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Date:: Mon Sep 23 08:34:00 2019 UTC
Message:: Replace fgetln() with getline() getline() is, per the latter's OpenBSD man page, safer and more portable than fgetln().
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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 oflag;
145 	int debug;
146 	char f1mark[PATH_MAX], f3mark[PATH_MAX]; /* markers for -E and -X */
147 
148 	char *buf;
149 
150 	BUF *diffbuf;
151 };
152 
153 
154 static int duplicate(struct range *, struct range *, struct diff3_state *);
155 static int edit(struct diff *, int, int, struct diff3_state *);
156 static char *getchange(FILE *, struct diff3_state *);
157 static char *get_line(FILE *, size_t *, struct diff3_state *);
158 static int number(char **);
159 static const struct got_error *readin(size_t *, char *, struct diff **,
160     struct diff3_state *);
161 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
162 static int skip(int, int, char *, struct diff3_state *);
163 static int edscript(int, struct diff3_state *);
164 static int merge(size_t, size_t, struct diff3_state *);
165 static void change(int, struct range *, int, struct diff3_state *);
166 static void keep(int, struct range *, struct diff3_state *);
167 static void prange(struct range *, struct diff3_state *);
168 static void repos(int, struct diff3_state *);
169 static void separate(const char *, struct diff3_state *);
170 static const struct got_error *increase(struct diff3_state *);
171 static const struct got_error *diff3_internal(char *, char *, char *,
172     char *, char *, const char *, const char *, struct diff3_state *,
173     const char *, const char *);
174 
175 static const struct got_error *
176 diff_output(BUF *diffbuf, const char *fmt, ...)
177 {
178 	va_list vap;
179 	int i;
180 	char *str;
181 	size_t newsize;
182 
183 	va_start(vap, fmt);
184 	i = vasprintf(&str, fmt, vap);
185 	va_end(vap);
186 	if (i == -1)
187 		return got_error_from_errno("vasprintf");
188 	buf_append(&newsize, diffbuf, str, strlen(str));
189 	free(str);
190 	return NULL;
191 }
192 
193 static const struct got_error*
194 diffreg(BUF **d, const char *path1, const char *path2)
195 {
196 	const struct got_error *err = NULL;
197 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
198 	char *outpath = NULL;
199 	struct got_diff_state ds;
200 	struct got_diff_args args;
201 	int res;
202 
203 	*d = NULL;
204 
205 	f1 = fopen(path1, "r");
206 	if (f1 == NULL) {
207 		err = got_error_from_errno2("fopen", path1);
208 		goto done;
209 	}
210 	f2 = fopen(path2, "r");
211 	if (f1 == NULL) {
212 		err = got_error_from_errno2("fopen", path2);
213 		goto done;
214 	}
215 
216 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diffreg");
217 	if (err)
218 		goto done;
219 
220 	memset(&ds, 0, sizeof(ds));
221 	/* XXX should stat buffers be passed in args instead of ds? */
222 	if (stat(path1, &ds.stb1) == -1) {
223 		err = got_error_from_errno2("stat", path1);
224 		goto done;
225 	}
226 	if (stat(path2, &ds.stb2) == -1) {
227 		err = got_error_from_errno2("stat", path2);
228 		goto done;
229 	}
230 
231 	memset(&args, 0, sizeof(args));
232 	args.diff_format = D_NORMAL;
233 	args.label[0] = "";
234 	args.label[1] = "";
235 	args.diff_context = 0;
236 
237 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
238 	    outfile, NULL);
239 	if (err)
240 		goto done;
241 
242 	if (fflush(outfile) != 0) {
243 		err = got_error_from_errno2("fflush", outpath);
244 		goto done;
245 	}
246 
247 	*d = buf_load(outpath);
248 	if (*d == NULL)
249 		err = got_error_from_errno("buf_load");
250 done:
251 	if (outpath) {
252 		unlink(outpath);
253 		free(outpath);
254 	}
255 	if (outfile && fclose(outfile) != 0 && err == NULL)
256 		err = got_error_from_errno("fclose");
257 	if (f1 && fclose(f1) != 0 && err == NULL)
258 		err = got_error_from_errno("fclose");
259 	if (f2 && fclose(f2) != 0 && err == NULL)
260 		err = got_error_from_errno("fclose");
261 	return err;
262 }
263 
264 /*
265  * For merge(1).
