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Date:: Wed Oct 9 08:45:51 2019 UTC
Message:: diff3.c: do not use the same variables for both line numbers and byte offsets
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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 newo;
121 };
122 
123 struct diff3_state {
124 	size_t szchanges;
125 
126 	struct diff *d13;
127 	struct diff *d23;
128 
129 	/*
130 	 * "de" is used to gather editing scripts.  These are later spewed out
131 	 * in reverse order.  Its first element must be all zero, the "new"
132 	 * component of "de" contains line positions and byte positions.
133 	 * Array overlap indicates which sections in "de" correspond to lines
134 	 * that are different in all three files.
135 	 */
136 	struct diff *de;
137 	char *overlap;
138 	int overlapcnt;
139 	FILE *fp[3];
140 	int cline[3];		/* # of the last-read line in each file (0-2) */
141 
142 	/*
143 	 * the latest known correspondence between line numbers of the 3 files
144 	 * is stored in last[1-3];
145 	 */
146 	int last[4];
147 	char f1mark[PATH_MAX], f3mark[PATH_MAX]; /* markers for -E and -X */
148 
149 	char *buf;
150 
151 	BUF *diffbuf;
152 };
153 
154 
155 static const struct got_error *duplicate(int *, struct line_range *,
156     struct line_range *, struct diff3_state *);
157 static const struct got_error *edit(struct diff *, int, int *,
158     struct diff3_state *);
159 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
160 static const struct got_error *get_line(char **, FILE *, size_t *,
161     struct diff3_state *);
162 static int number(char **);
163 static const struct got_error *readin(size_t *, char *, struct diff **,
164     struct diff3_state *);
165 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
166 static const struct got_error *skip(size_t *, int, int, struct diff3_state *);
167 static const struct got_error *edscript(int, struct diff3_state *);
168 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
169 static const struct got_error *prange(struct line_range *, struct diff3_state *);
170 static const struct got_error *repos(int, 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     const char *, const char *);
175 
176 static const struct got_error *
177 diff_output(BUF *diffbuf, const char *fmt, ...)
178 {
179 	const struct got_error *err = NULL;
180 	va_list vap;
181 	int i;
182 	char *str;
183 	size_t newsize;
184 
185 	va_start(vap, fmt);
186 	i = vasprintf(&str, fmt, vap);
187 	va_end(vap);
188 	if (i == -1)
189 		return got_error_from_errno("vasprintf");
190 	err = buf_append(&newsize, diffbuf, str, strlen(str));
191 	free(str);
192 	return err;
193 }
194 
195 static const struct got_error*
196 diffreg(BUF **d, const char *path1, const char *path2)
197 {
198 	const struct got_error *err = NULL;
199 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
200 	char *outpath = NULL;
201 	struct got_diff_state ds;
202 	struct got_diff_args args;
203 	int res;
204 
205 	*d = NULL;
206 
207 	f1 = fopen(path1, "r");
208 	if (f1 == NULL) {
209 		err = got_error_from_errno2("fopen", path1);
210 		goto done;
211 	}
212 	f2 = fopen(path2, "r");
213 	if (f1 == NULL) {
214 		err = got_error_from_errno2("fopen", path2);
215 		goto done;
216 	}
217 
218 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diffreg");
219 	if (err)
220 		goto done;
221 
222 	memset(&ds, 0, sizeof(ds));
223 	/* XXX should stat buffers be passed in args instead of ds? */
224 	if (stat(path1, &ds.stb1) == -1) {
225 		err = got_error_from_errno2("stat", path1);
226 		goto done;
227 	}
228 	if (stat(path2, &ds.stb2) == -1) {
229 		err = got_error_from_errno2("stat", path2);
230 		goto done;
231 	}
232 
233 	memset(&args, 0, sizeof(args));
234 	args.diff_format = D_NORMAL;
235 	args.label[0] = "";
236 	args.label[1] = "";
237 	args.diff_context = 0;
238 
239 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
240 	    outfile, NULL);
241 	if (err)
242 		goto done;
243 
244 	if (fflush(outfile) != 0) {
245 		err = got_error_from_errno2("fflush", outpath);
246 		goto done;
247 	}
248 
249 	err = buf_load(d, outpath);
250 done:
251 	if (outpath) {
252 		if (unlink(outpath) == -1 && err == NULL)
253 			err = got_error_from_errno2("unlink", outpath);
254 		free(outpath);
255 	}
256 	if (outfile && fclose(outfile) != 0 && err == NULL)
257 		err = got_error_from_errno("fclose");
258 	if (f1 && fclose(f1) != 0 && err == NULL)
259 		err = got_error_from_errno("fclose");
260 	if (f2 && fclose(f2) != 0 && err == NULL)
261 		err = got_error_from_errno("fclose");
262 	return err;
263 }
264 
265 /*
266  * For merge(1).
