1 /*	$OpenBSD: diff3.c,v 1.41 2016/10/18 21:06:52 millert Exp $	*/
2 
3 /*
4  * Copyright (C) Caldera International Inc.  2001-2002.
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code and documentation must retain the above
11  *    copyright notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *	This product includes software developed or owned by Caldera
18  *	International, Inc.
19  * 4. Neither the name of Caldera International, Inc. nor the names of other
20  *    contributors may be used to endorse or promote products derived from
21  *    this software without specific prior written permission.
22  *
23  * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
24  * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
25  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
27  * IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
28  * INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
29  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
30  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
32  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
33  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
34  * POSSIBILITY OF SUCH DAMAGE.
35  */
36 /*-
37  * Copyright (c) 1991, 1993
38  *	The Regents of the University of California.  All rights reserved.
39  *
40  * Redistribution and use in source and binary forms, with or without
41  * modification, are permitted provided that the following conditions
42  * are met:
43  * 1. Redistributions of source code must retain the above copyright
44  *    notice, this list of conditions and the following disclaimer.
45  * 2. Redistributions in binary form must reproduce the above copyright
46  *    notice, this list of conditions and the following disclaimer in the
47  *    documentation and/or other materials provided with the distribution.
48  * 3. Neither the name of the University nor the names of its contributors
49  *    may be used to endorse or promote products derived from this software
50  *    without specific prior written permission.
51  *
52  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
53  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
54  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
55  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
56  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
57  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
58  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
59  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
60  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
61  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
62  * SUCH DAMAGE.
63  *
64  *	@(#)diff3.c	8.1 (Berkeley) 6/6/93
65  */
66 
67 #include <sys/stat.h>
68 #include <sys/queue.h>
69 
70 #include <ctype.h>
71 #include <limits.h>
72 #include <stdio.h>
73 #include <stdarg.h>
74 #include <stdlib.h>
75 #include <string.h>
76 #include <time.h>
77 #include <unistd.h>
78 
79 #include "got_error.h"
80 #include "got_opentemp.h"
81 #include "got_object.h"
82 
83 #include "buf.h"
84 #include "rcsutil.h"
85 #include "got_lib_diff.h"
86 #include "worklist.h"
87 
88 #ifndef nitems
89 #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
90 #endif
91 
92 /* diff3 - 3-way differential file comparison */
93 
94 /* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
95  *
96  * d13 = diff report on f1 vs f3
97  * d23 = diff report on f2 vs f3
98  * f1, f2, f3 the 3 files
99  * if changes in f1 overlap with changes in f3, m1 and m3 are used
100  * to mark the overlaps; otherwise, the file names f1 and f3 are used
101  * (only for options E and X).
102  */
103 
104 /*
105  * "from" is first in range of changed lines; "to" is last+1
106  * from=to=line after point of insertion for added lines.
107  */
108 struct range {
109 	int from;
110 	int to;
111 };
112 
113 struct diff {
114 	struct range old;
115 	struct range new;
116 };
117 
118 struct diff3_state {
119 	size_t szchanges;
120 
121 	struct diff *d13;
122 	struct diff *d23;
123 
124 	/*
125 	 * "de" is used to gather editing scripts.  These are later spewed out
126 	 * in reverse order.  Its first element must be all zero, the "new"
127 	 * component of "de" contains line positions or byte positions
128 	 * depending on when you look (!?).  Array overlap indicates which
129 	 * sections in "de" correspond to lines that are different in all
130 	 * three files.
