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Date:: Fri Feb 8 14:10:49 2019 UTC
Message:: allow callers of diff3 code to detect merge conflicts
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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 	size_t bufsize;
150 
151 	BUF *diffbuf;
152 };
153 
154 
155 static int duplicate(struct range *, struct range *, struct diff3_state *);
156 static int edit(struct diff *, int, int, struct diff3_state *);
157 static char *getchange(FILE *, struct diff3_state *);
158 static char *get_line(FILE *, size_t *, struct diff3_state *);
159 static int number(char **);
160 static const struct got_error *readin(size_t *, char *, struct diff **,
161     struct diff3_state *);
162 static int ed_patch_lines(struct rcs_lines *, struct rcs_lines *);
163 static int skip(int, int, char *, struct diff3_state *);
164 static int edscript(int, struct diff3_state *);
165 static int merge(size_t, size_t, struct diff3_state *);
166 static void change(int, struct range *, int, struct diff3_state *);
167 static void keep(int, struct range *, struct diff3_state *);
168 static void prange(struct range *, struct diff3_state *);
169 static void repos(int, struct diff3_state *);
170 static void separate(const char *, struct diff3_state *);
171 static const struct got_error *increase(struct diff3_state *);
172 static const struct got_error *diff3_internal(char *, char *, char *,
173     char *, char *, const char *, const char *, struct diff3_state *,
174     const char *, const char *);
175 
176 static const struct got_error *
177 diff_output(BUF *diffbuf, const char *fmt, ...)
178 {
179 	va_list vap;
180 	int i;
181 	char *str;
182 	size_t newsize;
183 
184 	va_start(vap, fmt);
185 	i = vasprintf(&str, fmt, vap);
186 	va_end(vap);
187 	if (i == -1)
188 		return got_error_from_errno();
189 	buf_append(&newsize, diffbuf, str, strlen(str));
190 	free(str);
191 	return NULL;
192 }
193 
194 static const struct got_error*
195 diffreg(BUF **d, const char *path1, const char *path2)
196 {
197 	const struct got_error *err = NULL;
198 	FILE *f1 = NULL, *f2 = NULL, *outfile = NULL;
199 	char *outpath = NULL;
200 	struct got_diff_state ds;
201 	struct got_diff_args args;
202 	int res;
203 
204 	*d = NULL;
205 
206 	f1 = fopen(path1, "r");
207 	if (f1 == NULL) {
208 		err = got_error_from_errno();
209 		goto done;
210 	}
211 	f2 = fopen(path2, "r");
212 	if (f1 == NULL) {
213 		err = got_error_from_errno();
214 		goto done;
215 	}
216 
217 	err = got_opentemp_named(&outpath, &outfile, "/tmp/got-diffreg");
218 	if (err)
219 		goto done;
220 
221 	memset(&ds, 0, sizeof(ds));
222 	/* XXX should stat buffers be passed in args instead of ds? */
223 	if (stat(path1, &ds.stb1) == -1) {
224 		err = got_error_from_errno();
225 		goto done;
226 	}
227 	if (stat(path2, &ds.stb2) == -1) {
228 		err = got_error_from_errno();
229 		goto done;
230 	}
231 
232 	memset(&args, 0, sizeof(args));
233 	args.diff_format = D_NORMAL;
234 	args.label[0] = "";
235 	args.label[1] = "";
236 	args.diff_context = 0;
237 
238 	err = got_diffreg(&res, f1, f2, D_FORCEASCII, &args, &ds,
239 	    outfile, NULL);
240 	if (err)
241 		goto done;
242 
243 	fflush(outfile);
244 
245 	*d = buf_load(outpath);
246 	if (*d == NULL)
247 		err = got_error_from_errno();
248 done:
249 	if (outpath) {
250 		unlink(outpath);
251 		free(outpath);
252 	}
253 	if (outfile)
254 		fclose(outfile);
255 	if (f1)
256 		fclose(f1);
257 	if (f2)
258 		fclose(f2);
259 	return err;
260 }
261 
262 /*
263  * For merge(1).
