Gotweb

Blob

Date:: Wed Oct 9 07:35:37 2019 UTC
Message:: do not leak open file in diff3.c's readin() error paths
Actions:: History | Blame | Raw File
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 	char f1mark[PATH_MAX], f3mark[PATH_MAX]; /* markers for -E and -X */
144 
145 	char *buf;
146 
147 	BUF *diffbuf;
148 };
149 
150 
151 static const struct got_error *duplicate(int *, struct range *, struct range *,
152     struct diff3_state *);
153 static const struct got_error *edit(struct diff *, int, int *,
154     struct diff3_state *);
155 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
156 static const struct got_error *get_line(char **, FILE *, size_t *,
157     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 const struct got_error *skip(int *, int, int, struct diff3_state *);
163 static const struct got_error *edscript(int, struct diff3_state *);
164 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
165 static const struct got_error *prange(struct range *, struct diff3_state *);
166 static const struct got_error *repos(int, struct diff3_state *);
167 static const struct got_error *increase(struct diff3_state *);
168 static const struct got_error *diff3_internal(char *, char *, char *,
169     char *, char *, const char *, const char *, struct diff3_state *,
170     const char *, const char *);
171 
172 static const struct got_error *
173 diff_output(BUF *diffbuf, const char *fmt, ...)
174 {
175 	const struct got_error *err = NULL;
176 	va_list vap;
177 	int i;
178 	char *str;
179 	size_t newsize;
180 
181 	va_start(vap, fmt);
182 	i = vasprintf(&str, fmt, vap);
183 	va_end(vap);
184 	if (i == -1)
185 		return got_error_from_errno("vasprintf");
186 	err = buf_append(&newsize, diffbuf, str, strlen(str));
187 	free(str);
188 	return err;
189 }
190 
191 static const struct got_error*
192 diffreg(BUF **d, const char *path1, const char *path2)
193 {
194 	const struct got_error *err = NULL;
195 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
196 	char *outpath = NULL;
197 	struct got_diff_state ds;
198 	struct got_diff_args args;
199 	int res;
200 
201 	*d = NULL;
202 
203 	f1 = fopen(path1, "r");
204 	if (f1 == NULL) {
205 		err = got_error_from_errno2("fopen", path1);
206 		goto done;
207 	}
208 	f2 = fopen(path2, "r");
209 	if (f1 == NULL) {
210 		err = got_error_from_errno2("fopen", path2);
211 		goto done;
212 	}
213 
214 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diffreg");
215 	if (err)
216 		goto done;
217 
218 	memset(&ds, 0, sizeof(ds));
219 	/* XXX should stat buffers be passed in args instead of ds? */
220 	if (stat(path1, &ds.stb1) == -1) {
221 		err = got_error_from_errno2("stat", path1);
222 		goto done;
223 	}
224 	if (stat(path2, &ds.stb2) == -1) {
225 		err = got_error_from_errno2("stat", path2);
226 		goto done;
227 	}
228 
229 	memset(&args, 0, sizeof(args));
230 	args.diff_format = D_NORMAL;
231 	args.label[0] = "";
232 	args.label[1] = "";
233 	args.diff_context = 0;
234 
235 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
236 	    outfile, NULL);
237 	if (err)
238 		goto done;
239 
240 	if (fflush(outfile) != 0) {
241 		err = got_error_from_errno2("fflush", outpath);
242 		goto done;
243 	}
244 
245 	err = buf_load(d, outpath);
246 done:
247 	if (outpath) {
248 		unlink(outpath);
249 		free(outpath);
250 	}
251 	if (outfile && fclose(outfile) != 0 && err == NULL)
252 		err = got_error_from_errno("fclose");
253 	if (f1 && fclose(f1) != 0 && err == NULL)
254 		err = got_error_from_errno("fclose");
255 	if (f2 && fclose(f2) != 0 && err == NULL)
256 		err = got_error_from_errno("fclose");
257 	return err;
258 }
259 
260 /*
261  * For merge(1).