131 	 */
132 	struct diff *de;
133 	char *overlap;
134 	int overlapcnt;
135 	FILE *fp[3];
136 	int cline[3];		/* # of the last-read line in each file (0-2) */
137 
138 	/*
139 	 * the latest known correspondence between line numbers of the 3 files
140 	 * is stored in last[1-3];
141 	 */
142 	int last[4];
143 	int eflag;
144 	int oflag;
145 	int debug;
146 	char f1mark[PATH_MAX], f3mark[PATH_MAX]; /* markers for -E and -X */
147 
148 	char *buf;
149 	size_t bufsize;
150 };
151 
152 static BUF *diffbuf;
153 
154 static int duplicate(struct range *, struct range *, struct diff3_state *);
155 static int edit(struct diff *, int, int, struct diff3_state *);
156 static char *getchange(FILE *, struct diff3_state *);
157 static char *get_line(FILE *, size_t *, struct diff3_state *);
158 static int number(char **);
159 static const struct got_error *readin(size_t *, char *, struct diff **,
160     struct diff3_state *);
161 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
162 static int skip(int, int, char *, struct diff3_state *);
163 static int edscript(int, struct diff3_state *);
164 static int merge(size_t, size_t, struct diff3_state *);
165 static void change(int, struct range *, int, struct diff3_state *);
166 static void keep(int, struct range *, struct diff3_state *);
167 static void prange(struct range *);
168 static void repos(int, struct diff3_state *);
169 static void separate(const char *);
170 static const struct got_error *increase(struct diff3_state *);
171 static const struct got_error *diff3_internal(char *, char *, char *,
172     char *, char *, const char *, const char *, struct diff3_state *);
173 
174 int diff3_conflicts = 0;
175 
176 static const struct got_error *
177 diff_output(const char *fmt, ...)
178 {
179 	va_list vap;
180 	int i;
181 	char *str;
182 	size_t newsize;
183 
184 	va_start(vap, fmt);
185 	i = vasprintf(&str, fmt, vap);
186 	va_end(vap);
187 	if (i == -1)
188 		return got_error_from_errno();
189 	if (diffbuf != NULL)
190 		buf_append(&newsize, diffbuf, str, strlen(str));
191 	else
192 		printf("%s", str);
193 	free(str);
194 	return NULL;
195 }
196 
197 static const struct got_error*
198 diffreg(BUF **d, const char *path1, const char *path2)
199 {
200 	const struct got_error *err = NULL;
201 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
202 	char *outpath = NULL;
203 	struct got_diff_state ds;
204 	struct got_diff_args args;
205 	int res;
206 
207 	*d = NULL;
208 
209 	f1 = fopen(path1, "r");
210 	if (f1 == NULL) {
211 		err = got_error_from_errno();
212 		goto done;
213 	}
214 	f2 = fopen(path2, "r");
215 	if (f1 == NULL) {
216 		err = got_error_from_errno();
217 		goto done;
218 	}
219 
220 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diff");
221 	if (err)
222 		goto done;
223 
224 	memset(&ds, 0, sizeof(ds));
225 	/* XXX should stat buffers be passed in args instead of ds? */
226 	if (stat(path1, &ds.stb1) == -1) {
227 		err = got_error_from_errno();
228 		goto done;
229 	}
230 	if (stat(path2, &ds.stb2) == -1) {
231 		err = got_error_from_errno();
232 		goto done;
233 	}
234 
235 	memset(&args, 0, sizeof(args));
236 	args.diff_format = D_NORMAL;
237 	args.label[0] = "";
238 	args.label[1] = "";
239 	args.diff_context = 0;
240 
241 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
242 	    outfile, NULL);
243 	if (err)
244 		goto done;
245 
246 	*d = buf_load(outpath);
247 	if (*d == NULL)
248 		err = got_error_from_errno();
249 done:
250 	free(outpath);
251 	if (outfile)
252 		fclose(outfile);
253 	if (f1)
254 		fclose(f1);
255 	if (f2)
256 		fclose(f2);
257 	return err;
258 }
259 
260 /*
261  * For merge(1).
