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 	BUF *diffbuf;
152 };
153 
154 
155 static int duplicate(struct range *, struct range *, struct diff3_state *);
156 static int edit(struct diff *, int, int, struct diff3_state *);
157 static char *getchange(FILE *, struct diff3_state *);
158 static char *get_line(FILE *, size_t *, struct diff3_state *);
159 static int number(char **);
160 static const struct got_error *readin(size_t *, char *, struct diff **,
161     struct diff3_state *);
162 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
163 static int skip(int, int, char *, struct diff3_state *);
164 static int edscript(int, struct diff3_state *);
165 static int merge(size_t, size_t, struct diff3_state *);
166 static void change(int, struct range *, int, struct diff3_state *);
167 static void keep(int, struct range *, struct diff3_state *);
168 static void prange(struct range *, struct diff3_state *);
169 static void repos(int, struct diff3_state *);
170 static void separate(const char *, struct diff3_state *);
171 static const struct got_error *increase(struct diff3_state *);
172 static const struct got_error *diff3_internal(char *, char *, char *,
173     char *, char *, const char *, const char *, struct diff3_state *);
174 
175 static const struct got_error *
176 diff_output(BUF *diffbuf, const char *fmt, ...)
177 {
178 	va_list vap;
179 	int i;
180 	char *str;
181 	size_t newsize;
182 
183 	va_start(vap, fmt);
184 	i = vasprintf(&str, fmt, vap);
185 	va_end(vap);
186 	if (i == -1)
187 		return got_error_from_errno();
188 	buf_append(&newsize, diffbuf, str, strlen(str));
189 	free(str);
190 	return NULL;
191 }
192 
193 static const struct got_error*
194 diffreg(BUF **d, const char *path1, const char *path2)
195 {
196 	const struct got_error *err = NULL;
197 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
198 	char *outpath = NULL;
199 	struct got_diff_state ds;
200 	struct got_diff_args args;
201 	int res;
202 
203 	*d = NULL;
204 
205 	f1 = fopen(path1, "r");
206 	if (f1 == NULL) {
207 		err = got_error_from_errno();
208 		goto done;
209 	}
210 	f2 = fopen(path2, "r");
211 	if (f1 == NULL) {
212 		err = got_error_from_errno();
213 		goto done;
214 	}
215 
216 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diff");
217 	if (err)
218 		goto done;
219 
220 	memset(&ds, 0, sizeof(ds));
221 	/* XXX should stat buffers be passed in args instead of ds? */
222 	if (stat(path1, &ds.stb1) == -1) {
223 		err = got_error_from_errno();
224 		goto done;
225 	}
226 	if (stat(path2, &ds.stb2) == -1) {
227 		err = got_error_from_errno();
228 		goto done;
229 	}
230 
231 	memset(&args, 0, sizeof(args));
232 	args.diff_format = D_NORMAL;
233 	args.label[0] = "";
234 	args.label[1] = "";
235 	args.diff_context = 0;
236 
237 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
238 	    outfile, NULL);
239 	if (err)
240 		goto done;
241 
242 	*d = buf_load(outpath);
243 	if (*d == NULL)
244 		err = got_error_from_errno();
245 done:
246 	free(outpath);
247 	if (outfile)
248 		fclose(outfile);
249 	if (f1)
250 		fclose(f1);
251 	if (f2)
252 		fclose(f2);
253 	return err;
254 }
255 
256 /*
257  * For merge(1).
