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Date:: Thu Jun 17 09:01:05 2021 UTC
Message:: use Patience diff for merging during cherrypick/backout/histedit/rebase This has been shown to prevent mis-merges in some cases. It's probably not a final solution. We should look at what Git's "recursive merge" is doing and implement something similar. Keep using Myers during update/unstage. The advantage of Myers is that it produces smaller conflict chunks, and there are no known cases of mis-merges which affect update/unstage.
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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 
87 #ifndef nitems
88 #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
89 #endif
90 
91 /* diff3 - 3-way differential file comparison */
92 
93 /* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
94  *
95  * d13 = diff report on f1 vs f3
96  * d23 = diff report on f2 vs f3
97  * f1, f2, f3 the 3 files
98  * if changes in f1 overlap with changes in f3, m1 and m3 are used
99  * to mark the overlaps; otherwise, the file names f1 and f3 are used
100  * (only for options E and X).
101  */
102 
103 /*
104  * "from" is first in range of changed lines; "to" is last+1
105  * from=to=line after point of insertion for added lines.
106  */
107 struct line_range {
108 	int from;
109 	int to;
110 };
111 
112 struct off_range {
113 	off_t from;
114 	off_t to;
115 };
116 
117 struct diff {
118 	struct line_range old;
119 	struct line_range new;
120 	struct off_range oldo;
121 	struct off_range newo;
122 };
123 
124 struct diff3_state {
125 	size_t szchanges;
126 
127 	struct diff *d13;
128 	struct diff *d23;
129 
130 	/*
131 	 * "de" is used to gather editing scripts.  These are later spewed out
132 	 * in reverse order.  Its first element must be all zero, the "new"
133 	 * component of "de" contains line positions, and "oldo" and "newo"
134 	 * components contain byte positions.
135 	 * Array overlap indicates which sections in "de" correspond to lines
136 	 * that are different in all three files.
137 	 */
138 	struct diff *de;
139 	char *overlap;
140 	int overlapcnt;
141 	FILE *fp[3];
142 	int cline[3];		/* # of the last-read line in each file (0-2) */
143 
144 	/*
145 	 * the latest known correspondence between line numbers of the 3 files
146 	 * is stored in last[1-3];
147 	 */
148 	int last[4];
149 	char f1mark[PATH_MAX];
150 	char f2mark[PATH_MAX];
151 	char f3mark[PATH_MAX];
152 
153 	char *buf;
154 
155 	BUF *diffbuf;
156 };
157 
158 
159 static const struct got_error *duplicate(int *, int, struct line_range *,
160     struct line_range *, struct diff3_state *);
161 static const struct got_error *edit(struct diff *, int, int *,
162     struct diff3_state *);
163 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
164 static const struct got_error *get_line(char **, FILE *, size_t *,
165     struct diff3_state *);
166 static int number(char **);
167 static const struct got_error *readin(size_t *, char *, struct diff **,
168     struct diff3_state *);
169 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
170 static const struct got_error *skip(size_t *, int, int, struct diff3_state *);
171 static const struct got_error *edscript(int, struct diff3_state *);
172 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
173 static const struct got_error *prange(struct line_range *, struct diff3_state *);
174 static const struct got_error *repos(int, struct diff3_state *);
175 static const struct got_error *increase(struct diff3_state *);
176 static const struct got_error *diff3_internal(char *, char *, char *,
177     char *, char *, const char *, const char *, struct diff3_state *,
178     const char *, const char *, const char *);
179 
180 static const struct got_error *
181 diff_output(BUF *diffbuf, const char *fmt, ...)
