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Date:: Sun Oct 6 18:23:02 2019 UTC
Message:: check for errors from fseek(3) in diff3.c's edscript()
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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 #include "worklist.h"
87 
88 #ifndef nitems
89 #define nitems(_a) (sizeof(_a) / sizeof((_a)[0]))
90 #endif
91 
92 /* diff3 - 3-way differential file comparison */
93 
94 /* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
95  *
96  * d13 = diff report on f1 vs f3
97  * d23 = diff report on f2 vs f3
98  * f1, f2, f3 the 3 files
99  * if changes in f1 overlap with changes in f3, m1 and m3 are used
100  * to mark the overlaps; otherwise, the file names f1 and f3 are used
101  * (only for options E and X).
102  */
103 
104 /*
105  * "from" is first in range of changed lines; "to" is last+1
106  * from=to=line after point of insertion for added lines.
107  */
108 struct range {
109 	int from;
110 	int to;
111 };
112 
113 struct diff {
114 	struct range old;
115 	struct range new;
116 };
117 
118 struct diff3_state {
119 	size_t szchanges;
120 
121 	struct diff *d13;
122 	struct diff *d23;
123 
124 	/*
125 	 * "de" is used to gather editing scripts.  These are later spewed out
126 	 * in reverse order.  Its first element must be all zero, the "new"
127 	 * component of "de" contains line positions or byte positions
128 	 * depending on when you look (!?).  Array overlap indicates which
129 	 * sections in "de" correspond to lines that are different in all
130 	 * three files.
131 	 */
132 	struct diff *de;
133 	char *overlap;
134 	int overlapcnt;
135 	FILE *fp[3];
136 	int cline[3];		/* # of the last-read line in each file (0-2) */
137 
138 	/*
139 	 * the latest known correspondence between line numbers of the 3 files
140 	 * is stored in last[1-3];
141 	 */
142 	int last[4];
143 	int eflag;
144 	int debug;
145 	char f1mark[PATH_MAX], f3mark[PATH_MAX]; /* markers for -E and -X */
146 
147 	char *buf;
148 
149 	BUF *diffbuf;
150 };
151 
152 
153 static const struct got_error *duplicate(int *, struct range *, struct range *,
154     struct diff3_state *);
155 static const struct got_error *edit(struct diff *, int, int *,
156     struct diff3_state *);
157 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
158 static const struct got_error *get_line(char **, FILE *, size_t *,
159     struct diff3_state *);
160 static int number(char **);
161 static const struct got_error *readin(size_t *, char *, struct diff **,
162     struct diff3_state *);
163 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
164 static const struct got_error *skip(int *, int, int, char *,
165     struct diff3_state *);
166 static const struct got_error *edscript(int, struct diff3_state *);
167 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
168 static const struct got_error *change(int, struct range *, int,
169     struct diff3_state *);
170 static const struct got_error *keep(int, struct range *, struct diff3_state *);
171 static const struct got_error *prange(struct range *, struct diff3_state *);
172 static const struct got_error *repos(int, struct diff3_state *);
173 static const struct got_error *separate(const char *, struct diff3_state *);
174 static const struct got_error *increase(struct diff3_state *);
175 static const struct got_error *diff3_internal(char *, char *, char *,
176     char *, char *, const char *, const char *, struct diff3_state *,
177     const char *, const char *);
178 
179 static const struct got_error *
180 diff_output(BUF *diffbuf, const char *fmt, ...)
