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Date:: Sun Oct 6 18:59:31 2019 UTC
Message:: some whitespace fixes in diff3.c
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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 	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, char *,
163     struct diff3_state *);
164 static const struct got_error *edscript(int, struct diff3_state *);
165 static const struct got_error *merge(size_t, size_t, struct diff3_state *);
166 static const struct got_error *prange(struct range *, struct diff3_state *);
167 static const struct got_error *repos(int, struct diff3_state *);
168 static const struct got_error *increase(struct diff3_state *);
169 static const struct got_error *diff3_internal(char *, char *, char *,
170     char *, char *, const char *, const char *, struct diff3_state *,
171     const char *, const char *);
172 
173 static const struct got_error *
174 diff_output(BUF *diffbuf, const char *fmt, ...)
175 {
176 	const struct got_error *err = NULL;
177 	va_list vap;
178 	int i;
179 	char *str;
180 	size_t newsize;
181 
182 	va_start(vap, fmt);
183 	i = vasprintf(&str, fmt, vap);
184 	va_end(vap);
185 	if (i == -1)
186 		return got_error_from_errno("vasprintf");
187 	err = buf_append(&newsize, diffbuf, str, strlen(str));
188 	free(str);
189 	return err;
190 }
191 
192 static const struct got_error*
193 diffreg(BUF **d, const char *path1, const char *path2)
194 {
195 	const struct got_error *err = NULL;
196 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
197 	char *outpath = NULL;
198 	struct got_diff_state ds;
199 	struct got_diff_args args;
200 	int res;
201 
202 	*d = NULL;
203 
204 	f1 = fopen(path1, "r");
205 	if (f1 == NULL) {
206 		err = got_error_from_errno2("fopen", path1);
207 		goto done;
208 	}
209 	f2 = fopen(path2, "r");
210 	if (f1 == NULL) {
211 		err = got_error_from_errno2("fopen", path2);
212 		goto done;
213 	}
214 
215 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diffreg");
216 	if (err)
217 		goto done;
218 
219 	memset(&ds, 0, sizeof(ds));
220 	/* XXX should stat buffers be passed in args instead of ds? */
221 	if (stat(path1, &ds.stb1) == -1) {
222 		err = got_error_from_errno2("stat", path1);
223 		goto done;
224 	}
225 	if (stat(path2, &ds.stb2) == -1) {
226 		err = got_error_from_errno2("stat", path2);
227 		goto done;
228 	}
229 
230 	memset(&args, 0, sizeof(args));
231 	args.diff_format = D_NORMAL;
232 	args.label[0] = "";
233 	args.label[1] = "";
234 	args.diff_context = 0;
235 
236 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
237 	    outfile, NULL);
238 	if (err)
239 		goto done;
240 
241 	if (fflush(outfile) != 0) {
242 		err = got_error_from_errno2("fflush", outpath);
243 		goto done;
244 	}
245 
246 	*d = buf_load(outpath);
247 	if (*d == NULL)
248 		err = got_error_from_errno("buf_load");
249 done:
250 	if (outpath) {
251 		unlink(outpath);
252 		free(outpath);
253 	}
254 	if (outfile && fclose(outfile) != 0 && err == NULL)
255 		err = got_error_from_errno("fclose");
256 	if (f1 && fclose(f1) != 0 && err == NULL)
257 		err = got_error_from_errno("fclose");
258 	if (f2 && fclose(f2) != 0 && err == NULL)
259 		err = got_error_from_errno("fclose");
260 	return err;
261 }
262 
263 /*
264  * For merge(1).