258  */
259 const struct got_error *
260 got_merge_diff3(int outfd, const char *p1, const char *p2, const char *p3)
261 {
262 	const struct got_error *err = NULL;
263 	char *dp13, *dp23, *path1, *path2, *path3;
264 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
265 	u_char *data, *patch;
266 	size_t dlen, plen;
267 	struct wklhead temp_files;
268 	struct diff3_state *d3s;
269 	int i;
270 
271 	d3s = calloc(1, sizeof(*d3s));
272 	if (d3s == NULL)
273 		return got_error_from_errno();
274 	d3s->eflag = 3; /* default -E for compatibility with former RCS */
275 	d3s->oflag = 1; /* default -E for compatibility with former RCS */
276 
277 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
278 	dp13 = dp23 = path1 = path2 = path3 = NULL;
279 	data = patch = NULL;
280 
281 	if ((b1 = buf_load(p1)) == NULL)
282 		goto out;
283 	if ((b2 = buf_load(p2)) == NULL)
284 		goto out;
285 	if ((b3 = buf_load(p3)) == NULL)
286 		goto out;
287 
288 	diffb = buf_alloc(128);
289 
290 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
291 		err = got_error_from_errno();
292 		goto out;
293 	}
294 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
295 		err = got_error_from_errno();
296 		goto out;
297 	}
298 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
299 		err = got_error_from_errno();
300 		goto out;
301 	}
302 
303 	err = buf_write_stmp(b1, path1, &temp_files);
304 	if (err)
305 		goto out;
306 	err = buf_write_stmp(b2, path2, &temp_files);
307 	if (err)
308 		goto out;
309 	err = buf_write_stmp(b3, path3, &temp_files);
310 	if (err)
311 		goto out;
312 
313 	buf_free(b2);
314 	b2 = NULL;
315 
316 	err = diffreg(&d1, path1, path3);
317 	if (err) {
318 		buf_free(diffb);
319 		diffb = NULL;
320 		goto out;
321 
322 	}
323 	err = diffreg(&d2, path2, path3);
324 	if (err) {
325 		buf_free(diffb);
326 		diffb = NULL;
327 		goto out;
328 	}
329 
330 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
331 		err = got_error_from_errno();
332 		goto out;
333 	}
334 	err = buf_write_stmp(d1, dp13, &temp_files);
335 	if (err)
336 		goto out;
337 
338 	buf_free(d1);
339 	d1 = NULL;
340 
341 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
342 		err = got_error_from_errno();
343 		goto out;
344 	}
345 	err = buf_write_stmp(d2, dp23, &temp_files);
346 	if (err)
347 		goto out;
348 
349 	buf_free(d2);
350 	d2 = NULL;
351 
352 	d3s->diffbuf = diffb;
353 	err = diff3_internal(dp13, dp23, path1, path2, path3, p1, p3,
354 	    d3s);
355 	if (err) {
356 		buf_free(diffb);
357 		diffb = NULL;
358 		goto out;
359 	}
360 
361 	plen = buf_len(diffb);
362 	patch = buf_release(diffb);
363 	dlen = buf_len(b1);
364 	data = buf_release(b1);
365 
366 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
367 out:
368 	buf_free(b2);
369 	buf_free(b3);
370 	buf_free(d1);
371 	buf_free(d2);
372 
373 	(void)unlink(path1);
374 	(void)unlink(path2);
375 	(void)unlink(path3);
376 	(void)unlink(dp13);
377 	(void)unlink(dp23);
378 
379 	free(path1);
380 	free(path2);
381 	free(path3);
382 	free(dp13);
383 	free(dp23);
384 	free(data);
385 	free(patch);
386 
387 	worklist_clean(&temp_files, worklist_unlink);
388 
389 	for (i = 0; i < nitems(d3s->fp); i++) {
390 		if (d3s->fp[i])
391 			fclose(d3s->fp[i]);
392 	}
393 	free(d3s);
394 	if (err == NULL && diffb) {
395 		if (buf_write_fd(diffb, outfd) < 0)
396 			err = got_error_from_errno();
397 	}
398 	buf_free(diffb);
399 	return err;
400 }
401 
402 static const struct got_error *
403 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
404     const char *fmark, const char *rmark, struct diff3_state *d3s)
405 {
406 	const struct got_error *err = NULL;
407 	ssize_t m, n;
408 	int i;
409 
410 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark), "<<<<<<< %s", fmark);
411 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
412 		return got_error(GOT_ERR_NO_SPACE);