262  */
263 const struct got_error *
264 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
265     const char *p3, const char *label1, const char *label3)
266 {
267 	const struct got_error *err = NULL;
268 	char *dp13, *dp23, *path1, *path2, *path3;
269 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
270 	u_char *data, *patch;
271 	size_t dlen, plen;
272 	struct wklhead temp_files;
273 	struct diff3_state *d3s;
274 	int i;
275 
276 	*overlapcnt = 0;
277 
278 	SLIST_INIT(&temp_files);
279 
280 	d3s = calloc(1, sizeof(*d3s));
281 	if (d3s == NULL)
282 		return got_error_from_errno("calloc");
283 
284 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
285 	dp13 = dp23 = path1 = path2 = path3 = NULL;
286 	data = patch = NULL;
287 
288 	err = buf_load(&b1, p1);
289 	if (err)
290 		goto out;
291 	err = buf_load(&b2, p2);
292 	if (err)
293 		goto out;
294 	err = buf_load(&b3, p3);
295 	if (err)
296 		goto out;
297 
298 	err = buf_alloc(&diffb, 128);
299 	if (err)
300 		goto out;
301 
302 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
303 		err = got_error_from_errno("asprintf");
304 		goto out;
305 	}
306 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
307 		err = got_error_from_errno("asprintf");
308 		goto out;
309 	}
310 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
311 		err = got_error_from_errno("asprintf");
312 		goto out;
313 	}
314 
315 	err = buf_write_stmp(b1, path1, &temp_files);
316 	if (err)
317 		goto out;
318 	err = buf_write_stmp(b2, path2, &temp_files);
319 	if (err)
320 		goto out;
321 	err = buf_write_stmp(b3, path3, &temp_files);
322 	if (err)
323 		goto out;
324 
325 	buf_free(b2);
326 	b2 = NULL;
327 
328 	err = diffreg(&d1, path1, path3);
329 	if (err) {
330 		buf_free(diffb);
331 		diffb = NULL;
332 		goto out;
333 
334 	}
335 	err = diffreg(&d2, path2, path3);
336 	if (err) {
337 		buf_free(diffb);
338 		diffb = NULL;
339 		goto out;
340 	}
341 
342 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
343 		err = got_error_from_errno("asprintf");
344 		goto out;
345 	}
346 	err = buf_write_stmp(d1, dp13, &temp_files);
347 	if (err)
348 		goto out;
349 
350 	buf_free(d1);
351 	d1 = NULL;
352 
353 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
354 		err = got_error_from_errno("asprintf");
355 		goto out;
356 	}
357 	err = buf_write_stmp(d2, dp23, &temp_files);
358 	if (err)
359 		goto out;
360 
361 	buf_free(d2);
362 	d2 = NULL;
363 
364 	d3s->diffbuf = diffb;
365 	err = diff3_internal(dp13, dp23, path1, path2, path3,
366 	    label1, label3, d3s, label1, label3);
367 	if (err) {
368 		buf_free(diffb);
369 		diffb = NULL;
370 		goto out;
371 	}
372 
373 	plen = buf_len(diffb);
374 	patch = buf_release(diffb);
375 	dlen = buf_len(b1);
376 	data = buf_release(b1);
377 
378 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
379 out:
380 	buf_free(b2);
381 	buf_free(b3);
382 	buf_free(d1);
383 	buf_free(d2);
384 
385 	(void)unlink(path1);
386 	(void)unlink(path2);
387 	(void)unlink(path3);
388 	(void)unlink(dp13);
389 	(void)unlink(dp23);
390 
391 	free(path1);
392 	free(path2);
393 	free(path3);
394 	free(dp13);
395 	free(dp23);
396 	free(data);
397 	free(patch);
398 
399 	worklist_clean(&temp_files, worklist_unlink);
400 
401 	for (i = 0; i < nitems(d3s->fp); i++) {
402 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
403 			err = got_error_from_errno("fclose");
404 	}
405 	if (err == NULL && diffb) {
406 		if (buf_write_fd(diffb, outfd) < 0)
407 			err = got_error_from_errno("buf_write_fd");
408 		*overlapcnt = d3s->overlapcnt;
409 	}
410 	free(d3s);
411 	buf_free(diffb);
412 	return err;
413 }
414 
415 static const struct got_error *
416 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
417     const char *fmark, const char *rmark, struct diff3_state *d3s,
418     const char *label1, const char *label3)