265  */
266 const struct got_error *
267 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
268     const char *p3, const char *label1, const char *label3)
269 {
270 	const struct got_error *err = NULL;
271 	char *dp13, *dp23, *path1, *path2, *path3;
272 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
273 	u_char *data, *patch;
274 	size_t dlen, plen;
275 	struct wklhead temp_files;
276 	struct diff3_state *d3s;
277 	int i;
278 
279 	*overlapcnt = 0;
280 
281 	SLIST_INIT(&temp_files);
282 
283 	d3s = calloc(1, sizeof(*d3s));
284 	if (d3s == NULL)
285 		return got_error_from_errno("calloc");
286 
287 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
288 	dp13 = dp23 = path1 = path2 = path3 = NULL;
289 	data = patch = NULL;
290 
291 	if ((b1 = buf_load(p1)) == NULL)
292 		goto out;
293 	if ((b2 = buf_load(p2)) == NULL)
294 		goto out;
295 	if ((b3 = buf_load(p3)) == NULL)
296 		goto out;
297 
298 	diffb = buf_alloc(128);
299 
300 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
301 		err = got_error_from_errno("asprintf");
302 		goto out;
303 	}
304 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
305 		err = got_error_from_errno("asprintf");
306 		goto out;
307 	}
308 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
309 		err = got_error_from_errno("asprintf");
310 		goto out;
311 	}
312 
313 	err = buf_write_stmp(b1, path1, &temp_files);
314 	if (err)
315 		goto out;
316 	err = buf_write_stmp(b2, path2, &temp_files);
317 	if (err)
318 		goto out;
319 	err = buf_write_stmp(b3, path3, &temp_files);
320 	if (err)
321 		goto out;
322 
323 	buf_free(b2);
324 	b2 = NULL;
325 
326 	err = diffreg(&d1, path1, path3);
327 	if (err) {
328 		buf_free(diffb);
329 		diffb = NULL;
330 		goto out;
331 
332 	}
333 	err = diffreg(&d2, path2, path3);
334 	if (err) {
335 		buf_free(diffb);
336 		diffb = NULL;
337 		goto out;
338 	}
339 
340 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
341 		err = got_error_from_errno("asprintf");
342 		goto out;
343 	}
344 	err = buf_write_stmp(d1, dp13, &temp_files);
345 	if (err)
346 		goto out;
347 
348 	buf_free(d1);
349 	d1 = NULL;
350 
351 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
352 		err = got_error_from_errno("asprintf");
353 		goto out;
354 	}
355 	err = buf_write_stmp(d2, dp23, &temp_files);
356 	if (err)
357 		goto out;
358 
359 	buf_free(d2);
360 	d2 = NULL;
361 
362 	d3s->diffbuf = diffb;
363 	err = diff3_internal(dp13, dp23, path1, path2, path3,
364 	    label1, label3, d3s, label1, label3);
365 	if (err) {
366 		buf_free(diffb);
367 		diffb = NULL;
368 		goto out;
369 	}
370 
371 	plen = buf_len(diffb);
372 	patch = buf_release(diffb);
373 	dlen = buf_len(b1);
374 	data = buf_release(b1);
375 
376 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
377 out:
378 	buf_free(b2);
379 	buf_free(b3);
380 	buf_free(d1);
381 	buf_free(d2);
382 
383 	(void)unlink(path1);
384 	(void)unlink(path2);
385 	(void)unlink(path3);
386 	(void)unlink(dp13);
387 	(void)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 	worklist_clean(&temp_files, worklist_unlink);
398 
399 	for (i = 0; i < nitems(d3s->fp); i++) {
400 		if (d3s->fp[i] && fclose(d3s->fp[i]) != 0 && err == NULL)
401 			err = got_error_from_errno("fclose");
402 	}
403 	if (err == NULL && diffb) {
404 		if (buf_write_fd(diffb, outfd) < 0)
405 			err = got_error_from_errno("buf_write_fd");
406 		*overlapcnt = d3s->overlapcnt;
407 	}
408 	free(d3s);
409 	buf_free(diffb);
410 	return err;
411 }
412 
413 static const struct got_error *
414 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
415     const char *fmark, const char *rmark, struct diff3_state *d3s,
416     const char *label1, const char *label3)
417 {
418 	const struct got_error *err = NULL;
419 	ssize_t m, n;
420 	int i;
421 
422 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark),
423 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_BEGIN, label1);
424 	if (i < 0 || i >= (int)sizeof(d3s->f1mark))