262  */
263 const struct got_error *
264 got_merge_diff3(int outfd, const char *p1, const char *p2, const char *p3)
265 {
266 	const struct got_error *err = NULL;
267 	char *dp13, *dp23, *path1, *path2, *path3;
268 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
269 	u_char *data, *patch;
270 	size_t dlen, plen;
271 	struct wklhead temp_files;
272 	struct diff3_state *d3s;
273 	int i;
274 
275 	d3s = calloc(1, sizeof(*d3s));
276 	if (d3s == NULL)
277 		return got_error_from_errno();
278 	d3s->eflag = 3; /* default -E for compatibility with former RCS */
279 	d3s->oflag = 1; /* default -E for compatibility with former RCS */
280 
281 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
282 	dp13 = dp23 = path1 = path2 = path3 = NULL;
283 	data = patch = NULL;
284 
285 	if ((b1 = buf_load(p1)) == NULL)
286 		goto out;
287 	if ((b2 = buf_load(p2)) == NULL)
288 		goto out;
289 	if ((b3 = buf_load(p3)) == NULL)
290 		goto out;
291 
292 	diffb = buf_alloc(128);
293 
294 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
295 		err = got_error_from_errno();
296 		goto out;
297 	}
298 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
299 		err = got_error_from_errno();
300 		goto out;
301 	}
302 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
303 		err = got_error_from_errno();
304 		goto out;
305 	}
306 
307 	err = buf_write_stmp(b1, path1, &temp_files);
308 	if (err)
309 		goto out;
310 	err = buf_write_stmp(b2, path2, &temp_files);
311 	if (err)
312 		goto out;
313 	err = buf_write_stmp(b3, path3, &temp_files);
314 	if (err)
315 		goto out;
316 
317 	buf_free(b2);
318 	b2 = NULL;
319 
320 	err = diffreg(&d1, path1, path3);
321 	if (err) {
322 		buf_free(diffb);
323 		diffb = NULL;
324 		goto out;
325 
326 	}
327 	err = diffreg(&d2, path2, path3);
328 	if (err) {
329 		buf_free(diffb);
330 		diffb = NULL;
331 		goto out;
332 	}
333 
334 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
335 		err = got_error_from_errno();
336 		goto out;
337 	}
338 	err = buf_write_stmp(d1, dp13, &temp_files);
339 	if (err)
340 		goto out;
341 
342 	buf_free(d1);
343 	d1 = NULL;
344 
345 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
346 		err = got_error_from_errno();
347 		goto out;
348 	}
349 	err = buf_write_stmp(d2, dp23, &temp_files);
350 	if (err)
351 		goto out;
352 
353 	buf_free(d2);
354 	d2 = NULL;
355 
356 	diffbuf = diffb;
357 	err = diff3_internal(dp13, dp23, path1, path2, path3, p1, p3,
358 	    d3s);
359 	if (err) {
360 		buf_free(diffb);
361 		diffb = NULL;
362 		goto out;
363 	}
364 
365 	plen = buf_len(diffb);
366 	patch = buf_release(diffb);
367 	dlen = buf_len(b1);
368 	data = buf_release(b1);
369 
370 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
371 out:
372 	buf_free(b2);
373 	buf_free(b3);
374 	buf_free(d1);
375 	buf_free(d2);
376 
377 	(void)unlink(path1);
378 	(void)unlink(path2);
379 	(void)unlink(path3);
380 	(void)unlink(dp13);
381 	(void)unlink(dp23);
382 
383 	free(path1);
384 	free(path2);
385 	free(path3);
386 	free(dp13);
387 	free(dp23);
388 	free(data);
389 	free(patch);
390 
391 	worklist_clean(&temp_files, worklist_unlink);
392 
393 	for (i = 0; i < nitems(d3s->fp); i++) {
394 		if (d3s->fp[i])
395 			fclose(d3s->fp[i]);
396 	}
397 	free(d3s);
398 	if (err == NULL && diffb) {
399 		if (buf_write_fd(diffb, outfd) < 0)
400 			err = got_error_from_errno();
401 	}
402 	buf_free(diffb);
403 	return err;
404 }
405 
406 static const struct got_error *
407 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
408     const char *fmark, const char *rmark, struct diff3_state *d3s)
409 {
410 	const struct got_error *err = NULL;
411 	ssize_t m, n;
412 	int i;
413 
414 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark), "<<<<<<< %s", fmark);
415 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
416 		return got_error(GOT_ERR_NO_SPACE);