181 {
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 	buf_append(&newsize, diffbuf, str, strlen(str));
193 	free(str);
194 	return NULL;
195 }
196 
197 static const struct got_error*
198 diffreg(BUF **d, const char *path1, const char *path2)
199 {
200 	const struct got_error *err = NULL;
201 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
202 	char *outpath = NULL;
203 	struct got_diff_state ds;
204 	struct got_diff_args args;
205 	int res;
206 
207 	*d = NULL;
208 
209 	f1 = fopen(path1, "r");
210 	if (f1 == NULL) {
211 		err = got_error_from_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 	*d = buf_load(outpath);
252 	if (*d == NULL)
253 		err = got_error_from_errno("buf_load");
254 done:
255 	if (outpath) {
256 		unlink(outpath);
257 		free(outpath);
258 	}
259 	if (outfile && fclose(outfile) != 0 && err == NULL)
260 		err = got_error_from_errno("fclose");
261 	if (f1 && fclose(f1) != 0 && err == NULL)
262 		err = got_error_from_errno("fclose");
263 	if (f2 && fclose(f2) != 0 && err == NULL)
264 		err = got_error_from_errno("fclose");
265 	return err;
266 }
267 
268 /*
269  * For merge(1).
270  */
271 const struct got_error *
272 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
273     const char *p3, const char *label1, const char *label3)
274 {
275 	const struct got_error *err = NULL;
276 	char *dp13, *dp23, *path1, *path2, *path3;
277 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
278 	u_char *data, *patch;
279 	size_t dlen, plen;
280 	struct wklhead temp_files;
281 	struct diff3_state *d3s;
282 	int i;
283 
284 	*overlapcnt = 0;
285 
286 	SLIST_INIT(&temp_files);
287 
288 	d3s = calloc(1, sizeof(*d3s));
289 	if (d3s == NULL)
290 		return got_error_from_errno("calloc");
291 	d3s->eflag = 3; /* default -E for compatibility with former RCS */
292 
293 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
294 	dp13 = dp23 = path1 = path2 = path3 = NULL;
295 	data = patch = NULL;
296 
297 	if ((b1 = buf_load(p1)) == NULL)
298 		goto out;
299 	if ((b2 = buf_load(p2)) == NULL)
300 		goto out;
301 	if ((b3 = buf_load(p3)) == NULL)
302 		goto out;
303 
304 	diffb = buf_alloc(128);
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, &temp_files);
320 	if (err)
321 		goto out;
322 	err = buf_write_stmp(b2, path2, &temp_files);
323 	if (err)
324 		goto out;
325 	err = buf_write_stmp(b3, path3, &temp_files);
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, &temp_files);
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, &temp_files);
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 	(void)unlink(path1);
390 	(void)unlink(path2);
391 	(void)unlink(path3);
392 	(void)unlink(dp13);
393 	(void)unlink(dp23);
394 
395 	free(path1);
396 	free(path2);
397 	free(path3);
398 	free(dp13);
399 	free(dp23);
400 	free(data);
401 	free(patch);
402 
403 	worklist_clean(&temp_files, worklist_unlink);
404 
405 	for (i = 0; i < nitems(d3s->fp); i++) {
406 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
407 			err = got_error_from_errno("fclose");
408 	}
409 	if (err == NULL && diffb) {
410 		if (buf_write_fd(diffb, outfd) < 0)
411 			err = got_error_from_errno("buf_write_fd");
412 		*overlapcnt = d3s->overlapcnt;
413 	}
414 	free(d3s);
415 	buf_free(diffb);
416 	return err;
417 }
418 
419 static const struct got_error *
420 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
421     const char *fmark, const char *rmark, struct diff3_state *d3s,
422     const char *label1, const char *label3)
423 {
424 	const struct got_error *err = NULL;
425 	ssize_t m, n;
426 	int i;
427 
428 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
429 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
430 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
431 		return got_error(GOT_ERR_NO_SPACE);
432 
433 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
