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Date:: Sat Nov 21 15:34:19 2020 UTC
Message:: consistently label removed files as "/dev/null" in diff headers
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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];
150 	char f2mark[PATH_MAX];
151 	char f3mark[PATH_MAX];
152 
153 	char *buf;
154 
155 	BUF *diffbuf;
156 };
157 
158 
159 static const struct got_error *duplicate(int *, int, struct line_range *,
160     struct line_range *, struct diff3_state *);
161 static const struct got_error *edit(struct diff *, int, int *,
162     struct diff3_state *);
163 static const struct got_error *getchange(char **, FILE *, struct diff3_state *);
164 static const struct got_error *get_line(char **, FILE *, size_t *,
165     struct diff3_state *);
166 static int number(char **);
167 static const struct got_error *readin(size_t *, char *, struct diff **,
168     struct diff3_state *);
169 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
170 static const struct got_error *skip(size_t *, int, int, struct diff3_state *);
171 static const struct got_error *edscript(int, struct diff3_state *);
172 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
173 static const struct got_error *prange(struct line_range *, struct diff3_state *);
174 static const struct got_error *repos(int, struct diff3_state *);
175 static const struct got_error *increase(struct diff3_state *);
176 static const struct got_error *diff3_internal(char *, char *, char *,
177     char *, char *, const char *, const char *, struct diff3_state *,
178     const char *, const char *, const char *);
179 
180 static const struct got_error *
181 diff_output(BUF *diffbuf, const char *fmt, ...)
182 {
183 	const struct got_error *err = NULL;
184 	va_list vap;
185 	int i;
186 	char *str;
187 	size_t newsize;
188 
189 	va_start(vap, fmt);
190 	i = vasprintf(&str, fmt, vap);
191 	va_end(vap);
192 	if (i == -1)
193 		return got_error_from_errno("vasprintf");
194 	err = buf_append(&newsize, diffbuf, str, strlen(str));
195 	free(str);
196 	return err;
197 }
198 
199 static const struct got_error*
200 diffreg(BUF **d, const char *path1, const char *path2)
201 {
202 	const struct got_error *err = NULL;
203 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
204 	char *outpath = NULL;
205 	struct got_diffreg_result *diffreg_result = NULL;
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,
221 	    GOT_TMPDIR_STR "/got-diffreg");
222 	if (err)
223 		goto done;
224 
225 	err = got_diffreg(&diffreg_result, f1, f2,
226 	    GOT_DIFF_ALGORITHM_PATIENCE, 0, 1);
227 	if (err)
228 		goto done;
229 
230 	err = got_diffreg_output(NULL, NULL, diffreg_result, 1, 1, "", "",
231 	    GOT_DIFF_OUTPUT_EDSCRIPT, 0, outfile);
232 	if (err)
233 		goto done;
234 
235 	if (fflush(outfile) != 0) {
236 		err = got_error_from_errno2("fflush", outpath);
237 		goto done;
238 	}
239 
240 	err = buf_load(d, outpath);
241 done:
242 	if (outpath) {
243 		if (unlink(outpath) == -1 && err == NULL)
244 			err = got_error_from_errno2("unlink", outpath);
245 		free(outpath);
246 	}
247 	if (outfile && fclose(outfile) != 0 && err == NULL)
248 		err = got_error_from_errno("fclose");
249 	if (f1 && fclose(f1) != 0 && err == NULL)
250 		err = got_error_from_errno("fclose");
251 	if (f2 && fclose(f2) != 0 && err == NULL)
252 		err = got_error_from_errno("fclose");
253 	return err;
254 }
255 
256 /*
257  * For merge(1).