182 {
183 	const struct got_error *err = NULL;
184 	va_list vap;
185 	int i;
186 	char *str;
187 	size_t newsize;
188 
189 	va_start(vap, fmt);
190 	i = vasprintf(&str, fmt, vap);
191 	va_end(vap);
192 	if (i == -1)
193 		return got_error_from_errno("vasprintf");
194 	err = buf_append(&newsize, diffbuf, str, strlen(str));
195 	free(str);
196 	return err;
197 }
198 
199 static const struct got_error*
200 diffreg(BUF **d, const char *path1, const char *path2,
201     enum got_diff_algorithm diff_algo)
202 {
203 	const struct got_error *err = NULL;
204 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
205 	char *outpath = NULL;
206 	struct got_diffreg_result *diffreg_result = NULL;
207 
208 	*d = NULL;
209 
210 	f1 = fopen(path1, "r");
211 	if (f1 == NULL) {
212 		err = got_error_from_errno2("fopen", path1);
213 		goto done;
214 	}
215 	f2 = fopen(path2, "r");
216 	if (f1 == NULL) {
217 		err = got_error_from_errno2("fopen", path2);
218 		goto done;
219 	}
220 
221 	err = got_opentemp_named(&outpath, &outfile,
222 	    GOT_TMPDIR_STR "/got-diffreg");
223 	if (err)
224 		goto done;
225 
226 	err = got_diffreg(&diffreg_result, f1, f2, diff_algo, 0, 1);
227 	if (err)
228 		goto done;
229 
230 	err = got_diffreg_output(NULL, NULL, diffreg_result, 1, 1, "", "",
231 	    GOT_DIFF_OUTPUT_EDSCRIPT, 0, outfile);
232 	if (err)
233 		goto done;
234 
235 	if (fflush(outfile) != 0) {
236 		err = got_error_from_errno2("fflush", outpath);
237 		goto done;
238 	}
239 	if (fseek(outfile, 0L, SEEK_SET) == -1) {
240 		err = got_ferror(outfile, GOT_ERR_IO);
241 		goto done;
242 	}
243 
244 	err = buf_load(d, outfile);
245 done:
246 	if (outpath) {
247 		if (unlink(outpath) == -1 && err == NULL)
248 			err = got_error_from_errno2("unlink", outpath);
249 		free(outpath);
250 	}
251 	if (outfile && fclose(outfile) == EOF && err == NULL)
252 		err = got_error_from_errno("fclose");
253 	if (f1 && fclose(f1) == EOF && err == NULL)
254 		err = got_error_from_errno("fclose");
255 	if (f2 && fclose(f2) == EOF && err == NULL)
256 		err = got_error_from_errno("fclose");
257 	return err;
258 }
259 
260 /*
261  * For merge(1).
262  */
263 const struct got_error *
264 got_merge_diff3(int *overlapcnt, int outfd, FILE *f1, FILE *f2,
265     FILE *f3, const char *label1, const char *label2, const char *label3,
266     enum got_diff_algorithm diff_algo)
267 {
268 	const struct got_error *err = NULL;
269 	char *dp13, *dp23, *path1, *path2, *path3;
270 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
271 	u_char *data, *patch;
272 	size_t dlen, plen, i;
273 	struct diff3_state *d3s;
274 
275 	*overlapcnt = 0;
276 
277 	d3s = calloc(1, sizeof(*d3s));
278 	if (d3s == NULL)
279 		return got_error_from_errno("calloc");
280 
281 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
282 	dp13 = dp23 = path1 = path2 = path3 = NULL;
283 	data = patch = NULL;
284 
285 	err = buf_load(&b1, f1);
286 	if (err)
287 		goto out;
288 	err = buf_load(&b2, f2);
289 	if (err)
290 		goto out;
291 	err = buf_load(&b3, f3);
292 	if (err)
293 		goto out;
294 
295 	err = buf_alloc(&diffb, 128);
296 	if (err)
297 		goto out;
298 
299 	if (asprintf(&path1, GOT_TMPDIR_STR "/got-diff1.XXXXXXXX") == -1) {
300 		err = got_error_from_errno("asprintf");
301 		goto out;
302 	}
303 	if (asprintf(&path2, GOT_TMPDIR_STR "/got-diff2.XXXXXXXX") == -1) {
304 		err = got_error_from_errno("asprintf");
305 		goto out;
306 	}
307 	if (asprintf(&path3, GOT_TMPDIR_STR "/got-diff3.XXXXXXXX") == -1) {