417 
418 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark), ">>>>>>> %s", rmark);
419 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
420 		return got_error(GOT_ERR_NO_SPACE);
421 
422 	err = increase(d3s);
423 	if (err)
424 		return err;
425 
426 	err = readin(&m, dp13, &d3s->d13, d3s);
427 	if (err)
428 		return err;
429 	err = readin(&n, dp23, &d3s->d23, d3s);
430 	if (err)
431 		return err;
432 
433 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
434 		return got_error_from_errno();
435 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
436 		return got_error_from_errno();
437 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
438 		return got_error_from_errno();
439 
440 	if (merge(m, n, d3s) < 0)
441 		return got_error_from_errno();
442 	return NULL;
443 }
444 
445 static int
446 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
447 {
448 	char op, *ep;
449 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
450 	int start, end, i, lineno;
451 	u_char tmp;
452 
453 	dlp = TAILQ_FIRST(&(dlines->l_lines));
454 	lp = TAILQ_FIRST(&(plines->l_lines));
455 
456 	end = 0;
457 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
458 	    lp = TAILQ_NEXT(lp, l_list)) {
459 		/* Skip blank lines */
460 		if (lp->l_len < 2)
461 			continue;
462 
463 		/* NUL-terminate line buffer for strtol() safety. */
464 		tmp = lp->l_line[lp->l_len - 1];
465 		lp->l_line[lp->l_len - 1] = '\0';
466 
467 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
468 		op = lp->l_line[lp->l_len - 2];
469 		start = (int)strtol(lp->l_line, &ep, 10);
470 
471 		/* Restore the last byte of the buffer */
472 		lp->l_line[lp->l_len - 1] = tmp;
473 
474 		if (op == 'a') {
475 			if (start > dlines->l_nblines ||
476 			    start < 0 || *ep != 'a')
477 				return -1;
478 		} else if (op == 'c') {
479 			if (start > dlines->l_nblines ||
480 			    start < 0 || (*ep != ',' && *ep != 'c'))
481 				return -1;
482 
483 			if (*ep == ',') {
484 				ep++;
485 				end = (int)strtol(ep, &ep, 10);
486 				if (end < 0 || *ep != 'c')
487 					return -1;
488 			} else {
489 				end = start;
490 			}
491 		}
492 
493 
494 		for (;;) {
495 			if (dlp == NULL)
496 				break;
497 			if (dlp->l_lineno == start)
498 				break;
499 			if (dlp->l_lineno > start) {
500 				dlp = TAILQ_PREV(dlp, tqh, l_list);
501 			} else if (dlp->l_lineno < start) {
502 				ndlp = TAILQ_NEXT(dlp, l_list);
503 				if (ndlp->l_lineno > start)
504 					break;
505 				dlp = ndlp;
506 			}
507 		}
508 
509 		if (dlp == NULL)
510 			return -1;
511 
512 
513 		if (op == 'c') {
514 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
515 			for (i = 0; i <= (end - start); i++) {
516 				ndlp = TAILQ_NEXT(dlp, l_list);
517 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
518 				dlp = ndlp;
519 			}
520 			dlp = insert_after;
521 		}
522 
523 		if (op == 'a' || op == 'c') {
524 			for (;;) {
525 				ndlp = lp;
526 				lp = TAILQ_NEXT(lp, l_list);
527 				if (lp == NULL)
528 					return -1;
529 
530 				if (!memcmp(lp->l_line, ".", 1))
531 					break;
532 
533 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
534 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
535 				    lp, l_list);
536 				dlp = lp;
537 
538 				lp->l_lineno = start;
539 				lp = ndlp;
540 			}
541 		}
542 
543 		/*
544 		 * always resort lines as the markers might be put at the
545 		 * same line as we first started editing.
546 		 */
547 		lineno = 0;
548 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
549 			sort->l_lineno = lineno++;
550 		dlines->l_nblines = lineno - 1;
551 	}
552 
553 	return (0);
554 }
555 
556 /*
557  * Pick up the line numbers of all changes from one change file.
558  * (This puts the numbers in a vector, which is not strictly necessary,
559  * since the vector is processed in one sequential pass.
