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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], f3mark[PATH_MAX]; /* markers for -E and -X */
150 
151 	char *buf;
152 
153 	BUF *diffbuf;
154 };
155 
156 
157 static const struct got_error *duplicate(int *, int, struct line_range *,
158     struct line_range *, struct diff3_state *);
159 static const struct got_error *edit(struct diff *, int, int *,
160     struct diff3_state *);
161 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
162 static const struct got_error *get_line(char **, FILE *, size_t *,
163     struct diff3_state *);
164 static int number(char **);
165 static const struct got_error *readin(size_t *, char *, struct diff **,
166     struct diff3_state *);
167 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
168 static const struct got_error *skip(size_t *, int, int, struct diff3_state *);
169 static const struct got_error *edscript(int, struct diff3_state *);
170 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
171 static const struct got_error *prange(struct line_range *, struct diff3_state *);
172 static const struct got_error *repos(int, struct diff3_state *);
173 static const struct got_error *increase(struct diff3_state *);
174 static const struct got_error *diff3_internal(char *, char *, char *,
175     char *, char *, const char *, const char *, struct diff3_state *,
176     const char *, const char *);
177 
178 static const struct got_error *
179 diff_output(BUF *diffbuf, const char *fmt, ...)
180 {
181 	const struct got_error *err = NULL;
182 	va_list vap;
183 	int i;
184 	char *str;
185 	size_t newsize;
186 
187 	va_start(vap, fmt);
188 	i = vasprintf(&str, fmt, vap);
189 	va_end(vap);
190 	if (i == -1)
191 		return got_error_from_errno("vasprintf");
192 	err = buf_append(&newsize, diffbuf, str, strlen(str));
193 	free(str);
194 	return err;
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_errno2("fopen", path1);
212 		goto done;
213 	}
214 	f2 = fopen(path2, "r");
215 	if (f1 == NULL) {
216 		err = got_error_from_errno2("fopen", path2);
217 		goto done;
218 	}
219 
220 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diffreg");
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_errno2("stat", path1);
228 		goto done;
229 	}
230 	if (stat(path2, &ds.stb2) == -1) {
231 		err = got_error_from_errno2("stat", path2);
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 	if (fflush(outfile) != 0) {
247 		err = got_error_from_errno2("fflush", outpath);
248 		goto done;
249 	}
250 
251 	err = buf_load(d, outpath);
252 done:
253 	if (outpath) {
254 		if (unlink(outpath) == -1 && err == NULL)
255 			err = got_error_from_errno2("unlink", outpath);
256 		free(outpath);
257 	}
258 	if (outfile && fclose(outfile) != 0 && err == NULL)
259 		err = got_error_from_errno("fclose");
260 	if (f1 && fclose(f1) != 0 && err == NULL)
261 		err = got_error_from_errno("fclose");
262 	if (f2 && fclose(f2) != 0 && err == NULL)
263 		err = got_error_from_errno("fclose");
264 	return err;
265 }
266 
267 /*
268  * For merge(1).