419 {
420 	const struct got_error *err = NULL;
421 	ssize_t m, n;
422 	int i;
423 
424 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
425 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
426 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
427 		return got_error(GOT_ERR_NO_SPACE);
428 
429 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
430 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
431 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
432 		return got_error(GOT_ERR_NO_SPACE);
433 
434 	err = increase(d3s);
435 	if (err)
436 		return err;
437 
438 	err = readin(&m, dp13, &d3s->d13, d3s);
439 	if (err)
440 		return err;
441 	err = readin(&n, dp23, &d3s->d23, d3s);
442 	if (err)
443 		return err;
444 
445 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
446 		return got_error_from_errno2("fopen", path1);
447 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
448 		return got_error_from_errno2("fopen", path2);
449 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
450 		return got_error_from_errno2("fopen", path3);
451 
452 	return merge(m, n, d3s);
453 }
454 
455 static int
456 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
457 {
458 	char op, *ep;
459 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
460 	int start, end, i, lineno;
461 	u_char tmp;
462 
463 	dlp = TAILQ_FIRST(&(dlines->l_lines));
464 	lp = TAILQ_FIRST(&(plines->l_lines));
465 
466 	end = 0;
467 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
468 	    lp = TAILQ_NEXT(lp, l_list)) {
469 		/* Skip blank lines */
470 		if (lp->l_len < 2)
471 			continue;
472 
473 		/* NUL-terminate line buffer for strtol() safety. */
474 		tmp = lp->l_line[lp->l_len - 1];
475 		lp->l_line[lp->l_len - 1] = '\0';
476 
477 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
478 		op = lp->l_line[lp->l_len - 2];
479 		start = (int)strtol(lp->l_line, &ep, 10);
480 
481 		/* Restore the last byte of the buffer */
482 		lp->l_line[lp->l_len - 1] = tmp;
483 
484 		if (op == 'a') {
485 			if (start > dlines->l_nblines ||
486 			    start < 0 || *ep != 'a')
487 				return -1;
488 		} else if (op == 'c') {
489 			if (start > dlines->l_nblines ||
490 			    start < 0 || (*ep != ',' && *ep != 'c'))
491 				return -1;
492 
493 			if (*ep == ',') {
494 				ep++;
495 				end = (int)strtol(ep, &ep, 10);
496 				if (end < 0 || *ep != 'c')
497 					return -1;
498 			} else {
499 				end = start;
500 			}
501 		}
502 
503 
504 		for (;;) {
505 			if (dlp == NULL)
506 				break;
507 			if (dlp->l_lineno == start)
508 				break;
509 			if (dlp->l_lineno > start) {
510 				dlp = TAILQ_PREV(dlp, tqh, l_list);
511 			} else if (dlp->l_lineno < start) {
512 				ndlp = TAILQ_NEXT(dlp, l_list);
513 				if (ndlp->l_lineno > start)
514 					break;
515 				dlp = ndlp;
516 			}
517 		}
518 
519 		if (dlp == NULL)
520 			return -1;
521 
522 
523 		if (op == 'c') {
524 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
525 			for (i = 0; i <= (end - start); i++) {
526 				ndlp = TAILQ_NEXT(dlp, l_list);
527 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
528 				dlp = ndlp;
529 			}
530 			dlp = insert_after;
531 		}
532 
533 		if (op == 'a' || op == 'c') {
534 			for (;;) {
535 				ndlp = lp;
536 				lp = TAILQ_NEXT(lp, l_list);
537 				if (lp == NULL)
538 					return -1;
539 
540 				if (lp->l_len == 2 &&
541 				    lp->l_line[0] == '.' &&
542 				    lp->l_line[1] == '\n')
543 					break;
544 
545 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
546 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
547 				    lp, l_list);
548 				dlp = lp;
549 
550 				lp->l_lineno = start;
551 				lp = ndlp;
552 			}
553 		}
554 
555 		/*
556 		 * always resort lines as the markers might be put at the
557 		 * same line as we first started editing.