425 		return got_error(GOT_ERR_NO_SPACE);
426 
427 	i = snprintf(d3s->f3mark, sizeof(d3s->f3mark),
428 	    "%s %s", GOT_DIFF_CONFLICT_MARKER_END, label3);
429 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
430 		return got_error(GOT_ERR_NO_SPACE);
431 
432 	err = increase(d3s);
433 	if (err)
434 		return err;
435 
436 	err = readin(&m, dp13, &d3s->d13, d3s);
437 	if (err)
438 		return err;
439 	err = readin(&n, dp23, &d3s->d23, d3s);
440 	if (err)
441 		return err;
442 
443 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
444 		return got_error_from_errno2("fopen", path1);
445 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
446 		return got_error_from_errno2("fopen", path2);
447 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
448 		return got_error_from_errno2("fopen", path3);
449 
450 	return merge(m, n, d3s);
451 }
452 
453 static int
454 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
455 {
456 	char op, *ep;
457 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
458 	int start, end, i, lineno;
459 	u_char tmp;
460 
461 	dlp = TAILQ_FIRST(&(dlines->l_lines));
462 	lp = TAILQ_FIRST(&(plines->l_lines));
463 
464 	end = 0;
465 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
466 	    lp = TAILQ_NEXT(lp, l_list)) {
467 		/* Skip blank lines */
468 		if (lp->l_len < 2)
469 			continue;
470 
471 		/* NUL-terminate line buffer for strtol() safety. */
472 		tmp = lp->l_line[lp->l_len - 1];
473 		lp->l_line[lp->l_len - 1] = '\0';
474 
475 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
476 		op = lp->l_line[lp->l_len - 2];
477 		start = (int)strtol(lp->l_line, &ep, 10);
478 
479 		/* Restore the last byte of the buffer */
480 		lp->l_line[lp->l_len - 1] = tmp;
481 
482 		if (op == 'a') {
483 			if (start > dlines->l_nblines ||
484 			    start < 0 || *ep != 'a')
485 				return -1;
486 		} else if (op == 'c') {
487 			if (start > dlines->l_nblines ||
488 			    start < 0 || (*ep != ',' && *ep != 'c'))
489 				return -1;
490 
491 			if (*ep == ',') {
492 				ep++;
493 				end = (int)strtol(ep, &ep, 10);
494 				if (end < 0 || *ep != 'c')
495 					return -1;
496 			} else {
497 				end = start;
498 			}
499 		}
500 
501 
502 		for (;;) {
503 			if (dlp == NULL)
504 				break;
505 			if (dlp->l_lineno == start)
506 				break;
507 			if (dlp->l_lineno > start) {
508 				dlp = TAILQ_PREV(dlp, tqh, l_list);
509 			} else if (dlp->l_lineno < start) {
510 				ndlp = TAILQ_NEXT(dlp, l_list);
511 				if (ndlp->l_lineno > start)
512 					break;
513 				dlp = ndlp;
514 			}
515 		}
516 
517 		if (dlp == NULL)
518 			return -1;
519 
520 
521 		if (op == 'c') {
522 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
523 			for (i = 0; i <= (end - start); i++) {
524 				ndlp = TAILQ_NEXT(dlp, l_list);
525 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
526 				dlp = ndlp;
527 			}
528 			dlp = insert_after;
529 		}
530 
531 		if (op == 'a' || op == 'c') {
532 			for (;;) {
533 				ndlp = lp;
534 				lp = TAILQ_NEXT(lp, l_list);
535 				if (lp == NULL)
536 					return -1;
537 
538 				if (lp->l_len == 2 &&
539 				    lp->l_line[0] == '.' &&
540 				    lp->l_line[1] == '\n')
541 					break;
542 
543 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
544 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
545 				    lp, l_list);
546 				dlp = lp;
547 
548 				lp->l_lineno = start;
549 				lp = ndlp;
550 			}
551 		}
552 
553 		/*
554 		 * always resort lines as the markers might be put at the
555 		 * same line as we first started editing.
556 		 */
557 		lineno = 0;
558 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
559 			sort->l_lineno = lineno++;
560 		dlines->l_nblines = lineno - 1;
561 	}
562 
563 	return (0);
564 }
565 
566 /*
567  * Pick up the line numbers of all changes from one change file.
568  * (This puts the numbers in a vector, which is not strictly necessary,
569  * since the vector is processed in one sequential pass.
