color].s = cb.s;
                                        sp->s_level[color] = nframes;
                                } else if (nframes < sp->s_level[color])
                                        sp->s_level[color] = nframes;
                        }
                        BIT_SET(tmpmap, s);
                }
                if (nforce == 0)
                        memcpy(forcemap, tmpmap, sizeof(tmpmap));
                else {
                        for (i = 0; i < MAPSZ; i++)
                                forcemap[i] &= tmpmap[i];
                }
                nforce++;
        }

        /* mark the frame as being part of a <1,x> combo */
        board[cbp->c_vertex].s_flg |= FFLAG << cbp->c_dir;
}

/*
 * Add combo to the end of the list.
 */
void
appendcombo(struct combostr *cbp)
{
        struct combostr *pcbp, *ncbp;

        combolen++;
        ncbp = sortcombos;
        if (ncbp == (struct combostr *)0) {
                sortcombos = cbp;
                cbp->c_next = cbp;
                cbp->c_prev = cbp;
                return;
        }
        pcbp = ncbp->c_prev;
        cbp->c_next = ncbp;
        cbp->c_prev = pcbp;
        ncbp->c_prev = cbp;
        pcbp->c_next = cbp;
}

/*
 * Return zero if it is valid to combine frame 'fcbp' with the frames
 * in 'cbp' and forms a linked chain of frames (i.e., a tree; no loops).
 * Return positive if combining frame 'fcbp' to the frames in 'cbp'
 * would form some kind of valid loop. Also return the intersection spots
 * in 'vertices[]' beside the known intersection at spot 'osp'.
 * Return -1 if 'fcbp' should not be combined with 'cbp'.
 * 's' is the combo value for frame 'fcpb'.
 */
int
checkframes(struct combostr *cbp, struct combostr *fcbp, struct spotstr *osp,
    int s, struct ovlp_info *vertices)
{
        struct combostr *tcbp, *lcbp = NULL;
        int i, n, mask, flg, verts, idx, fcnt;
        union comboval cb;
        u_char *str;
        short *ip;

        cb.s = s;
        fcnt = cb.c.a - 2;
        verts = 0;
        flg = 0;
        idx = cbp->c_nframes;
        n = (fcbp - frames) * FAREA;
        str = &overlap[n];
        ip = &intersect[n];
        /*
         * i == which overlap bit to test based on whether 'fcbp' is
         * an open or closed frame.
         */
        i = cb.c.b ? 2 : 0;
        for (; (tcbp = cbp->c_link[1]) != NULL; lcbp = cbp, cbp = cbp->c_link[0]) {
                if (tcbp == fcbp)
                        return (-1);    /* fcbp is already included */

                /* check for intersection of 'tcbp' with 'fcbp' */
                idx--;
                mask = str[tcbp - frames];
                flg = cbp->c_flg;
                n = i + ((flg & C_OPEN_1) != 0);
                if (mask & (1 << n)) {
                        /*
                         * The two frames are not independent if they
                         * both lie in the same line and intersect at
                         * more than one point.
                         */
                        if (tcbp->c_dir == fcbp->c_dir && (mask & (0x10 << n)))
                                return (-1);
                        /*
                         * If this is not the spot we are attaching
                         * 'fcbp' to and it is a reasonable intersection
                         * spot, then there might be a loop.
                         */
                        n = ip[tcbp - frames];
                        if (osp != &board[n]) {
                                /* check to see if this is a valid loop */
                                if (verts)
                                        return (-1);
                                if (fcnt == 0 || cbp->c_framecnt[1] == 0)
                                        return (-1);
                                /*
                                 * Check to be sure the intersection is not
                                 * one of the end points if it is an open
                                 * ended frame.
                                 */
                                if ((flg & C_OPEN_1) &&
                                    (n == tcbp->c_vertex ||
                                     n == tcbp->c_vertex + 5 * dd[tcbp->c_dir]))
                                        return (-1);    /* invalid overlap */
                                if (cb.c.b &&
                                    (n == fcbp->c_vertex ||
                                     n == fcbp->c_vertex + 5 * dd[fcbp->c_dir]))
                                        return (-1);    /* invalid overlap */

