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Date:: Thu Feb 7 10:30:27 2019 UTC
Message:: add unmodified buf.c, buf.h, and diff3.c from OpenRCS
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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 <ctype.h>
68 #include <err.h>
69 #include <stdio.h>
70 #include <stdlib.h>
71 #include <string.h>
72 #include <time.h>
73 #include <unistd.h>
74 
75 #include "diff.h"
76 #include "rcsprog.h"
77 
78 /* diff3 - 3-way differential file comparison */
79 
80 /* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
81  *
82  * d13 = diff report on f1 vs f3
83  * d23 = diff report on f2 vs f3
84  * f1, f2, f3 the 3 files
85  * if changes in f1 overlap with changes in f3, m1 and m3 are used
86  * to mark the overlaps; otherwise, the file names f1 and f3 are used
87  * (only for options E and X).
88  */
89 
90 /*
91  * "from" is first in range of changed lines; "to" is last+1
92  * from=to=line after point of insertion for added lines.
93  */
94 struct range {
95 	int from;
96 	int to;
97 };
98 
99 struct diff {
100 	struct range old;
101 	struct range new;
102 };
103 
104 static size_t szchanges;
105 
106 static struct diff *d13;
107 static struct diff *d23;
108 
109 /*
110  * "de" is used to gather editing scripts.  These are later spewed out in
111  * reverse order.  Its first element must be all zero, the "new" component
112  * of "de" contains line positions or byte positions depending on when you
113  * look (!?).  Array overlap indicates which sections in "de" correspond to
114  * lines that are different in all three files.
115  */
116 static struct diff *de;
117 static char *overlap;
118 static int overlapcnt = 0;
119 static FILE *fp[3];
120 static int cline[3];		/* # of the last-read line in each file (0-2) */
121 
122 /*
123  * the latest known correspondence between line numbers of the 3 files
124  * is stored in last[1-3];
125  */
126 static int last[4];
127 static int eflag = 3;	/* default -E for compatibility with former RCS */
128 static int oflag = 1;	/* default -E for compatibility with former RCS */
129 static int debug  = 0;
130 static char f1mark[PATH_MAX], f3mark[PATH_MAX];	/* markers for -E and -X */
131 
132 static int duplicate(struct range *, struct range *);
133 static int edit(struct diff *, int, int);
134 static char *getchange(FILE *);
135 static char *get_line(FILE *, size_t *);
136 static int number(char **);
137 static ssize_t readin(char *, struct diff **);
138 static int skip(int, int, char *);
139 static int edscript(int);
140 static int merge(size_t, size_t);
141 static void change(int, struct range *, int);
142 static void keep(int, struct range *);
143 static void prange(struct range *);
144 static void repos(int);
145 static void separate(const char *);
146 static void increase(void);
147 static int diff3_internal(int, char **, const char *, const char *);
148 
149 int diff3_conflicts = 0;
150 
151 /*
152  * For merge(1).