267  */
268 const struct got_error *
269 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
270     const char *p3, const char *label1, const char *label3)
271 {
272 	const struct got_error *err = NULL;
273 	char *dp13, *dp23, *path1, *path2, *path3;
274 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
275 	u_char *data, *patch;
276 	size_t dlen, plen;
277 	struct diff3_state *d3s;
278 	int i;
279 
280 	*overlapcnt = 0;
281 
282 	d3s = calloc(1, sizeof(*d3s));
283 	if (d3s == NULL)
284 		return got_error_from_errno("calloc");
285 
286 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
287 	dp13 = dp23 = path1 = path2 = path3 = NULL;
288 	data = patch = NULL;
289 
290 	err = buf_load(&b1, p1);
291 	if (err)
292 		goto out;
293 	err = buf_load(&b2, p2);
294 	if (err)
295 		goto out;
296 	err = buf_load(&b3, p3);
297 	if (err)
298 		goto out;
299 
300 	err = buf_alloc(&diffb, 128);
301 	if (err)
302 		goto out;
303 
304 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
305 		err = got_error_from_errno("asprintf");
306 		goto out;
307 	}
308 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
309 		err = got_error_from_errno("asprintf");
310 		goto out;
311 	}
312 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
313 		err = got_error_from_errno("asprintf");
314 		goto out;
315 	}
316 
317 	err = buf_write_stmp(b1, path1);
318 	if (err)
319 		goto out;
320 	err = buf_write_stmp(b2, path2);
321 	if (err)
322 		goto out;
323 	err = buf_write_stmp(b3, path3);
324 	if (err)
325 		goto out;
326 
327 	buf_free(b2);
328 	b2 = NULL;
329 
330 	err = diffreg(&d1, path1, path3);
331 	if (err) {
332 		buf_free(diffb);
333 		diffb = NULL;
334 		goto out;
335 
336 	}
337 	err = diffreg(&d2, path2, path3);
338 	if (err) {
339 		buf_free(diffb);
340 		diffb = NULL;
341 		goto out;
342 	}
343 
344 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
345 		err = got_error_from_errno("asprintf");
346 		goto out;
347 	}
348 	err = buf_write_stmp(d1, dp13);
349 	if (err)
350 		goto out;
351 
352 	buf_free(d1);
353 	d1 = NULL;
354 
355 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
356 		err = got_error_from_errno("asprintf");
357 		goto out;
358 	}
359 	err = buf_write_stmp(d2, dp23);
360 	if (err)
361 		goto out;
362 
363 	buf_free(d2);
364 	d2 = NULL;
365 
366 	d3s->diffbuf = diffb;
367 	err = diff3_internal(dp13, dp23, path1, path2, path3,
368 	    label1, label3, d3s, label1, label3);
369 	if (err) {
370 		buf_free(diffb);
371 		diffb = NULL;
372 		goto out;
373 	}
374 
375 	plen = buf_len(diffb);
376 	patch = buf_release(diffb);
377 	dlen = buf_len(b1);
378 	data = buf_release(b1);
379 
380 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
381 out:
382 	buf_free(b2);
383 	buf_free(b3);
384 	buf_free(d1);
385 	buf_free(d2);
386 
387 	if (unlink(path1) == -1 && err == NULL)
388 		err = got_error_from_errno2("unlink", path1);
389 	if (unlink(path2) == -1 && err == NULL)
390 		err = got_error_from_errno2("unlink", path2);
391 	if (unlink(path3) == -1 && err == NULL)
392 		err = got_error_from_errno2("unlink", path3);
393 	if (unlink(dp13) == -1 && err == NULL)
394 		err = got_error_from_errno2("unlink", dp13);
395 	if (unlink(dp23) == -1 && err == NULL)
396 		err = got_error_from_errno2("unlink", dp23);
397 
398 	free(path1);
399 	free(path2);
400 	free(path3);
401 	free(dp13);
402 	free(dp23);
403 	free(data);
404 	free(patch);
405 
406 	for (i = 0; i < nitems(d3s->fp); i++) {
407 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
408 			err = got_error_from_errno("fclose");
409 	}
410 	if (err == NULL && diffb) {
411 		if (buf_write_fd(diffb, outfd) < 0)
412 			err = got_error_from_errno("buf_write_fd");
413 		*overlapcnt = d3s->overlapcnt;
414 	}
415 	free(d3s);
416 	buf_free(diffb);
417 	return err;
418 }
419 
420 static const struct got_error *
421 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
