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      1 /*	$NetBSD: pickmove.c,v 1.68 2022/05/29 22:03:29 rillig Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1994
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Ralph Campbell.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 /*	@(#)pickmove.c	8.2 (Berkeley) 5/3/95	*/
     37 __RCSID("$NetBSD: pickmove.c,v 1.68 2022/05/29 22:03:29 rillig Exp $");
     38 
     39 #include <stdlib.h>
     40 #include <string.h>
     41 #include <curses.h>
     42 #include <limits.h>
     43 
     44 #include "gomoku.h"
     45 
     46 #define BITS_PER_INT	(sizeof(int) * CHAR_BIT)
     47 #define MAPSZ		(BAREA / BITS_PER_INT)
     48 
     49 #define BIT_SET(a, b)	((a)[(b)/BITS_PER_INT] |= (1U << ((b) % BITS_PER_INT)))
     50 #define BIT_TEST(a, b)	(((a)[(b)/BITS_PER_INT] & (1U << ((b) % BITS_PER_INT))) != 0)
     51 
     52 /*
     53  * This structure is used to store overlap information between frames.
     54  */
     55 struct overlap_info {
     56 	spot_index	o_intersect;	/* intersection spot */
     57 	u_char		o_off;		/* offset in frame of intersection */
     58 	u_char		o_frameindex;	/* intersection frame index */
     59 };
     60 
     61 static struct combostr *hashcombos[FAREA];/* hash list for finding duplicates */
     62 static struct combostr *sortcombos;	/* combos at higher levels */
     63 static int combolen;			/* number of combos in sortcombos */
     64 static player_color nextcolor;		/* color of next move */
     65 static int elistcnt;			/* count of struct elist allocated */
     66 static int combocnt;			/* count of struct combostr allocated */
     67 static unsigned int forcemap[MAPSZ];	/* map for blocking <1,x> combos */
     68 static unsigned int tmpmap[MAPSZ];	/* map for blocking <1,x> combos */
     69 static int nforce;			/* count of opponent <1,x> combos */
     70 
     71 static bool better(spot_index, spot_index, player_color);
     72 static void scanframes(player_color);
     73 static void makecombo2(struct combostr *, struct spotstr *, u_char, u_short);
     74 static void addframes(unsigned int);
     75 static void makecombo(struct combostr *, struct spotstr *, u_char, u_short);
     76 static void appendcombo(struct combostr *);
     77 static void updatecombo(struct combostr *, player_color);
     78 static void makeempty(struct combostr *);
     79 static int checkframes(struct combostr *, struct combostr *, struct spotstr *,
     80 		    u_short, struct overlap_info *);
     81 static bool sortcombo(struct combostr **, struct combostr **, struct combostr *);
     82 #if !defined(DEBUG)
     83 static void printcombo(struct combostr *, char *, size_t);
     84 #endif
     85 
     86 spot_index
     87 pickmove(player_color us)
     88 {
     89 
     90 	/* first move is easy */
     91 	if (game.nmoves == 0)
     92 		return PT((BSZ + 1) / 2, (BSZ + 1) / 2);
     93 
     94 	/* initialize all the board values */
     95 	for (spot_index s = PT(BSZ, BSZ) + 1; s-- > PT(1, 1); ) {
     96 		struct spotstr *sp = &board[s];
     97 		sp->s_combo[BLACK].s = 0x601;
     98 		sp->s_combo[WHITE].s = 0x601;
     99 		sp->s_level[BLACK] = 255;
    100 		sp->s_level[WHITE] = 255;
    101 		sp->s_nforce[BLACK] = 0;
    102 		sp->s_nforce[WHITE] = 0;
    103 		sp->s_flags &= ~(FFLAGALL | MFLAGALL);
    104 	}
    105 
    106 	nforce = 0;
    107 	memset(forcemap, 0, sizeof(forcemap));
    108 
    109 	/* compute new values */
    110 	player_color them = us != BLACK ? BLACK : WHITE;
    111 	nextcolor = us;
    112 	/*
    113 	 * TODO: Scanning for both frames misses that after loading the game
    114 	 *  K10 J9 M10 J10 O10 J11 Q10 J8 and playing K9, there are 2
    115 	 *  immediate winning moves J12 and J7. Finding the winning move
    116 	 *  takes too long.
    117 	 */
    118 	scanframes(BLACK);
    119 	scanframes(WHITE);
    120 
    121 	/* find the spot with the highest value */
    122 	spot_index os = PT(BSZ, BSZ);		/* our spot */
    123 	spot_index ts = PT(BSZ, BSZ);		/* their spot */
    124 	for (spot_index s = PT(BSZ, BSZ); s-- > PT(1, 1); ) {
    125 		const struct spotstr *sp = &board[s];
    126 		if (sp->s_occ != EMPTY)
    127 			continue;
    128 
    129 		if (debug > 0 &&
    130 		    (sp->s_combo[BLACK].cv_force == 1 ||
    131 		     sp->s_combo[WHITE].cv_force == 1)) {
    132 			debuglog("- %s %x/%d %d %x/%d %d %d",
    133 			    stoc(s),
    134 			    sp->s_combo[BLACK].s, sp->s_level[BLACK],
    135 			    sp->s_nforce[BLACK],
    136 			    sp->s_combo[WHITE].s, sp->s_level[WHITE],
    137 			    sp->s_nforce[WHITE],
    138 			    sp->s_wval);
    139 		}
    140 
    141 		if (better(s, os, us))		/* pick our best move */
    142 			os = s;
    143 		if (better(s, ts, them))	/* pick their best move */
    144 			ts = s;
    145 	}
    146 
    147 	if (debug > 0) {
    148 		spot_index bs = us == BLACK ? os : ts;
    149 		spot_index ws = us == BLACK ? ts : os;
    150 		const struct spotstr *bsp = &board[bs];
    151 		const struct spotstr *wsp = &board[ws];
    152 
    153 		debuglog("B %s %x/%d %d %x/%d %d %d",
    154 		    stoc(bs),
    155 		    bsp->s_combo[BLACK].s, bsp->s_level[BLACK],
    156 		    bsp->s_nforce[BLACK],
    157 		    bsp->s_combo[WHITE].s, bsp->s_level[WHITE],
    158 		    bsp->s_nforce[WHITE], bsp->s_wval);
    159 		debuglog("W %s %x/%d %d %x/%d %d %d",
    160 		    stoc(ws),
    161 		    wsp->s_combo[WHITE].s, wsp->s_level[WHITE],
    162 		    wsp->s_nforce[WHITE],
    163 		    wsp->s_combo[BLACK].s, wsp->s_level[BLACK],
    164 		    wsp->s_nforce[BLACK], wsp->s_wval);
    165 
    166 		/*
    167 		 * Check for more than one force that can't all be blocked
    168 		 * with one move.
    169 		 */
    170 		if (board[ts].s_combo[them].cv_force == 1 &&
    171 		    !BIT_TEST(forcemap, ts))
    172 			debuglog("*** Can't be blocked");
    173 	}
    174 
    175 	union comboval ocv = board[os].s_combo[us];
    176 	union comboval tcv = board[ts].s_combo[them];
    177 
    178 	/*
    179 	 * Block their combo only if we have to (i.e., if they are one move
    180 	 * away from completing a force, and we don't have a force that
    181 	 * we can complete which takes fewer moves to win).
    182 	 */
    183 	if (tcv.cv_force <= 1 &&
    184 	    !(ocv.cv_force <= 1 &&
    185 	      tcv.cv_force + tcv.cv_win >= ocv.cv_force + ocv.cv_win))
    186 		return ts;
    187 	return os;
    188 }
    189 
    190 /*
    191  * Return true if spot 'as' is better than spot 'bs' for color 'us'.