264  */
265 const struct got_error *
266 got_merge_diff3(int *overlapcnt, int outfd, const char *p1, const char *p2,
267     const char *p3, const char *label1, const char *label3)
268 {
269 	const struct got_error *err = NULL;
270 	char *dp13, *dp23, *path1, *path2, *path3;
271 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
272 	u_char *data, *patch;
273 	size_t dlen, plen;
274 	struct wklhead temp_files;
275 	struct diff3_state *d3s;
276 	int i;
277 
278 	*overlapcnt = 0;
279 
280 	SLIST_INIT(&temp_files);
281 
282 	d3s = calloc(1, sizeof(*d3s));
283 	if (d3s == NULL)
284 		return got_error_from_errno();
285 	d3s->eflag = 3; /* default -E for compatibility with former RCS */
286 	d3s->oflag = 1; /* default -E for compatibility with former RCS */
287 
288 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
289 	dp13 = dp23 = path1 = path2 = path3 = NULL;
290 	data = patch = NULL;
291 
292 	if ((b1 = buf_load(p1)) == NULL)
293 		goto out;
294 	if ((b2 = buf_load(p2)) == NULL)
295 		goto out;
296 	if ((b3 = buf_load(p3)) == NULL)
297 		goto out;
298 
299 	diffb = buf_alloc(128);
300 
301 	if (asprintf(&path1, "/tmp/got-diff1.XXXXXXXX") == -1) {
302 		err = got_error_from_errno();
303 		goto out;
304 	}
305 	if (asprintf(&path2, "/tmp/got-diff2.XXXXXXXX") == -1) {
306 		err = got_error_from_errno();
307 		goto out;
308 	}
309 	if (asprintf(&path3, "/tmp/got-diff3.XXXXXXXX") == -1) {
310 		err = got_error_from_errno();
311 		goto out;
312 	}
313 
314 	err = buf_write_stmp(b1, path1, &temp_files);
315 	if (err)
316 		goto out;
317 	err = buf_write_stmp(b2, path2, &temp_files);
318 	if (err)
319 		goto out;
320 	err = buf_write_stmp(b3, path3, &temp_files);
321 	if (err)
322 		goto out;
323 
324 	buf_free(b2);
325 	b2 = NULL;
326 
327 	err = diffreg(&d1, path1, path3);
328 	if (err) {
329 		buf_free(diffb);
330 		diffb = NULL;
331 		goto out;
332 
333 	}
334 	err = diffreg(&d2, path2, path3);
335 	if (err) {
336 		buf_free(diffb);
337 		diffb = NULL;
338 		goto out;
339 	}
340 
341 	if (asprintf(&dp13, "/tmp/got-d13.XXXXXXXXXX") == -1) {
342 		err = got_error_from_errno();
343 		goto out;
344 	}
345 	err = buf_write_stmp(d1, dp13, &temp_files);
346 	if (err)
347 		goto out;
348 
349 	buf_free(d1);
350 	d1 = NULL;
351 
352 	if (asprintf(&dp23, "/tmp/got-d23.XXXXXXXXXX") == -1) {
353 		err = got_error_from_errno();
354 		goto out;
355 	}
356 	err = buf_write_stmp(d2, dp23, &temp_files);
357 	if (err)
358 		goto out;
359 
360 	buf_free(d2);
361 	d2 = NULL;
362 
363 	d3s->diffbuf = diffb;
364 	err = diff3_internal(dp13, dp23, path1, path2, path3,
365 	    label1, label3, d3s, label1, label3);
366 	if (err) {
367 		buf_free(diffb);
368 		diffb = NULL;
369 		goto out;
370 	}
371 
372 	plen = buf_len(diffb);
373 	patch = buf_release(diffb);
374 	dlen = buf_len(b1);
375 	data = buf_release(b1);
376 
377 	diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines);
378 out:
379 	buf_free(b2);
380 	buf_free(b3);
381 	buf_free(d1);
382 	buf_free(d2);
383 
384 	(void)unlink(path1);
385 	(void)unlink(path2);
386 	(void)unlink(path3);
387 	(void)unlink(dp13);
388 	(void)unlink(dp23);
389 
390 	free(path1);
391 	free(path2);
392 	free(path3);
393 	free(dp13);
394 	free(dp23);
395 	free(data);
396 	free(patch);
397 
398 	worklist_clean(&temp_files, worklist_unlink);
399 
400 	for (i = 0; i < nitems(d3s->fp); i++) {
401 		if (d3s->fp[i])
402 			fclose(d3s->fp[i]);
403 	}
404 	if (err == NULL && diffb) {
405 		if (buf_write_fd(diffb, outfd) < 0)
406 			err = got_error_from_errno();
407 		*overlapcnt = d3s->overlapcnt;
408 	}
409 	free(d3s);
410 	buf_free(diffb);
411 	return err;
412 }
413 
414 static const struct got_error *