266  */
267 const struct got_error *
268 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
269     const char *p3, const char *label1, const char *label3)
270 {
271 	const struct got_error *err = NULL;
272 	char *dp13, *dp23, *path1, *path2, *path3;
273 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
274 	u_char *data, *patch;
275 	size_t dlen, plen;
276 	struct wklhead temp_files;
277 	struct diff3_state *d3s;
278 	int i;
279 
280 	*overlapcnt = 0;
281 
282 	SLIST_INIT(&temp_files);
283 
284 	d3s = calloc(1, sizeof(*d3s));
285 	if (d3s == NULL)
286 		return got_error_from_errno("calloc");
287 	d3s->eflag = 3; /* default -E for compatibility with former RCS */
288 	d3s->oflag = 1; /* default -E for compatibility with former RCS */
289 
290 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
291 	dp13 = dp23 = path1 = path2 = path3 = NULL;
292 	data = patch = NULL;
293 
294 	if ((b1 = buf_load(p1)) == NULL)
295 		goto out;
296 	if ((b2 = buf_load(p2)) == NULL)
297 		goto out;
298 	if ((b3 = buf_load(p3)) == NULL)
299 		goto out;
300 
301 	diffb = buf_alloc(128);
302 
303 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
304 		err = got_error_from_errno("asprintf");
305 		goto out;
306 	}
307 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
308 		err = got_error_from_errno("asprintf");
309 		goto out;
310 	}
311 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
312 		err = got_error_from_errno("asprintf");
313 		goto out;
314 	}
315 
316 	err = buf_write_stmp(b1, path1, &temp_files);
317 	if (err)
318 		goto out;
319 	err = buf_write_stmp(b2, path2, &temp_files);
320 	if (err)
321 		goto out;
322 	err = buf_write_stmp(b3, path3, &temp_files);
323 	if (err)
324 		goto out;
325 
326 	buf_free(b2);
327 	b2 = NULL;
328 
329 	err = diffreg(&d1, path1, path3);
330 	if (err) {
331 		buf_free(diffb);
332 		diffb = NULL;
333 		goto out;
334 
335 	}
336 	err = diffreg(&d2, path2, path3);
337 	if (err) {
338 		buf_free(diffb);
339 		diffb = NULL;
340 		goto out;
341 	}
342 
343 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
344 		err = got_error_from_errno("asprintf");
345 		goto out;
346 	}
347 	err = buf_write_stmp(d1, dp13, &temp_files);
348 	if (err)
349 		goto out;
350 
351 	buf_free(d1);
352 	d1 = NULL;
353 
354 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
355 		err = got_error_from_errno("asprintf");
356 		goto out;
357 	}
358 	err = buf_write_stmp(d2, dp23, &temp_files);
359 	if (err)
360 		goto out;
361 
362 	buf_free(d2);
363 	d2 = NULL;
364 
365 	d3s->diffbuf = diffb;
366 	err = diff3_internal(dp13, dp23, path1, path2, path3,
367 	    label1, label3, d3s, label1, label3);
368 	if (err) {
369 		buf_free(diffb);
370 		diffb = NULL;
371 		goto out;
372 	}
373 
374 	plen = buf_len(diffb);
375 	patch = buf_release(diffb);
376 	dlen = buf_len(b1);
377 	data = buf_release(b1);
378 
379 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
380 out:
381 	buf_free(b2);
382 	buf_free(b3);
383 	buf_free(d1);
384 	buf_free(d2);
385 
386 	(void)unlink(path1);
387 	(void)unlink(path2);
388 	(void)unlink(path3);
389 	(void)unlink(dp13);
390 	(void)unlink(dp23);
391 
392 	free(path1);
393 	free(path2);
394 	free(path3);
395 	free(dp13);
396 	free(dp23);
397 	free(data);
398 	free(patch);
399 
400 	worklist_clean(&temp_files, worklist_unlink);
401 
402 	for (i = 0; i < nitems(d3s->fp); i++) {
403 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
404 			err = got_error_from_errno("fclose");
405 	}
406 	if (err == NULL && diffb) {
407 		if (buf_write_fd(diffb, outfd) < 0)
408 			err = got_error_from_errno("buf_write_fd");
409 		*overlapcnt = d3s->overlapcnt;
410 	}
411 	free(d3s);
412 	buf_free(diffb);
413 	return err;
414 }
415 
416 static const struct got_error *
417 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
418     const char *fmark, const char *rmark, struct diff3_state *d3s,
419     const char *label1, const char *label3)
420 {
421 	const struct got_error *err = NULL;
422 	ssize_t m, n;
423 	int i;
424 