434 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
435 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
436 		return got_error(GOT_ERR_NO_SPACE);
437 
438 	err = increase(d3s);
439 	if (err)
440 		return err;
441 
442 	err = readin(&m, dp13, &d3s->d13, d3s);
443 	if (err)
444 		return err;
445 	err = readin(&n, dp23, &d3s->d23, d3s);
446 	if (err)
447 		return err;
448 
449 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
450 		return got_error_from_errno2("fopen", path1);
451 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
452 		return got_error_from_errno2("fopen", path2);
453 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
454 		return got_error_from_errno2("fopen", path3);
455 
456 	return merge(m, n, d3s);
457 }
458 
459 static int
460 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
461 {
462 	char op, *ep;
463 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
464 	int start, end, i, lineno;
465 	u_char tmp;
466 
467 	dlp = TAILQ_FIRST(&(dlines->l_lines));
468 	lp = TAILQ_FIRST(&(plines->l_lines));
469 
470 	end = 0;
471 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
472 	    lp = TAILQ_NEXT(lp, l_list)) {
473 		/* Skip blank lines */
474 		if (lp->l_len < 2)
475 			continue;
476 
477 		/* NUL-terminate line buffer for strtol() safety. */
478 		tmp = lp->l_line[lp->l_len - 1];
479 		lp->l_line[lp->l_len - 1] = '\0';
480 
481 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
482 		op = lp->l_line[lp->l_len - 2];
483 		start = (int)strtol(lp->l_line, &ep, 10);
484 
485 		/* Restore the last byte of the buffer */
486 		lp->l_line[lp->l_len - 1] = tmp;
487 
488 		if (op == 'a') {
489 			if (start > dlines->l_nblines ||
490 			    start < 0 || *ep != 'a')
491 				return -1;
492 		} else if (op == 'c') {
493 			if (start > dlines->l_nblines ||
494 			    start < 0 || (*ep != ',' && *ep != 'c'))
495 				return -1;
496 
497 			if (*ep == ',') {
498 				ep++;
499 				end = (int)strtol(ep, &ep, 10);
500 				if (end < 0 || *ep != 'c')
501 					return -1;
502 			} else {
503 				end = start;
504 			}
505 		}
506 
507 
508 		for (;;) {
509 			if (dlp == NULL)
510 				break;
511 			if (dlp->l_lineno == start)
512 				break;
513 			if (dlp->l_lineno > start) {
514 				dlp = TAILQ_PREV(dlp, tqh, l_list);
515 			} else if (dlp->l_lineno < start) {
516 				ndlp = TAILQ_NEXT(dlp, l_list);
517 				if (ndlp->l_lineno > start)
518 					break;
519 				dlp = ndlp;
520 			}
521 		}
522 
523 		if (dlp == NULL)
524 			return -1;
525 
526 
527 		if (op == 'c') {
528 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
529 			for (i = 0; i <= (end - start); i++) {
530 				ndlp = TAILQ_NEXT(dlp, l_list);
531 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
532 				dlp = ndlp;
533 			}
534 			dlp = insert_after;
535 		}
536 
537 		if (op == 'a' || op == 'c') {
538 			for (;;) {
539 				ndlp = lp;
540 				lp = TAILQ_NEXT(lp, l_list);
541 				if (lp == NULL)
542 					return -1;
543 
544 				if (lp->l_len == 2 &&
545 				    lp->l_line[0] == '.' &&
546 				    lp->l_line[1] == '\n')
547 					break;
548 
549 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
550 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
551 				    lp, l_list);
552 				dlp = lp;
553 
554 				lp->l_lineno = start;
555 				lp = ndlp;
556 			}
557 		}
558 
559 		/*
560 		 * always resort lines as the markers might be put at the
561 		 * same line as we first started editing.
562 		 */
563 		lineno = 0;
564 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
565 			sort->l_lineno = lineno++;
566 		dlines->l_nblines = lineno - 1;
567 	}
568 
569 	return (0);
570 }
571 
572 /*
573  * Pick up the line numbers of all changes from one change file.
574  * (This puts the numbers in a vector, which is not strictly necessary,
575  * since the vector is processed in one sequential pass.