269  */
270 const struct got_error *
271 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
272     const char *p3, const char *label1, const char *label3)
273 {
274 	const struct got_error *err = NULL;
275 	char *dp13, *dp23, *path1, *path2, *path3;
276 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
277 	u_char *data, *patch;
278 	size_t dlen, plen;
279 	struct diff3_state *d3s;
280 	int i;
281 
282 	*overlapcnt = 0;
283 
284 	d3s = calloc(1, sizeof(*d3s));
285 	if (d3s == NULL)
286 		return got_error_from_errno("calloc");
287 
288 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
289 	dp13 = dp23 = path1 = path2 = path3 = NULL;
290 	data = patch = NULL;
291 
292 	err = buf_load(&b1, p1);
293 	if (err)
294 		goto out;
295 	err = buf_load(&b2, p2);
296 	if (err)
297 		goto out;
298 	err = buf_load(&b3, p3);
299 	if (err)
300 		goto out;
301 
302 	err = buf_alloc(&diffb, 128);
303 	if (err)
304 		goto out;
305 
306 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
307 		err = got_error_from_errno("asprintf");
308 		goto out;
309 	}
310 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
311 		err = got_error_from_errno("asprintf");
312 		goto out;
313 	}
314 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
315 		err = got_error_from_errno("asprintf");
316 		goto out;
317 	}
318 
319 	err = buf_write_stmp(b1, path1);
320 	if (err)
321 		goto out;
322 	err = buf_write_stmp(b2, path2);
323 	if (err)
324 		goto out;
325 	err = buf_write_stmp(b3, path3);
326 	if (err)
327 		goto out;
328 
329 	buf_free(b2);
330 	b2 = NULL;
331 
332 	err = diffreg(&d1, path1, path3);
333 	if (err) {
334 		buf_free(diffb);
335 		diffb = NULL;
336 		goto out;
337 
338 	}
339 	err = diffreg(&d2, path2, path3);
340 	if (err) {
341 		buf_free(diffb);
342 		diffb = NULL;
343 		goto out;
344 	}
345 
346 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
347 		err = got_error_from_errno("asprintf");
348 		goto out;
349 	}
350 	err = buf_write_stmp(d1, dp13);
351 	if (err)
352 		goto out;
353 
354 	buf_free(d1);
355 	d1 = NULL;
356 
357 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
358 		err = got_error_from_errno("asprintf");
359 		goto out;
360 	}
361 	err = buf_write_stmp(d2, dp23);
362 	if (err)
363 		goto out;
364 
365 	buf_free(d2);
366 	d2 = NULL;
367 
368 	d3s->diffbuf = diffb;
369 	err = diff3_internal(dp13, dp23, path1, path2, path3,
370 	    label1, label3, d3s, label1, label3);
371 	if (err) {
372 		buf_free(diffb);
373 		diffb = NULL;
374 		goto out;
375 	}
376 
377 	plen = buf_len(diffb);
378 	patch = buf_release(diffb);
379 	dlen = buf_len(b1);
380 	data = buf_release(b1);
381 
382 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
383 out:
384 	buf_free(b2);
385 	buf_free(b3);
386 	buf_free(d1);
387 	buf_free(d2);
388 
389 	if (unlink(path1) == -1 && err == NULL)
390 		err = got_error_from_errno2("unlink", path1);
391 	if (unlink(path2) == -1 && err == NULL)
392 		err = got_error_from_errno2("unlink", path2);
393 	if (unlink(path3) == -1 && err == NULL)
394 		err = got_error_from_errno2("unlink", path3);
395 	if (unlink(dp13) == -1 && err == NULL)
396 		err = got_error_from_errno2("unlink", dp13);
397 	if (unlink(dp23) == -1 && err == NULL)
398 		err = got_error_from_errno2("unlink", dp23);
399 
400 	free(path1);
401 	free(path2);
402 	free(path3);
403 	free(dp13);
404 	free(dp23);
405 	free(data);
406 	free(patch);
407 
408 	for (i = 0; i < nitems(d3s->fp); i++) {
409 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
410 			err = got_error_from_errno("fclose");
411 	}
412 	if (err == NULL && diffb) {
413 		if (buf_write_fd(diffb, outfd) < 0)
414 			err = got_error_from_errno("buf_write_fd");
415 		*overlapcnt = d3s->overlapcnt;
416 	}
417 	free(d3s);
418 	buf_free(diffb);
419 	return err;
420 }
421 
422 static const struct got_error *
423 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