    192  */
    193 static bool
    194 better(spot_index as, spot_index bs, player_color us)
    195 {
    196 	const struct spotstr *asp = &board[as];
    197 	const struct spotstr *bsp = &board[bs];
    198 
    199 	if (/* .... */ asp->s_combo[us].s != bsp->s_combo[us].s)
    200 		return asp->s_combo[us].s < bsp->s_combo[us].s;
    201 	if (/* .... */ asp->s_level[us] != bsp->s_level[us])
    202 		return asp->s_level[us] < bsp->s_level[us];
    203 	if (/* .... */ asp->s_nforce[us] != bsp->s_nforce[us])
    204 		return asp->s_nforce[us] > bsp->s_nforce[us];
    205 
    206 	player_color them = us != BLACK ? BLACK : WHITE;
    207 	if (BIT_TEST(forcemap, as) != BIT_TEST(forcemap, bs))
    208 		return BIT_TEST(forcemap, as);
    209 
    210 	if (/* .... */ asp->s_combo[them].s != bsp->s_combo[them].s)
    211 		return asp->s_combo[them].s < bsp->s_combo[them].s;
    212 	if (/* .... */ asp->s_level[them] != bsp->s_level[them])
    213 		return asp->s_level[them] < bsp->s_level[them];
    214 	if (/* .... */ asp->s_nforce[them] != bsp->s_nforce[them])
    215 		return asp->s_nforce[them] > bsp->s_nforce[them];
    216 
    217 	if (/* .... */ asp->s_wval != bsp->s_wval)
    218 		return asp->s_wval > bsp->s_wval;
    219 
    220 	return (random() & 1) != 0;
    221 }
    222 
    223 static player_color curcolor;	/* implicit parameter to makecombo() */
    224 static unsigned int curlevel;	/* implicit parameter to makecombo() */
    225 
    226 static bool
    227 four_in_a_row(player_color color, spot_index s, direction r)
    228 {
    229 
    230 	struct spotstr *sp = &board[s];
    231 	union comboval cb = { .s = sp->s_fval[color][r].s };
    232 	if (cb.s >= 0x101)
    233 		return false;
    234 
    235 	for (int off = 5 + cb.cv_win, d = dd[r]; off-- > 0; sp += d) {
    236 		if (sp->s_occ != EMPTY)
    237 			continue;
    238 		sp->s_combo[color].s = cb.s;
    239 		sp->s_level[color] = 1;
    240 	}
    241 	return true;
    242 }
    243 
    244 /*
    245  * Scan the sorted list of non-empty frames and
    246  * update the minimum combo values for each empty spot.
    247  * Also, try to combine frames to find more complex (chained) moves.
    248  */
    249 static void
    250 scanframes(player_color color)
    251 {
    252 	struct combostr *ecbp;
    253 	struct spotstr *sp;
    254 	union comboval *cp;
    255 	struct elist *nep;
    256 	int r, n;
    257 	union comboval cb;
    258 
    259 	curcolor = color;
    260 
    261 	/* check for empty list of frames */
    262 	struct combostr *cbp = sortframes[color];
    263 	if (cbp == NULL)
    264 		return;
    265 
    266 	if (four_in_a_row(color, cbp->c_vertex, cbp->c_dir))
    267 		return;
    268 
    269 	/*
    270 	 * Update the minimum combo value for each spot in the frame
    271 	 * and try making all combinations of two frames intersecting at
    272 	 * an empty spot.
    273 	 */
    274 	n = combolen;
    275 	ecbp = cbp;
    276 	do {
    277 		sp = &board[cbp->c_vertex];
    278 		cp = &sp->s_fval[color][r = cbp->c_dir];
    279 		int delta = dd[r];
    280 
    281 		u_char off;
    282 		if (cp->cv_win != 0) {
    283 			/*
    284 			 * Since this is the first spot of an open-ended
    285 			 * frame, we treat it as a closed frame.
    286 			 */
    287 			cb.cv_force = cp->cv_force + 1;
    288 			cb.cv_win = 0;
    289 			if (cb.s < sp->s_combo[color].s) {
    290 				sp->s_combo[color].s = cb.s;
    291 				sp->s_level[color] = 1;
    292 			}
    293 			/*
    294 			 * Try combining other frames that intersect
    295 			 * at this spot.
    296 			 */
    297 			makecombo2(cbp, sp, 0, cb.s);
    298 			if (cp->s != 0x101)
    299 				cb.s = cp->s;
    300 			else if (color != nextcolor)
    301 				memset(tmpmap, 0, sizeof(tmpmap));
    302 			sp += delta;
    303 			off = 1;
    304 		} else {
    305 			cb.s = cp->s;
    306 			off = 0;
    307 		}
    308 
    309 		for (; off < 5; off++, sp += delta) {	/* for each spot */
    310 			if (sp->s_occ != EMPTY)
    311 				continue;
    312 			if (cp->s < sp->s_combo[color].s) {
    313 				sp->s_combo[color].s = cp->s;
    314 				sp->s_level[color] = 1;
    315 			}
    316 			if (cp->s == 0x101) {
    317 				sp->s_nforce[color]++;
    318 				if (color != nextcolor) {
    319 					/* XXX: suspicious use of 'n' */
    320 					n = (spot_index)(sp - board);
    321 					BIT_SET(tmpmap, (spot_index)n);
    322 				}
    323 			}
    324 			/*
    325 			 * Try combining other frames that intersect
    326 			 * at this spot.
    327 			 */
    328 			makecombo2(cbp, sp, off, cb.s);
    329 		}
    330 
    331 		if (cp->s == 0x101 && color != nextcolor) {
    332 			if (nforce == 0)
    333 				memcpy(forcemap, tmpmap, sizeof(tmpmap));
    334 			else {
    335 				for (int i = 0; (unsigned int)i < MAPSZ; i++)
    336 					forcemap[i] &= tmpmap[i];
    337 			}
    338 		}
    339 
    340 		/* mark frame as having been processed */
    341 		board[cbp->c_vertex].s_flags |= MFLAG << r;
    342 	} while ((cbp = cbp->c_next) != ecbp);
    343 
    344 	/*
    345 	 * Try to make new 3rd level combos, 4th level, etc.
    346 	 * Limit the search depth early in the game.
    347 	 */
    348 	for (unsigned int level = 2;
    349 	     level <= 1 + game.nmoves / 2 && combolen > n; level++) {
    350 		if (level >= 9)
    351 			break;	/* Do not think too long. */
    352 		if (debug > 0) {
    353 			debuglog("%cL%u %d %d %d", "BW"[color],
    354 			    level, combolen - n, combocnt, elistcnt);
    355 			refresh();
    356 		}
    357 		n = combolen;
    358 		addframes(level);
    359 	}
    360 
    361 	/* scan for combos at empty spots */
    362 	for (spot_index s = PT(BSZ, BSZ) + 1; s-- > PT(1, 1); ) {
    363 		sp = &board[s];
    364 
    365 		for (struct elist *ep = sp->s_empty; ep != NULL; ep = nep) {
    366 			cbp = ep->e_combo;
    367 			if (cbp->c_combo.s <= sp->s_combo[color].s) {
    368 				if (cbp->c_combo.s != sp->s_combo[color].s) {
    369 					sp->s_combo[color].s = cbp->c_combo.s;
    370 					sp->s_level[color] = cbp->c_nframes;
    371 				} else if (cbp->c_nframes < sp->s_level[color])
    372 					sp->s_level[color] = cbp->c_nframes;
    373 			}
    374 			nep = ep->e_next;
    375 			free(ep);
    376 			elistcnt--;
    377 		}
    378 		sp->s_empty = NULL;
    379 
    380 		for (struct elist *ep = sp->s_nempty; ep != NULL; ep = nep) {
    381 			cbp = ep->e_combo;
    382 			if (cbp->c_combo.s <= sp->s_combo[color].s) {
    383 				if (cbp->c_combo.s != sp->s_combo[color].s) {
    384 					sp->s_combo[color].s = cbp->c_combo.s;
    385 					sp->s_level[color] = cbp->c_nframes;
    386 				} else if (cbp->c_nframes < sp->s_level[color])
    387 					sp->s_level[color] = cbp->c_nframes;
    388 			}
    389 			nep = ep->e_next;
    390 			free(ep);
    391 			elistcnt--;
    392 		}
    393 		sp->s_nempty = NULL;
    394 	}
    395 
    396 	/* remove old combos */
    397 	if ((cbp = sortcombos) != NULL) {
    398 		struct combostr *ncbp;
    399 
    400 		/* scan the list */
    401 		ecbp = cbp;
    402 		do {
    403 			ncbp = cbp->c_next;
    404 			free(cbp);
    405 			combocnt--;
    406 		} while ((cbp = ncbp) != ecbp);
    407 		sortcombos = NULL;
    408 	}
    409 	combolen = 0;
    410 
    411 #ifdef DEBUG
    412 	if (combocnt != 0) {
    413 		debuglog("scanframes: %c combocnt %d", "BW"[color],
    414 			combocnt);
    415 		whatsup(0);
    416 	}
    417 	if (elistcnt != 0) {
    418 		debuglog("scanframes: %c elistcnt %d", "BW"[color],
    419 			elistcnt);
    420 		whatsup(0);
    421 	}
    422 #endif
    423 }
    424 
    425 /*
    426  * Compute all level 2 combos of frames intersecting spot 'osp'
    427  * within the frame 'ocbp' and combo value 'cv'.