570  * The vector could be optimized out of existence)
571  */
572 static const struct got_error *
573 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
574 {
575 	const struct got_error *err = NULL;
576 	int a, b, c, d;
577 	char kind, *p;
578 	size_t i;
579 
580 	*n = 0;
581 
582 	d3s->fp[0] = fopen(name, "r");
583 	if (d3s->fp[0] == NULL)
584 		return got_error_from_errno2("fopen", name);
585 	err = getchange(&p, d3s->fp[0], d3s);
586 	if (err)
587 		return err;
588 	for (i = 0; p; i++) {
589 		if (i >= d3s->szchanges - 1) {
590 			err = increase(d3s);
591 			if (err)
592 				return err;
593 		}
594 		a = b = number(&p);
595 		if (*p == ',') {
596 			p++;
597 			b = number(&p);
598 		}
599 		kind = *p++;
600 		c = d = number(&p);
601 		if (*p == ',') {
602 			p++;
603 			d = number(&p);
604 		}
605 		if (kind == 'a')
606 			a++;
607 		if (kind == 'd')
608 			c++;
609 		b++;
610 		d++;
611 		(*dd)[i].old.from = a;
612 		(*dd)[i].old.to = b;
613 		(*dd)[i].new.from = c;
614 		(*dd)[i].new.to = d;
615 
616 		err = getchange(&p, d3s->fp[0], d3s);
617 		if (err)
618 			return err;
619 	}
620 
621 	if (i) {
622 		(*dd)[i].old.from = (*dd)[i - 1].old.to;
623 		(*dd)[i].new.from = (*dd)[i - 1].new.to;
624 	}
625 
626 	if (fclose(d3s->fp[0]) != 0)
627 		err = got_error_from_errno("fclose");
628 
629 	*n = i;
630 	return err;
631 }
632 
633 static int
634 number(char **lc)
635 {
636 	int nn;
637 
638 	nn = 0;
639 	while (isdigit((unsigned char)(**lc)))
640 		nn = nn*10 + *(*lc)++ - '0';
641 
642 	return (nn);
643 }
644 
645 static const struct got_error *
646 getchange(char **line, FILE *b, struct diff3_state *d3s)
647 {
648 	const struct got_error *err = NULL;
649 
650 	*line = NULL;
651 	do {
652 		if (*line && isdigit((unsigned char)(*line)[0]))
653 			return NULL;
654 		err = get_line(line, b, NULL, d3s);
655 		if (err)
656 			return err;
657 	} while (*line);
658 
659 	return NULL;
660 }
661 
662 static const struct got_error *
663 get_line(char **ret, FILE *b, size_t *n, struct diff3_state *d3s)
664 {
665 	const struct got_error *err = NULL;
666 	char *cp = NULL;
667 	size_t size;
668 	ssize_t len;
669 	char *new;
670 
671 	*ret = NULL;
672 
673 	len = getline(&cp, &size, b);
674 	if (len == -1) {
675 		if (ferror(b))
676 			err = got_error_from_errno("getline");
677 		goto done;
678 	}
679 
680 	if (cp[len - 1] != '\n') {
681 		len++;
682 		if (len + 1 > size) {
683 			new = realloc(cp, len + 1);
684 			if (new == NULL) {
685 				err = got_error_from_errno("realloc");
686 				goto done;
687 			}
688 			cp = new;
689 		}
690 		cp[len - 1] = '\n';
691 		cp[len] = '\0';
692 	}
693 
694 	free(d3s->buf);
695 	*ret = d3s->buf = cp;
696 	cp = NULL;
697 	if (n != NULL)
698 		*n = len;
699 done:
700 	free(cp);
701 	return err;
702 }
703 
704 static const struct got_error *
705 merge(size_t m1, size_t m2, struct diff3_state *d3s)
706 {
707 	const struct got_error *err = NULL;
708 	struct diff *d1, *d2;
709 	int dpl, j, t1, t2;
710 
711 	d1 = d3s->d13;
712 	d2 = d3s->d23;
713 	j = 0;
714 	for (;;) {
715 		t1 = (d1 < d3s->d13 + m1);
716 		t2 = (d2 < d3s->d23 + m2);
717 		if (!t1 && !t2)
718 			break;
719 
720 		/* first file is different from others */
721 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
722 			/* stuff peculiar to 1st file */
723 			d1++;
724 			continue;
725 		}
726 
727 		/* second file is different from others */
728 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
729 			d2++;
730 			continue;
731 		}
732 
733 		/*
734 		 * Merge overlapping changes in first file
735 		 * this happens after extension (see below).