558 		 */
559 		lineno = 0;
560 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
561 			sort->l_lineno = lineno++;
562 		dlines->l_nblines = lineno - 1;
563 	}
564 
565 	return (0);
566 }
567 
568 /*
569  * Pick up the line numbers of all changes from one change file.
570  * (This puts the numbers in a vector, which is not strictly necessary,
571  * since the vector is processed in one sequential pass.
572  * The vector could be optimized out of existence)
573  */
574 static const struct got_error *
575 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
576 {
577 	const struct got_error *err = NULL;
578 	FILE *f;
579 	int a, b, c, d;
580 	char kind, *p;
581 	size_t i;
582 
583 	*n = 0;
584 
585 	f = fopen(name, "r");
586 	if (f == NULL)
587 		return got_error_from_errno2("fopen", name);
588 	err = getchange(&p, f, d3s);
589 	if (err)
590 		goto done;
591 	for (i = 0; p; i++) {
592 		if (i >= d3s->szchanges - 1) {
593 			err = increase(d3s);
594 			if (err)
595 				goto done;
596 		}
597 		a = b = number(&p);
598 		if (*p == ',') {
599 			p++;
600 			b = number(&p);
601 		}
602 		kind = *p++;
603 		c = d = number(&p);
604 		if (*p == ',') {
605 			p++;
606 			d = number(&p);
607 		}
608 		if (kind == 'a')
609 			a++;
610 		if (kind == 'd')
611 			c++;
612 		b++;
613 		d++;
614 		(*dd)[i].old.from = a;
615 		(*dd)[i].old.to = b;
616 		(*dd)[i].new.from = c;
617 		(*dd)[i].new.to = d;
618 
619 		err = getchange(&p, f, d3s);
620 		if (err)
621 			goto done;
622 	}
623 
624 	if (i) {
625 		(*dd)[i].old.from = (*dd)[i - 1].old.to;
626 		(*dd)[i].new.from = (*dd)[i - 1].new.to;
627 	}
628 done:
629 	if (fclose(f) != 0 && err == NULL)
630 		err = got_error_from_errno("fclose");
631 	if (err == NULL)
632 		*n = i;
633 	return err;
634 }
635 
636 static int
637 number(char **lc)
638 {
639 	int nn;
640 
641 	nn = 0;
642 	while (isdigit((unsigned char)(**lc)))
643 		nn = nn*10 + *(*lc)++ - '0';
644 
645 	return (nn);
646 }
647 
648 static const struct got_error *
649 getchange(char **line, FILE *b, struct diff3_state *d3s)
650 {
651 	const struct got_error *err = NULL;
652 
653 	*line = NULL;
654 	do {
655 		if (*line && isdigit((unsigned char)(*line)[0]))
656 			return NULL;
657 		err = get_line(line, b, NULL, d3s);
658 		if (err)
659 			return err;
660 	} while (*line);
661 
662 	return NULL;
663 }
664 
665 static const struct got_error *
666 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
667 {
668 	const struct got_error *err = NULL;
669 	char *cp = NULL;
670 	size_t size;
671 	ssize_t len;
672 	char *new;
673 
674 	*ret = NULL;
675 
676 	len = getline(&cp, &size, b);
677 	if (len == -1) {
678 		if (ferror(b))
679 			err = got_error_from_errno("getline");
680 		goto done;
681 	}
682 
683 	if (cp[len - 1] != '\n') {
684 		len++;
685 		if (len + 1 > size) {
686 			new = realloc(cp, len + 1);
687 			if (new == NULL) {
688 				err = got_error_from_errno("realloc");
689 				goto done;
690 			}
691 			cp = new;
692 		}
693 		cp[len - 1] = '\n';
694 		cp[len] = '\0';
695 	}
696 
697 	free(d3s->buf);
698 	*ret = d3s->buf = cp;
699 	cp = NULL;
700 	if (n != NULL)
701 		*n = len;
702 done:
703 	free(cp);
704 	return err;
705 }
706 
707 static const struct got_error *
708 merge(size_t m1, size_t m2, struct diff3_state *d3s)
709 {
710 	const struct got_error *err = NULL;
711 	struct diff *d1, *d2;
712 	int dpl, j, t1, t2;
713 
714 	d1 = d3s->d13;
715 	d2 = d3s->d23;
716 	j = 0;
717 	for (;;) {
718 		t1 = (d1 < d3s->d13 + m1);
719 		t2 = (d2 < d3s->d23 + m2);
720 		if (!t1 && !t2)
721 			break;
722 
723 		/* first file is different from others */
724 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
725 			/* stuff peculiar to 1st file */
726 			d1++;
727 			continue;
728 		}
729 
730 		/* second file is different from others */
731 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
732 			d2++;
733 			continue;
734 		}
735 
736 		/*
737 		 * Merge overlapping changes in first file
738 		 * this happens after extension (see below).