422     const char *fmark, const char *rmark, struct diff3_state *d3s,
423     const char *label1, const char *label3)
424 {
425 	const struct got_error *err = NULL;
426 	ssize_t m, n;
427 	int i;
428 
429 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
430 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
431 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
432 		return got_error(GOT_ERR_NO_SPACE);
433 
434 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
435 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
436 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
437 		return got_error(GOT_ERR_NO_SPACE);
438 
439 	err = increase(d3s);
440 	if (err)
441 		return err;
442 
443 	err = readin(&m, dp13, &d3s->d13, d3s);
444 	if (err)
445 		return err;
446 	err = readin(&n, dp23, &d3s->d23, d3s);
447 	if (err)
448 		return err;
449 
450 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
451 		return got_error_from_errno2("fopen", path1);
452 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
453 		return got_error_from_errno2("fopen", path2);
454 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
455 		return got_error_from_errno2("fopen", path3);
456 
457 	return merge(m, n, d3s);
458 }
459 
460 static int
461 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
462 {
463 	char op, *ep;
464 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
465 	int start, end, i, lineno;
466 	u_char tmp;
467 
468 	dlp = TAILQ_FIRST(&(dlines->l_lines));
469 	lp = TAILQ_FIRST(&(plines->l_lines));
470 
471 	end = 0;
472 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
473 	    lp = TAILQ_NEXT(lp, l_list)) {
474 		/* Skip blank lines */
475 		if (lp->l_len < 2)
476 			continue;
477 
478 		/* NUL-terminate line buffer for strtol() safety. */
479 		tmp = lp->l_line[lp->l_len - 1];
480 		lp->l_line[lp->l_len - 1] = '\0';
481 
482 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
483 		op = lp->l_line[lp->l_len - 2];
484 		start = (int)strtol(lp->l_line, &ep, 10);
485 
486 		/* Restore the last byte of the buffer */
487 		lp->l_line[lp->l_len - 1] = tmp;
488 
489 		if (op == 'a') {
490 			if (start > dlines->l_nblines ||
491 			    start < 0 || *ep != 'a')
492 				return -1;
493 		} else if (op == 'c') {
494 			if (start > dlines->l_nblines ||
495 			    start < 0 || (*ep != ',' && *ep != 'c'))
496 				return -1;
497 
498 			if (*ep == ',') {
499 				ep++;
500 				end = (int)strtol(ep, &ep, 10);
501 				if (end < 0 || *ep != 'c')
502 					return -1;
503 			} else {
504 				end = start;
505 			}
506 		}
507 
508 
509 		for (;;) {
510 			if (dlp == NULL)
511 				break;
512 			if (dlp->l_lineno == start)
513 				break;
514 			if (dlp->l_lineno > start) {
515 				dlp = TAILQ_PREV(dlp, tqh, l_list);
516 			} else if (dlp->l_lineno < start) {
517 				ndlp = TAILQ_NEXT(dlp, l_list);
518 				if (ndlp->l_lineno > start)
519 					break;
520 				dlp = ndlp;
521 			}
522 		}
523 
524 		if (dlp == NULL)
525 			return -1;
526 
527 
528 		if (op == 'c') {
529 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
530 			for (i = 0; i <= (end - start); i++) {
531 				ndlp = TAILQ_NEXT(dlp, l_list);
532 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
533 				dlp = ndlp;
534 			}
535 			dlp = insert_after;
536 		}
537 
538 		if (op == 'a' || op == 'c') {
539 			for (;;) {
540 				ndlp = lp;
541 				lp = TAILQ_NEXT(lp, l_list);
542 				if (lp == NULL)
543 					return -1;
544 
545 				if (lp->l_len == 2 &&
546 				    lp->l_line[0] == '.' &&
547 				    lp->l_line[1] == '\n')
548 					break;
549 
550 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
551 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
552 				    lp, l_list);
553 				dlp = lp;
554 
555 				lp->l_lineno = start;
556 				lp = ndlp;
557 			}
558 		}
559 
560 		/*
561 		 * always resort lines as the markers might be put at the
562 		 * same line as we first started editing.