258  */
259 const struct got_error *
260 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
261     const char *p3, const char *label1, const char *label2, const char *label3)
262 {
263 	const struct got_error *err = NULL;
264 	char *dp13, *dp23, *path1, *path2, *path3;
265 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
266 	u_char *data, *patch;
267 	size_t dlen, plen;
268 	struct diff3_state *d3s;
269 	int i;
270 
271 	*overlapcnt = 0;
272 
273 	d3s = calloc(1, sizeof(*d3s));
274 	if (d3s == NULL)
275 		return got_error_from_errno("calloc");
276 
277 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
278 	dp13 = dp23 = path1 = path2 = path3 = NULL;
279 	data = patch = NULL;
280 
281 	err = buf_load(&b1, p1);
282 	if (err)
283 		goto out;
284 	err = buf_load(&b2, p2);
285 	if (err)
286 		goto out;
287 	err = buf_load(&b3, p3);
288 	if (err)
289 		goto out;
290 
291 	err = buf_alloc(&diffb, 128);
292 	if (err)
293 		goto out;
294 
295 	if (asprintf(&path1, GOT_TMPDIR_STR "/got-diff1.XXXXXXXX") == -1) {
296 		err = got_error_from_errno("asprintf");
297 		goto out;
298 	}
299 	if (asprintf(&path2, GOT_TMPDIR_STR "/got-diff2.XXXXXXXX") == -1) {
300 		err = got_error_from_errno("asprintf");
301 		goto out;
302 	}
303 	if (asprintf(&path3, GOT_TMPDIR_STR "/got-diff3.XXXXXXXX") == -1) {
304 		err = got_error_from_errno("asprintf");
305 		goto out;
306 	}
307 
308 	err = buf_write_stmp(b1, path1);
309 	if (err)
310 		goto out;
311 	err = buf_write_stmp(b2, path2);
312 	if (err)
313 		goto out;
314 	err = buf_write_stmp(b3, path3);
315 	if (err)
316 		goto out;
317 
318 	buf_free(b2);
319 	b2 = NULL;
320 
321 	err = diffreg(&d1, path1, path3);
322 	if (err) {
323 		buf_free(diffb);
324 		diffb = NULL;
325 		goto out;
326 
327 	}
328 	err = diffreg(&d2, path2, path3);
329 	if (err) {
330 		buf_free(diffb);
331 		diffb = NULL;
332 		goto out;
333 	}
334 
335 	if (asprintf(&dp13, GOT_TMPDIR_STR "/got-d13.XXXXXXXXXX") == -1) {
336 		err = got_error_from_errno("asprintf");
337 		goto out;
338 	}
339 	err = buf_write_stmp(d1, dp13);
340 	if (err)
341 		goto out;
342 
343 	buf_free(d1);
344 	d1 = NULL;
345 
346 	if (asprintf(&dp23, GOT_TMPDIR_STR "/got-d23.XXXXXXXXXX") == -1) {
347 		err = got_error_from_errno("asprintf");
348 		goto out;
349 	}
350 	err = buf_write_stmp(d2, dp23);
351 	if (err)
352 		goto out;
353 
354 	buf_free(d2);
355 	d2 = NULL;
356 
357 	d3s->diffbuf = diffb;
358 	err = diff3_internal(dp13, dp23, path1, path2, path3,
359 	    label1, label3, d3s, label1, label2, label3);
360 	if (err) {
361 		buf_free(diffb);
362 		diffb = NULL;
363 		goto out;
364 	}
365 
366 	plen = buf_len(diffb);
367 	patch = buf_release(diffb);
368 	dlen = buf_len(b1);
369 	data = buf_release(b1);
370 
371 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
372 out:
373 	buf_free(b2);
374 	buf_free(b3);
375 	buf_free(d1);
376 	buf_free(d2);
377 
378 	if (unlink(path1) == -1 && err == NULL)
379 		err = got_error_from_errno2("unlink", path1);
380 	if (unlink(path2) == -1 && err == NULL)
381 		err = got_error_from_errno2("unlink", path2);
382 	if (unlink(path3) == -1 && err == NULL)
383 		err = got_error_from_errno2("unlink", path3);
384 	if (unlink(dp13) == -1 && err == NULL)
385 		err = got_error_from_errno2("unlink", dp13);
386 	if (unlink(dp23) == -1 && err == NULL)
387 		err = got_error_from_errno2("unlink", dp23);
388 
389 	free(path1);
390 	free(path2);
391 	free(path3);
392 	free(dp13);
393 	free(dp23);
394 	free(data);
395 	free(patch);
396 
397 	for (i = 0; i < nitems(d3s->fp); i++) {
398 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