739 		 */
740 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
741 			d1[1].old.from = d1->old.from;
742 			d1[1].new.from = d1->new.from;
743 			d1++;
744 			continue;
745 		}
746 
747 		/* merge overlapping changes in second */
748 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
749 			d2[1].old.from = d2->old.from;
750 			d2[1].new.from = d2->new.from;
751 			d2++;
752 			continue;
753 		}
754 		/* stuff peculiar to third file or different in all */
755 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
756 			err = duplicate(&dpl, &d1->old, &d2->old, d3s);
757 			if (err)
758 				return err;
759 
760 			/*
761 			 * dpl = 0 means all files differ
762 			 * dpl = 1 means files 1 and 2 identical
763 			 */
764 			err = edit(d1, dpl, &j, d3s);
765 			if (err)
766 				return err;
767 			d1++;
768 			d2++;
769 			continue;
770 		}
771 
772 		/*
773 		 * Overlapping changes from file 1 and 2; extend changes
774 		 * appropriately to make them coincide.
775 		 */
776 		if (d1->new.from < d2->new.from) {
777 			d2->old.from -= d2->new.from - d1->new.from;
778 			d2->new.from = d1->new.from;
779 		} else if (d2->new.from < d1->new.from) {
780 			d1->old.from -= d1->new.from - d2->new.from;
781 			d1->new.from = d2->new.from;
782 		}
783 		if (d1->new.to > d2->new.to) {
784 			d2->old.to += d1->new.to - d2->new.to;
785 			d2->new.to = d1->new.to;
786 		} else if (d2->new.to > d1->new.to) {
787 			d1->old.to += d2->new.to - d1->new.to;
788 			d1->new.to = d2->new.to;
789 		}
790 	}
791 
792 	return (edscript(j, d3s));
793 }
794 
795 /*
796  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
797  */
798 static const struct got_error *
799 prange(struct range *rold, struct diff3_state *d3s)
800 {
801 	const struct got_error *err = NULL;
802 
803 	if (rold->to <= rold->from) {
804 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
805 		if (err)
806 			return err;
807 	} else {
808 		err = diff_output(d3s->diffbuf, "%d", rold->from);
809 		if (err)
810 			return err;
811 		if (rold->to > rold->from + 1) {
812 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
813 			if (err)
814 				return err;
815 		}
816 		err = diff_output(d3s->diffbuf, "c\n");
817 		if (err)
818 			return err;
819 	}
820 
821 	return NULL;
822 }
823 
824 /* skip to just before line number from in file "i". */
825 static const struct got_error *
826 skip(int *nskipped, int i, int from, struct diff3_state *d3s)
827 {
828 	const struct got_error *err = NULL;
829 	size_t j, n;
830 	char *line;
831 
832 	*nskipped = 0;
833 	for (n = 0; d3s->cline[i] < from - 1; n += j) {
834 		err = get_line(&line, d3s->fp[i], &j, d3s);
835 		if (err)
836 			return err;
837 		d3s->cline[i]++;
838 	}
839 	*nskipped = n;
840 	return NULL;
841 }
842 
843 /*
844  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
845  * the same data as the new range (in file 2).