563 		 */
564 		lineno = 0;
565 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
566 			sort->l_lineno = lineno++;
567 		dlines->l_nblines = lineno - 1;
568 	}
569 
570 	return (0);
571 }
572 
573 /*
574  * Pick up the line numbers of all changes from one change file.
575  * (This puts the numbers in a vector, which is not strictly necessary,
576  * since the vector is processed in one sequential pass.
577  * The vector could be optimized out of existence)
578  */
579 static const struct got_error *
580 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
581 {
582 	const struct got_error *err = NULL;
583 	FILE *f;
584 	int a, b, c, d;
585 	char kind, *p;
586 	size_t i;
587 
588 	*n = 0;
589 
590 	f = fopen(name, "r");
591 	if (f == NULL)
592 		return got_error_from_errno2("fopen", name);
593 	err = getchange(&p, f, d3s);
594 	if (err)
595 		goto done;
596 	for (i = 0; p; i++) {
597 		if (i >= d3s->szchanges - 1) {
598 			err = increase(d3s);
599 			if (err)
600 				goto done;
601 		}
602 		a = b = number(&p);
603 		if (*p == ',') {
604 			p++;
605 			b = number(&p);
606 		}
607 		kind = *p++;
608 		c = d = number(&p);
609 		if (*p == ',') {
610 			p++;
611 			d = number(&p);
612 		}
613 		if (kind == 'a')
614 			a++;
615 		if (kind == 'd')
616 			c++;
617 		b++;
618 		d++;
619 		(*dd)[i].old.from = a;
620 		(*dd)[i].old.to = b;
621 		(*dd)[i].new.from = c;
622 		(*dd)[i].new.to = d;
623 
624 		err = getchange(&p, f, d3s);
625 		if (err)
626 			goto done;
627 	}
628 
629 	if (i) {
630 		(*dd)[i].old.from = (*dd)[i - 1].old.to;
631 		(*dd)[i].new.from = (*dd)[i - 1].new.to;
632 	}
633 done:
634 	if (fclose(f) != 0 && err == NULL)
635 		err = got_error_from_errno("fclose");
636 	if (err == NULL)
637 		*n = i;
638 	return err;
639 }
640 
641 static int
642 number(char **lc)
643 {
644 	int nn;
645 
646 	nn = 0;
647 	while (isdigit((unsigned char)(**lc)))
648 		nn = nn*10 + *(*lc)++ - '0';
649 
650 	return (nn);
651 }
652 
653 static const struct got_error *
654 getchange(char **line, FILE *b, struct diff3_state *d3s)
655 {
656 	const struct got_error *err = NULL;
657 
658 	*line = NULL;
659 	do {
660 		if (*line && isdigit((unsigned char)(*line)[0]))
661 			return NULL;
662 		err = get_line(line, b, NULL, d3s);
663 		if (err)
664 			return err;
665 	} while (*line);
666 
667 	return NULL;
668 }
669 
670 static const struct got_error *
671 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
672 {
673 	const struct got_error *err = NULL;
674 	char *cp = NULL;
675 	size_t size;
676 	ssize_t len;
677 	char *new;
678 
679 	*ret = NULL;
680 
681 	len = getline(&cp, &size, b);
682 	if (len == -1) {
683 		if (ferror(b))
684 			err = got_error_from_errno("getline");
685 		goto done;
686 	}
687 
688 	if (cp[len - 1] != '\n') {
689 		len++;
690 		if (len + 1 > size) {
691 			new = realloc(cp, len + 1);
692 			if (new == NULL) {
693 				err = got_error_from_errno("realloc");
694 				goto done;
695 			}
696 			cp = new;
697 		}
698 		cp[len - 1] = '\n';
699 		cp[len] = '\0';
700 	}
701 
702 	free(d3s->buf);
703 	*ret = d3s->buf = cp;
704 	cp = NULL;
705 	if (n != NULL)
706 		*n = len;
707 done:
708 	free(cp);
709 	return err;
710 }
711 
712 static const struct got_error *
713 merge(size_t m1, size_t m2, struct diff3_state *d3s)
714 {
715 	const struct got_error *err = NULL;
716 	struct diff *d1, *d2;
717 	int dpl, j, t1, t2;
718 
719 	d1 = d3s->d13;
720 	d2 = d3s->d23;
721 	j = 0;
722 	for (;;) {
723 		t1 = (d1 < d3s->d13 + m1);
724 		t2 = (d2 < d3s->d23 + m2);
725 		if (!t1 && !t2)
726 			break;
727 
728 		/* first file is different from others */
729 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
730 			/* stuff peculiar to 1st file */
731 			d1++;
732 			continue;
733 		}
734 
735 		/* second file is different from others */
736 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
737 			d2++;
738 			continue;
739 		}
740 
741 		/*
742 		 * Merge overlapping changes in first file
743 		 * this happens after extension (see below).