308 		err = got_error_from_errno("asprintf");
309 		goto out;
310 	}
311 
312 	err = buf_write_stmp(b1, path1);
313 	if (err)
314 		goto out;
315 	err = buf_write_stmp(b2, path2);
316 	if (err)
317 		goto out;
318 	err = buf_write_stmp(b3, path3);
319 	if (err)
320 		goto out;
321 
322 	buf_free(b2);
323 	b2 = NULL;
324 
325 	err = diffreg(&d1, path1, path3, diff_algo);
326 	if (err) {
327 		buf_free(diffb);
328 		diffb = NULL;
329 		goto out;
330 
331 	}
332 	err = diffreg(&d2, path2, path3, diff_algo);
333 	if (err) {
334 		buf_free(diffb);
335 		diffb = NULL;
336 		goto out;
337 	}
338 
339 	if (asprintf(&dp13, GOT_TMPDIR_STR "/got-d13.XXXXXXXXXX") == -1) {
340 		err = got_error_from_errno("asprintf");
341 		goto out;
342 	}
343 	err = buf_write_stmp(d1, dp13);
344 	if (err)
345 		goto out;
346 
347 	buf_free(d1);
348 	d1 = NULL;
349 
350 	if (asprintf(&dp23, GOT_TMPDIR_STR "/got-d23.XXXXXXXXXX") == -1) {
351 		err = got_error_from_errno("asprintf");
352 		goto out;
353 	}
354 	err = buf_write_stmp(d2, dp23);
355 	if (err)
356 		goto out;
357 
358 	buf_free(d2);
359 	d2 = NULL;
360 
361 	d3s->diffbuf = diffb;
362 	err = diff3_internal(dp13, dp23, path1, path2, path3,
363 	    label1, label3, d3s, label1, label2, label3);
364 	if (err) {
365 		buf_free(diffb);
366 		diffb = NULL;
367 		goto out;
368 	}
369 
370 	plen = buf_len(diffb);
371 	patch = buf_release(diffb);
372 	dlen = buf_len(b1);
373 	data = buf_release(b1);
374 
375 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
376 out:
377 	buf_free(b2);
378 	buf_free(b3);
379 	buf_free(d1);
380 	buf_free(d2);
381 
382 	if (unlink(path1) == -1 && err == NULL)
383 		err = got_error_from_errno2("unlink", path1);
384 	if (unlink(path2) == -1 && err == NULL)
385 		err = got_error_from_errno2("unlink", path2);
386 	if (unlink(path3) == -1 && err == NULL)
387 		err = got_error_from_errno2("unlink", path3);
388 	if (unlink(dp13) == -1 && err == NULL)
389 		err = got_error_from_errno2("unlink", dp13);
390 	if (unlink(dp23) == -1 && err == NULL)
391 		err = got_error_from_errno2("unlink", dp23);
392 
393 	free(path1);
394 	free(path2);
395 	free(path3);
396 	free(dp13);
397 	free(dp23);
398 	free(data);
399 	free(patch);
400 
401 	for (i = 0; i < nitems(d3s->fp); i++) {
402 		if (d3s->fp[i] && fclose(d3s->fp[i]) == EOF && err == NULL)
403 			err = got_error_from_errno("fclose");
404 	}
405 	if (err == NULL && diffb) {
406 		if (buf_write_fd(diffb, outfd) < 0)
407 			err = got_error_from_errno("buf_write_fd");
408 		*overlapcnt = d3s->overlapcnt;
409 	}
410 	free(d3s);
411 	buf_free(diffb);
412 	return err;
413 }
414 
415 static const struct got_error *
416 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
417     const char *fmark, const char *rmark, struct diff3_state *d3s,
418     const char *label1, const char *label2, const char *label3)
419 {
420 	const struct got_error *err = NULL;
421 	ssize_t m, n;
422 	int i;
423 
424 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
425 	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_BEGIN,
426 	    label1 ? " " : "", label1 ? label1 : "");
427 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
428 		return got_error(GOT_ERR_NO_SPACE);
429 
430 	i = snprintf(d3s->f2mark, sizeof(d3s->f2mark),
431 	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_ORIG,
432 	    label2 ? " " : "", label2 ? label2 : "");
433 	if (i < 0 || i >= (int)sizeof(d3s->f2mark))
434 		return got_error(GOT_ERR_NO_SPACE);
435 
436 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