    428  */
    429 static void
    430 makecombo2(struct combostr *ocbp, struct spotstr *osp, u_char off, u_short cv)
    431 {
    432 	struct combostr *ncbp;
    433 	int baseB, fcnt, emask;
    434 	union comboval ocb, fcb;
    435 	struct combostr **scbpp, *fcbp;
    436 	char tmp[128];
    437 
    438 	/* try to combine a new frame with those found so far */
    439 	ocb.s = cv;
    440 	baseB = ocb.cv_force + ocb.cv_win - 1;
    441 	fcnt = ocb.cv_force - 2;
    442 	emask = fcnt != 0 ? ((ocb.cv_win != 0 ? 0x1E : 0x1F) & ~(1 << off)) : 0;
    443 
    444 	for (direction r = 4; r-- > 0; ) {
    445 	    /* don't include frames that overlap in the same direction */
    446 	    if (r == ocbp->c_dir)
    447 		continue;
    448 
    449 	    int d = dd[r];
    450 	    /*
    451 	     * Frame A combined with B is the same value as B combined with A
    452 	     * so skip frames that have already been processed (MFLAG).
    453 	     * Also skip blocked frames (BFLAG) and frames that are <1,x>
    454 	     * since combining another frame with it isn't valid.
    455 	     */
    456 	    int bmask = (BFLAG | FFLAG | MFLAG) << r;
    457 	    struct spotstr *fsp = osp;
    458 
    459 	    for (u_char f = 0; f < 5; f++, fsp -= d) {	/* for each frame */
    460 		if (fsp->s_occ == BORDER)
    461 		    break;
    462 		if ((fsp->s_flags & bmask) != 0)
    463 		    continue;
    464 
    465 		/* don't include frames of the wrong color */
    466 		fcb.s = fsp->s_fval[curcolor][r].s;
    467 		if (fcb.cv_force >= 6)
    468 		    continue;
    469 
    470 		/*
    471 		 * Get the combo value for this frame.
    472 		 * If this is the end point of the frame,
    473 		 * use the closed ended value for the frame.
    474 		 */
    475 		if ((f == 0 && fcb.cv_win != 0) || fcb.s == 0x101) {
    476 		    fcb.cv_force++;
    477 		    fcb.cv_win = 0;
    478 		}
    479 
    480 		/* compute combo value */
    481 		int c = fcb.cv_force + ocb.cv_force - 3;
    482 		if (c > 4)
    483 		    continue;
    484 		int n = fcb.cv_force + fcb.cv_win - 1;
    485 		if (baseB < n)
    486 		    n = baseB;
    487 
    488 		/* make a new combo! */
    489 		ncbp = (struct combostr *)malloc(sizeof(struct combostr) +
    490 		    2 * sizeof(struct combostr *));
    491 		if (ncbp == NULL)
    492 		    panic("Out of memory!");
    493 		scbpp = (void *)(ncbp + 1);
    494 
    495 		fcbp = &frames[fsp->s_frame[r]];
    496 		if (ocbp < fcbp) {
    497 		    scbpp[0] = ocbp;
    498 		    scbpp[1] = fcbp;
    499 		} else {
    500 		    scbpp[0] = fcbp;
    501 		    scbpp[1] = ocbp;
    502 		}
    503 
    504 		ncbp->c_combo.cv_force = c;
    505 		ncbp->c_combo.cv_win = n;
    506 		ncbp->c_link[0] = ocbp;
    507 		ncbp->c_link[1] = fcbp;
    508 		ncbp->c_linkv[0].s = ocb.s;
    509 		ncbp->c_linkv[1].s = fcb.s;
    510 		ncbp->c_voff[0] = off;
    511 		ncbp->c_voff[1] = f;
    512 		ncbp->c_vertex = (spot_index)(osp - board);
    513 		ncbp->c_nframes = 2;
    514 		ncbp->c_dir = 0;
    515 		ncbp->c_frameindex = 0;
    516 		ncbp->c_flags = ocb.cv_win != 0 ? C_OPEN_0 : 0;
    517 		if (fcb.cv_win != 0)
    518 		    ncbp->c_flags |= C_OPEN_1;
    519 		ncbp->c_framecnt[0] = fcnt;
    520 		ncbp->c_emask[0] = emask;
    521 		ncbp->c_framecnt[1] = fcb.cv_force - 2;
    522 		ncbp->c_emask[1] = ncbp->c_framecnt[1] != 0 ?
    523 		    ((fcb.cv_win != 0 ? 0x1E : 0x1F) & ~(1 << f)) : 0;
    524 		combocnt++;
    525 
    526 		if ((c == 1 && debug > 1) || debug > 3) {
    527 		    debuglog("%c c %d %d m %x %x o %d %d",
    528 			"bw"[curcolor],
    529 			ncbp->c_framecnt[0], ncbp->c_framecnt[1],
    530 			ncbp->c_emask[0], ncbp->c_emask[1],
    531 			ncbp->c_voff[0], ncbp->c_voff[1]);
    532 		    printcombo(ncbp, tmp, sizeof(tmp));
    533 		    debuglog("%s", tmp);
    534 		}
    535 
    536 		if (c > 1) {
    537 		    /* record the empty spots that will complete this combo */
    538 		    makeempty(ncbp);
    539 
    540 		    /* add the new combo to the end of the list */
    541 		    appendcombo(ncbp);
    542 		} else {
    543 		    updatecombo(ncbp, curcolor);
    544 		    free(ncbp);
    545 		    combocnt--;
    546 		}
    547 #ifdef DEBUG
    548 		if ((c == 1 && debug > 1) || debug > 5) {
    549 		    markcombo(ncbp);
    550 		    bdisp();
    551 		    whatsup(0);
    552 		    clearcombo(ncbp, 0);
    553 		}
    554 #endif /* DEBUG */
    555 	    }
    556 	}
    557 }
    558 
    559 /*
    560  * Scan the sorted list of frames and try to add a frame to
    561  * combinations of 'level' number of frames.