415 diff3_internal(char *dp13, char *dp23, char *path1, char *path2, char *path3,
416     const char *fmark, const char *rmark, struct diff3_state *d3s,
417     const char *label1, const char *label3)
418 {
419 	const struct got_error *err = NULL;
420 	ssize_t m, n;
421 	int i;
422 
423 	i = snprintf(d3s->f1mark, sizeof(d3s->f1mark), "<<<<<<< %s", 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), ">>>>>>> %s", label3);
428 	if (i < 0 || i >= (int)sizeof(d3s->f3mark))
429 		return got_error(GOT_ERR_NO_SPACE);
430 
431 	err = increase(d3s);
432 	if (err)
433 		return err;
434 
435 	err = readin(&m, dp13, &d3s->d13, d3s);
436 	if (err)
437 		return err;
438 	err = readin(&n, dp23, &d3s->d23, d3s);
439 	if (err)
440 		return err;
441 
442 	if ((d3s->fp[0] = fopen(path1, "r")) == NULL)
443 		return got_error_from_errno();
444 	if ((d3s->fp[1] = fopen(path2, "r")) == NULL)
445 		return got_error_from_errno();
446 	if ((d3s->fp[2] = fopen(path3, "r")) == NULL)
447 		return got_error_from_errno();
448 
449 	if (merge(m, n, d3s) < 0)
450 		return got_error_from_errno();
451 	return NULL;
452 }
453 
454 static int
455 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
456 {
457 	char op, *ep;
458 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
459 	int start, end, i, lineno;
460 	u_char tmp;
461 
462 	dlp = TAILQ_FIRST(&(dlines->l_lines));
463 	lp = TAILQ_FIRST(&(plines->l_lines));
464 
465 	end = 0;
466 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
467 	    lp = TAILQ_NEXT(lp, l_list)) {
468 		/* Skip blank lines */
469 		if (lp->l_len < 2)
470 			continue;
471 
472 		/* NUL-terminate line buffer for strtol() safety. */
473 		tmp = lp->l_line[lp->l_len - 1];
474 		lp->l_line[lp->l_len - 1] = '\0';
475 
476 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
477 		op = lp->l_line[lp->l_len - 2];
478 		start = (int)strtol(lp->l_line, &ep, 10);
479 
480 		/* Restore the last byte of the buffer */
481 		lp->l_line[lp->l_len - 1] = tmp;
482 
483 		if (op == 'a') {
484 			if (start > dlines->l_nblines ||
485 			    start < 0 || *ep != 'a')
486 				return -1;
487 		} else if (op == 'c') {
488 			if (start > dlines->l_nblines ||
489 			    start < 0 || (*ep != ',' && *ep != 'c'))
490 				return -1;
491 
492 			if (*ep == ',') {
493 				ep++;
494 				end = (int)strtol(ep, &ep, 10);
495 				if (end < 0 || *ep != 'c')
496 					return -1;
497 			} else {
498 				end = start;
499 			}
500 		}
501 
502 
503 		for (;;) {
504 			if (dlp == NULL)
505 				break;
506 			if (dlp->l_lineno == start)
507 				break;
508 			if (dlp->l_lineno > start) {
509 				dlp = TAILQ_PREV(dlp, tqh, l_list);
510 			} else if (dlp->l_lineno < start) {
511 				ndlp = TAILQ_NEXT(dlp, l_list);
512 				if (ndlp->l_lineno > start)
513 					break;
514 				dlp = ndlp;
515 			}
516 		}
517 
518 		if (dlp == NULL)
519 			return -1;
520 
521 
522 		if (op == 'c') {
523 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
524 			for (i = 0; i <= (end - start); i++) {
525 				ndlp = TAILQ_NEXT(dlp, l_list);
526 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
527 				dlp = ndlp;
528 			}
529 			dlp = insert_after;
530 		}
531 
532 		if (op == 'a' || op == 'c') {
533 			for (;;) {
534 				ndlp = lp;
535 				lp = TAILQ_NEXT(lp, l_list);
536 				if (lp == NULL)
537 					return -1;
538 
539 				if (!memcmp(lp->l_line, ".", 1))
540 					break;
541 
542 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
543 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
544 				    lp, l_list);
545 				dlp = lp;
546 
547 				lp->l_lineno = start;
548 				lp = ndlp;
549 			}
550 		}
551 
552 		/*
553 		 * always resort lines as the markers might be put at the
554 		 * same line as we first started editing.