437 	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_END,
438 	    label3 ? " " : "", label3 ? label3 : "");
439 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
440 		return got_error(GOT_ERR_NO_SPACE);
441 
442 	err = increase(d3s);
443 	if (err)
444 		return err;
445 
446 	err = readin(&m, dp13, &d3s->d13, d3s);
447 	if (err)
448 		return err;
449 	err = readin(&n, dp23, &d3s->d23, d3s);
450 	if (err)
451 		return err;
452 
453 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
454 		return got_error_from_errno2("fopen", path1);
455 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
456 		return got_error_from_errno2("fopen", path2);
457 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
458 		return got_error_from_errno2("fopen", path3);
459 
460 	return merge(m, n, d3s);
461 }
462 
463 static int
464 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
465 {
466 	char op, *ep;
467 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
468 	int start, end, i, lineno;
469 	u_char tmp;
470 
471 	dlp = TAILQ_FIRST(&(dlines->l_lines));
472 	lp = TAILQ_FIRST(&(plines->l_lines));
473 
474 	end = 0;
475 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
476 	    lp = TAILQ_NEXT(lp, l_list)) {
477 		/* Skip blank lines */
478 		if (lp->l_len < 2)
479 			continue;
480 
481 		/* NUL-terminate line buffer for strtol() safety. */
482 		tmp = lp->l_line[lp->l_len - 1];
483 		lp->l_line[lp->l_len - 1] = '\0';
484 
485 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
486 		op = lp->l_line[lp->l_len - 2];
487 		start = (int)strtol(lp->l_line, &ep, 10);
488 
489 		/* Restore the last byte of the buffer */
490 		lp->l_line[lp->l_len - 1] = tmp;
491 
492 		if (op == 'a') {
493 			if (start > dlines->l_nblines ||
494 			    start < 0 || *ep != 'a')
495 				return -1;
496 		} else if (op == 'c') {
497 			if (start > dlines->l_nblines ||
498 			    start < 0 || (*ep != ',' && *ep != 'c'))
499 				return -1;
500 
501 			if (*ep == ',') {
502 				ep++;
503 				end = (int)strtol(ep, &ep, 10);
504 				if (end < 0 || *ep != 'c')
505 					return -1;
506 			} else {
507 				end = start;
508 			}
509 		}
510 
511 
512 		for (;;) {
513 			if (dlp == NULL)
514 				break;
515 			if (dlp->l_lineno == start)
516 				break;
517 			if (dlp->l_lineno > start) {
518 				dlp = TAILQ_PREV(dlp, tqh, l_list);
519 			} else if (dlp->l_lineno < start) {
520 				ndlp = TAILQ_NEXT(dlp, l_list);
521 				if (ndlp->l_lineno > start)
522 					break;
523 				dlp = ndlp;
524 			}
525 		}
526 
527 		if (dlp == NULL)
528 			return -1;
529 
530 
531 		if (op == 'c') {
532 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
533 			for (i = 0; i <= (end - start); i++) {
534 				ndlp = TAILQ_NEXT(dlp, l_list);
535 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
536 				dlp = ndlp;
537 			}
538 			dlp = insert_after;
539 		}
540 
541 		if (op == 'a' || op == 'c') {
542 			for (;;) {
543 				ndlp = lp;
544 				lp = TAILQ_NEXT(lp, l_list);
545 				if (lp == NULL)
546 					return -1;
547 
548 				if (lp->l_len == 2 &&
549 				    lp->l_line[0] == '.' &&
550 				    lp->l_line[1] == '\n')
551 					break;
552 
553 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
554 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
555 				    lp, l_list);
556 				dlp = lp;
557 
558 				lp->l_lineno = start;
559 				lp = ndlp;
560 			}
561 		}
562 
563 		/*
564 		 * always resort lines as the markers might be put at the
565 		 * same line as we first started editing.