                                vertices->o_intersect = n;
                                vertices->o_fcombo = cbp;
                                vertices->o_link = 1;
                                vertices->o_off = (n - tcbp->c_vertex) /
                                        dd[tcbp->c_dir];
                                vertices->o_frameindex = idx;
                                verts++;
                        }
                }
                n = i + ((flg & C_OPEN_0) != 0);
        }
        if (cbp == fcbp)
                return (-1);    /* fcbp is already included */

        /* check for intersection of 'cbp' with 'fcbp' */
        mask = str[cbp - frames];
        if (mask & (1 << n)) {
                /*
                 * The two frames are not independent if they
                 * both lie in the same line and intersect at
                 * more than one point.
                 */
                if (cbp->c_dir == fcbp->c_dir && (mask & (0x10 << n)))
                        return (-1);
                /*
                 * If this is not the spot we are attaching
                 * 'fcbp' to and it is a reasonable intersection
                 * spot, then there might be a loop.
                 */
                n = ip[cbp - frames];
                if (osp != &board[n]) {
                        /* check to see if this is a valid loop */
                        if (verts)
                                return (-1);
                        if (fcnt == 0 || lcbp->c_framecnt[0] == 0)
                                return (-1);
                        /*
                         * Check to be sure the intersection is not
                         * one of the end points if it is an open
                         * ended frame.
                         */
                        if ((flg & C_OPEN_0) &&
                            (n == cbp->c_vertex ||
                             n == cbp->c_vertex + 5 * dd[cbp->c_dir]))
                                return (-1);    /* invalid overlap */
                        if (cb.c.b &&
                            (n == fcbp->c_vertex ||
                             n == fcbp->c_vertex + 5 * dd[fcbp->c_dir]))
                                return (-1);    /* invalid overlap */

                        vertices->o_intersect = n;
                        vertices->o_fcombo = lcbp;
                        vertices->o_link = 0;
                        vertices->o_off = (n - cbp->c_vertex) /
                                dd[cbp->c_dir];
                        vertices->o_frameindex = 0;
                        verts++;
                }
        }
        return (verts);
}

/*
 * Merge sort the frame 'fcbp' and the sorted list of frames 'cbpp' and
 * store the result in 'scbpp'. 'curlevel' is the size of the 'cbpp' array.
 * Return true if this list of frames is already in the hash list.
 * Otherwise, add the new combo to the hash list.
 */
int
sortcombo(struct combostr **scbpp, struct combostr **cbpp,
    struct combostr *fcbp)
{
        struct combostr **spp, **cpp;
        struct combostr *cbp, *ecbp;
        int n, inx;

#ifdef DEBUG
        if (debug > 3) {
                char *str;

                snprintf(fmtbuf, sizeof fmtbuf,
                        "sortc: %s%c l%d", stoc(fcbp->c_vertex),
                        pdir[fcbp->c_dir], curlevel);
                dlog(fmtbuf);
                str = fmtbuf;
                for (cpp = cbpp; cpp < cbpp + curlevel; cpp++) {
                        snprintf(str, fmtbuf + sizeof fmtbuf - str,
                                " %s%c", stoc((*cpp)->c_vertex),
                                pdir[(*cpp)->c_dir]);
                        str += strlen(str);
                }
                dlog(fmtbuf);
        }
#endif /* DEBUG */

        /* first build the new sorted list */
        n = curlevel + 1;
        spp = scbpp + n;
        cpp = cbpp + curlevel;
        do {
                cpp--;
                if (fcbp > *cpp) {
                        *--spp = fcbp;
                        do
                                *--spp = *cpp;
                        while (cpp-- != cbpp);
                        goto inserted;
                }
                *--spp = *cpp;
        } while (cpp != cbpp);
        *--spp = fcbp;
inserted:

        /* now check to see if this list of frames has already been seen */
        cbp = hashcombos[inx = *scbpp - frames];
        if (cbp == (struct combostr *)0) {
                /*
                 * Easy case, this list hasn't been seen.
                 * Add it to the hash list.
                 */
                fcbp = (struct combostr *)
                        ((char *)scbpp - sizeof(struct combostr));
                hashcombos[inx] = fcbp;
                fcbp->c_next = fcbp->c_prev = fcbp;
                return (0);
        }
        ecbp = cbp;
        do {
                cbpp = (struct combostr **)(cbp + 1);
                cpp = cbpp + n;
                spp = scbpp + n;
                cbpp++; /* first frame is always the same */
                do {
                        if (*--spp != *--cpp)
                                goto next;
                } while (cpp != cbpp);
                /* we found a match */
#ifdef DEBUG
                if (debug > 3) {
                        char *str;

                        snprintf(fmtbuf, sizeof fmtbuf, "sort1: n%d", n);
                        dlog(fmtbuf);
                        str = fmtbuf;
                        for (cpp = scbpp; cpp < scbpp + n; cpp++) {
                                snprintf(str, fmtbuf + sizeof fmtbuf - str,
                                        " %s%c", stoc((*cpp)->c_vertex),
                                        pdir[(*cpp)->c_dir]);
                                str += strlen(str);
                        }
                        dlog(fmtbuf);
                        printcombo(cbp, fmtbuf, sizeof fmtbuf);
                        dlog(fmtbuf);
                        str = fmtbuf;
                        cbpp--;
                        for (cpp = cbpp; cpp < cbpp + n; cpp++) {
                                snprintf(str, fmtbuf + sizeof fmtbuf - str,
                                        " %s%c", stoc((*cpp)->c_vertex),
                                        pdir[(*cpp)->c_dir]);
                                str += strlen(str);
                        }
                        dlog(fmtbuf);
                }
#endif /* DEBUG */
                return (1);
        next:
                ;
        } while ((cbp = cbp->c_next) != ecbp);
        /*
         * This list of frames hasn't been seen.
         * Add it to the hash list.
         */
        ecbp = cbp->c_prev;
        fcbp = (struct combostr *)((char *)scbpp - sizeof(struct combostr));
        fcbp->c_next = cbp;
        fcbp->c_prev = ecbp;
        cbp->c_prev = fcbp;
        ecbp->c_next = fcbp;
        return (0);
}

/*
 * Print the combo into string 'str'.
 */
void
printcombo(struct combostr *cbp, char *str, size_t strl)
{
        char *basestr = str;
        struct combostr *tcbp;

        snprintf(str, strl, "%x/%d", cbp->c_combo.s, cbp->c_nframes);
        str += strlen(str);
        for (; (tcbp = cbp->c_link[1]) != NULL; cbp = cbp->c_link[0]) {
                snprintf(str, basestr + strl - str,
                        " %s%c%x", stoc(tcbp->c_vertex), pdir[tcbp->c_dir],
                        cbp->c_flg);
                str += strlen(str);
        }
        snprintf(str, basestr + strl - str,
                " %s%c", stoc(cbp->c_vertex), pdir[cbp->c_dir]);
}

#ifdef DEBUG
void
markcombo(struct combostr *ocbp)
{
        struct combostr *cbp, *tcbp, **cbpp;
        struct elist *ep, *nep, **epp;
        struct spotstr *sp;
        int s, d, m, i;
        int nframes;
        int r, n, flg, cmask, omask;

        /* should never happen but check anyway */
        if ((nframes = ocbp->c_nframes) >= MAXDEPTH)
                return;