413 
414 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark), ">>>>>>> %s", rmark);
415 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
416 		return got_error(GOT_ERR_NO_SPACE);
417 
418 	err = increase(d3s);
419 	if (err)
420 		return err;
421 
422 	err = readin(&m, dp13, &d3s->d13, d3s);
423 	if (err)
424 		return err;
425 	err = readin(&n, dp23, &d3s->d23, d3s);
426 	if (err)
427 		return err;
428 
429 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
430 		return got_error_from_errno();
431 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
432 		return got_error_from_errno();
433 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
434 		return got_error_from_errno();
435 
436 	if (merge(m, n, d3s) < 0)
437 		return got_error_from_errno();
438 	return NULL;
439 }
440 
441 static int
442 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
443 {
444 	char op, *ep;
445 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
446 	int start, end, i, lineno;
447 	u_char tmp;
448 
449 	dlp = TAILQ_FIRST(&(dlines->l_lines));
450 	lp = TAILQ_FIRST(&(plines->l_lines));
451 
452 	end = 0;
453 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
454 	    lp = TAILQ_NEXT(lp, l_list)) {
455 		/* Skip blank lines */
456 		if (lp->l_len < 2)
457 			continue;
458 
459 		/* NUL-terminate line buffer for strtol() safety. */
460 		tmp = lp->l_line[lp->l_len - 1];
461 		lp->l_line[lp->l_len - 1] = '\0';
462 
463 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
464 		op = lp->l_line[lp->l_len - 2];
465 		start = (int)strtol(lp->l_line, &ep, 10);
466 
467 		/* Restore the last byte of the buffer */
468 		lp->l_line[lp->l_len - 1] = tmp;
469 
470 		if (op == 'a') {
471 			if (start > dlines->l_nblines ||
472 			    start < 0 || *ep != 'a')
473 				return -1;
474 		} else if (op == 'c') {
475 			if (start > dlines->l_nblines ||
476 			    start < 0 || (*ep != ',' && *ep != 'c'))
477 				return -1;
478 
479 			if (*ep == ',') {
480 				ep++;
481 				end = (int)strtol(ep, &ep, 10);
482 				if (end < 0 || *ep != 'c')
483 					return -1;
484 			} else {
485 				end = start;
486 			}
487 		}
488 
489 
490 		for (;;) {
491 			if (dlp == NULL)
492 				break;
493 			if (dlp->l_lineno == start)
494 				break;
495 			if (dlp->l_lineno > start) {
496 				dlp = TAILQ_PREV(dlp, tqh, l_list);
497 			} else if (dlp->l_lineno < start) {
498 				ndlp = TAILQ_NEXT(dlp, l_list);
499 				if (ndlp->l_lineno > start)
500 					break;
501 				dlp = ndlp;
502 			}
503 		}
504 
505 		if (dlp == NULL)
506 			return -1;
507 
508 
509 		if (op == 'c') {
510 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
511 			for (i = 0; i <= (end - start); i++) {
512 				ndlp = TAILQ_NEXT(dlp, l_list);
513 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
514 				dlp = ndlp;
515 			}
516 			dlp = insert_after;
517 		}
518 
519 		if (op == 'a' || op == 'c') {
520 			for (;;) {
521 				ndlp = lp;
522 				lp = TAILQ_NEXT(lp, l_list);
523 				if (lp == NULL)
524 					return -1;
525 
526 				if (!memcmp(lp->l_line, ".", 1))
527 					break;
528 
529 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
530 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
531 				    lp, l_list);
532 				dlp = lp;
533 
534 				lp->l_lineno = start;
535 				lp = ndlp;
536 			}
537 		}
538 
539 		/*
540 		 * always resort lines as the markers might be put at the
541 		 * same line as we first started editing.
542 		 */
543 		lineno = 0;
544 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
545 			sort->l_lineno = lineno++;
546 		dlines->l_nblines = lineno - 1;
547 	}
548 
549 	return (0);
550 }
551 
552 /*
553  * Pick up the line numbers of all changes from one change file.
554  * (This puts the numbers in a vector, which is not strictly necessary,
555  * since the vector is processed in one sequential pass.