424     const char *fmark, const char *rmark, struct diff3_state *d3s,
425     const char *label1, const char *label3)
426 {
427 	const struct got_error *err = NULL;
428 	ssize_t m, n;
429 	int i;
430 
431 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
432 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
433 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
434 		return got_error(GOT_ERR_NO_SPACE);
435 
436 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
437 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
438 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
439 		return got_error(GOT_ERR_NO_SPACE);
440 
441 	err = increase(d3s);
442 	if (err)
443 		return err;
444 
445 	err = readin(&m, dp13, &d3s->d13, d3s);
446 	if (err)
447 		return err;
448 	err = readin(&n, dp23, &d3s->d23, d3s);
449 	if (err)
450 		return err;
451 
452 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
453 		return got_error_from_errno2("fopen", path1);
454 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
455 		return got_error_from_errno2("fopen", path2);
456 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
457 		return got_error_from_errno2("fopen", path3);
458 
459 	return merge(m, n, d3s);
460 }
461 
462 static int
463 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
464 {
465 	char op, *ep;
466 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
467 	int start, end, i, lineno;
468 	u_char tmp;
469 
470 	dlp = TAILQ_FIRST(&(dlines->l_lines));
471 	lp = TAILQ_FIRST(&(plines->l_lines));
472 
473 	end = 0;
474 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
475 	    lp = TAILQ_NEXT(lp, l_list)) {
476 		/* Skip blank lines */
477 		if (lp->l_len < 2)
478 			continue;
479 
480 		/* NUL-terminate line buffer for strtol() safety. */
481 		tmp = lp->l_line[lp->l_len - 1];
482 		lp->l_line[lp->l_len - 1] = '\0';
483 
484 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
485 		op = lp->l_line[lp->l_len - 2];
486 		start = (int)strtol(lp->l_line, &ep, 10);
487 
488 		/* Restore the last byte of the buffer */
489 		lp->l_line[lp->l_len - 1] = tmp;
490 
491 		if (op == 'a') {
492 			if (start > dlines->l_nblines ||
493 			    start < 0 || *ep != 'a')
494 				return -1;
495 		} else if (op == 'c') {
496 			if (start > dlines->l_nblines ||
497 			    start < 0 || (*ep != ',' && *ep != 'c'))
498 				return -1;
499 
500 			if (*ep == ',') {
501 				ep++;
502 				end = (int)strtol(ep, &ep, 10);
503 				if (end < 0 || *ep != 'c')
504 					return -1;
505 			} else {
506 				end = start;
507 			}
508 		}
509 
510 
511 		for (;;) {
512 			if (dlp == NULL)
513 				break;
514 			if (dlp->l_lineno == start)
515 				break;
516 			if (dlp->l_lineno > start) {
517 				dlp = TAILQ_PREV(dlp, tqh, l_list);
518 			} else if (dlp->l_lineno < start) {
519 				ndlp = TAILQ_NEXT(dlp, l_list);
520 				if (ndlp->l_lineno > start)
521 					break;
522 				dlp = ndlp;
523 			}
524 		}
525 
526 		if (dlp == NULL)
527 			return -1;
528 
529 
530 		if (op == 'c') {
531 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
532 			for (i = 0; i <= (end - start); i++) {
533 				ndlp = TAILQ_NEXT(dlp, l_list);
534 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
535 				dlp = ndlp;
536 			}
537 			dlp = insert_after;
538 		}
539 
540 		if (op == 'a' || op == 'c') {
541 			for (;;) {
542 				ndlp = lp;
543 				lp = TAILQ_NEXT(lp, l_list);
544 				if (lp == NULL)
545 					return -1;
546 
547 				if (lp->l_len == 2 &&
548 				    lp->l_line[0] == '.' &&
549 				    lp->l_line[1] == '\n')
550 					break;
551 
552 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
553 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
554 				    lp, l_list);
555 				dlp = lp;
556 
557 				lp->l_lineno = start;
558 				lp = ndlp;
559 			}
560 		}
561 
562 		/*
563 		 * always resort lines as the markers might be put at the
564 		 * same line as we first started editing.