153  */
154 BUF *
155 merge_diff3(char **av, int flags)
156 {
157 	int argc;
158 	char *argv[5], *dp13, *dp23, *path1, *path2, *path3;
159 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
160 	u_char *data, *patch;
161 	size_t dlen, plen;
162 
163 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
164 	dp13 = dp23 = path1 = path2 = path3 = NULL;
165 	data = patch = NULL;
166 
167 	if ((flags & MERGE_EFLAG) && !(flags & MERGE_OFLAG))
168 		oflag = 0;
169 
170 	if ((b1 = buf_load(av[0])) == NULL)
171 		goto out;
172 	if ((b2 = buf_load(av[1])) == NULL)
173 		goto out;
174 	if ((b3 = buf_load(av[2])) == NULL)
175 		goto out;
176 
177 	d1 = buf_alloc(128);
178 	d2 = buf_alloc(128);
179 	diffb = buf_alloc(128);
180 
181 	(void)xasprintf(&path1, "%s/diff1.XXXXXXXXXX", rcs_tmpdir);
182 	(void)xasprintf(&path2, "%s/diff2.XXXXXXXXXX", rcs_tmpdir);
183 	(void)xasprintf(&path3, "%s/diff3.XXXXXXXXXX", rcs_tmpdir);
184 
185 	buf_write_stmp(b1, path1);
186 	buf_write_stmp(b2, path2);
187 	buf_write_stmp(b3, path3);
188 
189 	buf_free(b2);
190 	b2 = NULL;
191 
192 	if ((diffreg(path1, path3, d1, D_FORCEASCII) == D_ERROR) ||
193 	    (diffreg(path2, path3, d2, D_FORCEASCII) == D_ERROR)) {
194 		buf_free(diffb);
195 		diffb = NULL;
196 		goto out;
197 	}
198 
199 	(void)xasprintf(&dp13, "%s/d13.XXXXXXXXXX", rcs_tmpdir);
200 	buf_write_stmp(d1, dp13);
201 
202 	buf_free(d1);
203 	d1 = NULL;
204 
205 	(void)xasprintf(&dp23, "%s/d23.XXXXXXXXXX", rcs_tmpdir);
206 	buf_write_stmp(d2, dp23);
207 
208 	buf_free(d2);
209 	d2 = NULL;
210 
211 	argc = 0;
212 	diffbuf = diffb;
213 	argv[argc++] = dp13;
214 	argv[argc++] = dp23;
215 	argv[argc++] = path1;
216 	argv[argc++] = path2;
217 	argv[argc++] = path3;
218 
219 	diff3_conflicts = diff3_internal(argc, argv, av[0], av[2]);
220 	if (diff3_conflicts < 0) {
221 		buf_free(diffb);
222 		diffb = NULL;
223 		goto out;
224 	}
225 
226 	plen = buf_len(diffb);
227 	patch = buf_release(diffb);
228 	dlen = buf_len(b1);
229 	data = buf_release(b1);
230 
231 	if ((diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines)) == NULL)
232 		goto out;
233 
234 	if (!(flags & QUIET) && diff3_conflicts != 0)
235 		warnx("warning: overlaps or other problems during merge");
236 
237 out:
238 	buf_free(b2);
239 	buf_free(b3);
240 	buf_free(d1);
241 	buf_free(d2);
242 
243 	(void)unlink(path1);
244 	(void)unlink(path2);
245 	(void)unlink(path3);
246 	(void)unlink(dp13);
247 	(void)unlink(dp23);
248 
249 	free(path1);
250 	free(path2);
251 	free(path3);
252 	free(dp13);
253 	free(dp23);
254 	free(data);
255 	free(patch);
256 
257 	return (diffb);
258 }
259 
260 BUF *
261 rcs_diff3(RCSFILE *rf, char *workfile, RCSNUM *rev1, RCSNUM *rev2, int flags)
262 {
263 	int argc;
264 	char *argv[5], r1[RCS_REV_BUFSZ], r2[RCS_REV_BUFSZ];
265 	char *dp13, *dp23, *path1, *path2, *path3;
266 	BUF *b1, *b2, *b3, *d1, *d2, *diffb;
267 	size_t dlen, plen;
268 	u_char *data, *patch;
269 
270 	b1 = b2 = b3 = d1 = d2 = diffb = NULL;
271 	dp13 = dp23 = path1 = path2 = path3 = NULL;
272 	data = patch = NULL;
273 
274 	if ((flags & MERGE_EFLAG) && !(flags & MERGE_OFLAG))
275 		oflag = 0;
276 
277 	rcsnum_tostr(rev1, r1, sizeof(r1));