555 		 */
556 		lineno = 0;
557 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
558 			sort->l_lineno = lineno++;
559 		dlines->l_nblines = lineno - 1;
560 	}
561 
562 	return (0);
563 }
564 
565 /*
566  * Pick up the line numbers of all changes from one change file.
567  * (This puts the numbers in a vector, which is not strictly necessary,
568  * since the vector is processed in one sequential pass.
569  * The vector could be optimized out of existence)
570  */
571 static const struct got_error *
572 readin(size_t *n, char *name, struct diff **dd, struct diff3_state *d3s)
573 {
574 	const struct got_error *err = NULL;
575 	int a, b, c, d;
576 	char kind, *p;
577 	size_t i;
578 
579 	*n = 0;
580 
581 	d3s->fp[0] = fopen(name, "r");
582 	if (d3s->fp[0] == NULL)
583 		return got_error_from_errno();
584 	for (i = 0; (p = getchange(d3s->fp[0], d3s)); i++) {
585 		if (i >= d3s->szchanges - 1) {
586 			err = increase(d3s);
587 			if (err)
588 				return err;
589 		}
590 		a = b = number(&p);
591 		if (*p == ',') {
592 			p++;
593 			b = number(&p);
594 		}
595 		kind = *p++;
596 		c = d = number(&p);
597 		if (*p==',') {
598 			p++;
599 			d = number(&p);
600 		}
601 		if (kind == 'a')
602 			a++;
603 		if (kind == 'd')
604 			c++;
605 		b++;
606 		d++;
607 		(*dd)[i].old.from = a;
608 		(*dd)[i].old.to = b;
609 		(*dd)[i].new.from = c;
610 		(*dd)[i].new.to = d;
611 	}
612 
613 	if (i) {
614 		(*dd)[i].old.from = (*dd)[i-1].old.to;
615 		(*dd)[i].new.from = (*dd)[i-1].new.to;
616 	}
617 
618 	(void)fclose(d3s->fp[0]);
619 
620 	*n = i;
621 	return NULL;
622 }
623 
624 static int
625 number(char **lc)
626 {
627 	int nn;
628 
629 	nn = 0;
630 	while (isdigit((unsigned char)(**lc)))
631 		nn = nn*10 + *(*lc)++ - '0';
632 
633 	return (nn);
634 }
635 
636 static char *
637 getchange(FILE *b, struct diff3_state *d3s)
638 {
639 	char *line;
640 
641 	while ((line = get_line(b, NULL, d3s))) {
642 		if (isdigit((unsigned char)line[0]))
643 			return (line);
644 	}
645 
646 	return (NULL);
647 }
648 
649 static char *
650 get_line(FILE *b, size_t *n, struct diff3_state *d3s)
651 {
652 	char *cp;
653 	size_t len;
654 	char *new;
655 
656 	if ((cp = fgetln(b, &len)) == NULL)
657 		return (NULL);
658 
659 	if (cp[len - 1] != '\n')
660 		len++;
661 	if (len + 1 > d3s->bufsize) {
662 		do {
663 			d3s->bufsize += 1024;
664 		} while (len + 1 > d3s->bufsize);
665 		new = reallocarray(d3s->buf, 1, d3s->bufsize);
666 		if (new == NULL)
667 			return NULL;
668 		d3s->buf = new;
669 	}
670 	memcpy(d3s->buf, cp, len - 1);
671 	d3s->buf[len - 1] = '\n';
672 	d3s->buf[len] = '\0';