744 		 */
745 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
746 			d1[1].old.from = d1->old.from;
747 			d1[1].new.from = d1->new.from;
748 			d1++;
749 			continue;
750 		}
751 
752 		/* merge overlapping changes in second */
753 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
754 			d2[1].old.from = d2->old.from;
755 			d2[1].new.from = d2->new.from;
756 			d2++;
757 			continue;
758 		}
759 		/* stuff peculiar to third file or different in all */
760 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
761 			err = duplicate(&dpl, &d1->old, &d2->old, d3s);
762 			if (err)
763 				return err;
764 
765 			/*
766 			 * dpl = 0 means all files differ
767 			 * dpl = 1 means files 1 and 2 identical
768 			 */
769 			err = edit(d1, dpl, &j, d3s);
770 			if (err)
771 				return err;
772 			d1++;
773 			d2++;
774 			continue;
775 		}
776 
777 		/*
778 		 * Overlapping changes from file 1 and 2; extend changes
779 		 * appropriately to make them coincide.
780 		 */
781 		if (d1->new.from < d2->new.from) {
782 			d2->old.from -= d2->new.from - d1->new.from;
783 			d2->new.from = d1->new.from;
784 		} else if (d2->new.from < d1->new.from) {
785 			d1->old.from -= d1->new.from - d2->new.from;
786 			d1->new.from = d2->new.from;
787 		}
788 		if (d1->new.to > d2->new.to) {
789 			d2->old.to += d1->new.to - d2->new.to;
790 			d2->new.to = d1->new.to;
791 		} else if (d2->new.to > d1->new.to) {
792 			d1->old.to += d2->new.to - d1->new.to;
793 			d1->new.to = d2->new.to;
794 		}
795 	}
796 
797 	return (edscript(j, d3s));
798 }
799 
800 /*
801  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
802  */
803 static const struct got_error *
804 prange(struct line_range *rold, struct diff3_state *d3s)
805 {
806 	const struct got_error *err = NULL;
807 
808 	if (rold->to <= rold->from) {
809 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
810 		if (err)
811 			return err;
812 	} else {
813 		err = diff_output(d3s->diffbuf, "%d", rold->from);
814 		if (err)
815 			return err;
816 		if (rold->to > rold->from + 1) {
817 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
818 			if (err)
819 				return err;
820 		}
821 		err = diff_output(d3s->diffbuf, "c\n");
822 		if (err)
823 			return err;
824 	}
825 
826 	return NULL;
827 }
828 
829 /*
830  * Skip to just before line number from in file "i".
831  * Return the number of bytes skipped in *nskipped.
832  */
833 static const struct got_error *
834 skip(size_t *nskipped, int i, int from, struct diff3_state *d3s)
835 {
836 	const struct got_error *err = NULL;
837 	size_t len, n;
838 	char *line;
839 
840 	*nskipped = 0;
841 	for (n = 0; d3s->cline[i] < from - 1; n += len) {
842 		err = get_line(&line, d3s->fp[i], &len, d3s);
843 		if (err)
844 			return err;
845 		d3s->cline[i]++;
846 	}
847 	*nskipped = n;
848 	return NULL;
849 }
850 
851 /*
852  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
853  * the same data as the new range (in file 2).