565 		 */
566 		lineno = 0;
567 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
568 			sort->l_lineno = lineno++;
569 		dlines->l_nblines = lineno - 1;
570 	}
571 
572 	return (0);
573 }
574 
575 /*
576  * Pick up the line numbers of all changes from one change file.
577  * (This puts the numbers in a vector, which is not strictly necessary,
578  * since the vector is processed in one sequential pass.
579  * The vector could be optimized out of existence)
580  */
581 static const struct got_error *
582 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
583 {
584 	const struct got_error *err = NULL;
585 	FILE *f;
586 	int a, b, c, d;
587 	char kind, *p;
588 	size_t i;
589 
590 	*n = 0;
591 
592 	f = fopen(name, "r");
593 	if (f == NULL)
594 		return got_error_from_errno2("fopen", name);
595 	err = getchange(&p, f, d3s);
596 	if (err)
597 		goto done;
598 	for (i = 0; p; i++) {
599 		if (i >= d3s->szchanges - 1) {
600 			err = increase(d3s);
601 			if (err)
602 				goto done;
603 		}
604 		a = b = number(&p);
605 		if (*p == ',') {
606 			p++;
607 			b = number(&p);
608 		}
609 		kind = *p++;
610 		c = d = number(&p);
611 		if (*p == ',') {
612 			p++;
613 			d = number(&p);
614 		}
615 		if (kind == 'a')
616 			a++;
617 		if (kind == 'd')
618 			c++;
619 		b++;
620 		d++;
621 		(*dd)[i].old.from = a;
622 		(*dd)[i].old.to = b;
623 		(*dd)[i].new.from = c;
624 		(*dd)[i].new.to = d;
625 
626 		err = getchange(&p, f, d3s);
627 		if (err)
628 			goto done;
629 	}
630 
631 	if (i) {
632 		(*dd)[i].old.from = (*dd)[i - 1].old.to;
633 		(*dd)[i].new.from = (*dd)[i - 1].new.to;
634 	}
635 done:
636 	if (fclose(f) != 0 && err == NULL)
637 		err = got_error_from_errno("fclose");
638 	if (err == NULL)
639 		*n = i;
640 	return err;
641 }
642 
643 static int
644 number(char **lc)
645 {
646 	int nn;
647 
648 	nn = 0;
649 	while (isdigit((unsigned char)(**lc)))
650 		nn = nn*10 + *(*lc)++ - '0';
651 
652 	return (nn);
653 }
654 
655 static const struct got_error *
656 getchange(char **line, FILE *b, struct diff3_state *d3s)
657 {
658 	const struct got_error *err = NULL;
659 
660 	*line = NULL;
661 	do {
662 		if (*line && isdigit((unsigned char)(*line)[0]))
663 			return NULL;
664 		err = get_line(line, b, NULL, d3s);
665 		if (err)
666 			return err;
667 	} while (*line);
668 
669 	return NULL;
670 }
671 
672 static const struct got_error *
673 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
674 {
675 	const struct got_error *err = NULL;
676 	char *cp = NULL;
677 	size_t size;
678 	ssize_t len;
679 	char *new;
680 
681 	*ret = NULL;
682 
683 	len = getline(&cp, &size, b);
684 	if (len == -1) {
685 		if (ferror(b))
686 			err = got_error_from_errno("getline");
687 		goto done;
688 	}
689 
690 	if (cp[len - 1] != '\n') {
691 		len++;
692 		if (len + 1 > size) {
693 			new = realloc(cp, len + 1);
694 			if (new == NULL) {
695 				err = got_error_from_errno("realloc");
696 				goto done;
697 			}
698 			cp = new;
699 		}
700 		cp[len - 1] = '\n';
701 		cp[len] = '\0';
702 	}
703 
704 	free(d3s->buf);
705 	*ret = d3s->buf = cp;
706 	cp = NULL;
707 	if (n != NULL)
708 		*n = len;
709 done:
710 	free(cp);
711 	return err;
712 }
713 
714 static const struct got_error *
715 merge(size_t m1, size_t m2, struct diff3_state *d3s)
716 {
717 	const struct got_error *err = NULL;
718 	struct diff *d1, *d2;
719 	int dpl, j, t1, t2;
720 
721 	d1 = d3s->d13;
722 	d2 = d3s->d23;
723 	j = 0;
724 	for (;;) {
725 		t1 = (d1 < d3s->d13 + m1);
726 		t2 = (d2 < d3s->d23 + m2);
727 		if (!t1 && !t2)
728 			break;
729 
730 		/* first file is different from others */
731 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
732 			/* stuff peculiar to 1st file */
733 			d1++;
734 			continue;
735 		}
736 
737 		/* second file is different from others */
738 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
739 			d2++;
740 			continue;
741 		}
742 
743 		/*
744 		 * Merge overlapping changes in first file
745 		 * this happens after extension (see below).