673 	if (n != NULL)
674 		*n = len;
675 
676 	return (d3s->buf);
677 }
678 
679 static int
680 merge(size_t m1, size_t m2, struct diff3_state *d3s)
681 {
682 	struct diff *d1, *d2, *d3;
683 	int dpl, j, t1, t2;
684 
685 	d1 = d3s->d13;
686 	d2 = d3s->d23;
687 	j = 0;
688 	for (;;) {
689 		t1 = (d1 < d3s->d13 + m1);
690 		t2 = (d2 < d3s->d23 + m2);
691 		if (!t1 && !t2)
692 			break;
693 
694 		if (d3s->debug) {
695 			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
696 			d1->old.from, d1->old.to,
697 			d1->new.from, d1->new.to,
698 			d2->old.from, d2->old.to,
699 			d2->new.from, d2->new.to);
700 		}
701 
702 		/* first file is different from others */
703 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
704 			/* stuff peculiar to 1st file */
705 			if (d3s->eflag == 0) {
706 				separate("1", d3s);
707 				change(1, &d1->old, 0, d3s);
708 				keep(2, &d1->new, d3s);
709 				change(3, &d1->new, 0, d3s);
710 			}
711 			d1++;
712 			continue;
713 		}
714 
715 		/* second file is different from others */
716 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
717 			if (d3s->eflag == 0) {
718 				separate("2", d3s);
719 				keep(1, &d2->new, d3s);
720 				change(2, &d2->old, 0, d3s);
721 				change(3, &d2->new, 0, d3s);
722 			}
723 			d2++;
724 			continue;
725 		}
726 
727 		/*
728 		 * Merge overlapping changes in first file
729 		 * this happens after extension (see below).
730 		 */
731 		if (d1 + 1 < d3s->d13 + m1 && d1->new.to >= d1[1].new.from) {
732 			d1[1].old.from = d1->old.from;
733 			d1[1].new.from = d1->new.from;
734 			d1++;
735 			continue;
736 		}
737 
738 		/* merge overlapping changes in second */
739 		if (d2 + 1 < d3s->d23 + m2 && d2->new.to >= d2[1].new.from) {
740 			d2[1].old.from = d2->old.from;
741 			d2[1].new.from = d2->new.from;
742 			d2++;
743 			continue;
744 		}
745 		/* stuff peculiar to third file or different in all */
746 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
747 			dpl = duplicate(&d1->old, &d2->old, d3s);
748 			if (dpl == -1)
749 				return (-1);
750 
751 			/*
752 			 * dpl = 0 means all files differ
753 			 * dpl = 1 means files 1 and 2 identical
754 			 */
755 			if (d3s->eflag == 0) {
756 				separate(dpl ? "3" : "", d3s);
757 				change(1, &d1->old, dpl, d3s);
758 				change(2, &d2->old, 0, d3s);
759 				d3 = d1->old.to > d1->old.from ? d1 : d2;
760 				change(3, &d3->new, 0, d3s);
761 			} else
762 				j = edit(d1, dpl, j, d3s);
763 			d1++;
764 			d2++;
765 			continue;
766 		}
767 
768 		/*
769 		 * Overlapping changes from file 1 and 2; extend changes
770 		 * appropriately to make them coincide.