556  * The vector could be optimized out of existence)
557  */
558 static const struct got_error *
559 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
560 {
561 	const struct got_error *err = NULL;
562 	int a, b, c, d;
563 	char kind, *p;
564 	size_t i;
565 
566 	*n = 0;
567 
568 	d3s->fp[0] = fopen(name, "r");
569 	if (d3s->fp[0] == NULL)
570 		return got_error_from_errno();
571 	for (i = 0; (p = getchange(d3s->fp[0], d3s)); i++) {
572 		if (i >= d3s->szchanges - 1) {
573 			err = increase(d3s);
574 			if (err)
575 				return err;
576 		}
577 		a = b = number(&p);
578 		if (*p == ',') {
579 			p++;
580 			b = number(&p);
581 		}
582 		kind = *p++;
583 		c = d = number(&p);
584 		if (*p==',') {
585 			p++;
586 			d = number(&p);
587 		}
588 		if (kind == 'a')
589 			a++;
590 		if (kind == 'd')
591 			c++;
592 		b++;
593 		d++;
594 		(*dd)[i].old.from = a;
595 		(*dd)[i].old.to = b;
596 		(*dd)[i].new.from = c;
597 		(*dd)[i].new.to = d;
598 	}
599 
600 	if (i) {
601 		(*dd)[i].old.from = (*dd)[i-1].old.to;
602 		(*dd)[i].new.from = (*dd)[i-1].new.to;
603 	}
604 
605 	(void)fclose(d3s->fp[0]);
606 
607 	*n = i;
608 	return NULL;
609 }
610 
611 static int
612 number(char **lc)
613 {
614 	int nn;
615 
616 	nn = 0;
617 	while (isdigit((unsigned char)(**lc)))
618 		nn = nn*10 + *(*lc)++ - '0';
619 
620 	return (nn);
621 }
622 
623 static char *
624 getchange(FILE *b, struct diff3_state *d3s)
625 {
626 	char *line;
627 
628 	while ((line = get_line(b, NULL, d3s))) {
629 		if (isdigit((unsigned char)line[0]))
630 			return (line);
631 	}
632 
633 	return (NULL);
634 }
635 
636 static char *
637 get_line(FILE *b, size_t *n, struct diff3_state *d3s)
638 {
639 	char *cp;
640 	size_t len;
641 	char *new;
642 
643 	if ((cp = fgetln(b, &len)) == NULL)
644 		return (NULL);
645 
646 	if (cp[len - 1] != '\n')
647 		len++;
648 	if (len + 1 > d3s->bufsize) {
649 		do {
650 			d3s->bufsize += 1024;
651 		} while (len + 1 > d3s->bufsize);
652 		new = reallocarray(d3s->buf, 1, d3s->bufsize);
653 		if (new == NULL)
654 			return NULL;
655 		d3s->buf = new;
656 	}
657 	memcpy(d3s->buf, cp, len - 1);
658 	d3s->buf[len - 1] = '\n';
659 	d3s->buf[len] = '\0';
660 	if (n != NULL)
661 		*n = len;
662 
663 	return (d3s->buf);
664 }
665 
666 static int
667 merge(size_t m1, size_t m2, struct diff3_state *d3s)
668 {
669 	struct diff *d1, *d2, *d3;
670 	int dpl, j, t1, t2;
671 
672 	d1 = d3s->d13;
673 	d2 = d3s->d23;
674 	j = 0;
675 	for (;;) {
676 		t1 = (d1 < d3s->d13 + m1);
677 		t2 = (d2 < d3s->d23 + m2);
678 		if (!t1 && !t2)
679 			break;
680 
681 		if (d3s->debug) {
682 			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
683 			d1->old.from, d1->old.to,
684 			d1->new.from, d1->new.to,
685 			d2->old.from, d2->old.to,
686 			d2->new.from, d2->new.to);
687 		}
688 
689 		/* first file is different from others */
690 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
691 			/* stuff peculiar to 1st file */
692 			if (d3s->eflag == 0) {
693 				separate("1", d3s);
694 				change(1, &d1->old, 0, d3s);
695 				keep(2, &d1->new, d3s);
696 				change(3, &d1->new, 0, d3s);
697 			}
698 			d1++;
699 			continue;
700 		}
701 
702 		/* second file is different from others */
703 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
704 			if (d3s->eflag == 0) {
705 				separate("2", d3s);
706 				keep(1, &d2->new, d3s);
707 				change(2, &d2->old, 0, d3s);
708 				change(3, &d2->new, 0, d3s);
709 			}
710 			d2++;
711 			continue;
712 		}
713 
714 		/*
715 		 * Merge overlapping changes in first file
716 		 * this happens after extension (see below).