425 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
426 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
427 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
428 		return got_error(GOT_ERR_NO_SPACE);
429 
430 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
431 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
432 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
433 		return got_error(GOT_ERR_NO_SPACE);
434 
435 	err = increase(d3s);
436 	if (err)
437 		return err;
438 
439 	err = readin(&m, dp13, &d3s->d13, d3s);
440 	if (err)
441 		return err;
442 	err = readin(&n, dp23, &d3s->d23, d3s);
443 	if (err)
444 		return err;
445 
446 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
447 		return got_error_from_errno2("fopen", path1);
448 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
449 		return got_error_from_errno2("fopen", path2);
450 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
451 		return got_error_from_errno2("fopen", path3);
452 
453 	if (merge(m, n, d3s) < 0)
454 		return got_error_from_errno("merge");
455 	return NULL;
456 }
457 
458 static int
459 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
460 {
461 	char op, *ep;
462 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
463 	int start, end, i, lineno;
464 	u_char tmp;
465 
466 	dlp = TAILQ_FIRST(&(dlines->l_lines));
467 	lp = TAILQ_FIRST(&(plines->l_lines));
468 
469 	end = 0;
470 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
471 	    lp = TAILQ_NEXT(lp, l_list)) {
472 		/* Skip blank lines */
473 		if (lp->l_len < 2)
474 			continue;
475 
476 		/* NUL-terminate line buffer for strtol() safety. */
477 		tmp = lp->l_line[lp->l_len - 1];
478 		lp->l_line[lp->l_len - 1] = '\0';
479 
480 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
481 		op = lp->l_line[lp->l_len - 2];
482 		start = (int)strtol(lp->l_line, &ep, 10);
483 
484 		/* Restore the last byte of the buffer */
485 		lp->l_line[lp->l_len - 1] = tmp;
486 
487 		if (op == 'a') {
488 			if (start > dlines->l_nblines ||
489 			    start < 0 || *ep != 'a')
490 				return -1;
491 		} else if (op == 'c') {
492 			if (start > dlines->l_nblines ||
493 			    start < 0 || (*ep != ',' && *ep != 'c'))
494 				return -1;
495 
496 			if (*ep == ',') {
497 				ep++;
498 				end = (int)strtol(ep, &ep, 10);
499 				if (end < 0 || *ep != 'c')
500 					return -1;
501 			} else {
502 				end = start;
503 			}
504 		}
505 
506 
507 		for (;;) {
508 			if (dlp == NULL)
509 				break;
510 			if (dlp->l_lineno == start)
511 				break;
512 			if (dlp->l_lineno > start) {
513 				dlp = TAILQ_PREV(dlp, tqh, l_list);
514 			} else if (dlp->l_lineno < start) {
515 				ndlp = TAILQ_NEXT(dlp, l_list);
516 				if (ndlp->l_lineno > start)
517 					break;
518 				dlp = ndlp;
519 			}
520 		}
521 
522 		if (dlp == NULL)
523 			return -1;
524 
525 
526 		if (op == 'c') {
527 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
528 			for (i = 0; i <= (end - start); i++) {
529 				ndlp = TAILQ_NEXT(dlp, l_list);
530 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
531 				dlp = ndlp;
532 			}
533 			dlp = insert_after;
534 		}
535 
536 		if (op == 'a' || op == 'c') {
537 			for (;;) {
538 				ndlp = lp;
539 				lp = TAILQ_NEXT(lp, l_list);
540 				if (lp == NULL)
541 					return -1;
542 
543 				if (lp->l_len == 2 &&
544 				    lp->l_line[0] == '.' &&
545 				    lp->l_line[1] == '\n')
546 					break;
547 
548 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
549 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
550 				    lp, l_list);
551 				dlp = lp;
552 
553 				lp->l_lineno = start;
554 				lp = ndlp;
555 			}
556 		}
557 
558 		/*
559 		 * always resort lines as the markers might be put at the
560 		 * same line as we first started editing.
561 		 */
562 		lineno = 0;
563 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
564 			sort->l_lineno = lineno++;
565 		dlines->l_nblines = lineno - 1;
566 	}
567 
568 	return (0);
569 }
570 
571 /*
572  * Pick up the line numbers of all changes from one change file.