576  * The vector could be optimized out of existence)
577  */
578 static const struct got_error *
579 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
580 {
581 	const struct got_error *err = NULL;
582 	int a, b, c, d;
583 	char kind, *p;
584 	size_t i;
585 
586 	*n = 0;
587 
588 	d3s->fp[0] = fopen(name, "r");
589 	if (d3s->fp[0] == NULL)
590 		return got_error_from_errno2("fopen", name);
591 	err = getchange(&p, d3s->fp[0], d3s);
592 	if (err)
593 		return err;
594 	for (i = 0; p; i++) {
595 		if (i >= d3s->szchanges - 1) {
596 			err = increase(d3s);
597 			if (err)
598 				return err;
599 		}
600 		a = b = number(&p);
601 		if (*p == ',') {
602 			p++;
603 			b = number(&p);
604 		}
605 		kind = *p++;
606 		c = d = number(&p);
607 		if (*p==',') {
608 			p++;
609 			d = number(&p);
610 		}
611 		if (kind == 'a')
612 			a++;
613 		if (kind == 'd')
614 			c++;
615 		b++;
616 		d++;
617 		(*dd)[i].old.from = a;
618 		(*dd)[i].old.to = b;
619 		(*dd)[i].new.from = c;
620 		(*dd)[i].new.to = d;
621 
622 		err = getchange(&p, d3s->fp[0], d3s);
623 		if (err)
624 			return err;
625 	}
626 
627 	if (i) {
628 		(*dd)[i].old.from = (*dd)[i-1].old.to;
629 		(*dd)[i].new.from = (*dd)[i-1].new.to;
630 	}
631 
632 	if (fclose(d3s->fp[0]) != 0)
633 		err = got_error_from_errno("fclose");
634 
635 	*n = i;
636 	return err;
637 }
638 
639 static int
640 number(char **lc)
641 {
642 	int nn;
643 
644 	nn = 0;
645 	while (isdigit((unsigned char)(**lc)))
646 		nn = nn*10 + *(*lc)++ - '0';
647 
648 	return (nn);
649 }
650 
651 static const struct got_error *
652 getchange(char **line, FILE *b, struct diff3_state *d3s)
653 {
654 	const struct got_error *err = NULL;
655 
656 	*line = NULL;
657 	do {
658 		if (*line && isdigit((unsigned char)(*line)[0]))
659 			return NULL;
660 		err = get_line(line, b, NULL, d3s);
661 		if (err)
662 			return err;
663 	} while (*line);
664 
665 	return NULL;
666 }
667 
668 static const struct got_error *
669 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
670 {
671 	const struct got_error *err = NULL;
672 	char *cp = NULL;
673 	size_t size;
674 	ssize_t len;
675 	char *new;
676 
677 	*ret = NULL;
678 
679 	len = getline(&cp, &size, b);
680 	if (len == -1) {
681 		if (ferror(b))
682 			err = got_error_from_errno("getline");
683 		goto done;
684 	}
685 
686 	if (cp[len - 1] != '\n') {
687 		len++;
688 		if (len + 1 > size) {
689 			new = realloc(cp, len + 1);
690 			if (new == NULL) {
691 				err = got_error_from_errno("realloc");
692 				goto done;
693 			}
694 			cp = new;
695 		}
696 		cp[len - 1] = '\n';
697 		cp[len] = '\0';
698 	}
699 
700 	free(d3s->buf);
701 	*ret = d3s->buf = cp;
702 	cp = NULL;
703 	if (n != NULL)
704 		*n = len;
705 done:
706 	free(cp);
707 	return err;
708 }
709 
710 static const struct got_error *
711 merge(size_t m1, size_t m2, struct diff3_state *d3s)
712 {
713 	const struct got_error *err = NULL;
714 	struct diff *d1, *d2, *d3;
715 	int dpl, j, t1, t2;
716 
717 	d1 = d3s->d13;
718 	d2 = d3s->d23;
719 	j = 0;
720 	for (;;) {
721 		t1 = (d1 < d3s->d13 + m1);
722 		t2 = (d2 < d3s->d23 + m2);
723 		if (!t1 && !t2)
724 			break;
725 
726 		if (d3s->debug) {
727 			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
728 			d1->old.from, d1->old.to,
729 			d1->new.from, d1->new.to,
730 			d2->old.from, d2->old.to,
731 			d2->new.from, d2->new.to);
732 		}
733 
734 		/* first file is different from others */
735 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
736 			/* stuff peculiar to 1st file */
737 			if (d3s->eflag == 0) {
738 				err = separate("1", d3s);
739 				if (err)
740 					return err;
741 				err = change(1, &d1->old, 0, d3s);
742 				if (err)
743 					return err;
744 				err = keep(2, &d1->new, d3s);
745 				if (err)
746 					return err;
747 				err = change(3, &d1->new, 0, d3s);
748 				if (err)
749 					return err;
750 			}
751 			d1++;
752 			continue;
753 		}
754 
755 		/* second file is different from others */
756 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
757 			if (d3s->eflag == 0) {
758 				err = separate("2", d3s);
759 				if (err)
760 					return err;
761 				err = keep(1, &d2->new, d3s);
762 				if (err)
763 					return err;
764 				err = change(2, &d2->old, 0, d3s);
765 				if (err)
766 					return err;
767 				err = change(3, &d2->new, 0, d3s);
768 				if (err)
769 					return err;
770 			}
771 			d2++;
772 			continue;
773 		}
774 
775 		/*
776 		 * Merge overlapping changes in first file
777 		 * this happens after extension (see below).