746 		 */
747 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
748 			d1[1].old.from = d1->old.from;
749 			d1[1].new.from = d1->new.from;
750 			d1++;
751 			continue;
752 		}
753 
754 		/* merge overlapping changes in second */
755 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
756 			d2[1].old.from = d2->old.from;
757 			d2[1].new.from = d2->new.from;
758 			d2++;
759 			continue;
760 		}
761 		/* stuff peculiar to third file or different in all */
762 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
763 			err = duplicate(&dpl, j, &d1->old, &d2->old, d3s);
764 			if (err)
765 				return err;
766 
767 			/*
768 			 * dpl = 0 means all files differ
769 			 * dpl = 1 means files 1 and 2 identical
770 			 */
771 			err = edit(d1, dpl, &j, d3s);
772 			if (err)
773 				return err;
774 			d1++;
775 			d2++;
776 			continue;
777 		}
778 
779 		/*
780 		 * Overlapping changes from file 1 and 2; extend changes
781 		 * appropriately to make them coincide.
782 		 */
783 		if (d1->new.from < d2->new.from) {
784 			d2->old.from -= d2->new.from - d1->new.from;
785 			d2->new.from = d1->new.from;
786 		} else if (d2->new.from < d1->new.from) {
787 			d1->old.from -= d1->new.from - d2->new.from;
788 			d1->new.from = d2->new.from;
789 		}
790 		if (d1->new.to > d2->new.to) {
791 			d2->old.to += d1->new.to - d2->new.to;
792 			d2->new.to = d1->new.to;
793 		} else if (d2->new.to > d1->new.to) {
794 			d1->old.to += d2->new.to - d1->new.to;
795 			d1->new.to = d2->new.to;
796 		}
797 	}
798 
799 	return (edscript(j, d3s));
800 }
801 
802 /*
803  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
804  */
805 static const struct got_error *
806 prange(struct line_range *rold, struct diff3_state *d3s)
807 {
808 	const struct got_error *err = NULL;
809 
810 	if (rold->to <= rold->from) {
811 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
812 		if (err)
813 			return err;
814 	} else {
815 		err = diff_output(d3s->diffbuf, "%d", rold->from);
816 		if (err)
817 			return err;
818 		if (rold->to > rold->from + 1) {
819 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
820 			if (err)
821 				return err;
822 		}
823 		err = diff_output(d3s->diffbuf, "c\n");
824 		if (err)
825 			return err;
826 	}
827 
828 	return NULL;
829 }
830 
831 /*
832  * Skip to just before line number from in file "i".
833  * Return the number of bytes skipped in *nskipped.
834  */
835 static const struct got_error *
836 skip(size_t *nskipped, int i, int from, struct diff3_state *d3s)
837 {
838 	const struct got_error *err = NULL;
839 	size_t len, n;
840 	char *line;
841 
842 	*nskipped = 0;
843 	for (n = 0; d3s->cline[i] < from - 1; n += len) {
844 		err = get_line(&line, d3s->fp[i], &len, d3s);
845 		if (err)
846 			return err;
847 		d3s->cline[i]++;
848 	}
849 	*nskipped = n;
850 	return NULL;
851 }
852 
853 /*
854  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
855  * the same data as the new range (in file 2).