278 	rcsnum_tostr(rev2, r2, sizeof(r2));
279 
280 	if ((b1 = buf_load(workfile)) == NULL)
281 		goto out;
282 
283 	if (!(flags & QUIET))
284 		(void)fprintf(stderr, "retrieving revision %s\n", r1);
285 	if ((b2 = rcs_getrev(rf, rev1)) == NULL)
286 		goto out;
287 
288 	if (!(flags & QUIET))
289 		(void)fprintf(stderr, "retrieving revision %s\n", r2);
290 	if ((b3 = rcs_getrev(rf, rev2)) == NULL)
291 		goto out;
292 
293 	d1 = buf_alloc(128);
294 	d2 = buf_alloc(128);
295 	diffb = buf_alloc(128);
296 
297 	(void)xasprintf(&path1, "%s/diff1.XXXXXXXXXX", rcs_tmpdir);
298 	(void)xasprintf(&path2, "%s/diff2.XXXXXXXXXX", rcs_tmpdir);
299 	(void)xasprintf(&path3, "%s/diff3.XXXXXXXXXX", rcs_tmpdir);
300 
301 	buf_write_stmp(b1, path1);
302 	buf_write_stmp(b2, path2);
303 	buf_write_stmp(b3, path3);
304 
305 	buf_free(b2);
306 	b2 = NULL;
307 
308 	if ((diffreg(path1, path3, d1, D_FORCEASCII) == D_ERROR) ||
309 	    (diffreg(path2, path3, d2, D_FORCEASCII) == D_ERROR)) {
310 		buf_free(diffb);
311 		diffb = NULL;
312 		goto out;
313 	}
314 
315 	(void)xasprintf(&dp13, "%s/d13.XXXXXXXXXX", rcs_tmpdir);
316 	buf_write_stmp(d1, dp13);
317 
318 	buf_free(d1);
319 	d1 = NULL;
320 
321 	(void)xasprintf(&dp23, "%s/d23.XXXXXXXXXX", rcs_tmpdir);
322 	buf_write_stmp(d2, dp23);
323 
324 	buf_free(d2);
325 	d2 = NULL;
326 
327 	argc = 0;
328 	diffbuf = diffb;
329 	argv[argc++] = dp13;
330 	argv[argc++] = dp23;
331 	argv[argc++] = path1;
332 	argv[argc++] = path2;
333 	argv[argc++] = path3;
334 
335 	diff3_conflicts = diff3_internal(argc, argv, workfile, r2);
336 	if (diff3_conflicts < 0) {
337 		buf_free(diffb);
338 		diffb = NULL;
339 		goto out;
340 	}
341 
342 	plen = buf_len(diffb);
343 	patch = buf_release(diffb);
344 	dlen = buf_len(b1);
345 	data = buf_release(b1);
346 
347 	if ((diffb = rcs_patchfile(data, dlen, patch, plen, ed_patch_lines)) == NULL)
348 		goto out;
349 
350 	if (!(flags & QUIET) && diff3_conflicts != 0)
351 		warnx("warning: overlaps or other problems during merge");
352 
353 out:
354 	buf_free(b2);
355 	buf_free(b3);
356 	buf_free(d1);
357 	buf_free(d2);
358 
359 	(void)unlink(path1);
360 	(void)unlink(path2);
361 	(void)unlink(path3);
362 	(void)unlink(dp13);
363 	(void)unlink(dp23);
364 
365 	free(path1);
366 	free(path2);
367 	free(path3);
368 	free(dp13);
369 	free(dp23);
370 	free(data);
371 	free(patch);
372 
373 	return (diffb);
374 }
375 
376 static int
377 diff3_internal(int argc, char **argv, const char *fmark, const char *rmark)
378 {
379 	ssize_t m, n;
380 	int i;
381 
382 	if (argc < 5)
383 		return (-1);
384 
385 	if (oflag) {
386 		i = snprintf(f1mark, sizeof(f1mark), "<<<<<<< %s", fmark);
387 		if (i < 0 || i >= (int)sizeof(f1mark))
388 			errx(1, "diff3_internal: string truncated");
389 
390 		i = snprintf(f3mark, sizeof(f3mark), ">>>>>>> %s", rmark);
391 		if (i < 0 || i >= (int)sizeof(f3mark))
392 			errx(1, "diff3_internal: string truncated");
393 	}
394 
395 	increase();
396 	if ((m = readin(argv[0], &d13)) < 0) {
397 		warn("%s", argv[0]);
398 		return (-1);
399 	}
400 	if ((n = readin(argv[1], &d23)) < 0) {
401 		warn("%s", argv[1]);
402 		return (-1);