566 		 */
567 		lineno = 0;
568 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
569 			sort->l_lineno = lineno++;
570 		dlines->l_nblines = lineno - 1;
571 	}
572 
573 	return (0);
574 }
575 
576 /*
577  * Pick up the line numbers of all changes from one change file.
578  * (This puts the numbers in a vector, which is not strictly necessary,
579  * since the vector is processed in one sequential pass.
580  * The vector could be optimized out of existence)
581  */
582 static const struct got_error *
583 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
584 {
585 	const struct got_error *err = NULL;
586 	FILE *f;
587 	int a, b, c, d;
588 	char kind, *p;
589 	size_t i = 0;
590 
591 	*n = 0;
592 
593 	f = fopen(name, "r");
594 	if (f == NULL)
595 		return got_error_from_errno2("fopen", name);
596 	err = getchange(&p, f, d3s);
597 	if (err)
598 		goto done;
599 	for (i = 0; p; i++) {
600 		if (i >= d3s->szchanges - 1) {
601 			err = increase(d3s);
602 			if (err)
603 				goto done;
604 		}
605 		a = b = number(&p);
606 		if (*p == ',') {
607 			p++;
608 			b = number(&p);
609 		}
610 		kind = *p++;
611 		c = d = number(&p);
612 		if (*p == ',') {
613 			p++;
614 			d = number(&p);
615 		}
616 		if (kind == 'a')
617 			a++;
618 		if (kind == 'd')
619 			c++;
620 		b++;
621 		d++;
622 		(*dd)[i].old.from = a;
623 		(*dd)[i].old.to = b;
624 		(*dd)[i].new.from = c;
625 		(*dd)[i].new.to = d;
626 
627 		err = getchange(&p, f, d3s);
628 		if (err)
629 			goto done;
630 	}
631 
632 	if (i) {
633 		(*dd)[i].old.from = (*dd)[i - 1].old.to;
634 		(*dd)[i].new.from = (*dd)[i - 1].new.to;
635 	}
636 done:
637 	if (fclose(f) == EOF && err == NULL)
638 		err = got_error_from_errno("fclose");
639 	if (err == NULL)
640 		*n = i;
641 	return err;
642 }
643 
644 static int
645 number(char **lc)
646 {
647 	int nn;
648 
649 	nn = 0;
650 	while (isdigit((unsigned char)(**lc)))
651 		nn = nn*10 + *(*lc)++ - '0';
652 
653 	return (nn);
654 }
655 
656 static const struct got_error *
657 getchange(char **line, FILE *b, struct diff3_state *d3s)
658 {
659 	const struct got_error *err = NULL;
660 
661 	*line = NULL;
662 	do {
663 		if (*line && isdigit((unsigned char)(*line)[0]))
664 			return NULL;
665 		err = get_line(line, b, NULL, d3s);
666 		if (err)
667 			return err;
668 	} while (*line);
669 
670 	return NULL;
671 }
672 
673 static const struct got_error *
674 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
675 {
676 	const struct got_error *err = NULL;
677 	char *cp = NULL;
678 	size_t size;
679 	ssize_t len;
680 	char *new;
681 
682 	*ret = NULL;
683 
684 	len = getline(&cp, &size, b);
685 	if (len == -1) {
686 		if (ferror(b))
687 			err = got_error_from_errno("getline");
688 		goto done;
689 	}
690 
691 	if (cp[len - 1] != '\n') {
692 		len++;
693 		if (len + 1 > size) {
694 			new = realloc(cp, len + 1);
695 			if (new == NULL) {
696 				err = got_error_from_errno("realloc");
697 				goto done;
698 			}
699 			cp = new;
700 		}
701 		cp[len - 1] = '\n';
702 		cp[len] = '\0';
703 	}
704 
705 	free(d3s->buf);
706 	*ret = d3s->buf = cp;
707 	cp = NULL;
708 	if (n != NULL)
709 		*n = len;
710 done:
711 	free(cp);
712 	return err;
713 }
714 
715 static const struct got_error *
716 merge(size_t m1, size_t m2, struct diff3_state *d3s)
717 {
718 	const struct got_error *err = NULL;
719 	struct diff *d1, *d2;
720 	int dpl, j, t1, t2;
721 
722 	d1 = d3s->d13;
723 	d2 = d3s->d23;
724 	j = 0;
725 	for (;;) {
726 		t1 = (d1 < d3s->d13 + m1);
727 		t2 = (d2 < d3s->d23 + m2);
728 		if (!t1 && !t2)
729 			break;
730 
731 		/* first file is different from others */
732 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
733 			/* stuff peculiar to 1st file */
734 			d1++;
735 			continue;
736 		}
737 
738 		/* second file is different from others */
739 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
740 			d2++;
741 			continue;
742 		}
743 
744 		/*
745 		 * Merge overlapping changes in first file
746 		 * this happens after extension (see below).