    562  */
    563 static void
    564 addframes(unsigned int level)
    565 {
    566 	struct combostr *cbp, *ecbp;
    567 	struct spotstr *fsp;
    568 	struct elist *nep;
    569 	int r;
    570 	struct combostr **cbpp, *pcbp;
    571 	union comboval fcb, cb;
    572 
    573 	curlevel = level;
    574 
    575 	/* scan for combos at empty spots */
    576 	player_color c = curcolor;
    577 	for (spot_index s = PT(BSZ, BSZ) + 1; s-- > PT(1, 1); ) {
    578 		struct spotstr *sp = &board[s];
    579 		for (struct elist *ep = sp->s_empty; ep != NULL; ep = nep) {
    580 			cbp = ep->e_combo;
    581 			if (cbp->c_combo.s <= sp->s_combo[c].s) {
    582 				if (cbp->c_combo.s != sp->s_combo[c].s) {
    583 					sp->s_combo[c].s = cbp->c_combo.s;
    584 					sp->s_level[c] = cbp->c_nframes;
    585 				} else if (cbp->c_nframes < sp->s_level[c])
    586 					sp->s_level[c] = cbp->c_nframes;
    587 			}
    588 			nep = ep->e_next;
    589 			free(ep);
    590 			elistcnt--;
    591 		}
    592 		sp->s_empty = sp->s_nempty;
    593 		sp->s_nempty = NULL;
    594 	}
    595 
    596 	/* try to add frames to the uncompleted combos at level curlevel */
    597 	cbp = ecbp = sortframes[curcolor];
    598 	do {
    599 		fsp = &board[cbp->c_vertex];
    600 		r = cbp->c_dir;
    601 		/* skip frames that are part of a <1,x> combo */
    602 		if ((fsp->s_flags & (FFLAG << r)) != 0)
    603 			continue;
    604 
    605 		/*
    606 		 * Don't include <1,x> combo frames,
    607 		 * treat it as a closed three in a row instead.
    608 		 */
    609 		fcb.s = fsp->s_fval[curcolor][r].s;
    610 		if (fcb.s == 0x101)
    611 			fcb.s = 0x200;
    612 
    613 		/*
    614 		 * If this is an open-ended frame, use
    615 		 * the combo value with the end closed.
    616 		 */
    617 		if (fsp->s_occ == EMPTY) {
    618 			if (fcb.cv_win != 0) {
    619 				cb.cv_force = fcb.cv_force + 1;
    620 				cb.cv_win = 0;
    621 			} else
    622 				cb.s = fcb.s;
    623 			makecombo(cbp, fsp, 0, cb.s);
    624 		}
    625 
    626 		/*
    627 		 * The next four spots are handled the same for both
    628 		 * open and closed ended frames.
    629 		 */
    630 		int d = dd[r];
    631 		struct spotstr *sp = fsp + d;
    632 		for (u_char off = 1; off < 5; off++, sp += d) {
    633 			if (sp->s_occ != EMPTY)
    634 				continue;
    635 			makecombo(cbp, sp, off, fcb.s);
    636 		}
    637 	} while ((cbp = cbp->c_next) != ecbp);
    638 
    639 	/* put all the combos in the hash list on the sorted list */
    640 	cbpp = &hashcombos[FAREA];
    641 	do {
    642 		cbp = *--cbpp;
    643 		if (cbp == NULL)
    644 			continue;
    645 		*cbpp = NULL;
    646 		ecbp = sortcombos;
    647 		if (ecbp == NULL)
    648 			sortcombos = cbp;
    649 		else {
    650 			/* append to sort list */
    651 			pcbp = ecbp->c_prev;
    652 			pcbp->c_next = cbp;
    653 			ecbp->c_prev = cbp->c_prev;
    654 			cbp->c_prev->c_next = ecbp;
    655 			cbp->c_prev = pcbp;
    656 		}
    657 	} while (cbpp != hashcombos);
    658 }
    659 
    660 /*
    661  * Compute all level N combos of frames intersecting spot 'osp'
    662  * within the frame 'ocbp' and combo value 'cv'.
    663  */
    664 static void
    665 makecombo(struct combostr *ocbp, struct spotstr *osp, u_char off, u_short cv)
    666 {
    667 	struct combostr *cbp;
    668 	struct spotstr *sp;
    669 	struct combostr **scbpp;
    670 	int baseB, fcnt, emask, verts;
    671 	union comboval ocb;
    672 	struct overlap_info ovi;
    673 	char tmp[128];
    674 
    675 	ocb.s = cv;
    676 	baseB = ocb.cv_force + ocb.cv_win - 1;
    677 	fcnt = ocb.cv_force - 2;
    678 	emask = fcnt != 0 ? ((ocb.cv_win != 0 ? 0x1E : 0x1F) & ~(1 << off)) : 0;
    679 	for (struct elist *ep = osp->s_empty; ep != NULL; ep = ep->e_next) {
    680 	    /* check for various kinds of overlap */
    681 	    cbp = ep->e_combo;
    682 	    verts = checkframes(cbp, ocbp, osp, cv, &ovi);
    683 	    if (verts < 0)
    684 		continue;
    685 
    686 	    /* check to see if this frame forms a valid loop */
    687 	    if (verts > 0) {
    688 		sp = &board[ovi.o_intersect];
    689 #ifdef DEBUG
    690 		if (sp->s_occ != EMPTY) {
    691 		    debuglog("loop: %c %s", "BW"[curcolor],
    692 			stoc((spot_index)(sp - board)));
    693 		    whatsup(0);
    694 		}
    695 #endif
    696 		/*
    697 		 * It is a valid loop if the intersection spot
    698 		 * of the frame we are trying to attach is one
    699 		 * of the completion spots of the combostr
    700 		 * we are trying to attach the frame to.
    701 		 */
    702 		for (struct elist *nep = sp->s_empty;
    703 			nep != NULL; nep = nep->e_next) {
    704 		    if (nep->e_combo == cbp)
    705 			goto fnd;
    706 		    if (nep->e_combo->c_nframes < cbp->c_nframes)
    707 			break;
    708 		}
    709 		/* frame overlaps but not at a valid spot */
    710 		continue;
    711 	    fnd:
    712 		;
    713 	    }
    714 
    715 	    /* compute the first half of the combo value */
    716 	    int c = cbp->c_combo.cv_force + ocb.cv_force - verts - 3;
    717 	    if (c > 4)
    718 		continue;
    719 
    720 	    /* compute the second half of the combo value */
    721 	    int n = ep->e_fval.cv_force + ep->e_fval.cv_win - 1;
    722 	    if (baseB < n)
    723 		n = baseB;
    724 
    725 	    /* make a new combo! */
    726 	    struct combostr *ncbp = malloc(sizeof(struct combostr) +
    727 		(cbp->c_nframes + 1) * sizeof(struct combostr *));
    728 	    if (ncbp == NULL)
    729 		panic("Out of memory!");
    730 	    scbpp = (void *)(ncbp + 1);
    731 	    if (sortcombo(scbpp, (void *)(cbp + 1), ocbp)) {
    732 		free(ncbp);
    733 		continue;
    734 	    }
    735 	    combocnt++;
    736 
    737 	    ncbp->c_combo.cv_force = c;
    738 	    ncbp->c_combo.cv_win = n;
    739 	    ncbp->c_link[0] = cbp;
    740 	    ncbp->c_link[1] = ocbp;
    741 	    ncbp->c_linkv[1].s = ocb.s;
    742 	    ncbp->c_voff[1] = off;
    743 	    ncbp->c_vertex = (spot_index)(osp - board);
    744 	    ncbp->c_nframes = cbp->c_nframes + 1;
    745 	    ncbp->c_flags = ocb.cv_win != 0 ? C_OPEN_1 : 0;
    746 	    ncbp->c_frameindex = ep->e_frameindex;
    747 	    /*
    748 	     * Update the completion spot mask of the frame we
    749 	     * are attaching 'ocbp' to so the intersection isn't
    750 	     * listed twice.