399 			err = got_error_from_errno("fclose");
400 	}
401 	if (err == NULL && diffb) {
402 		if (buf_write_fd(diffb, outfd) < 0)
403 			err = got_error_from_errno("buf_write_fd");
404 		*overlapcnt = d3s->overlapcnt;
405 	}
406 	free(d3s);
407 	buf_free(diffb);
408 	return err;
409 }
410 
411 static const struct got_error *
412 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
413     const char *fmark, const char *rmark, struct diff3_state *d3s,
414     const char *label1, const char *label2, const char *label3)
415 {
416 	const struct got_error *err = NULL;
417 	ssize_t m, n;
418 	int i;
419 
420 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
421 	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_BEGIN,
422 	    label1 ? " " : "", label1 ? label1 : "");
423 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
424 		return got_error(GOT_ERR_NO_SPACE);
425 
426 	i = snprintf(d3s->f2mark, sizeof(d3s->f2mark),
427 	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_ORIG,
428 	    label2 ? " " : "", label2 ? label2 : "");
429 	if (i < 0 || i >= (int)sizeof(d3s->f2mark))
430 		return got_error(GOT_ERR_NO_SPACE);
431 
432 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
433 	    "%s%s%s", GOT_DIFF_CONFLICT_MARKER_END,
434 	    label3 ? " " : "", label3 ? 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 	FILE *f;
583 	int a, b, c, d;
584 	char kind, *p;
585 	size_t i = 0;
586 
587 	*n = 0;
588 
589 	f = fopen(name, "r");
590 	if (f == NULL)
591 		return got_error_from_errno2("fopen", name);
592 	err = getchange(&p, f, d3s);
593 	if (err)
594 		goto done;
595 	for (i = 0; p; i++) {
596 		if (i >= d3s->szchanges - 1) {
597 			err = increase(d3s);
598 			if (err)
599 				goto done;
600 		}
601 		a = b = number(&p);
602 		if (*p == ',') {
603 			p++;
604 			b = number(&p);
605 		}
606 		kind = *p++;
607 		c = d = number(&p);
608 		if (*p == ',') {
609 			p++;
610 			d = number(&p);
611 		}
612 		if (kind == 'a')
613 			a++;
614 		if (kind == 'd')
615 			c++;
616 		b++;
617 		d++;
618 		(*dd)[i].old.from = a;
619 		(*dd)[i].old.to = b;
620 		(*dd)[i].new.from = c;
621 		(*dd)[i].new.to = d;
622 
623 		err = getchange(&p, f, d3s);
624 		if (err)
625 			goto done;
626 	}
627 
628 	if (i) {
629 		(*dd)[i].old.from = (*dd)[i - 1].old.to;
630 		(*dd)[i].new.from = (*dd)[i - 1].new.to;
631 	}
632 done:
633 	if (fclose(f) != 0 && err == NULL)
634 		err = got_error_from_errno("fclose");
635 	if (err == NULL)
636 		*n = i;
637 	return err;
638 }
639 
640 static int
641 number(char **lc)
642 {
643 	int nn;
644 
645 	nn = 0;
646 	while (isdigit((unsigned char)(**lc)))
647 		nn = nn*10 + *(*lc)++ - '0';
648 
649 	return (nn);
650 }
651 
652 static const struct got_error *
653 getchange(char **line, FILE *b, struct diff3_state *d3s)
654 {
655 	const struct got_error *err = NULL;
656 
657 	*line = NULL;
658 	do {
659 		if (*line && isdigit((unsigned char)(*line)[0]))
660 			return NULL;
661 		err = get_line(line, b, NULL, d3s);
662 		if (err)
663 			return err;
664 	} while (*line);
665 
666 	return NULL;
667 }
668 
669 static const struct got_error *
670 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
671 {
672 	const struct got_error *err = NULL;
673 	char *cp = NULL;
674 	size_t size;
675 	ssize_t len;
676 	char *new;
677 
678 	*ret = NULL;
679 
680 	len = getline(&cp, &size, b);
681 	if (len == -1) {
682 		if (ferror(b))
683 			err = got_error_from_errno("getline");
684 		goto done;
685 	}
686 
687 	if (cp[len - 1] != '\n') {
688 		len++;
689 		if (len + 1 > size) {