717 		 */
718 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
719 			d1[1].old.from = d1->old.from;
720 			d1[1].new.from = d1->new.from;
721 			d1++;
722 			continue;
723 		}
724 
725 		/* merge overlapping changes in second */
726 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
727 			d2[1].old.from = d2->old.from;
728 			d2[1].new.from = d2->new.from;
729 			d2++;
730 			continue;
731 		}
732 		/* stuff peculiar to third file or different in all */
733 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
734 			dpl = duplicate(&d1->old, &d2->old, d3s);
735 			if (dpl == -1)
736 				return (-1);
737 
738 			/*
739 			 * dpl = 0 means all files differ
740 			 * dpl = 1 means files 1 and 2 identical
741 			 */
742 			if (d3s->eflag == 0) {
743 				separate(dpl ? "3" : "", d3s);
744 				change(1, &d1->old, dpl, d3s);
745 				change(2, &d2->old, 0, d3s);
746 				d3 = d1->old.to > d1->old.from ? d1 : d2;
747 				change(3, &d3->new, 0, d3s);
748 			} else
749 				j = edit(d1, dpl, j, d3s);
750 			d1++;
751 			d2++;
752 			continue;
753 		}
754 
755 		/*
756 		 * Overlapping changes from file 1 and 2; extend changes
757 		 * appropriately to make them coincide.
758 		 */
759 		if (d1->new.from < d2->new.from) {
760 			d2->old.from -= d2->new.from-d1->new.from;
761 			d2->new.from = d1->new.from;
762 		} else if (d2->new.from < d1->new.from) {
763 			d1->old.from -= d1->new.from-d2->new.from;
764 			d1->new.from = d2->new.from;
765 		}
766 		if (d1->new.to > d2->new.to) {
767 			d2->old.to += d1->new.to - d2->new.to;
768 			d2->new.to = d1->new.to;
769 		} else if (d2->new.to > d1->new.to) {
770 			d1->old.to += d2->new.to - d1->new.to;
771 			d1->new.to = d2->new.to;
772 		}
773 	}
774 
775 	return (edscript(j, d3s));
776 }
777 
778 static void
779 separate(const char *s, struct diff3_state *d3s)
780 {
781 	diff_output(d3s->diffbuf, "====%s\n", s);
782 }
783 
784 /*
785  * The range of lines rold.from thru rold.to in file i is to be changed.
786  * It is to be printed only if it does not duplicate something to be
787  * printed later.
788  */
789 static void
790 change(int i, struct range *rold, int fdup, struct diff3_state *d3s)
791 {
792 	diff_output(d3s->diffbuf, "%d:", i);
793 	d3s->last[i] = rold->to;
794 	prange(rold, d3s);
795 	if (fdup || d3s->debug)
796 		return;
797 	i--;
798 	(void)skip(i, rold->from, NULL, d3s);
799 	(void)skip(i, rold->to, "  ", d3s);
800 }
801 
802 /*
803  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
804  */
805 static void
806 prange(struct range *rold, struct diff3_state *d3s)
807 {
808 	if (rold->to <= rold->from)
809 		diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
810 	else {
811 		diff_output(d3s->diffbuf, "%d", rold->from);
812 		if (rold->to > rold->from+1)
813 			diff_output(d3s->diffbuf, ",%d", rold->to - 1);
814 		diff_output(d3s->diffbuf, "c\n");
815 	}
816 }
817 
818 /*
819  * No difference was reported by diff between file 1 (or 2) and file 3,
820  * and an artificial dummy difference (trange) must be ginned up to
821  * correspond to the change reported in the other file.