560  * The vector could be optimized out of existence)
561  */
562 static const struct got_error *
563 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
564 {
565 	const struct got_error *err = NULL;
566 	int a, b, c, d;
567 	char kind, *p;
568 	size_t i;
569 
570 	d3s->fp[0] = fopen(name, "r");
571 	if (d3s->fp[0] == NULL)
572 		return got_error_from_errno();
573 	for (i = 0; (p = getchange(d3s->fp[0], d3s)); i++) {
574 		if (i >= d3s->szchanges - 1) {
575 			err = increase(d3s);
576 			if (err)
577 				return err;
578 		}
579 		a = b = number(&p);
580 		if (*p == ',') {
581 			p++;
582 			b = number(&p);
583 		}
584 		kind = *p++;
585 		c = d = number(&p);
586 		if (*p==',') {
587 			p++;
588 			d = number(&p);
589 		}
590 		if (kind == 'a')
591 			a++;
592 		if (kind == 'd')
593 			c++;
594 		b++;
595 		d++;
596 		(*dd)[i].old.from = a;
597 		(*dd)[i].old.to = b;
598 		(*dd)[i].new.from = c;
599 		(*dd)[i].new.to = d;
600 	}
601 
602 	if (i) {
603 		(*dd)[i].old.from = (*dd)[i-1].old.to;
604 		(*dd)[i].new.from = (*dd)[i-1].new.to;
605 	}
606 
607 	(void)fclose(d3s->fp[0]);
608 
609 	return NULL;
610 }
611 
612 static int
613 number(char **lc)
614 {
615 	int nn;
616 
617 	nn = 0;
618 	while (isdigit((unsigned char)(**lc)))
619 		nn = nn*10 + *(*lc)++ - '0';
620 
621 	return (nn);
622 }
623 
624 static char *
625 getchange(FILE *b, struct diff3_state *d3s)
626 {
627 	char *line;
628 
629 	while ((line = get_line(b, NULL, d3s))) {
630 		if (isdigit((unsigned char)line[0]))
631 			return (line);
632 	}
633 
634 	return (NULL);
635 }
636 
637 static char *
638 get_line(FILE *b, size_t *n, struct diff3_state *d3s)
639 {
640 	char *cp;
641 	size_t len;
642 	char *new;
643 
644 	if ((cp = fgetln(b, &len)) == NULL)
645 		return (NULL);
646 
647 	if (cp[len - 1] != '\n')
648 		len++;
649 	if (len + 1 > d3s->bufsize) {
650 		do {
651 			d3s->bufsize += 1024;
652 		} while (len + 1 > d3s->bufsize);
653 		new = reallocarray(d3s->buf, 1, d3s->bufsize);
654 		if (new == NULL)
655 			return NULL;
656 		d3s->buf = new;
657 	}
658 	memcpy(d3s->buf, cp, len - 1);
659 	d3s->buf[len - 1] = '\n';
660 	d3s->buf[len] = '\0';
661 	if (n != NULL)
662 		*n = len;
663 
664 	return (d3s->buf);
665 }
666 
667 static int
668 merge(size_t m1, size_t m2, struct diff3_state *d3s)
669 {
670 	struct diff *d1, *d2, *d3;
671 	int dpl, j, t1, t2;
672 
673 	d1 = d3s->d13;
674 	d2 = d3s->d23;
675 	j = 0;
676 	for (;;) {
677 		t1 = (d1 < d3s->d13 + m1);
678 		t2 = (d2 < d3s->d23 + m2);
679 		if (!t1 && !t2)
680 			break;
681 
682 		if (d3s->debug) {
683 			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
684 			d1->old.from, d1->old.to,
685 			d1->new.from, d1->new.to,
686 			d2->old.from, d2->old.to,
687 			d2->new.from, d2->new.to);
688 		}
689 
690 		/* first file is different from others */
691 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
692 			/* stuff peculiar to 1st file */
693 			if (d3s->eflag == 0) {
694 				separate("1");
695 				change(1, &d1->old, 0, d3s);
696 				keep(2, &d1->new, d3s);
697 				change(3, &d1->new, 0, d3s);
698 			}
699 			d1++;
700 			continue;
701 		}
702 
703 		/* second file is different from others */
704 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
705 			if (d3s->eflag == 0) {
706 				separate("2");
707 				keep(1, &d2->new, d3s);
708 				change(2, &d2->old, 0, d3s);
709 				change(3, &d2->new, 0, d3s);
710 			}
711 			d2++;
712 			continue;
713 		}
714 
715 		/*
716 		 * Merge overlapping changes in first file
717 		 * this happens after extension (see below).