771 		 */
772 		if (d1->new.from < d2->new.from) {
773 			d2->old.from -= d2->new.from-d1->new.from;
774 			d2->new.from = d1->new.from;
775 		} else if (d2->new.from < d1->new.from) {
776 			d1->old.from -= d1->new.from-d2->new.from;
777 			d1->new.from = d2->new.from;
778 		}
779 		if (d1->new.to > d2->new.to) {
780 			d2->old.to += d1->new.to - d2->new.to;
781 			d2->new.to = d1->new.to;
782 		} else if (d2->new.to > d1->new.to) {
783 			d1->old.to += d2->new.to - d1->new.to;
784 			d1->new.to = d2->new.to;
785 		}
786 	}
787 
788 	return (edscript(j, d3s));
789 }
790 
791 static void
792 separate(const char *s, struct diff3_state *d3s)
793 {
794 	diff_output(d3s->diffbuf, "====%s\n", s);
795 }
796 
797 /*
798  * The range of lines rold.from thru rold.to in file i is to be changed.
799  * It is to be printed only if it does not duplicate something to be
800  * printed later.
801  */
802 static void
803 change(int i, struct range *rold, int fdup, struct diff3_state *d3s)
804 {
805 	diff_output(d3s->diffbuf, "%d:", i);
806 	d3s->last[i] = rold->to;
807 	prange(rold, d3s);
808 	if (fdup || d3s->debug)
809 		return;
810 	i--;
811 	(void)skip(i, rold->from, NULL, d3s);
812 	(void)skip(i, rold->to, "  ", d3s);
813 }
814 
815 /*
816  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
817  */
818 static void
819 prange(struct range *rold, struct diff3_state *d3s)
820 {
821 	if (rold->to <= rold->from)
822 		diff_output(d3s->diffbuf, "%da\n", rold->from - 1);
823 	else {
824 		diff_output(d3s->diffbuf, "%d", rold->from);
825 		if (rold->to > rold->from+1)
826 			diff_output(d3s->diffbuf, ",%d", rold->to - 1);
827 		diff_output(d3s->diffbuf, "c\n");
828 	}
829 }
830 
831 /*
832  * No difference was reported by diff between file 1 (or 2) and file 3,
833  * and an artificial dummy difference (trange) must be ginned up to
834  * correspond to the change reported in the other file.
835  */
836 static void
837 keep(int i, struct range *rnew, struct diff3_state *d3s)
838 {
839 	int delta;
840 	struct range trange;
841 
842 	delta = d3s->last[3] - d3s->last[i];
843 	trange.from = rnew->from - delta;
844 	trange.to = rnew->to - delta;
845 	change(i, &trange, 1, d3s);
846 }
847 
848 /*
849  * skip to just before line number from in file "i".  If "pr" is non-NULL,
850  * print all skipped stuff with string pr as a prefix.
851  */
852 static int
853 skip(int i, int from, char *pr, struct diff3_state *d3s)
854 {
855 	size_t j, n;
856 	char *line;
857 
858 	for (n = 0; d3s->cline[i] < from - 1; n += j) {
859 		if ((line = get_line(d3s->fp[i], &j, d3s)) == NULL)
860 			return (-1);
861 		if (pr != NULL)
862 			diff_output(d3s->diffbuf, "%s%s", pr, line);
863 		d3s->cline[i]++;
864 	}
865 	return ((int) n);
866 }
867 
868 /*
869  * Return 1 or 0 according as the old range (in file 1) contains exactly
870  * the same data as the new range (in file 2).