736 		 */
737 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
738 			d1[1].old.from = d1->old.from;
739 			d1[1].new.from = d1->new.from;
740 			d1++;
741 			continue;
742 		}
743 
744 		/* merge overlapping changes in second */
745 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
746 			d2[1].old.from = d2->old.from;
747 			d2[1].new.from = d2->new.from;
748 			d2++;
749 			continue;
750 		}
751 		/* stuff peculiar to third file or different in all */
752 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
753 			err = duplicate(&dpl, &d1->old, &d2->old, d3s);
754 			if (err)
755 				return err;
756 
757 			/*
758 			 * dpl = 0 means all files differ
759 			 * dpl = 1 means files 1 and 2 identical
760 			 */
761 			err = edit(d1, dpl, &j, d3s);
762 			if (err)
763 				return err;
764 			d1++;
765 			d2++;
766 			continue;
767 		}
768 
769 		/*
770 		 * Overlapping changes from file 1 and 2; extend changes
771 		 * appropriately to make them coincide.
772 		 */
773 		if (d1->new.from < d2->new.from) {
774 			d2->old.from -= d2->new.from - d1->new.from;
775 			d2->new.from = d1->new.from;
776 		} else if (d2->new.from < d1->new.from) {
777 			d1->old.from -= d1->new.from - d2->new.from;
778 			d1->new.from = d2->new.from;
779 		}
780 		if (d1->new.to > d2->new.to) {
781 			d2->old.to += d1->new.to - d2->new.to;
782 			d2->new.to = d1->new.to;
783 		} else if (d2->new.to > d1->new.to) {
784 			d1->old.to += d2->new.to - d1->new.to;
785 			d1->new.to = d2->new.to;
786 		}
787 	}
788 
789 	return (edscript(j, d3s));
790 }
791 
792 /*
793  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
794  */
795 static const struct got_error *
796 prange(struct range *rold, struct diff3_state *d3s)
797 {
798 	const struct got_error *err = NULL;
799 
800 	if (rold->to <= rold->from) {
801 		err = diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
802 		if (err)
803 			return err;
804 	} else {
805 		err = diff_output(d3s->diffbuf, "%d", rold->from);
806 		if (err)
807 			return err;
808 		if (rold->to > rold->from + 1) {
809 			err = diff_output(d3s->diffbuf, ",%d", rold->to - 1);
810 			if (err)
811 				return err;
812 		}
813 		err = diff_output(d3s->diffbuf, "c\n");
814 		if (err)
815 			return err;
816 	}
817 
818 	return NULL;
819 }
820 
821 /*
822  * skip to just before line number from in file "i".  If "pr" is non-NULL,
823  * print all skipped stuff with string pr as a prefix.
824  */
825 static const struct got_error *
826 skip(int *nskipped, int i, int from, char *pr, 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 		if (pr != NULL) {
838 			err = diff_output(d3s->diffbuf, "%s%s", pr, line);
839 			if (err)
840 				return err;
841 		}
842 		d3s->cline[i]++;
843 	}
844 	*nskipped = n;
845 	return NULL;
846 }
847 
848 /*
849  * Set *dpl to 1 or 0 according as the old range (in file 1) contains exactly
850  * the same data as the new range (in file 2).
851  */
852 static const struct got_error *
853 duplicate(int *dpl, struct range *r1, struct range *r2, struct diff3_state *d3s)
854 {
855 	const struct got_error *err = NULL;
856 	int c,d;
857 	int nchar;
858 	int nline, nskipped;
859 
860 	*dpl = 0;
861 
862 	if (r1->to - r1->from != r2->to - r2->from)
863 		return NULL;
864 
865 	err = skip(&nskipped, 0, r1->from, NULL, d3s);
866 	if (err)
867 		return err;
868 	err = skip(&nskipped, 1, r2->from, NULL, d3s);
869 	if (err)
870 		return err;
871 	nchar = 0;
872 	for (nline = 0; nline < r1->to - r1->from; nline++) {
873 		do {
874 			c = getc(d3s->fp[0]);
875 			if (c == EOF)
876 				return got_ferror(d3s->fp[0], GOT_ERR_EOF);
877 			d = getc(d3s->fp[1]);
878 			if (d == EOF)
879 				return got_ferror(d3s->fp[1], GOT_ERR_EOF);
880 			nchar++;
881 			if (c != d)
882 				return repos(nchar, d3s);