    751 	     */
    752 	    ncbp->c_framecnt[0] = ep->e_framecnt;
    753 	    ncbp->c_emask[0] = ep->e_emask;
    754 	    if (verts != 0) {
    755 		ncbp->c_flags |= C_LOOP;
    756 		ncbp->c_dir = ovi.o_frameindex;
    757 		ncbp->c_framecnt[1] = fcnt - 1;
    758 		if (ncbp->c_framecnt[1] != 0) {
    759 		    n = (ovi.o_intersect - ocbp->c_vertex) / dd[ocbp->c_dir];
    760 		    ncbp->c_emask[1] = emask & ~(1 << n);
    761 		} else
    762 		    ncbp->c_emask[1] = 0;
    763 		ncbp->c_voff[0] = ovi.o_off;
    764 	    } else {
    765 		ncbp->c_dir = 0;
    766 		ncbp->c_framecnt[1] = fcnt;
    767 		ncbp->c_emask[1] = emask;
    768 		ncbp->c_voff[0] = ep->e_off;
    769 	    }
    770 
    771 	    if ((c == 1 && debug > 1) || debug > 3) {
    772 		debuglog("%c v%d i%d d%d c %d %d m %x %x o %d %d",
    773 		    "bw"[curcolor], verts, ncbp->c_frameindex, ncbp->c_dir,
    774 		    ncbp->c_framecnt[0], ncbp->c_framecnt[1],
    775 		    ncbp->c_emask[0], ncbp->c_emask[1],
    776 		    ncbp->c_voff[0], ncbp->c_voff[1]);
    777 		printcombo(ncbp, tmp, sizeof(tmp));
    778 		debuglog("%s", tmp);
    779 	    }
    780 	    if (c > 1) {
    781 		/* record the empty spots that will complete this combo */
    782 		makeempty(ncbp);
    783 		combolen++;
    784 	    } else {
    785 		/* update board values */
    786 		updatecombo(ncbp, curcolor);
    787 	    }
    788 #ifdef DEBUG
    789 	    if ((c == 1 && debug > 1) || debug > 4) {
    790 		markcombo(ncbp);
    791 		bdisp();
    792 		whatsup(0);
    793 		clearcombo(ncbp, 0);
    794 	    }
    795 #endif /* DEBUG */
    796 	}
    797 }
    798 
    799 #define MAXDEPTH	100
    800 static struct elist einfo[MAXDEPTH];
    801 static struct combostr *ecombo[MAXDEPTH];	/* separate from elist to save space */
    802 
    803 /*
    804  * Add the combostr 'ocbp' to the empty spots list for each empty spot
    805  * in 'ocbp' that will complete the combo.
    806  */
    807 static void
    808 makeempty(struct combostr *ocbp)
    809 {
    810 	struct combostr *cbp, **cbpp;
    811 	struct elist *ep, *nep;
    812 	struct spotstr *sp;
    813 	int d, emask, i;
    814 	int nframes;
    815 	char tmp[128];
    816 
    817 	if (debug > 2) {
    818 		printcombo(ocbp, tmp, sizeof(tmp));
    819 		debuglog("E%c %s", "bw"[curcolor], tmp);
    820 	}
    821 
    822 	/* should never happen but check anyway */
    823 	if ((nframes = ocbp->c_nframes) >= MAXDEPTH)
    824 		return;
    825 
    826 	/*
    827 	 * The lower level combo can be pointed to by more than one
    828 	 * higher level 'struct combostr' so we can't modify the
    829 	 * lower level. Therefore, higher level combos store the
    830 	 * real mask of the lower level frame in c_emask[0] and the
    831 	 * frame number in c_frameindex.
    832 	 *
    833 	 * First we traverse the tree from top to bottom and save the
    834 	 * connection info. Then we traverse the tree from bottom to
    835 	 * top overwriting lower levels with the newer emask information.
    836 	 */
    837 	ep = &einfo[nframes];
    838 	cbpp = &ecombo[nframes];
    839 	for (cbp = ocbp; cbp->c_link[1] != NULL; cbp = cbp->c_link[0]) {
    840 		ep--;
    841 		ep->e_combo = cbp;
    842 		*--cbpp = cbp->c_link[1];
    843 		ep->e_off = cbp->c_voff[1];
    844 		ep->e_frameindex = cbp->c_frameindex;
    845 		ep->e_fval.s = cbp->c_linkv[1].s;
    846 		ep->e_framecnt = cbp->c_framecnt[1];
    847 		ep->e_emask = cbp->c_emask[1];
    848 	}
    849 	cbp = ep->e_combo;
    850 	ep--;
    851 	ep->e_combo = cbp;
    852 	*--cbpp = cbp->c_link[0];
    853 	ep->e_off = cbp->c_voff[0];
    854 	ep->e_frameindex = 0;
    855 	ep->e_fval.s = cbp->c_linkv[0].s;
    856 	ep->e_framecnt = cbp->c_framecnt[0];
    857 	ep->e_emask = cbp->c_emask[0];
    858 
    859 	/* now update the emask info */
    860 	int n = 0;
    861 	for (i = 2, ep += 2; i < nframes; i++, ep++) {
    862 		cbp = ep->e_combo;
    863 		nep = &einfo[ep->e_frameindex];
    864 		nep->e_framecnt = cbp->c_framecnt[0];
    865 		nep->e_emask = cbp->c_emask[0];
    866 
    867 		if ((cbp->c_flags & C_LOOP) != 0) {
    868 			n++;
    869 			/*
    870 			 * Account for the fact that this frame connects
    871 			 * to a previous one (thus forming a loop).
    872 			 */
    873 			nep = &einfo[cbp->c_dir];
    874 			if (--nep->e_framecnt != 0)
    875 				nep->e_emask &= ~(1 << cbp->c_voff[0]);
    876 			else
    877 				nep->e_emask = 0;
    878 		}
    879 	}
    880 
    881 	/*
    882 	 * We only need to update the emask values of "complete" loops
    883 	 * to include the intersection spots.
    884 	 */
    885 	if (n != 0 && ocbp->c_combo.cv_force == 2) {
    886 		/* process loops from the top down */
    887 		ep = &einfo[nframes];
    888 		do {
    889 			ep--;
    890 			cbp = ep->e_combo;
    891 			if ((cbp->c_flags & C_LOOP) == 0)
    892 				continue;
    893 
    894 			/*
    895 			 * Update the emask values to include the
    896 			 * intersection spots.
    897 			 */
    898 			nep = &einfo[cbp->c_dir];
    899 			nep->e_framecnt = 1;
    900 			nep->e_emask = 1 << cbp->c_voff[0];
    901 			ep->e_framecnt = 1;
    902 			ep->e_emask = 1 << ep->e_off;
    903 			ep = &einfo[ep->e_frameindex];
    904 			do {
    905 				ep->e_framecnt = 1;
    906 				ep->e_emask = 1 << ep->e_off;
    907 				ep = &einfo[ep->e_frameindex];
    908 			} while (ep > nep);
    909 		} while (ep != einfo);
    910 	}
    911 
    912 	/* check all the frames for completion spots */
    913 	for (i = 0, ep = einfo, cbpp = ecombo; i < nframes; i++, ep++, cbpp++) {
    914 		/* skip this frame if there are no incomplete spots in it */
    915 		if ((emask = ep->e_emask) == 0)
    916 			continue;
    917 		cbp = *cbpp;
    918 		sp = &board[cbp->c_vertex];
    919 		d = dd[cbp->c_dir];
    920 		for (int off = 0, m = 1; off < 5; off++, sp += d, m <<= 1) {
    921 			if (sp->s_occ != EMPTY || (emask & m) == 0)
    922 				continue;
    923 
    924 			/* add the combo to the list of empty spots */
    925 			nep = (struct elist *)malloc(sizeof(struct elist));
    926 			if (nep == NULL)
    927 				panic("Out of memory!");
    928 			nep->e_combo = ocbp;
    929 			nep->e_off = off;
    930 			nep->e_frameindex = i;
    931 			if (ep->e_framecnt > 1) {
    932 				nep->e_framecnt = ep->e_framecnt - 1;
    933 				nep->e_emask = emask & ~m;
    934 			} else {
    935 				nep->e_framecnt = 0;
    936 				nep->e_emask = 0;
    937 			}
    938 			nep->e_fval.s = ep->e_fval.s;
    939 			if (debug > 2) {
    940 				debuglog("e %s o%d i%d c%d m%x %x",
    941 				    stoc((spot_index)(sp - board)),
    942 				    nep->e_off,
    943 				    nep->e_frameindex,
    944 				    nep->e_framecnt,
    945 				    nep->e_emask,
    946 				    nep->e_fval.s);
    947 			}
    948 
    949 			/* sort by the number of frames in the combo */
    950 			nep->e_next = sp->s_nempty;
    951 			sp->s_nempty = nep;
    952 			elistcnt++;
    953 		}
    954 	}
    955 }
    956 
    957 /*
    958  * Update the board value based on the combostr.