854  */
855 static const struct got_error *
856 duplicate(int *dpl, struct line_range *r1, struct line_range *r2,
857     struct diff3_state *d3s)
858 {
859 	const struct got_error *err = NULL;
860 	int c,d;
861 	int nchar;
862 	int nline;
863 	size_t nskipped;
864 
865 	*dpl = 0;
866 
867 	if (r1->to - r1->from != r2->to - r2->from)
868 		return NULL;
869 
870 	err = skip(&nskipped, 0, r1->from, d3s);
871 	if (err)
872 		return err;
873 	err = skip(&nskipped, 1, r2->from, d3s);
874 	if (err)
875 		return err;
876 	nchar = 0;
877 	for (nline = 0; nline < r1->to - r1->from; nline++) {
878 		do {
879 			c = getc(d3s->fp[0]);
880 			if (c == EOF)
881 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
882 			d = getc(d3s->fp[1]);
883 			if (d == EOF)
884 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
885 			nchar++;
886 			if (c != d)
887 				return repos(nchar, d3s);
888 		} while (c != '\n');
889 	}
890 	err = repos(nchar, d3s);
891 	if (err)
892 		return err;
893 	*dpl = 1;
894 	return NULL;
895 }
896 
897 static const struct got_error *
898 repos(int nchar, struct diff3_state *d3s)
899 {
900 	int i;
901 
902 	for (i = 0; i < 2; i++) {
903 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
904 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
905 	}
906 
907 	return NULL;
908 }
909 
910 /*
911  * collect an editing script for later regurgitation
912  */
913 static const struct got_error *
914 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
915 {
916 	const struct got_error *err = NULL;
917 	size_t nskipped;
918 
919 	if (((fdup + 1) & 3) == 0)
920 		return NULL;
921 	(*j)++;
922 	d3s->overlap[*j] = !fdup;
923 	if (!fdup)
924 		d3s->overlapcnt++;
925 	d3s->de[*j].old.from = diff->old.from;
926 	d3s->de[*j].old.to = diff->old.to;
927 
928 	err = skip(&nskipped, 2, diff->new.from, d3s);
929 	if (err)
930 		return err;
931 	d3s->de[*j].newo.from = d3s->de[*j - 1].newo.to + nskipped;
932 
933 	err = skip(&nskipped, 2, diff->new.to, d3s);
934 	if (err)
935 		return err;
936 	d3s->de[*j].newo.to = d3s->de[*j].newo.from + nskipped;
937 	return NULL;
938 }
939 
940 /* regurgitate */
941 static const struct got_error *
942 edscript(int n, struct diff3_state *d3s)
943 {
944 	const struct got_error *err = NULL;
945 	off_t k, len;
946 	char block[BUFSIZ+1];
947 
948 	for (; n > 0; n--) {
949 		if (!d3s->overlap[n]) {
950 			err = prange(&d3s->de[n].old, d3s);
951 			if (err)
952 				return err;
953 		} else {
954 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
955 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
956 			if (err)
957 				return err;
958 		}
959 		if (fseeko(d3s->fp[2], d3s->de[n].newo.from, SEEK_SET)
960 		    == -1)
961 			return got_error_from_errno("fseek");
962 		k = d3s->de[n].newo.to - d3s->de[n].newo.from;
963 		for (; k > 0; k -= len) {
964 			len = k > BUFSIZ ? BUFSIZ : k;
965 			if (fread(block, 1, len, d3s->fp[2]) != (size_t)len)
966 				return got_ferror(d3s->fp[2], GOT_ERR_IO);
967 			block[len] = '\0';
968 			err = diff_output(d3s->diffbuf, "%s", block);
969 			if (err)
970 				return err;
971 		}
972 
973 		if (!d3s->overlap[n]) {
974 			err = diff_output(d3s->diffbuf, ".\n");
975 			if (err)
976 				return err;
977 		} else {
978 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
979 			if (err)
980 				return err;
981 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
982 			    d3s->de[n].old.from - 1, d3s->f1mark);
983 			if (err)
984 				return err;
985 		}
986 	}
987 
988 	return NULL;
989 }
990 
991 static const struct got_error *
992 increase(struct diff3_state *d3s)
993 {
994 	size_t newsz, incr;
995 	struct diff *d;
996 	char *s;
997 
998 	/* are the memset(3) calls needed? */
999 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
1000 	incr = newsz - d3s->szchanges;
1001 
1002 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
1003 	if (d == NULL)
1004 		return got_error_from_errno("reallocarray");
1005 	d3s->d13 = d;
1006 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
1007 
1008 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1009 	if (d == NULL)
1010 		return got_error_from_errno("reallocarray");
1011 	d3s->d23 = d;
1012 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1013 
1014 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1015 	if (d == NULL)
1016 		return got_error_from_errno("reallocarray");
1017 	d3s->de = d;
1018 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1019 
1020 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1021 	if (s == NULL)
1022 		return got_error_from_errno("reallocarray");
1023 	d3s->overlap = s;
1024 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1025 	d3s->szchanges = newsz;
1026 
1027 	return NULL;
1028 }