573  * (This puts the numbers in a vector, which is not strictly necessary,
574  * since the vector is processed in one sequential pass.
575  * The vector could be optimized out of existence)
576  */
577 static const struct got_error *
578 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
579 {
580 	const struct got_error *err = NULL;
581 	int a, b, c, d;
582 	char kind, *p;
583 	size_t i;
584 
585 	*n = 0;
586 
587 	d3s->fp[0] = fopen(name, "r");
588 	if (d3s->fp[0] == NULL)
589 		return got_error_from_errno2("fopen", name);
590 	for (i = 0; (p = getchange(d3s->fp[0], d3s)); i++) {
591 		if (i >= d3s->szchanges - 1) {
592 			err = increase(d3s);
593 			if (err)
594 				return err;
595 		}
596 		a = b = number(&p);
597 		if (*p == ',') {
598 			p++;
599 			b = number(&p);
600 		}
601 		kind = *p++;
602 		c = d = number(&p);
603 		if (*p==',') {
604 			p++;
605 			d = number(&p);
606 		}
607 		if (kind == 'a')
608 			a++;
609 		if (kind == 'd')
610 			c++;
611 		b++;
612 		d++;
613 		(*dd)[i].old.from = a;
614 		(*dd)[i].old.to = b;
615 		(*dd)[i].new.from = c;
616 		(*dd)[i].new.to = d;
617 	}
618 
619 	if (i) {
620 		(*dd)[i].old.from = (*dd)[i-1].old.to;
621 		(*dd)[i].new.from = (*dd)[i-1].new.to;
622 	}
623 
624 	if (fclose(d3s->fp[0]) != 0)
625 		err = got_error_from_errno("fclose");
626 
627 	*n = i;
628 	return err;
629 }
630 
631 static int
632 number(char **lc)
633 {
634 	int nn;
635 
636 	nn = 0;
637 	while (isdigit((unsigned char)(**lc)))
638 		nn = nn*10 + *(*lc)++ - '0';
639 
640 	return (nn);
641 }
642 
643 static char *
644 getchange(FILE *b, struct diff3_state *d3s)
645 {
646 	char *line;
647 
648 	while ((line = get_line(b, NULL, d3s))) {
649 		if (isdigit((unsigned char)line[0]))
650 			return (line);
651 	}
652 
653 	return (NULL);
654 }
655 
656 static char *
657 get_line(FILE *b, size_t *n, struct diff3_state *d3s)
658 {
659 	char *cp = NULL;
660 	size_t size, len;
661 	char *new;
662 	char *ret = NULL;
663 
664 	len = getline(&cp, &size, b);
665 	if (len == -1)
666 		goto done;
667 
668 	if (cp[len - 1] != '\n') {
669 		len++;
670 		if (len + 1 > size) {
671 			new = realloc(cp, len + 1);
672 			if (new == NULL)
673 				goto done;
674 			cp = new;
675 		}
676 		cp[len - 1] = '\n';
677 		cp[len] = '\0';
678 	}
679 
680 	free(d3s->buf);
681 	ret = d3s->buf = cp;
682 	cp = NULL;
683 	if (n != NULL)
684 		*n = len;
685 done:
686 	free(cp);
687 	return (ret);
688 }
689 
690 static int
691 merge(size_t m1, size_t m2, struct diff3_state *d3s)
692 {
693 	struct diff *d1, *d2, *d3;
694 	int dpl, j, t1, t2;
695 
696 	d1 = d3s->d13;
697 	d2 = d3s->d23;
698 	j = 0;
699 	for (;;) {
700 		t1 = (d1 < d3s->d13 + m1);
701 		t2 = (d2 < d3s->d23 + m2);
702 		if (!t1 && !t2)
703 			break;
704 
705 		if (d3s->debug) {
706 			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
707 			d1->old.from, d1->old.to,
708 			d1->new.from, d1->new.to,
709 			d2->old.from, d2->old.to,
710 			d2->new.from, d2->new.to);
711 		}
712 
713 		/* first file is different from others */
714 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
715 			/* stuff peculiar to 1st file */
716 			if (d3s->eflag == 0) {
717 				separate("1", d3s);
718 				change(1, &d1->old, 0, d3s);
719 				keep(2, &d1->new, d3s);
720 				change(3, &d1->new, 0, d3s);
721 			}
722 			d1++;
723 			continue;
724 		}
725 
726 		/* second file is different from others */
727 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
728 			if (d3s->eflag == 0) {
729 				separate("2", d3s);
730 				keep(1, &d2->new, d3s);
731 				change(2, &d2->old, 0, d3s);
732 				change(3, &d2->new, 0, d3s);
733 			}
734 			d2++;
735 			continue;
736 		}
737 
738 		/*
739 		 * Merge overlapping changes in first file
740 		 * this happens after extension (see below).