718 		 */
719 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
720 			d1[1].old.from = d1->old.from;
721 			d1[1].new.from = d1->new.from;
722 			d1++;
723 			continue;
724 		}
725 
726 		/* merge overlapping changes in second */
727 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
728 			d2[1].old.from = d2->old.from;
729 			d2[1].new.from = d2->new.from;
730 			d2++;
731 			continue;
732 		}
733 		/* stuff peculiar to third file or different in all */
734 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
735 			dpl = duplicate(&d1->old, &d2->old, d3s);
736 			if (dpl == -1)
737 				return (-1);
738 
739 			/*
740 			 * dpl = 0 means all files differ
741 			 * dpl = 1 means files 1 and 2 identical
742 			 */
743 			if (d3s->eflag == 0) {
744 				separate(dpl ? "3" : "");
745 				change(1, &d1->old, dpl, d3s);
746 				change(2, &d2->old, 0, d3s);
747 				d3 = d1->old.to > d1->old.from ? d1 : d2;
748 				change(3, &d3->new, 0, d3s);
749 			} else
750 				j = edit(d1, dpl, j, d3s);
751 			d1++;
752 			d2++;
753 			continue;
754 		}
755 
756 		/*
757 		 * Overlapping changes from file 1 and 2; extend changes
758 		 * appropriately to make them coincide.
759 		 */
760 		if (d1->new.from < d2->new.from) {
761 			d2->old.from -= d2->new.from-d1->new.from;
762 			d2->new.from = d1->new.from;
763 		} else if (d2->new.from < d1->new.from) {
764 			d1->old.from -= d1->new.from-d2->new.from;
765 			d1->new.from = d2->new.from;
766 		}
767 		if (d1->new.to > d2->new.to) {
768 			d2->old.to += d1->new.to - d2->new.to;
769 			d2->new.to = d1->new.to;
770 		} else if (d2->new.to > d1->new.to) {
771 			d1->old.to += d2->new.to - d1->new.to;
772 			d1->new.to = d2->new.to;
773 		}
774 	}
775 
776 	return (edscript(j, d3s));
777 }
778 
779 static void
780 separate(const char *s)
781 {
782 	diff_output("====%s\n", s);
783 }
784 
785 /*
786  * The range of lines rold.from thru rold.to in file i is to be changed.
787  * It is to be printed only if it does not duplicate something to be
788  * printed later.
789  */
790 static void
791 change(int i, struct range *rold, int fdup, struct diff3_state *d3s)
792 {
793 	diff_output("%d:", i);
794 	d3s->last[i] = rold->to;
795 	prange(rold);
796 	if (fdup || d3s->debug)
797 		return;
798 	i--;
799 	(void)skip(i, rold->from, NULL, d3s);
800 	(void)skip(i, rold->to, "  ", d3s);
801 }
802 
803 /*
804  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
805  */
806 static void
807 prange(struct range *rold)
808 {
809 	if (rold->to <= rold->from)
810 		diff_output("%da\n", rold->from - 1);
811 	else {
812 		diff_output("%d", rold->from);
813 		if (rold->to > rold->from+1)
814 			diff_output(",%d", rold->to - 1);
815 		diff_output("c\n");
816 	}
817 }
818 
819 /*
820  * No difference was reported by diff between file 1 (or 2) and file 3,
821  * and an artificial dummy difference (trange) must be ginned up to
822  * correspond to the change reported in the other file.
823  */
824 static void
825 keep(int i, struct range *rnew, struct diff3_state *d3s)
826 {
827 	int delta;
828 	struct range trange;
829 
830 	delta = d3s->last[3] - d3s->last[i];
831 	trange.from = rnew->from - delta;
832 	trange.to = rnew->to - delta;
833 	change(i, &trange, 1, d3s);
834 }
835 
836 /*
837  * skip to just before line number from in file "i".  If "pr" is non-NULL,
838  * print all skipped stuff with string pr as a prefix.
839  */
840 static int
841 skip(int i, int from, char *pr, struct diff3_state *d3s)
842 {
843 	size_t j, n;
844 	char *line;
845 
846 	for (n = 0; d3s->cline[i] < from - 1; n += j) {
847 		if ((line = get_line(d3s->fp[i], &j, d3s)) == NULL)
848 			return (-1);
849 		if (pr != NULL)
850 			diff_output("%s%s", pr, line);
851 		d3s->cline[i]++;
852 	}
853 	return ((int) n);
854 }
855 
856 /*
857  * Return 1 or 0 according as the old range (in file 1) contains exactly
858  * the same data as the new range (in file 2).