747 		 */
748 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
749 			d1[1].old.from = d1->old.from;
750 			d1[1].new.from = d1->new.from;
751 			d1++;
752 			continue;
753 		}
754 
755 		/* merge overlapping changes in second */
756 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
757 			d2[1].old.from = d2->old.from;
758 			d2[1].new.from = d2->new.from;
759 			d2++;
760 			continue;
761 		}
762 		/* stuff peculiar to third file or different in all */
763 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
764 			err = duplicate(&dpl, j, &d1->old, &d2->old, d3s);
765 			if (err)
766 				return err;
767 
768 			/*
769 			 * dpl = 0 means all files differ
770 			 * dpl = 1 means files 1 and 2 identical
771 			 */
772 			err = edit(d1, dpl, &j, d3s);
773 			if (err)
774 				return err;
775 			d1++;
776 			d2++;
777 			continue;
778 		}
779 
780 		/*
781 		 * Overlapping changes from file 1 and 2; extend changes
782 		 * appropriately to make them coincide.
783 		 */
784 		if (d1->new.from < d2->new.from) {
785 			d2->old.from -= d2->new.from - d1->new.from;
786 			d2->new.from = d1->new.from;
787 		} else if (d2->new.from < d1->new.from) {
788 			d1->old.from -= d1->new.from - d2->new.from;
789 			d1->new.from = d2->new.from;
790 		}
791 		if (d1->new.to > d2->new.to) {
792 			d2->old.to += d1->new.to - d2->new.to;
793 			d2->new.to = d1->new.to;
794 		} else if (d2->new.to > d1->new.to) {
795 			d1->old.to += d2->new.to - d1->new.to;
796 			d1->new.to = d2->new.to;
797 		}
798 	}
799 
800 	return (edscript(j, d3s));
801 }
802 
803 /*
804  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
805  */
806 static const struct got_error *
807 prange(struct line_range *rold, struct diff3_state *d3s)
808 {
809 	const struct got_error *err = NULL;
810 
811 	if (rold->to <= rold->from) {
812 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
813 		if (err)
814 			return err;
815 	} else {
816 		err = diff_output(d3s->diffbuf, "%d", rold->from);
817 		if (err)
818 			return err;
819 		if (rold->to > rold->from + 1) {
820 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
821 			if (err)
822 				return err;
823 		}
824 		err = diff_output(d3s->diffbuf, "c\n");
825 		if (err)
826 			return err;
827 	}
828 
829 	return NULL;
830 }
831 
832 /*
833  * Skip to just before line number from in file "i".
834  * Return the number of bytes skipped in *nskipped.
835  */
836 static const struct got_error *
837 skip(size_t *nskipped, int i, int from, struct diff3_state *d3s)
838 {
839 	const struct got_error *err = NULL;
840 	size_t len, n;
841 	char *line;
842 
843 	*nskipped = 0;
844 	for (n = 0; d3s->cline[i] < from - 1; n += len) {
845 		err = get_line(&line, d3s->fp[i], &len, d3s);
846 		if (err)
847 			return err;
848 		d3s->cline[i]++;
849 	}
850 	*nskipped = n;
851 	return NULL;
852 }
853 
854 /*
855  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
856  * the same data as the new range (in file 2).