741 		 */
742 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
743 			d1[1].old.from = d1->old.from;
744 			d1[1].new.from = d1->new.from;
745 			d1++;
746 			continue;
747 		}
748 
749 		/* merge overlapping changes in second */
750 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
751 			d2[1].old.from = d2->old.from;
752 			d2[1].new.from = d2->new.from;
753 			d2++;
754 			continue;
755 		}
756 		/* stuff peculiar to third file or different in all */
757 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
758 			dpl = duplicate(&d1->old, &d2->old, d3s);
759 			if (dpl == -1)
760 				return (-1);
761 
762 			/*
763 			 * dpl = 0 means all files differ
764 			 * dpl = 1 means files 1 and 2 identical
765 			 */
766 			if (d3s->eflag == 0) {
767 				separate(dpl ? "3" : "", d3s);
768 				change(1, &d1->old, dpl, d3s);
769 				change(2, &d2->old, 0, d3s);
770 				d3 = d1->old.to > d1->old.from ? d1 : d2;
771 				change(3, &d3->new, 0, d3s);
772 			} else
773 				j = edit(d1, dpl, j, d3s);
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 static void
803 separate(const char *s, struct diff3_state *d3s)
804 {
805 	diff_output(d3s->diffbuf, "====%s\n", s);
806 }
807 
808 /*
809  * The range of lines rold.from thru rold.to in file i is to be changed.
810  * It is to be printed only if it does not duplicate something to be
811  * printed later.
812  */
813 static void
814 change(int i, struct range *rold, int fdup, struct diff3_state *d3s)
815 {
816 	diff_output(d3s->diffbuf, "%d:", i);
817 	d3s->last[i] = rold->to;
818 	prange(rold, d3s);
819 	if (fdup || d3s->debug)
820 		return;
821 	i--;
822 	(void)skip(i, rold->from, NULL, d3s);
823 	(void)skip(i, rold->to, "  ", d3s);
824 }
825 
826 /*
827  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
828  */
829 static void
830 prange(struct range *rold, struct diff3_state *d3s)
831 {
832 	if (rold->to <= rold->from)
833 		diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
834 	else {
835 		diff_output(d3s->diffbuf, "%d", rold->from);
836 		if (rold->to > rold->from+1)
837 			diff_output(d3s->diffbuf, ",%d", rold->to - 1);
838 		diff_output(d3s->diffbuf, "c\n");
839 	}
840 }
841 
842 /*
843  * No difference was reported by diff between file 1 (or 2) and file 3,
844  * and an artificial dummy difference (trange) must be ginned up to
845  * correspond to the change reported in the other file.
846  */
847 static void
848 keep(int i, struct range *rnew, struct diff3_state *d3s)
849 {
850 	int delta;
851 	struct range trange;
852 
853 	delta = d3s->last[3] - d3s->last[i];
854 	trange.from = rnew->from - delta;
855 	trange.to = rnew->to - delta;
856 	change(i, &trange, 1, d3s);
857 }
858 
859 /*
860  * skip to just before line number from in file "i".  If "pr" is non-NULL,
861  * print all skipped stuff with string pr as a prefix.
862  */
863 static int
864 skip(int i, int from, char *pr, struct diff3_state *d3s)
865 {
866 	size_t j, n;
867 	char *line;
868 
869 	for (n = 0; d3s->cline[i] < from - 1; n += j) {
870 		if ((line = get_line(d3s->fp[i], &j, d3s)) == NULL)
871 			return (-1);
872 		if (pr != NULL)
873 			diff_output(d3s->diffbuf, "%s%s", pr, line);
874 		d3s->cline[i]++;
875 	}
876 	return ((int) n);
877 }
878 
879 /*
880  * Return 1 or 0 according as the old range (in file 1) contains exactly
881  * the same data as the new range (in file 2).