690 			new = realloc(cp, len + 1);
691 			if (new == NULL) {
692 				err = got_error_from_errno("realloc");
693 				goto done;
694 			}
695 			cp = new;
696 		}
697 		cp[len - 1] = '\n';
698 		cp[len] = '\0';
699 	}
700 
701 	free(d3s->buf);
702 	*ret = d3s->buf = cp;
703 	cp = NULL;
704 	if (n != NULL)
705 		*n = len;
706 done:
707 	free(cp);
708 	return err;
709 }
710 
711 static const struct got_error *
712 merge(size_t m1, size_t m2, struct diff3_state *d3s)
713 {
714 	const struct got_error *err = NULL;
715 	struct diff *d1, *d2;
716 	int dpl, j, t1, t2;
717 
718 	d1 = d3s->d13;
719 	d2 = d3s->d23;
720 	j = 0;
721 	for (;;) {
722 		t1 = (d1 < d3s->d13 + m1);
723 		t2 = (d2 < d3s->d23 + m2);
724 		if (!t1 && !t2)
725 			break;
726 
727 		/* first file is different from others */
728 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
729 			/* stuff peculiar to 1st file */
730 			d1++;
731 			continue;
732 		}
733 
734 		/* second file is different from others */
735 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
736 			d2++;
737 			continue;
738 		}
739 
740 		/*
741 		 * Merge overlapping changes in first file
742 		 * this happens after extension (see below).
743 		 */
744 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
745 			d1[1].old.from = d1->old.from;
746 			d1[1].new.from = d1->new.from;
747 			d1++;
748 			continue;
749 		}
750 
751 		/* merge overlapping changes in second */
752 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
753 			d2[1].old.from = d2->old.from;
754 			d2[1].new.from = d2->new.from;
755 			d2++;
756 			continue;
757 		}
758 		/* stuff peculiar to third file or different in all */
759 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
760 			err = duplicate(&dpl, j, &d1->old, &d2->old, d3s);
761 			if (err)
762 				return err;
763 
764 			/*
765 			 * dpl = 0 means all files differ
766 			 * dpl = 1 means files 1 and 2 identical
767 			 */
768 			err = edit(d1, dpl, &j, d3s);
769 			if (err)
770 				return err;
771 			d1++;
772 			d2++;
773 			continue;
774 		}
775 
776 		/*
777 		 * Overlapping changes from file 1 and 2; extend changes
778 		 * appropriately to make them coincide.
779 		 */
780 		if (d1->new.from < d2->new.from) {
781 			d2->old.from -= d2->new.from - d1->new.from;
782 			d2->new.from = d1->new.from;
783 		} else if (d2->new.from < d1->new.from) {
784 			d1->old.from -= d1->new.from - d2->new.from;
785 			d1->new.from = d2->new.from;
786 		}
787 		if (d1->new.to > d2->new.to) {
788 			d2->old.to += d1->new.to - d2->new.to;
789 			d2->new.to = d1->new.to;
790 		} else if (d2->new.to > d1->new.to) {
791 			d1->old.to += d2->new.to - d1->new.to;
792 			d1->new.to = d2->new.to;
793 		}
794 	}
795 
796 	return (edscript(j, d3s));
797 }
798 
799 /*
800  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
801  */
802 static const struct got_error *
803 prange(struct line_range *rold, struct diff3_state *d3s)
804 {
805 	const struct got_error *err = NULL;
806 
807 	if (rold->to <= rold->from) {
808 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
809 		if (err)
810 			return err;
811 	} else {
812 		err = diff_output(d3s->diffbuf, "%d", rold->from);
813 		if (err)
814 			return err;
815 		if (rold->to > rold->from + 1) {
816 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
817 			if (err)
818 				return err;
819 		}
820 		err = diff_output(d3s->diffbuf, "c\n");
821 		if (err)
822 			return err;
823 	}
824 
825 	return NULL;
826 }
827 
828 /*
829  * Skip to just before line number from in file "i".
830  * Return the number of bytes skipped in *nskipped.