    959  * This is called only if 'cbp' is a <1,x> combo.
    960  * We handle things differently depending on whether the next move
    961  * would be trying to "complete" the combo or trying to block it.
    962  */
    963 static void
    964 updatecombo(struct combostr *cbp, player_color color)
    965 {
    966 	struct combostr *tcbp;
    967 	union comboval cb;
    968 
    969 	int flags = 0;
    970 	/* save the top level value for the whole combo */
    971 	cb.cv_force = cbp->c_combo.cv_force;
    972 	u_char nframes = cbp->c_nframes;
    973 
    974 	if (color != nextcolor)
    975 		memset(tmpmap, 0, sizeof(tmpmap));
    976 
    977 	for (; (tcbp = cbp->c_link[1]) != NULL; cbp = cbp->c_link[0]) {
    978 		flags = cbp->c_flags;
    979 		cb.cv_win = cbp->c_combo.cv_win;
    980 		if (color == nextcolor) {
    981 			/* update the board value for the vertex */
    982 			struct spotstr *sp = &board[cbp->c_vertex];
    983 			sp->s_nforce[color]++;
    984 			if (cb.s <= sp->s_combo[color].s) {
    985 				if (cb.s != sp->s_combo[color].s) {
    986 					sp->s_combo[color].s = cb.s;
    987 					sp->s_level[color] = nframes;
    988 				} else if (nframes < sp->s_level[color])
    989 					sp->s_level[color] = nframes;
    990 			}
    991 		} else {
    992 			/* update the board values for each spot in frame */
    993 			spot_index s = tcbp->c_vertex;
    994 			struct spotstr *sp = &board[s];
    995 			int d = dd[tcbp->c_dir];
    996 			int off = (flags & C_OPEN_1) != 0 ? 6 : 5;
    997 			for (; --off >= 0; sp += d, s += d) {
    998 				if (sp->s_occ != EMPTY)
    999 					continue;
   1000 				sp->s_nforce[color]++;
   1001 				if (cb.s <= sp->s_combo[color].s) {
   1002 					if (cb.s != sp->s_combo[color].s) {
   1003 						sp->s_combo[color].s = cb.s;
   1004 						sp->s_level[color] = nframes;
   1005 					} else if (nframes < sp->s_level[color])
   1006 						sp->s_level[color] = nframes;
   1007 				}
   1008 				BIT_SET(tmpmap, s);
   1009 			}
   1010 		}
   1011 
   1012 		/* mark the frame as being part of a <1,x> combo */
   1013 		board[tcbp->c_vertex].s_flags |= FFLAG << tcbp->c_dir;
   1014 	}
   1015 
   1016 	if (color != nextcolor) {
   1017 		/* update the board values for each spot in frame */
   1018 		spot_index s = cbp->c_vertex;
   1019 		struct spotstr *sp = &board[s];
   1020 		int d = dd[cbp->c_dir];
   1021 		int off = (flags & C_OPEN_0) != 0 ? 6 : 5;
   1022 		for (; --off >= 0; sp += d, s += d) {
   1023 			if (sp->s_occ != EMPTY)
   1024 				continue;
   1025 			sp->s_nforce[color]++;
   1026 			if (cb.s <= sp->s_combo[color].s) {
   1027 				if (cb.s != sp->s_combo[color].s) {
   1028 					sp->s_combo[color].s = cb.s;
   1029 					sp->s_level[color] = nframes;
   1030 				} else if (nframes < sp->s_level[color])
   1031 					sp->s_level[color] = nframes;
   1032 			}
   1033 			BIT_SET(tmpmap, s);
   1034 		}
   1035 		if (nforce == 0)
   1036 			memcpy(forcemap, tmpmap, sizeof(tmpmap));
   1037 		else {
   1038 			for (int i = 0; (unsigned int)i < MAPSZ; i++)
   1039 				forcemap[i] &= tmpmap[i];
   1040 		}
   1041 		nforce++;
   1042 	}
   1043 
   1044 	/* mark the frame as being part of a <1,x> combo */
   1045 	board[cbp->c_vertex].s_flags |= FFLAG << cbp->c_dir;
   1046 }
   1047 
   1048 /*
   1049  * Add combo to the end of the list.
   1050  */
   1051 static void
   1052 appendcombo(struct combostr *cbp)
   1053 {
   1054 	struct combostr *pcbp, *ncbp;
   1055 
   1056 	combolen++;
   1057 	ncbp = sortcombos;
   1058 	if (ncbp == NULL) {
   1059 		sortcombos = cbp;
   1060 		cbp->c_next = cbp;
   1061 		cbp->c_prev = cbp;
   1062 		return;
   1063 	}
   1064 	pcbp = ncbp->c_prev;
   1065 	cbp->c_next = ncbp;
   1066 	cbp->c_prev = pcbp;
   1067 	ncbp->c_prev = cbp;
   1068 	pcbp->c_next = cbp;
   1069 }
   1070 
   1071 /*
   1072  * Return zero if it is valid to combine frame 'fcbp' with the frames
   1073  * in 'cbp' and forms a linked chain of frames (i.e., a tree; no loops).
   1074  * Return positive if combining frame 'fcbp' to the frames in 'cbp'
   1075  * would form some kind of valid loop. Also return the intersection spot
   1076  * in 'ovi' beside the known intersection at spot 'osp'.
   1077  * Return -1 if 'fcbp' should not be combined with 'cbp'.
   1078  * 'cv' is the combo value for frame 'fcbp'.
   1079  */
   1080 static int
   1081 checkframes(struct combostr *cbp, struct combostr *fcbp, struct spotstr *osp,
   1082 	    u_short cv, struct overlap_info *ovi)
   1083 {
   1084 	struct combostr *tcbp, *lcbp;
   1085 	int ovbit, n, mask, flags, fcnt;
   1086 	union comboval cb;
   1087 	u_char *str;
   1088 
   1089 	lcbp = NULL;
   1090 	flags = 0;
   1091 
   1092 	cb.s = cv;
   1093 	fcnt = cb.cv_force - 2;
   1094 	int verts = 0;
   1095 	u_char myindex = cbp->c_nframes;
   1096 	n = (frame_index)(fcbp - frames) * FAREA;
   1097 	str = &overlap[n];
   1098 	spot_index *ip = &intersect[n];
   1099 	/*
   1100 	 * ovbit == which overlap bit to test based on whether 'fcbp' is
   1101 	 * an open or closed frame.
   1102 	 */
   1103 	ovbit = cb.cv_win != 0 ? 2 : 0;
   1104 	for (; (tcbp = cbp->c_link[1]) != NULL;
   1105 	    lcbp = cbp, cbp = cbp->c_link[0]) {
   1106 		if (tcbp == fcbp)
   1107 			return -1;	/* fcbp is already included */
   1108 
   1109 		/* check for intersection of 'tcbp' with 'fcbp' */
   1110 		myindex--;
   1111 		mask = str[tcbp - frames];
   1112 		flags = cbp->c_flags;
   1113 		n = ovbit + ((flags & C_OPEN_1) != 0 ? 1 : 0);
   1114 		if ((mask & (1 << n)) != 0) {
   1115 			/*
   1116 			 * The two frames are not independent if they
   1117 			 * both lie in the same line and intersect at
   1118 			 * more than one point.
   1119 			 */
   1120 			if (tcbp->c_dir == fcbp->c_dir &&
   1121 			    (mask & (0x10 << n)) != 0)
   1122 				return -1;
   1123 			/*
   1124 			 * If this is not the spot we are attaching
   1125 			 * 'fcbp' to, and it is a reasonable intersection
   1126 			 * spot, then there might be a loop.