778 		 */
779 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
780 			d1[1].old.from = d1->old.from;
781 			d1[1].new.from = d1->new.from;
782 			d1++;
783 			continue;
784 		}
785 
786 		/* merge overlapping changes in second */
787 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
788 			d2[1].old.from = d2->old.from;
789 			d2[1].new.from = d2->new.from;
790 			d2++;
791 			continue;
792 		}
793 		/* stuff peculiar to third file or different in all */
794 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
795 			err = duplicate(&dpl, &d1->old, &d2->old, d3s);
796 			if (err)
797 				return err;
798 
799 			/*
800 			 * dpl = 0 means all files differ
801 			 * dpl = 1 means files 1 and 2 identical
802 			 */
803 			if (d3s->eflag == 0) {
804 				err = separate(dpl ? "3" : "", d3s);
805 				if (err)
806 					return err;
807 				err = change(1, &d1->old, dpl, d3s);
808 				if (err)
809 					return err;
810 				err = change(2, &d2->old, 0, d3s);
811 				if (err)
812 					return err;
813 				d3 = d1->old.to > d1->old.from ? d1 : d2;
814 				err = change(3, &d3->new, 0, d3s);
815 				if (err)
816 					return err;
817 			} else {
818 				err = edit(d1, dpl, &j, d3s);
819 				if (err)
820 					return err;
821 			}
822 			d1++;
823 			d2++;
824 			continue;
825 		}
826 
827 		/*
828 		 * Overlapping changes from file 1 and 2; extend changes
829 		 * appropriately to make them coincide.
830 		 */
831 		if (d1->new.from < d2->new.from) {
832 			d2->old.from -= d2->new.from-d1->new.from;
833 			d2->new.from = d1->new.from;
834 		} else if (d2->new.from < d1->new.from) {
835 			d1->old.from -= d1->new.from-d2->new.from;
836 			d1->new.from = d2->new.from;
837 		}
838 		if (d1->new.to > d2->new.to) {
839 			d2->old.to += d1->new.to - d2->new.to;
840 			d2->new.to = d1->new.to;
841 		} else if (d2->new.to > d1->new.to) {
842 			d1->old.to += d2->new.to - d1->new.to;
843 			d1->new.to = d2->new.to;
844 		}
845 	}
846 
847 	return (edscript(j, d3s));
848 }
849 
850 static const struct got_error *
851 separate(const char *s, struct diff3_state *d3s)
852 {
853 	return diff_output(d3s->diffbuf, "====%s\n", s);
854 }
855 
856 /*
857  * The range of lines rold.from thru rold.to in file i is to be changed.
858  * It is to be printed only if it does not duplicate something to be
859  * printed later.