846  */
847 static const struct got_error *
848 duplicate(int *dpl, struct range *r1, struct range *r2, struct diff3_state *d3s)
849 {
850 	const struct got_error *err = NULL;
851 	int c,d;
852 	int nchar;
853 	int nline, nskipped;
854 
855 	*dpl = 0;
856 
857 	if (r1->to - r1->from != r2->to - r2->from)
858 		return NULL;
859 
860 	err = skip(&nskipped, 0, r1->from, d3s);
861 	if (err)
862 		return err;
863 	err = skip(&nskipped, 1, r2->from, d3s);
864 	if (err)
865 		return err;
866 	nchar = 0;
867 	for (nline = 0; nline < r1->to - r1->from; nline++) {
868 		do {
869 			c = getc(d3s->fp[0]);
870 			if (c == EOF)
871 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
872 			d = getc(d3s->fp[1]);
873 			if (d == EOF)
874 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
875 			nchar++;
876 			if (c != d)
877 				return repos(nchar, d3s);
878 		} while (c != '\n');
879 	}
880 	err = repos(nchar, d3s);
881 	if (err)
882 		return err;
883 	*dpl = 1;
884 	return NULL;
885 }
886 
887 static const struct got_error *
888 repos(int nchar, struct diff3_state *d3s)
889 {
890 	int i;
891 
892 	for (i = 0; i < 2; i++) {
893 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
894 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
895 	}
896 
897 	return NULL;
898 }
899 
900 /*
901  * collect an editing script for later regurgitation
902  */
903 static const struct got_error *
904 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
905 {
906 	const struct got_error *err = NULL;
907 	int nskipped;
908 
909 	if (((fdup + 1) & 3) == 0)
910 		return NULL;
911 	(*j)++;
912 	d3s->overlap[*j] = !fdup;
913 	if (!fdup)
914 		d3s->overlapcnt++;
915 	d3s->de[*j].old.from = diff->old.from;
916 	d3s->de[*j].old.to = diff->old.to;
917 	err = skip(&nskipped, 2, diff->new.from, d3s);
918 	if (err)
919 		return err;
920 	d3s->de[*j].new.from = d3s->de[*j - 1].new.to + nskipped;
921 	err = skip(&nskipped, 2, diff->new.to, d3s);
922 	d3s->de[*j].new.to = d3s->de[*j].new.from + nskipped;
923 	return NULL;
924 }
925 
926 /* regurgitate */
927 static const struct got_error *
928 edscript(int n, struct diff3_state *d3s)
929 {
930 	const struct got_error *err = NULL;
931 	int j, k;
932 	char block[BUFSIZ+1];
933 
934 	for (; n > 0; n--) {
935 		if (!d3s->overlap[n]) {
936 			err = prange(&d3s->de[n].old, d3s);
937 			if (err)
938 				return err;
939 		} else {
940 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
941 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
942 			if (err)
943 				return err;
944 		}
945 		if (fseek(d3s->fp[2], (long)d3s->de[n].new.from, SEEK_SET)
946 		    == -1)
947 			return got_error_from_errno("fseek");
948 		k = d3s->de[n].new.to - d3s->de[n].new.from;
949 		for (; k > 0; k -= j) {
950 			j = k > BUFSIZ ? BUFSIZ : k;
951 			if (fread(block, 1, j, d3s->fp[2]) != (size_t)j)
952 				return got_ferror(d3s->fp[2], GOT_ERR_IO);
953 			block[j] = '\0';
954 			err = diff_output(d3s->diffbuf, "%s", block);
955 			if (err)
956 				return err;
957 		}
958 
959 		if (!d3s->overlap[n]) {
960 			err = diff_output(d3s->diffbuf, ".\n");
961 			if (err)
962 				return err;
963 		} else {
964 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
965 			if (err)
966 				return err;
967 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
968 			    d3s->de[n].old.from - 1, d3s->f1mark);
969 			if (err)
970 				return err;
971 		}
972 	}
973 
974 	return NULL;
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 }