856  *
857  * If this change could overlap, remember start/end offsets in file 2 so we
858  * can write out the original lines of text if a merge conflict occurs.
859  */
860 static const struct got_error *
861 duplicate(int *dpl, int j, struct line_range *r1, struct line_range *r2,
862     struct diff3_state *d3s)
863 {
864 	const struct got_error *err = NULL;
865 	int c,d;
866 	int nchar;
867 	int nline;
868 	size_t nskipped;
869 	off_t off;
870 
871 	*dpl = 0;
872 
873 	if (r1->to - r1->from != r2->to - r2->from)
874 		return NULL;
875 
876 	err = skip(&nskipped, 0, r1->from, d3s);
877 	if (err)
878 		return err;
879 	err = skip(&nskipped, 1, r2->from, d3s);
880 	if (err)
881 		return err;
882 
883 	off = ftello(d3s->fp[1]);
884 	if (off == -1)
885 		return got_error_from_errno("ftello");
886 	d3s->de[j + 1].oldo.from = off; /* original lines start here */
887 
888 	nchar = 0;
889 	for (nline = 0; nline < r1->to - r1->from; nline++) {
890 		do {
891 			c = getc(d3s->fp[0]);
892 			if (c == EOF)
893 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
894 			d = getc(d3s->fp[1]);
895 			if (d == EOF)
896 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
897 			nchar++;
898 			if (c != d) {
899 				long orig_line_len = nchar;
900 				while (d != '\n') {
901 					d = getc(d3s->fp[1]);
902 					if (d == EOF)
903 						break;
904 					orig_line_len++;
905 				}
906 				if (orig_line_len > nchar &&
907 				    fseek(d3s->fp[1], -(orig_line_len - nchar),
908 				    SEEK_CUR) == -1)
909 					return got_ferror(d3s->fp[1],
910 						GOT_ERR_IO);
911  				/* original lines end here */
912 				d3s->de[j + 1].oldo.to = off + orig_line_len;
913 				err = repos(nchar, d3s);
914 				if (err)
915 					return err;
916 				return NULL;
917 			}
918 		} while (c != '\n');
919 	}
920 	err = repos(nchar, d3s);
921 	if (err)
922 		return err;
923 	*dpl = 1;
924 	return NULL;
925 }
926 
927 static const struct got_error *
928 repos(int nchar, struct diff3_state *d3s)
929 {
930 	int i;
931 
932 	for (i = 0; i < 2; i++) {
933 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
934 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
935 	}
936 
937 	return NULL;
938 }
939 
940 /*
941  * collect an editing script for later regurgitation
942  */
943 static const struct got_error *
944 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
945 {
946 	const struct got_error *err = NULL;
947 	size_t nskipped;
948 
949 	if (((fdup + 1) & 3) == 0)
950 		return NULL;
951 	(*j)++;
952 	d3s->overlap[*j] = !fdup;
953 	if (!fdup)
954 		d3s->overlapcnt++;
955 	d3s->de[*j].old.from = diff->old.from;
956 	d3s->de[*j].old.to = diff->old.to;
957 
958 	err = skip(&nskipped, 2, diff->new.from, d3s);
959 	if (err)
960 		return err;
961 	d3s->de[*j].newo.from = d3s->de[*j - 1].newo.to + nskipped;
962 
963 	err = skip(&nskipped, 2, diff->new.to, d3s);
964 	if (err)
965 		return err;
966 	d3s->de[*j].newo.to = d3s->de[*j].newo.from + nskipped;
967 	return NULL;
968 }
969 
970 /* regurgitate */
971 static const struct got_error *
972 edscript(int n, struct diff3_state *d3s)
973 {
974 	const struct got_error *err = NULL;
975 	size_t k, len;
976 	char block[BUFSIZ+1];
977 
978 	for (; n > 0; n--) {
979 		if (!d3s->overlap[n]) {
980 			err = prange(&d3s->de[n].old, d3s);