860  */
861 static const struct got_error *
862 change(int i, struct range *rold, int fdup, struct diff3_state *d3s)
863 {
864 	const struct got_error *err = NULL;
865 	int nskipped;
866 
867 	err = diff_output(d3s->diffbuf, "%d:", i);
868 	if (err)
869 		return err;
870 	d3s->last[i] = rold->to;
871 	err = prange(rold, d3s);
872 	if (err)
873 		return err;
874 	if (fdup || d3s->debug)
875 		return NULL;
876 	i--;
877 	err = skip(&nskipped, i, rold->from, NULL, d3s);
878 	if (err)
879 		return err;
880 	return skip(&nskipped, i, rold->to, "  ", d3s);
881 }
882 
883 /*
884  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
885  */
886 static const struct got_error *
887 prange(struct range *rold, struct diff3_state *d3s)
888 {
889 	const struct got_error *err = NULL;
890 
891 	if (rold->to <= rold->from) {
892 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
893 		if (err)
894 			return err;
895 	} else {
896 		err = diff_output(d3s->diffbuf, "%d", rold->from);
897 		if (err)
898 			return err;
899 		if (rold->to > rold->from + 1) {
900 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
901 			if (err)
902 				return err;
903 		}
904 		err = diff_output(d3s->diffbuf, "c\n");
905 		if (err)
906 			return err;
907 	}
908 
909 	return NULL;
910 }
911 
912 /*
913  * No difference was reported by diff between file 1 (or 2) and file 3,
914  * and an artificial dummy difference (trange) must be ginned up to
915  * correspond to the change reported in the other file.
916  */
917 static const struct got_error *
918 keep(int i, struct range *rnew, struct diff3_state *d3s)
919 {
920 	int delta;
921 	struct range trange;
922 
923 	delta = d3s->last[3] - d3s->last[i];
924 	trange.from = rnew->from - delta;
925 	trange.to = rnew->to - delta;
926 	return change(i, &trange, 1, d3s);
927 }
928 
929 /*
930  * skip to just before line number from in file "i".  If "pr" is non-NULL,
931  * print all skipped stuff with string pr as a prefix.
932  */
933 static const struct got_error *
934 skip(int *nskipped, int i, int from, char *pr, struct diff3_state *d3s)
935 {
936 	const struct got_error *err = NULL;
937 	size_t j, n;
938 	char *line;
939 
940 	*nskipped = 0;
941 	for (n = 0; d3s->cline[i] < from - 1; n += j) {
942 		err = get_line(&line, d3s->fp[i], &j, d3s);
943 		if (err)
944 			return err;
945 		if (pr != NULL) {
946 			err = diff_output(d3s->diffbuf, "%s%s", pr, line);
947 			if (err)
948 				return err;
949 		}
950 		d3s->cline[i]++;
951 	}
952 	*nskipped = n;
953 	return NULL;
954 }
955 
956 /*
957  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
958  * the same data as the new range (in file 2).
959  */
960 static const struct got_error *
961 duplicate(int *dpl, struct range *r1, struct range *r2, struct diff3_state *d3s)
962 {
963 	const struct got_error *err = NULL;
964 	int c,d;
965 	int nchar;
966 	int nline, nskipped;
967 
968 	*dpl = 0;
969 
970 	if (r1->to-r1->from != r2->to-r2->from)
971 		return NULL;
972 
973 	err = skip(&nskipped, 0, r1->from, NULL, d3s);
974 	if (err)
975 		return err;
976 	err = skip(&nskipped, 1, r2->from, NULL, d3s);
977 	if (err)
978 		return err;
979 	nchar = 0;
980 	for (nline=0; nline < r1->to - r1->from; nline++) {
981 		do {
982 			c = getc(d3s->fp[0]);
983 			if (c == EOF)
984 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
985 			d = getc(d3s->fp[1]);
986 			if (d == EOF)
987 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
988 			nchar++;
989 			if (c != d)
990 				return repos(nchar, d3s);
991 		} while (c != '\n');
992 	}
993 	err = repos(nchar, d3s);
994 	if (err)
995 		return err;
996 	*dpl = 1;
997 	return NULL;
998 }
999 
1000 static const struct got_error *