831  */
832 static const struct got_error *
833 skip(size_t *nskipped, int i, int from, struct diff3_state *d3s)
834 {
835 	const struct got_error *err = NULL;
836 	size_t len, n;
837 	char *line;
838 
839 	*nskipped = 0;
840 	for (n = 0; d3s->cline[i] < from - 1; n += len) {
841 		err = get_line(&line, d3s->fp[i], &len, d3s);
842 		if (err)
843 			return err;
844 		d3s->cline[i]++;
845 	}
846 	*nskipped = n;
847 	return NULL;
848 }
849 
850 /*
851  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
852  * the same data as the new range (in file 2).
853  *
854  * If this change could overlap, remember start/end offsets in file 2 so we
855  * can write out the original lines of text if a merge conflict occurs.
856  */
857 static const struct got_error *
858 duplicate(int *dpl, int j, struct line_range *r1, struct line_range *r2,
859     struct diff3_state *d3s)
860 {
861 	const struct got_error *err = NULL;
862 	int c,d;
863 	int nchar;
864 	int nline;
865 	size_t nskipped;
866 	off_t off;
867 
868 	*dpl = 0;
869 
870 	if (r1->to - r1->from != r2->to - r2->from)
871 		return NULL;
872 
873 	err = skip(&nskipped, 0, r1->from, d3s);
874 	if (err)
875 		return err;
876 	err = skip(&nskipped, 1, r2->from, d3s);
877 	if (err)
878 		return err;
879 
880 	off = ftello(d3s->fp[1]);
881 	if (off == -1)
882 		return got_error_from_errno("ftello");
883 	d3s->de[j + 1].oldo.from = off; /* original lines start here */
884 
885 	nchar = 0;
886 	for (nline = 0; nline < r1->to - r1->from; nline++) {
887 		do {
888 			c = getc(d3s->fp[0]);
889 			if (c == EOF)
890 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
891 			d = getc(d3s->fp[1]);
892 			if (d == EOF)
893 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
894 			nchar++;
895 			if (c != d) {
896 				long orig_line_len = nchar;
897 				while (d != '\n') {
898 					d = getc(d3s->fp[1]);
899 					if (d == EOF)
900 						break;
901 					orig_line_len++;
902 				}
903 				if (orig_line_len > nchar &&
904 				    fseek(d3s->fp[1], -(orig_line_len - nchar),
905 				    SEEK_CUR) == -1)
906 					return got_ferror(d3s->fp[1],
907 						GOT_ERR_IO);
908  				/* original lines end here */
909 				d3s->de[j + 1].oldo.to = off + orig_line_len;
910 				err = repos(nchar, d3s);
911 				if (err)
912 					return err;
913 				return NULL;
914 			}
915 		} while (c != '\n');
916 	}
917 	err = repos(nchar, d3s);
918 	if (err)
919 		return err;
920 	*dpl = 1;
921 	return NULL;
922 }
923 
924 static const struct got_error *
925 repos(int nchar, struct diff3_state *d3s)
926 {
927 	int i;
928 
929 	for (i = 0; i < 2; i++) {
930 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
931 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
932 	}
933 
934 	return NULL;
935 }
936 
937 /*
938  * collect an editing script for later regurgitation
939  */
940 static const struct got_error *
941 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
942 {
943 	const struct got_error *err = NULL;
944 	size_t nskipped;
945 
946 	if (((fdup + 1) & 3) == 0)
947 		return NULL;
948 	(*j)++;
949 	d3s->overlap[*j] = !fdup;
950 	if (!fdup)
951 		d3s->overlapcnt++;
952 	d3s->de[*j].old.from = diff->old.from;
953 	d3s->de[*j].old.to = diff->old.to;
954 
955 	err = skip(&nskipped, 2, diff->new.from, d3s);
956 	if (err)
957 		return err;
958 	d3s->de[*j].newo.from = d3s->de[*j - 1].newo.to + nskipped;
959 
960 	err = skip(&nskipped, 2, diff->new.to, d3s);
961 	if (err)
962 		return err;
963 	d3s->de[*j].newo.to = d3s->de[*j].newo.from + nskipped;
964 	return NULL;
965 }
966 
967 /* regurgitate */
968 static const struct got_error *
969 edscript(int n, struct diff3_state *d3s)
970 {
971 	const struct got_error *err = NULL;