871  */
872 static int
873 duplicate(struct range *r1, struct range *r2, struct diff3_state *d3s)
874 {
875 	int c,d;
876 	int nchar;
877 	int nline;
878 
879 	if (r1->to-r1->from != r2->to-r2->from)
880 		return (0);
881 	(void)skip(0, r1->from, NULL, d3s);
882 	(void)skip(1, r2->from, NULL, d3s);
883 	nchar = 0;
884 	for (nline=0; nline < r1->to - r1->from; nline++) {
885 		do {
886 			c = getc(d3s->fp[0]);
887 			d = getc(d3s->fp[1]);
888 			if (c == -1 || d== -1)
889 				return (-1);
890 			nchar++;
891 			if (c != d) {
892 				repos(nchar, d3s);
893 				return (0);
894 			}
895 		} while (c != '\n');
896 	}
897 	repos(nchar, d3s);
898 	return (1);
899 }
900 
901 static void
902 repos(int nchar, struct diff3_state *d3s)
903 {
904 	int i;
905 
906 	for (i = 0; i < 2; i++)
907 		(void)fseek(d3s->fp[i], (long)-nchar, SEEK_CUR);
908 }
909 
910 /*
911  * collect an editing script for later regurgitation
912  */
913 static int
914 edit(struct diff *diff, int fdup, int j, struct diff3_state *d3s)
915 {
916 	if (((fdup + 1) & d3s->eflag) == 0)
917 		return (j);
918 	j++;
919 	d3s->overlap[j] = !fdup;
920 	if (!fdup)
921 		d3s->overlapcnt++;
922 	d3s->de[j].old.from = diff->old.from;
923 	d3s->de[j].old.to = diff->old.to;
924 	d3s->de[j].new.from =
925 	    d3s->de[j-1].new.to + skip(2, diff->new.from, NULL, d3s);
926 	d3s->de[j].new.to =
927 	    d3s->de[j].new.from + skip(2, diff->new.to, NULL, d3s);
928 	return (j);
929 }
930 
931 /* regurgitate */
932 static int
933 edscript(int n, struct diff3_state *d3s)
934 {
935 	int j, k;
936 	char block[BUFSIZ+1];
937 
938 	for (; n > 0; n--) {
939 		if (!d3s->oflag || !d3s->overlap[n])
940 			prange(&d3s->de[n].old, d3s);
941 		else
942 			diff_output(d3s->diffbuf, "%da\n=======\n",
943 			    d3s->de[n].old.to -1);
944 		(void)fseek(d3s->fp[2], (long)d3s->de[n].new.from, SEEK_SET);
945 		k = d3s->de[n].new.to - d3s->de[n].new.from;
946 		for (; k > 0; k-= j) {
947 			j = k > BUFSIZ ? BUFSIZ : k;
948 			if (fread(block, 1, j, d3s->fp[2]) != (size_t)j)
949 				return (-1);
950 			block[j] = '\0';
951 			diff_output(d3s->diffbuf, "%s", block);
952 		}
953 
954 		if (!d3s->oflag || !d3s->overlap[n])
955 			diff_output(d3s->diffbuf, ".\n");
956 		else {
957 			diff_output(d3s->diffbuf, "%s\n.\n", d3s->f3mark);
958 			diff_output(d3s->diffbuf, "%da\n%s\n.\n",
959 			    d3s->de[n].old.from - 1, d3s->f1mark);
960 		}
961 	}
962 
963 	return (d3s->overlapcnt);
964 }
965 
966 static const struct got_error *
967 increase(struct diff3_state *d3s)
968 {
969 	size_t newsz, incr;
970 	struct diff *d;
971 	char *s;
972 
973 	/* are the memset(3) calls needed? */
974 	newsz = d3s->szchanges == 0 ? 64 : 2 * d3s->szchanges;
975 	incr = newsz - d3s->szchanges;
976 
977 	d = reallocarray(d3s->d13, newsz, sizeof(*d3s->d13));
978 	if (d == NULL)
979 		return got_error_from_errno();
980 	d3s->d13 = d;
981 	memset(d3s->d13 + d3s->szchanges, 0, incr * sizeof(*d3s->d13));
982 
983 	d = reallocarray(d3s->d23, newsz, sizeof(*d3s->d23));
984 	if (d == NULL)
985 		return got_error_from_errno();
986 	d3s->d23 = d;
987 	memset(d3s->d23 + d3s->szchanges, 0, incr * sizeof(*d3s->d23));
988 
989 	d = reallocarray(d3s->de, newsz, sizeof(*d3s->de));
990 	if (d == NULL)
991 		return got_error_from_errno();
992 	d3s->de = d;
993 	memset(d3s->de + d3s->szchanges, 0, incr * sizeof(*d3s->de));
994 
995 	s = reallocarray(d3s->overlap, newsz, sizeof(*d3s->overlap));
996 	if (s == NULL)
997 		return got_error_from_errno();
998 	d3s->overlap = s;
999 	memset(d3s->overlap + d3s->szchanges, 0, incr * sizeof(*d3s->overlap));
1000 	d3s->szchanges = newsz;
1001 
1002 	return NULL;
1003 }