   1127 			 */
   1128 			spot_index s = ip[tcbp - frames];
   1129 			if (osp != &board[s]) {
   1130 				/* check to see if this is a valid loop */
   1131 				if (verts != 0)
   1132 					return -1;
   1133 				if (fcnt == 0 || cbp->c_framecnt[1] == 0)
   1134 					return -1;
   1135 				/*
   1136 				 * Check to be sure the intersection is not
   1137 				 * one of the end points if it is an
   1138 				 * open-ended frame.
   1139 				 */
   1140 				if ((flags & C_OPEN_1) != 0 &&
   1141 				    (s == tcbp->c_vertex ||
   1142 				     s == tcbp->c_vertex + 5 * dd[tcbp->c_dir]))
   1143 					return -1;	/* invalid overlap */
   1144 				if (cb.cv_win != 0 &&
   1145 				    (s == fcbp->c_vertex ||
   1146 				     s == fcbp->c_vertex + 5 * dd[fcbp->c_dir]))
   1147 					return -1;	/* invalid overlap */
   1148 
   1149 				ovi->o_intersect = s;
   1150 				ovi->o_off =
   1151 				    (s - tcbp->c_vertex) / dd[tcbp->c_dir];
   1152 				ovi->o_frameindex = myindex;
   1153 				verts++;
   1154 			}
   1155 		}
   1156 		n = ovbit + ((flags & C_OPEN_0) != 0 ? 1 : 0);
   1157 	}
   1158 	if (cbp == fcbp)
   1159 		return -1;	/* fcbp is already included */
   1160 
   1161 	/* check for intersection of 'cbp' with 'fcbp' */
   1162 	mask = str[cbp - frames];
   1163 	if ((mask & (1 << n)) != 0) {
   1164 		/*
   1165 		 * The two frames are not independent if they
   1166 		 * both lie in the same line and intersect at
   1167 		 * more than one point.
   1168 		 */
   1169 		if (cbp->c_dir == fcbp->c_dir && (mask & (0x10 << n)) != 0)
   1170 			return -1;
   1171 		/*
   1172 		 * If this is not the spot we are attaching
   1173 		 * 'fcbp' to, and it is a reasonable intersection
   1174 		 * spot, then there might be a loop.
   1175 		 */
   1176 		spot_index s = ip[cbp - frames];
   1177 		if (osp != &board[s]) {
   1178 			/* check to see if this is a valid loop */
   1179 			if (verts != 0)
   1180 				return -1;
   1181 			if (fcnt == 0 || lcbp->c_framecnt[0] == 0)
   1182 				return -1;
   1183 			/*
   1184 			 * Check to be sure the intersection is not
   1185 			 * one of the end points if it is an open-ended
   1186 			 * frame.
   1187 			 */
   1188 			if ((flags & C_OPEN_0) != 0 &&
   1189 			    (s == cbp->c_vertex ||
   1190 			     s == cbp->c_vertex + 5 * dd[cbp->c_dir]))
   1191 				return -1;	/* invalid overlap */
   1192 			if (cb.cv_win != 0 &&
   1193 			    (s == fcbp->c_vertex ||
   1194 			     s == fcbp->c_vertex + 5 * dd[fcbp->c_dir]))
   1195 				return -1;	/* invalid overlap */
   1196 
   1197 			ovi->o_intersect = s;
   1198 			ovi->o_off = (s - cbp->c_vertex) / dd[cbp->c_dir];
   1199 			ovi->o_frameindex = 0;
   1200 			verts++;
   1201 		}
   1202 	}
   1203 	return verts;
   1204 }
   1205 
   1206 /*
   1207  * Merge sort the frame 'fcbp' and the sorted list of frames 'cbpp' and
   1208  * store the result in 'scbpp'. 'curlevel' is the size of the 'cbpp' array.
   1209  * Return true if this list of frames is already in the hash list.
   1210  * Otherwise, add the new combo to the hash list.
   1211  */
   1212 static bool
   1213 sortcombo(struct combostr **scbpp, struct combostr **cbpp,
   1214 	  struct combostr *fcbp)
   1215 {
   1216 	struct combostr **spp, **cpp;
   1217 	struct combostr *cbp, *ecbp;
   1218 	int inx;
   1219 
   1220 #ifdef DEBUG
   1221 	if (debug > 3) {
   1222 		char buf[128];
   1223 		size_t pos;
   1224 
   1225 		debuglog("sortc: %s%c l%u", stoc(fcbp->c_vertex),
   1226 			pdir[fcbp->c_dir], curlevel);
   1227 		pos = 0;
   1228 		for (cpp = cbpp; cpp < cbpp + curlevel; cpp++) {
   1229 			snprintf(buf + pos, sizeof(buf) - pos, " %s%c",
   1230 				stoc((*cpp)->c_vertex), pdir[(*cpp)->c_dir]);
   1231 			pos += strlen(buf + pos);
   1232 		}
   1233 		debuglog("%s", buf);
   1234 	}
   1235 #endif /* DEBUG */
   1236 
   1237 	/* first build the new sorted list */
   1238 	unsigned int n = curlevel + 1;
   1239 	spp = scbpp + n;
   1240 	cpp = cbpp + curlevel;
   1241 	do {
   1242 		cpp--;
   1243 		if (fcbp > *cpp) {
   1244 			*--spp = fcbp;
   1245 			do {
   1246 				*--spp = *cpp;
   1247 			} while (cpp-- != cbpp);
   1248 			goto inserted;
   1249 		}
   1250 		*--spp = *cpp;
   1251 	} while (cpp != cbpp);
   1252 	*--spp = fcbp;
   1253 inserted:
   1254 
   1255 	/* now check to see if this list of frames has already been seen */
   1256 	cbp = hashcombos[inx = (frame_index)(*scbpp - frames)];
   1257 	if (cbp == NULL) {
   1258 		/*
   1259 		 * Easy case, this list hasn't been seen.
   1260 		 * Add it to the hash list.
   1261 		 */
   1262 		fcbp = (void *)((char *)scbpp - sizeof(struct combostr));
   1263 		hashcombos[inx] = fcbp;
   1264 		fcbp->c_next = fcbp->c_prev = fcbp;
   1265 		return false;
   1266 	}
   1267 	ecbp = cbp;
   1268 	do {
   1269 		cbpp = (void *)(cbp + 1);
   1270 		cpp = cbpp + n;
   1271 		spp = scbpp + n;
   1272 		cbpp++;	/* first frame is always the same */
   1273 		do {
   1274 			if (*--spp != *--cpp)
   1275 				goto next;
   1276 		} while (cpp != cbpp);
   1277 		/* we found a match */
   1278 #ifdef DEBUG
   1279 		if (debug > 3) {
   1280 			char buf[128];
   1281 			size_t pos;
   1282 
   1283 			debuglog("sort1: n%u", n);
   1284 			pos = 0;
   1285 			for (cpp = scbpp; cpp < scbpp + n; cpp++) {
   1286 				snprintf(buf + pos, sizeof(buf) - pos, " %s%c",
   1287 					stoc((*cpp)->c_vertex),
   1288 					pdir[(*cpp)->c_dir]);
   1289 				pos += strlen(buf + pos);
   1290 			}
   1291 			debuglog("%s", buf);
   1292 			printcombo(cbp, buf, sizeof(buf));
   1293 			debuglog("%s", buf);
   1294 			cbpp--;
   1295 			pos = 0;
   1296 			for (cpp = cbpp; cpp < cbpp + n; cpp++) {
   1297 				snprintf(buf + pos, sizeof(buf) - pos, " %s%c",
   1298 					stoc((*cpp)->c_vertex),
   1299 					pdir[(*cpp)->c_dir]);
   1300 				pos += strlen(buf + pos);
   1301 			}
   1302 			debuglog("%s", buf);
   1303 		}
   1304 #endif /* DEBUG */
   1305 		return true;
   1306 	next:
   1307 		;
   1308 	} while ((cbp = cbp->c_next) != ecbp);
   1309 	/*
   1310 	 * This list of frames hasn't been seen.