        /*
         * The lower level combo can be pointed to by more than one
         * higher level 'struct combostr' so we can't modify the
         * lower level. Therefore, higher level combos store the
         * real mask of the lower level frame in c_emask[0] and the
         * frame number in c_frameindex.
         *
         * First we traverse the tree from top to bottom and save the
         * connection info. Then we traverse the tree from bottom to
         * top overwriting lower levels with the newer emask information.
         */
        ep = &einfo[nframes];
        cbpp = &ecombo[nframes];
        for (cbp = ocbp; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
                ep--;
                ep->e_combo = cbp;
                *--cbpp = cbp->c_link[1];
                ep->e_off = cbp->c_voff[1];
                ep->e_frameindex = cbp->c_frameindex;
                ep->e_fval.s = cbp->c_linkv[1].s;
                ep->e_framecnt = cbp->c_framecnt[1];
                ep->e_emask = cbp->c_emask[1];
        }
        cbp = ep->e_combo;
        ep--;
        ep->e_combo = cbp;
        *--cbpp = cbp->c_link[0];
        ep->e_off = cbp->c_voff[0];
        ep->e_frameindex = 0;
        ep->e_fval.s = cbp->c_linkv[0].s;
        ep->e_framecnt = cbp->c_framecnt[0];
        ep->e_emask = cbp->c_emask[0];

        /* now update the emask info */
        s = 0;
        for (i = 2, ep += 2; i < nframes; i++, ep++) {
                cbp = ep->e_combo;
                nep = &einfo[ep->e_frameindex];
                nep->e_framecnt = cbp->c_framecnt[0];
                nep->e_emask = cbp->c_emask[0];

                if (cbp->c_flg & C_LOOP) {
                        s++;
                        /*
                         * Account for the fact that this frame connects
                         * to a previous one (thus forming a loop).
                         */
                        nep = &einfo[cbp->c_dir];
                        if (--nep->e_framecnt)
                                nep->e_emask &= ~(1 << cbp->c_voff[0]);
                        else
                                nep->e_emask = 0;
                }
        }

        /*
         * We only need to update the emask values of "complete" loops
         * to include the intersection spots.
         */
        if (s && ocbp->c_combo.c.a == 2) {
                /* process loops from the top down */
                ep = &einfo[nframes];
                do {
                        ep--;
                        cbp = ep->e_combo;
                        if (!(cbp->c_flg & C_LOOP))
                                continue;

                        /*
                         * Update the emask values to include the
                         * intersection spots.
                         */
                        nep = &einfo[cbp->c_dir];
                        nep->e_framecnt = 1;
                        nep->e_emask = 1 << cbp->c_voff[0];
                        ep->e_framecnt = 1;
                        ep->e_emask = 1 << ep->e_off;
                        ep = &einfo[ep->e_frameindex];
                        do {
                                ep->e_framecnt = 1;
                                ep->e_emask = 1 << ep->e_off;
                                ep = &einfo[ep->e_frameindex];
                        } while (ep > nep);
                } while (ep != einfo);
        }

        /* mark all the frames with the completion spots */
        for (i = 0, ep = einfo, cbpp = ecombo; i < nframes; i++, ep++, cbpp++) {
                m = ep->e_emask;
                cbp = *cbpp;
                sp = &board[cbp->c_vertex];
                d = dd[s = cbp->c_dir];
                cmask = CFLAG << s;
                omask = (IFLAG | CFLAG) << s;
                s = ep->e_fval.c.b ? 6 : 5;
                for (; --s >= 0; sp += d, m >>= 1)
                        sp->s_flg |= (m & 1) ? omask : cmask;
        }
}

void
clearcombo(struct combostr *cbp, int open)
{
        struct spotstr *sp;
        struct combostr *tcbp;
        int d, n, mask;

        for (; tcbp = cbp->c_link[1]; cbp = cbp->c_link[0]) {
                clearcombo(tcbp, cbp->c_flg & C_OPEN_1);
                open = cbp->c_flg & C_OPEN_0;
        }
        sp = &board[cbp->c_vertex];
        d = dd[n = cbp->c_dir];
        mask = ~((IFLAG | CFLAG) << n);
        n = open ? 6 : 5;
        for (; --n >= 0; sp += d)
                sp->s_flg &= mask;
}

int
list_eq(struct combostr **scbpp, struct combostr **cbpp, int n)
{
        struct combostr **spp, **cpp;

        spp = scbpp + n;
        cpp = cbpp + n;
        do {
                if (*--spp != *--cpp)
                        return (0);
        } while (cpp != cbpp);
        /* we found a match */
        return (1);
}
#endif /* DEBUG */