822  */
823 static void
824 keep(int i, struct range *rnew, struct diff3_state *d3s)
825 {
826 	int delta;
827 	struct range trange;
828 
829 	delta = d3s->last[3] - d3s->last[i];
830 	trange.from = rnew->from - delta;
831 	trange.to = rnew->to - delta;
832 	change(i, &trange, 1, d3s);
833 }
834 
835 /*
836  * skip to just before line number from in file "i".  If "pr" is non-NULL,
837  * print all skipped stuff with string pr as a prefix.
838  */
839 static int
840 skip(int i, int from, char *pr, struct diff3_state *d3s)
841 {
842 	size_t j, n;
843 	char *line;
844 
845 	for (n = 0; d3s->cline[i] < from - 1; n += j) {
846 		if ((line = get_line(d3s->fp[i], &j, d3s)) == NULL)
847 			return (-1);
848 		if (pr != NULL)
849 			diff_output(d3s->diffbuf, "%s%s", pr, line);
850 		d3s->cline[i]++;
851 	}
852 	return ((int) n);
853 }
854 
855 /*
856  * Return 1 or 0 according as the old range (in file 1) contains exactly
857  * the same data as the new range (in file 2).
858  */
859 static int
860 duplicate(struct range *r1, struct range *r2, struct diff3_state *d3s)
861 {
862 	int c,d;
863 	int nchar;
864 	int nline;
865 
866 	if (r1->to-r1->from != r2->to-r2->from)
867 		return (0);
868 	(void)skip(0, r1->from, NULL, d3s);
869 	(void)skip(1, r2->from, NULL, d3s);
870 	nchar = 0;
871 	for (nline=0; nline < r1->to - r1->from; nline++) {
872 		do {
873 			c = getc(d3s->fp[0]);
874 			d = getc(d3s->fp[1]);
875 			if (c == -1 || d== -1)
876 				return (-1);
877 			nchar++;
878 			if (c != d) {
879 				repos(nchar, d3s);
880 				return (0);
881 			}
882 		} while (c != '\n');
883 	}
884 	repos(nchar, d3s);
885 	return (1);
886 }
887 
888 static void
889 repos(int nchar, struct diff3_state *d3s)
890 {
891 	int i;
892 
893 	for (i = 0; i < 2; i++)
894 		(void)fseek(d3s->fp[i], (long)-nchar, SEEK_CUR);
895 }
896 
897 /*
898  * collect an editing script for later regurgitation
899  */
900 static int
901 edit(struct diff *diff, int fdup, int j, struct diff3_state *d3s)
902 {
903 	if (((fdup + 1) & d3s->eflag) == 0)
904 		return (j);
905 	j++;
906 	d3s->overlap[j] = !fdup;
907 	if (!fdup)
908 		d3s->overlapcnt++;
909 	d3s->de[j].old.from = diff->old.from;
910 	d3s->de[j].old.to = diff->old.to;
911 	d3s->de[j].new.from =
912 	    d3s->de[j-1].new.to + skip(2, diff->new.from, NULL, d3s);
913 	d3s->de[j].new.to =
914 	    d3s->de[j].new.from + skip(2, diff->new.to, NULL, d3s);
915 	return (j);
916 }
917 
918 /* regurgitate */
919 static int
920 edscript(int n, struct diff3_state *d3s)
921 {
922 	int j, k;
923 	char block[BUFSIZ+1];
924 
925 	for (; n > 0; n--) {
926 		if (!d3s->oflag || !d3s->overlap[n])
927 			prange(&d3s->de[n].old, d3s);
928 		else
929 			diff_output(d3s->diffbuf, "%da\n=======\n",
930 			    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(d3s->diffbuf, "%s", block);
939 		}
940 
941 		if (!d3s->oflag || !d3s->overlap[n])
942 			diff_output(d3s->diffbuf, ".\n");
943 		else {
944 			diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
945 			diff_output(d3s->diffbuf, "%da\n%s\n.\n",
946 			    d3s->de[n].old.from - 1, 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 }