883 		} while (c != '\n');
884 	}
885 	err = repos(nchar, d3s);
886 	if (err)
887 		return err;
888 	*dpl = 1;
889 	return NULL;
890 }
891 
892 static const struct got_error *
893 repos(int nchar, struct diff3_state *d3s)
894 {
895 	int i;
896 
897 	for (i = 0; i < 2; i++) {
898 		if (fseek(d3s->fp[i], (long)-nchar, SEEK_CUR) == -1)
899 			return got_ferror(d3s->fp[i], GOT_ERR_IO);
900 	}
901 
902 	return NULL;
903 }
904 
905 /*
906  * collect an editing script for later regurgitation
907  */
908 static const struct got_error *
909 edit(struct diff *diff, int fdup, int *j, struct diff3_state *d3s)
910 {
911 	const struct got_error *err = NULL;
912 	int nskipped;
913 
914 	if (((fdup + 1) & 3) == 0)
915 		return NULL;
916 	(*j)++;
917 	d3s->overlap[*j] = !fdup;
918 	if (!fdup)
919 		d3s->overlapcnt++;
920 	d3s->de[*j].old.from = diff->old.from;
921 	d3s->de[*j].old.to = diff->old.to;
922 	err = skip(&nskipped, 2, diff->new.from, NULL, d3s);
923 	if (err)
924 		return err;
925 	d3s->de[*j].new.from = d3s->de[*j - 1].new.to + nskipped;
926 	err = skip(&nskipped, 2, diff->new.to, NULL, d3s);
927 	d3s->de[*j].new.to = d3s->de[*j].new.from + nskipped;
928 	return NULL;
929 }
930 
931 /* regurgitate */
932 static const struct got_error *
933 edscript(int n, struct diff3_state *d3s)
934 {
935 	const struct got_error *err = NULL;
936 	int j, k;
937 	char block[BUFSIZ+1];
938 
939 	for (; n > 0; n--) {
940 		if (!d3s->overlap[n]) {
941 			err = prange(&d3s->de[n].old, d3s);
942 			if (err)
943 				return err;
944 		} else {
945 			err = diff_output(d3s->diffbuf, "%da\n%s\n",
946 			    d3s->de[n].old.to -1, GOT_DIFF_CONFLICT_MARKER_SEP);
947 			if (err)
948 				return err;
949 		}
950 		if (fseek(d3s->fp[2], (long)d3s->de[n].new.from, SEEK_SET)
951 		    == -1)
952 			return got_error_from_errno("fseek");
953 		k = d3s->de[n].new.to - d3s->de[n].new.from;
954 		for (; k > 0; k -= j) {
955 			j = k > BUFSIZ ? BUFSIZ : k;
956 			if (fread(block, 1, j, d3s->fp[2]) != (size_t)j)
957 				return got_ferror(d3s->fp[2], GOT_ERR_IO);
958 			block[j] = '\0';
959 			err = diff_output(d3s->diffbuf, "%s", block);
960 			if (err)
961 				return err;
962 		}
963 
964 		if (!d3s->overlap[n]) {
965 			err = diff_output(d3s->diffbuf, ".\n");
966 			if (err)
967 				return err;
968 		} else {
969 			err = diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
970 			if (err)
971 				return err;
972 			err = diff_output(d3s->diffbuf, "%da\n%s\n.\n",
973 			    d3s->de[n].old.from - 1, d3s->f1mark);
974 			if (err)
975 				return err;
976 		}
977 	}
978 
979 	return NULL;
980 }
981 
982 static const struct got_error *
983 increase(struct diff3_state *d3s)
984 {
985 	size_t newsz, incr;
986 	struct diff *d;
987 	char *s;
988 
989 	/* are the memset(3) calls needed? */
990 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
991 	incr = newsz - d3s->szchanges;
992 
993 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
994 	if (d == NULL)
995 		return got_error_from_errno("reallocarray");
996 	d3s->d13 = d;
997 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
998 
999 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
1000 	if (d == NULL)
1001 		return got_error_from_errno("reallocarray");
1002 	d3s->d23 = d;
1003 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
1004 
1005 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
1006 	if (d == NULL)
1007 		return got_error_from_errno("reallocarray");
1008 	d3s->de = d;
1009 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
1010 
1011 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
1012 	if (s == NULL)
1013 		return got_error_from_errno("reallocarray");
1014 	d3s->overlap = s;
1015 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1016 	d3s->szchanges = newsz;
1017 
1018 	return NULL;
1019 }