972 	size_t k, len;
973 	char block[BUFSIZ+1];
974 
975 	for (; n > 0; n--) {
976 		if (!d3s->overlap[n]) {
977 			err = prange(&d3s->de[n].old, d3s);
978 			if (err)
979 				return err;
980 		} else if (d3s->de[n].oldo.from < d3s->de[n].oldo.to) {
981 			/* Output a block of 3-way diff base file content. */
982 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
983 			    d3s->de[n].old.to - 1, d3s->f2mark);
984 			if (err)
985 				return err;
986 			if (fseeko(d3s->fp[1], d3s->de[n].oldo.from, SEEK_SET)
987 			    == -1)
988 				return got_error_from_errno("fseeko");
989 			k = (size_t)(d3s->de[n].oldo.to - d3s->de[n].oldo.from);
990 			for (; k > 0; k -= len) {
991 				size_t r;
992 				len = k > BUFSIZ ? BUFSIZ : k;
993 				r = fread(block, 1, len, d3s->fp[1]);
994 				if (r == 0) {
995 					if (feof(d3s->fp[1]))
996 						break;
997 					return got_ferror(d3s->fp[1],
998 					    GOT_ERR_IO);
999 				}
1000 				if (r != len)
1001 					len = r;
1002 				block[len] = '\0';
1003 				err = diff_output(d3s->diffbuf, "%s", block);
1004 				if (err)
1005 					return err;
1006 			}
1007 			err = diff_output(d3s->diffbuf, "%s\n",
1008 			    GOT_DIFF_CONFLICT_MARKER_SEP);
1009 			if (err)
1010 				return err;
1011  		} else {
1012  			err = diff_output(d3s->diffbuf, "%da\n%s\n",
1013 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
1014 			if (err)
1015 				return err;
1016 		}
1017 		if (fseeko(d3s->fp[2], d3s->de[n].newo.from, SEEK_SET)
1018 		    == -1)
1019 			return got_error_from_errno("fseek");
1020 		k = (size_t)(d3s->de[n].newo.to - d3s->de[n].newo.from);
1021 		for (; k > 0; k -= len) {
1022 			size_t r;
1023 			len = k > BUFSIZ ? BUFSIZ : k;
1024 			r = fread(block, 1, len, d3s->fp[2]);
1025 			if (r == 0) {
1026 				if (feof(d3s->fp[2]))
1027 					break;
1028 				return got_ferror(d3s->fp[2],
1029 				    GOT_ERR_IO);
1030 			}
1031 			if (r != len)
1032 				len = r;
1033 			block[len] = '\0';
1034 			err = diff_output(d3s->diffbuf, "%s", block);
1035 			if (err)
1036 				return err;
1037 		}
1038 
1039 		if (!d3s->overlap[n]) {
1040 			err = diff_output(d3s->diffbuf, ".\n");
1041 			if (err)
1042 				return err;
1043 		} else {
1044 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
1045 			if (err)
1046 				return err;
1047 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
1048 			    d3s->de[n].old.from - 1, d3s->f1mark);
1049 			if (err)
1050 				return err;
1051 		}
1052 	}
1053 
1054 	return NULL;
1055 }
1056 
1057 static const struct got_error *
1058 increase(struct diff3_state *d3s)
1059 {
1060 	size_t newsz, incr;
1061 	struct diff *d;
1062 	char *s;
1063 
1064 	/* are the memset(3) calls needed? */
1065 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
1066 	incr = newsz - d3s->szchanges;
1067 
1068 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
1069 	if (d == NULL)
1070 		return got_error_from_errno("reallocarray");
1071 	d3s->d13 = d;
1072 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
1073 
1074 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1075 	if (d == NULL)
1076 		return got_error_from_errno("reallocarray");
1077 	d3s->d23 = d;
1078 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1079 
1080 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1081 	if (d == NULL)
1082 		return got_error_from_errno("reallocarray");
1083 	d3s->de = d;
1084 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1085 
1086 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1087 	if (s == NULL)
1088 		return got_error_from_errno("reallocarray");
1089 	d3s->overlap = s;
1090 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1091 	d3s->szchanges = newsz;
1092 
1093 	return NULL;
1094 }