   1311 	 * Add it to the hash list.
   1312 	 */
   1313 	ecbp = cbp->c_prev;
   1314 	fcbp = (void *)((char *)scbpp - sizeof(struct combostr));
   1315 	fcbp->c_next = cbp;
   1316 	fcbp->c_prev = ecbp;
   1317 	cbp->c_prev = fcbp;
   1318 	ecbp->c_next = fcbp;
   1319 	return false;
   1320 }
   1321 
   1322 /*
   1323  * Print the combo into string buffer 'buf'.
   1324  */
   1325 #if !defined(DEBUG)
   1326 static
   1327 #endif
   1328 void
   1329 printcombo(struct combostr *cbp, char *buf, size_t max)
   1330 {
   1331 	struct combostr *tcbp;
   1332 	size_t pos = 0;
   1333 
   1334 	snprintf(buf + pos, max - pos, "%x/%d",
   1335 	    cbp->c_combo.s, cbp->c_nframes);
   1336 	pos += strlen(buf + pos);
   1337 
   1338 	for (; (tcbp = cbp->c_link[1]) != NULL; cbp = cbp->c_link[0]) {
   1339 		snprintf(buf + pos, max - pos, " %s%c%x",
   1340 		    stoc(tcbp->c_vertex), pdir[tcbp->c_dir], cbp->c_flags);
   1341 		pos += strlen(buf + pos);
   1342 	}
   1343 	snprintf(buf + pos, max - pos, " %s%c",
   1344 	    stoc(cbp->c_vertex), pdir[cbp->c_dir]);
   1345 }
   1346 
   1347 #ifdef DEBUG
   1348 void
   1349 markcombo(struct combostr *ocbp)
   1350 {
   1351 	struct combostr *cbp, **cbpp;
   1352 	struct elist *ep, *nep;
   1353 	struct spotstr *sp;
   1354 	int d, m, i;
   1355 	int nframes;
   1356 	int cmask, omask;
   1357 
   1358 	/* should never happen but check anyway */
   1359 	if ((nframes = ocbp->c_nframes) >= MAXDEPTH)
   1360 		return;
   1361 
   1362 	/*
   1363 	 * The lower level combo can be pointed to by more than one
   1364 	 * higher level 'struct combostr' so we can't modify the
   1365 	 * lower level. Therefore, higher level combos store the
   1366 	 * real mask of the lower level frame in c_emask[0] and the
   1367 	 * frame number in c_frameindex.
   1368 	 *
   1369 	 * First we traverse the tree from top to bottom and save the
   1370 	 * connection info. Then we traverse the tree from bottom to
   1371 	 * top overwriting lower levels with the newer emask information.
   1372 	 */
   1373 	ep = &einfo[nframes];
   1374 	cbpp = &ecombo[nframes];
   1375 	for (cbp = ocbp; cbp->c_link[1] != NULL; cbp = cbp->c_link[0]) {
   1376 		ep--;
   1377 		ep->e_combo = cbp;
   1378 		*--cbpp = cbp->c_link[1];
   1379 		ep->e_off = cbp->c_voff[1];
   1380 		ep->e_frameindex = cbp->c_frameindex;
   1381 		ep->e_fval.s = cbp->c_linkv[1].s;
   1382 		ep->e_framecnt = cbp->c_framecnt[1];
   1383 		ep->e_emask = cbp->c_emask[1];
   1384 	}
   1385 	cbp = ep->e_combo;
   1386 	ep--;
   1387 	ep->e_combo = cbp;
   1388 	*--cbpp = cbp->c_link[0];
   1389 	ep->e_off = cbp->c_voff[0];
   1390 	ep->e_frameindex = 0;
   1391 	ep->e_fval.s = cbp->c_linkv[0].s;
   1392 	ep->e_framecnt = cbp->c_framecnt[0];
   1393 	ep->e_emask = cbp->c_emask[0];
   1394 
   1395 	/* now update the emask info */
   1396 	int n = 0;
   1397 	for (i = 2, ep += 2; i < nframes; i++, ep++) {
   1398 		cbp = ep->e_combo;
   1399 		nep = &einfo[ep->e_frameindex];
   1400 		nep->e_framecnt = cbp->c_framecnt[0];
   1401 		nep->e_emask = cbp->c_emask[0];
   1402 
   1403 		if ((cbp->c_flags & C_LOOP) != 0) {
   1404 			n++;
   1405 			/*
   1406 			 * Account for the fact that this frame connects
   1407 			 * to a previous one (thus forming a loop).
   1408 			 */
   1409 			nep = &einfo[cbp->c_dir];
   1410 			if (--nep->e_framecnt != 0)
   1411 				nep->e_emask &= ~(1 << cbp->c_voff[0]);
   1412 			else
   1413 				nep->e_emask = 0;
   1414 		}
   1415 	}
   1416 
   1417 	/*
   1418 	 * We only need to update the emask values of "complete" loops
   1419 	 * to include the intersection spots.
   1420 	 */
   1421 	if (n != 0 && ocbp->c_combo.cv_force == 2) {
   1422 		/* process loops from the top down */
   1423 		ep = &einfo[nframes];
   1424 		do {
   1425 			ep--;
   1426 			cbp = ep->e_combo;
   1427 			if ((cbp->c_flags & C_LOOP) == 0)
   1428 				continue;
   1429 
   1430 			/*
   1431 			 * Update the emask values to include the
   1432 			 * intersection spots.
   1433 			 */
   1434 			nep = &einfo[cbp->c_dir];
   1435 			nep->e_framecnt = 1;
   1436 			nep->e_emask = 1 << cbp->c_voff[0];
   1437 			ep->e_framecnt = 1;
   1438 			ep->e_emask = 1 << ep->e_off;
   1439 			ep = &einfo[ep->e_frameindex];
   1440 			do {
   1441 				ep->e_framecnt = 1;
   1442 				ep->e_emask = 1 << ep->e_off;
   1443 				ep = &einfo[ep->e_frameindex];
   1444 			} while (ep > nep);
   1445 		} while (ep != einfo);
   1446 	}
   1447 
   1448 	/* mark all the frames with the completion spots */
   1449 	for (i = 0, ep = einfo, cbpp = ecombo; i < nframes; i++, ep++, cbpp++) {
   1450 		m = ep->e_emask;
   1451 		cbp = *cbpp;
   1452 		sp = &board[cbp->c_vertex];
   1453 		d = dd[cbp->c_dir];
   1454 		cmask = CFLAG << cbp->c_dir;
   1455 		omask = (IFLAG | CFLAG) << cbp->c_dir;
   1456 		int off = ep->e_fval.cv_win != 0 ? 6 : 5;
   1457 		/* LINTED 117: bitwise '>>' on signed value possibly nonportable */
   1458 		for (; --off >= 0; sp += d, m >>= 1)
   1459 			sp->s_flags |= (m & 1) != 0 ? omask : cmask;
   1460 	}
   1461 }
   1462 
   1463 void
   1464 clearcombo(struct combostr *cbp, int open)
   1465 {
   1466 	struct combostr *tcbp;
   1467 
   1468 	for (; (tcbp = cbp->c_link[1]) != NULL; cbp = cbp->c_link[0]) {
   1469 		clearcombo(tcbp, cbp->c_flags & C_OPEN_1);
   1470 		open = cbp->c_flags & C_OPEN_0;
   1471 	}
   1472 
   1473 	struct spotstr *sp = &board[cbp->c_vertex];
   1474 	int d = dd[cbp->c_dir];
   1475 	int mask = ~((IFLAG | CFLAG) << cbp->c_dir);
   1476 	int n = open != 0 ? 6 : 5;
   1477 	for (; --n >= 0; sp += d)
   1478 		sp->s_flags &= mask;
   1479 }
   1480 #endif /* DEBUG */
   1481