981 			if (err)
982 				return err;
983 		} else if (d3s->de[n].oldo.from < d3s->de[n].oldo.to) {
984 			/* Output a block of 3-way diff base file content. */
985 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
986 			    d3s->de[n].old.to -1,
987 			    GOT_DIFF_CONFLICT_MARKER_ORIG);
988 			if (err)
989 				return err;
990 			if (fseeko(d3s->fp[1], d3s->de[n].oldo.from, SEEK_SET)
991 			    == -1)
992 				return got_error_from_errno("fseeko");
993 			k = (size_t)(d3s->de[n].oldo.to - d3s->de[n].oldo.from);
994 			for (; k > 0; k -= len) {
995 				len = k > BUFSIZ ? BUFSIZ : k;
996 				if (fread(block, 1, len, d3s->fp[1]) != len)
997 					return got_ferror(d3s->fp[1],
998 					    GOT_ERR_IO);
999 				block[len] = '\0';
1000 				err = diff_output(d3s->diffbuf, "%s", block);
1001 				if (err)
1002 					return err;
1003 			}
1004 			err = diff_output(d3s->diffbuf, "%s\n",
1005 			    GOT_DIFF_CONFLICT_MARKER_SEP);
1006 			if (err)
1007 				return err;
1008  		} else {
1009  			err = diff_output(d3s->diffbuf, "%da\n%s\n",
1010 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
1011 			if (err)
1012 				return err;
1013 		}
1014 		if (fseeko(d3s->fp[2], d3s->de[n].newo.from, SEEK_SET)
1015 		    == -1)
1016 			return got_error_from_errno("fseek");
1017 		k = (size_t)(d3s->de[n].newo.to - d3s->de[n].newo.from);
1018 		for (; k > 0; k -= len) {
1019 			len = k > BUFSIZ ? BUFSIZ : k;
1020 			if (fread(block, 1, len, d3s->fp[2]) != len)
1021 				return got_ferror(d3s->fp[2], GOT_ERR_IO);
1022 			block[len] = '\0';
1023 			err = diff_output(d3s->diffbuf, "%s", block);
1024 			if (err)
1025 				return err;
1026 		}
1027 
1028 		if (!d3s->overlap[n]) {
1029 			err = diff_output(d3s->diffbuf, ".\n");
1030 			if (err)
1031 				return err;
1032 		} else {
1033 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
1034 			if (err)
1035 				return err;
1036 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
1037 			    d3s->de[n].old.from - 1, d3s->f1mark);
1038 			if (err)
1039 				return err;
1040 		}
1041 	}
1042 
1043 	return NULL;
1044 }
1045 
1046 static const struct got_error *
1047 increase(struct diff3_state *d3s)
1048 {
1049 	size_t newsz, incr;
1050 	struct diff *d;
1051 	char *s;
1052 
1053 	/* are the memset(3) calls needed? */
1054 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
1055 	incr = newsz - d3s->szchanges;
1056 
1057 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
1058 	if (d == NULL)
1059 		return got_error_from_errno("reallocarray");
1060 	d3s->d13 = d;
1061 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
1062 
1063 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1064 	if (d == NULL)
1065 		return got_error_from_errno("reallocarray");
1066 	d3s->d23 = d;
1067 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1068 
1069 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1070 	if (d == NULL)
1071 		return got_error_from_errno("reallocarray");
1072 	d3s->de = d;
1073 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1074 
1075 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1076 	if (s == NULL)
1077 		return got_error_from_errno("reallocarray");
1078 	d3s->overlap = s;
1079 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1080 	d3s->szchanges = newsz;
1081 
1082 	return NULL;
1083 }