882  */
883 static int
884 duplicate(struct range *r1, struct range *r2, struct diff3_state *d3s)
885 {
886 	int c,d;
887 	int nchar;
888 	int nline;
889 
890 	if (r1->to-r1->from != r2->to-r2->from)
891 		return (0);
892 	(void)skip(0, r1->from, NULL, d3s);
893 	(void)skip(1, r2->from, NULL, d3s);
894 	nchar = 0;
895 	for (nline=0; nline < r1->to - r1->from; nline++) {
896 		do {
897 			c = getc(d3s->fp[0]);
898 			d = getc(d3s->fp[1]);
899 			if (c == -1 || d== -1)
900 				return (-1);
901 			nchar++;
902 			if (c != d) {
903 				repos(nchar, d3s);
904 				return (0);
905 			}
906 		} while (c != '\n');
907 	}
908 	repos(nchar, d3s);
909 	return (1);
910 }
911 
912 static void
913 repos(int nchar, struct diff3_state *d3s)
914 {
915 	int i;
916 
917 	for (i = 0; i < 2; i++)
918 		(void)fseek(d3s->fp[i], (long)-nchar, SEEK_CUR);
919 }
920 
921 /*
922  * collect an editing script for later regurgitation
923  */
924 static int
925 edit(struct diff *diff, int fdup, int j, struct diff3_state *d3s)
926 {
927 	if (((fdup + 1) & d3s->eflag) == 0)
928 		return (j);
929 	j++;
930 	d3s->overlap[j] = !fdup;
931 	if (!fdup)
932 		d3s->overlapcnt++;
933 	d3s->de[j].old.from = diff->old.from;
934 	d3s->de[j].old.to = diff->old.to;
935 	d3s->de[j].new.from =
936 	    d3s->de[j-1].new.to + skip(2, diff->new.from, NULL, d3s);
937 	d3s->de[j].new.to =
938 	    d3s->de[j].new.from + skip(2, diff->new.to, NULL, d3s);
939 	return (j);
940 }
941 
942 /* regurgitate */
943 static int
944 edscript(int n, struct diff3_state *d3s)
945 {
946 	int j, k;
947 	char block[BUFSIZ+1];
948 
949 	for (; n > 0; n--) {
950 		if (!d3s->oflag || !d3s->overlap[n])
951 			prange(&d3s->de[n].old, d3s);
952 		else
953 			diff_output(d3s->diffbuf, "%da\n%s\n",
954 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
955 		(void)fseek(d3s->fp[2], (long)d3s->de[n].new.from, SEEK_SET);
956 		k = d3s->de[n].new.to - d3s->de[n].new.from;
957 		for (; k > 0; k-= j) {
958 			j = k > BUFSIZ ? BUFSIZ : k;
959 			if (fread(block, 1, j, d3s->fp[2]) != (size_t)j)
960 				return (-1);
961 			block[j] = '\0';
962 			diff_output(d3s->diffbuf, "%s", block);
963 		}
964 
965 		if (!d3s->oflag || !d3s->overlap[n])
966 			diff_output(d3s->diffbuf, ".\n");
967 		else {
968 			diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
969 			diff_output(d3s->diffbuf, "%da\n%s\n.\n",
970 			    d3s->de[n].old.from - 1, d3s->f1mark);
971 		}
972 	}
973 
974 	return (d3s->overlapcnt);
975 }
976 
977 static const struct got_error *
978 increase(struct diff3_state *d3s)
979 {
980 	size_t newsz, incr;
981 	struct diff *d;
982 	char *s;
983 
984 	/* are the memset(3) calls needed? */
985 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
986 	incr = newsz - d3s->szchanges;
987 
988 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
989 	if (d == NULL)
990 		return got_error_from_errno("reallocarray");
991 	d3s->d13 = d;
992 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
993 
994 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
995 	if (d == NULL)
996 		return got_error_from_errno("reallocarray");
997 	d3s->d23 = d;
998 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
999 
1000 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1001 	if (d == NULL)
1002 		return got_error_from_errno("reallocarray");
1003 	d3s->de = d;
1004 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1005 
1006 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1007 	if (s == NULL)
1008 		return got_error_from_errno("reallocarray");
1009 	d3s->overlap = s;
1010 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1011 	d3s->szchanges = newsz;
1012 
1013 	return NULL;
1014 }