857  *
858  * If this change could overlap, remember start/end offsets in file 2 so we
859  * can write out the original lines of text if a merge conflict occurs.
860  */
861 static const struct got_error *
862 duplicate(int *dpl, int j, struct line_range *r1, struct line_range *r2,
863     struct diff3_state *d3s)
864 {
865 	const struct got_error *err = NULL;
866 	int c,d;
867 	int nchar;
868 	int nline;
869 	size_t nskipped;
870 	off_t off;
871 
872 	*dpl = 0;
873 
874 	if (r1->to - r1->from != r2->to - r2->from)
875 		return NULL;
876 
877 	err = skip(&nskipped, 0, r1->from, d3s);
878 	if (err)
879 		return err;
880 	err = skip(&nskipped, 1, r2->from, d3s);
881 	if (err)
882 		return err;
883 
884 	off = ftello(d3s->fp[1]);
885 	if (off == -1)
886 		return got_error_from_errno("ftello");
887 	d3s->de[j + 1].oldo.from = off; /* original lines start here */
888 
889 	nchar = 0;
890 	for (nline = 0; nline < r1->to - r1->from; nline++) {
891 		do {
892 			c = getc(d3s->fp[0]);
893 			d = getc(d3s->fp[1]);
894 			if (c == EOF && d == EOF)
895 				break;
896 			else if (c == EOF)
897 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
898 			else if (d == EOF)
899 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
900 			nchar++;
901 			if (c != d) {
902 				long orig_line_len = nchar;
903 				while (d != '\n') {
904 					d = getc(d3s->fp[1]);
905 					if (d == EOF)
906 						break;
907 					orig_line_len++;
908 				}
909 				if (orig_line_len > nchar &&
910 				    fseek(d3s->fp[1], -(orig_line_len - nchar),
911 				    SEEK_CUR) == -1)
912 					return got_ferror(d3s->fp[1],
913 						GOT_ERR_IO);
914  				/* original lines end here */
915 				d3s->de[j + 1].oldo.to = off + orig_line_len;
916 				err = repos(nchar, d3s);
917 				if (err)
918 					return err;
919 				return NULL;
920 			}
921 		} while (c != '\n');
922 	}
923 	err = repos(nchar, d3s);
924 	if (err)
925 		return err;
926 	*dpl = 1;
927 	return NULL;
928 }
929 
930 static const struct got_error *
931 repos(int nchar, struct diff3_state *d3s)
932 {
933 	int i;
934 
935 	for (i = 0; i < 2; i++) {
936 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
937 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
938 	}
939 
940 	return NULL;
941 }
942 
943 /*
944  * collect an editing script for later regurgitation
945  */
946 static const struct got_error *
947 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
948 {
949 	const struct got_error *err = NULL;
950 	size_t nskipped;
951 
952 	if (((fdup + 1) & 3) == 0)
953 		return NULL;
954 	(*j)++;
955 	d3s->overlap[*j] = !fdup;
956 	if (!fdup)
957 		d3s->overlapcnt++;
958 	d3s->de[*j].old.from = diff->old.from;
959 	d3s->de[*j].old.to = diff->old.to;
960 
961 	err = skip(&nskipped, 2, diff->new.from, d3s);
962 	if (err)
963 		return err;
964 	d3s->de[*j].newo.from = d3s->de[*j - 1].newo.to + nskipped;
965 
966 	err = skip(&nskipped, 2, diff->new.to, d3s);
967 	if (err)
968 		return err;
969 	d3s->de[*j].newo.to = d3s->de[*j].newo.from + nskipped;
970 	return NULL;
971 }
972 
973 /* regurgitate */
974 static const struct got_error *
975 edscript(int n, struct diff3_state *d3s)
976 {
977 	const struct got_error *err = NULL;
978 	size_t k, len;
979 	char block[BUFSIZ+1];
980 
981 	for (; n > 0; n--) {
982 		if (!d3s->overlap[n]) {
983 			err = prange(&d3s->de[n].old, d3s);
984 			if (err)
985 				return err;
986 		} else if (d3s->de[n].oldo.from < d3s->de[n].oldo.to) {