1001 repos(int nchar, struct diff3_state *d3s)
1002 {
1003 	int i;
1004 
1005 	for (i = 0; i < 2; i++) {
1006 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
1007 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
1008 	}
1009 
1010 	return NULL;
1011 }
1012 
1013 /*
1014  * collect an editing script for later regurgitation
1015  */
1016 static const struct got_error *
1017 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
1018 {
1019 	const struct got_error *err = NULL;
1020 	int nskipped;
1021 
1022 	if (((fdup + 1) & d3s->eflag) == 0)
1023 		return NULL;
1024 	(*j)++;
1025 	d3s->overlap[*j] = !fdup;
1026 	if (!fdup)
1027 		d3s->overlapcnt++;
1028 	d3s->de[*j].old.from = diff->old.from;
1029 	d3s->de[*j].old.to = diff->old.to;
1030 	err = skip(&nskipped, 2, diff->new.from, NULL, d3s);
1031 	if (err)
1032 		return err;
1033 	d3s->de[*j].new.from = d3s->de[*j - 1].new.to +  nskipped;
1034 	err = skip(&nskipped, 2, diff->new.to, NULL, d3s);
1035 	d3s->de[*j].new.to = d3s->de[*j].new.from +  nskipped;
1036 	return NULL;
1037 }
1038 
1039 /* regurgitate */
1040 static const struct got_error *
1041 edscript(int n, struct diff3_state *d3s)
1042 {
1043 	const struct got_error *err = NULL;
1044 	int j, k;
1045 	char block[BUFSIZ+1];
1046 
1047 	for (; n > 0; n--) {
1048 		if (!d3s->overlap[n]) {
1049 			err = prange(&d3s->de[n].old, d3s);
1050 			if (err)
1051 				return err;
1052 		} else {
1053 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
1054 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
1055 			if (err)
1056 				return err;
1057 		}
1058 		if (fseek(d3s->fp[2], (long)d3s->de[n].new.from, SEEK_SET)
1059 		    == -1)
1060 			return got_error_from_errno("fseek");
1061 		k = d3s->de[n].new.to - d3s->de[n].new.from;
1062 		for (; k > 0; k-= j) {
1063 			j = k > BUFSIZ ? BUFSIZ : k;
1064 			if (fread(block, 1, j, d3s->fp[2]) != (size_t)j)
1065 				return got_ferror(d3s->fp[2], GOT_ERR_IO);
1066 			block[j] = '\0';
1067 			err = diff_output(d3s->diffbuf, "%s", block);
1068 			if (err)
1069 				return err;
1070 		}
1071 
1072 		if (!d3s->overlap[n]) {
1073 			err = diff_output(d3s->diffbuf, ".\n");
1074 			if (err)
1075 				return err;
1076 		} else {
1077 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
1078 			if (err)
1079 				return err;
1080 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
1081 			    d3s->de[n].old.from - 1, d3s->f1mark);
1082 			if (err)
1083 				return err;
1084 		}
1085 	}
1086 
1087 	return NULL;
1088 }
1089 
1090 static const struct got_error *
1091 increase(struct diff3_state *d3s)
1092 {
1093 	size_t newsz, incr;
1094 	struct diff *d;
1095 	char *s;
1096 
1097 	/* are the memset(3) calls needed? */
1098 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
1099 	incr = newsz - d3s->szchanges;
1100 
1101 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
1102 	if (d == NULL)
1103 		return got_error_from_errno("reallocarray");
1104 	d3s->d13 = d;
1105 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
1106 
1107 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1108 	if (d == NULL)
1109 		return got_error_from_errno("reallocarray");
1110 	d3s->d23 = d;
1111 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1112 
1113 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1114 	if (d == NULL)
1115 		return got_error_from_errno("reallocarray");
1116 	d3s->de = d;
1117 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1118 
1119 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1120 	if (s == NULL)
1121 		return got_error_from_errno("reallocarray");
1122 	d3s->overlap = s;
1123 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1124 	d3s->szchanges = newsz;
1125 
1126 	return NULL;
1127 }