859  */
860 static int
861 duplicate(struct range *r1, struct range *r2, struct diff3_state *d3s)
862 {
863 	int c,d;
864 	int nchar;
865 	int nline;
866 
867 	if (r1->to-r1->from != r2->to-r2->from)
868 		return (0);
869 	(void)skip(0, r1->from, NULL, d3s);
870 	(void)skip(1, r2->from, NULL, d3s);
871 	nchar = 0;
872 	for (nline=0; nline < r1->to - r1->from; nline++) {
873 		do {
874 			c = getc(d3s->fp[0]);
875 			d = getc(d3s->fp[1]);
876 			if (c == -1 || d== -1)
877 				return (-1);
878 			nchar++;
879 			if (c != d) {
880 				repos(nchar, d3s);
881 				return (0);
882 			}
883 		} while (c != '\n');
884 	}
885 	repos(nchar, d3s);
886 	return (1);
887 }
888 
889 static void
890 repos(int nchar, struct diff3_state *d3s)
891 {
892 	int i;
893 
894 	for (i = 0; i < 2; i++)
895 		(void)fseek(d3s->fp[i], (long)-nchar, SEEK_CUR);
896 }
897 
898 /*
899  * collect an editing script for later regurgitation
900  */
901 static int
902 edit(struct diff *diff, int fdup, int j, struct diff3_state *d3s)
903 {
904 	if (((fdup + 1) & d3s->eflag) == 0)
905 		return (j);
906 	j++;
907 	d3s->overlap[j] = !fdup;
908 	if (!fdup)
909 		d3s->overlapcnt++;
910 	d3s->de[j].old.from = diff->old.from;
911 	d3s->de[j].old.to = diff->old.to;
912 	d3s->de[j].new.from =
913 	    d3s->de[j-1].new.to + skip(2, diff->new.from, NULL, d3s);
914 	d3s->de[j].new.to =
915 	    d3s->de[j].new.from + skip(2, diff->new.to, NULL, d3s);
916 	return (j);
917 }
918 
919 /* regurgitate */
920 static int
921 edscript(int n, struct diff3_state *d3s)
922 {
923 	int j, k;
924 	char block[BUFSIZ+1];
925 
926 	for (; n > 0; n--) {
927 		if (!d3s->oflag || !d3s->overlap[n])
928 			prange(&d3s->de[n].old);
929 		else
930 			diff_output("%da\n=======\n", d3s->de[n].old.to -1);
931 		(void)fseek(d3s->fp[2], (long)d3s->de[n].new.from, SEEK_SET);
932 		k = d3s->de[n].new.to - d3s->de[n].new.from;
933 		for (; k > 0; k-= j) {
934 			j = k > BUFSIZ ? BUFSIZ : k;
935 			if (fread(block, 1, j, d3s->fp[2]) != (size_t)j)
936 				return (-1);
937 			block[j] = '\0';
938 			diff_output("%s", block);
939 		}
940 
941 		if (!d3s->oflag || !d3s->overlap[n])
942 			diff_output(".\n");
943 		else {
944 			diff_output("%s\n.\n", d3s->f3mark);
945 			diff_output("%da\n%s\n.\n", d3s->de[n].old.from - 1,
946 			    d3s->f1mark);
947 		}
948 	}
949 
950 	return (d3s->overlapcnt);
951 }
952 
953 static const struct got_error *
954 increase(struct diff3_state *d3s)
955 {
956 	size_t newsz, incr;
957 	struct diff *d;
958 	char *s;
959 
960 	/* are the memset(3) calls needed? */
961 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
962 	incr = newsz - d3s->szchanges;
963 
964 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
965 	if (d == NULL)
966 		return got_error_from_errno();
967 	d3s->d13 = d;
968 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
969 
970 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
971 	if (d == NULL)
972 		return got_error_from_errno();
973 	d3s->d23 = d;
974 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
975 
976 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
977 	if (d == NULL)
978 		return got_error_from_errno();
979 	d3s->de = d;
980 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
981 
982 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
983 	if (s == NULL)
984 		return got_error_from_errno();
985 	d3s->overlap = s;
986 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
987 	d3s->szchanges = newsz;
988 
989 	return NULL;
990 }