987 			/* Output a block of 3-way diff base file content. */
988 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
989 			    d3s->de[n].old.to - 1, d3s->f2mark);
990 			if (err)
991 				return err;
992 			if (fseeko(d3s->fp[1], d3s->de[n].oldo.from, SEEK_SET)
993 			    == -1)
994 				return got_error_from_errno("fseeko");
995 			k = (size_t)(d3s->de[n].oldo.to - d3s->de[n].oldo.from);
996 			for (; k > 0; k -= len) {
997 				size_t r;
998 				len = k > BUFSIZ ? BUFSIZ : k;
999 				r = fread(block, 1, len, d3s->fp[1]);
1000 				if (r == 0) {
1001 					if (feof(d3s->fp[1]))
1002 						break;
1003 					return got_ferror(d3s->fp[1],
1004 					    GOT_ERR_IO);
1005 				}
1006 				if (r != len)
1007 					len = r;
1008 				block[len] = '\0';
1009 				err = diff_output(d3s->diffbuf, "%s", block);
1010 				if (err)
1011 					return err;
1012 			}
1013 			err = diff_output(d3s->diffbuf, "%s\n",
1014 			    GOT_DIFF_CONFLICT_MARKER_SEP);
1015 			if (err)
1016 				return err;
1017  		} else {
1018  			err = diff_output(d3s->diffbuf, "%da\n%s\n",
1019 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
1020 			if (err)
1021 				return err;
1022 		}
1023 		if (fseeko(d3s->fp[2], d3s->de[n].newo.from, SEEK_SET)
1024 		    == -1)
1025 			return got_error_from_errno("fseek");
1026 		k = (size_t)(d3s->de[n].newo.to - d3s->de[n].newo.from);
1027 		for (; k > 0; k -= len) {
1028 			size_t r;
1029 			len = k > BUFSIZ ? BUFSIZ : k;
1030 			r = fread(block, 1, len, d3s->fp[2]);
1031 			if (r == 0) {
1032 				if (feof(d3s->fp[2]))
1033 					break;
1034 				return got_ferror(d3s->fp[2],
1035 				    GOT_ERR_IO);
1036 			}
1037 			if (r != len)
1038 				len = r;
1039 			block[len] = '\0';
1040 			err = diff_output(d3s->diffbuf, "%s", block);
1041 			if (err)
1042 				return err;
1043 		}
1044 
1045 		if (!d3s->overlap[n]) {
1046 			err = diff_output(d3s->diffbuf, ".\n");
1047 			if (err)
1048 				return err;
1049 		} else {
1050 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
1051 			if (err)
1052 				return err;
1053 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
1054 			    d3s->de[n].old.from - 1, d3s->f1mark);
1055 			if (err)
1056 				return err;
1057 		}
1058 	}
1059 
1060 	return NULL;
1061 }
1062 
1063 static const struct got_error *
1064 increase(struct diff3_state *d3s)
1065 {
1066 	size_t newsz, incr;
1067 	struct diff *d;
1068 	char *s;
1069 
1070 	/* are the memset(3) calls needed? */
1071 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
1072 	incr = newsz - d3s->szchanges;
1073 
1074 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
1075 	if (d == NULL)
1076 		return got_error_from_errno("reallocarray");
1077 	d3s->d13 = d;
1078 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
1079 
1080 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1081 	if (d == NULL)
1082 		return got_error_from_errno("reallocarray");
1083 	d3s->d23 = d;
1084 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1085 
1086 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1087 	if (d == NULL)
1088 		return got_error_from_errno("reallocarray");
1089 	d3s->de = d;
1090 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1091 
1092 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1093 	if (s == NULL)
1094 		return got_error_from_errno("reallocarray");
1095 	d3s->overlap = s;
1096 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1097 	d3s->szchanges = newsz;
1098 
1099 	return NULL;
1100 }