403 	}
404 
405 	for (i = 0; i <= 2; i++)
406 		if ((fp[i] = fopen(argv[i + 2], "r")) == NULL) {
407 			warn("%s", argv[i + 2]);
408 			return (-1);
409 		}
410 
411 	return (merge(m, n));
412 }
413 
414 int
415 ed_patch_lines(struct rcs_lines *dlines, struct rcs_lines *plines)
416 {
417 	char op, *ep;
418 	struct rcs_line *sort, *lp, *dlp, *ndlp, *insert_after;
419 	int start, end, i, lineno;
420 	u_char tmp;
421 
422 	dlp = TAILQ_FIRST(&(dlines->l_lines));
423 	lp = TAILQ_FIRST(&(plines->l_lines));
424 
425 	end = 0;
426 	for (lp = TAILQ_NEXT(lp, l_list); lp != NULL;
427 	    lp = TAILQ_NEXT(lp, l_list)) {
428 		/* Skip blank lines */
429 		if (lp->l_len < 2)
430 			continue;
431 
432 		/* NUL-terminate line buffer for strtol() safety. */
433 		tmp = lp->l_line[lp->l_len - 1];
434 		lp->l_line[lp->l_len - 1] = '\0';
435 
436 		/* len - 1 is NUL terminator so we use len - 2 for 'op' */
437 		op = lp->l_line[lp->l_len - 2];
438 		start = (int)strtol(lp->l_line, &ep, 10);
439 
440 		/* Restore the last byte of the buffer */
441 		lp->l_line[lp->l_len - 1] = tmp;
442 
443 		if (op == 'a') {
444 			if (start > dlines->l_nblines ||
445 			    start < 0 || *ep != 'a')
446 				errx(1, "ed_patch_lines");
447 		} else if (op == 'c') {
448 			if (start > dlines->l_nblines ||
449 			    start < 0 || (*ep != ',' && *ep != 'c'))
450 				errx(1, "ed_patch_lines");
451 
452 			if (*ep == ',') {
453 				ep++;
454 				end = (int)strtol(ep, &ep, 10);
455 				if (end < 0 || *ep != 'c')
456 					errx(1, "ed_patch_lines");
457 			} else {
458 				end = start;
459 			}
460 		}
461 
462 
463 		for (;;) {
464 			if (dlp == NULL)
465 				break;
466 			if (dlp->l_lineno == start)
467 				break;
468 			if (dlp->l_lineno > start) {
469 				dlp = TAILQ_PREV(dlp, tqh, l_list);
470 			} else if (dlp->l_lineno < start) {
471 				ndlp = TAILQ_NEXT(dlp, l_list);
472 				if (ndlp->l_lineno > start)
473 					break;
474 				dlp = ndlp;
475 			}
476 		}
477 
478 		if (dlp == NULL)
479 			errx(1, "ed_patch_lines");
480 
481 
482 		if (op == 'c') {
483 			insert_after = TAILQ_PREV(dlp, tqh, l_list);
484 			for (i = 0; i <= (end - start); i++) {
485 				ndlp = TAILQ_NEXT(dlp, l_list);
486 				TAILQ_REMOVE(&(dlines->l_lines), dlp, l_list);
487 				dlp = ndlp;
488 			}
489 			dlp = insert_after;
490 		}
491 
492 		if (op == 'a' || op == 'c') {
493 			for (;;) {
494 				ndlp = lp;
495 				lp = TAILQ_NEXT(lp, l_list);
496 				if (lp == NULL)
497 					errx(1, "ed_patch_lines");
498 
499 				if (!memcmp(lp->l_line, ".", 1))
500 					break;
501 
502 				TAILQ_REMOVE(&(plines->l_lines), lp, l_list);
503 				TAILQ_INSERT_AFTER(&(dlines->l_lines), dlp,
504 				    lp, l_list);
505 				dlp = lp;
506 
507 				lp->l_lineno = start;
508 				lp = ndlp;
509 			}
510 		}
511 
512 		/*
513 		 * always resort lines as the markers might be put at the
514 		 * same line as we first started editing.
515 		 */
516 		lineno = 0;
517 		TAILQ_FOREACH(sort, &(dlines->l_lines), l_list)
518 			sort->l_lineno = lineno++;
519 		dlines->l_nblines = lineno - 1;
520 	}
521 
522 	return (0);
523 }
524 
525 /*
526  * Pick up the line numbers of all changes from one change file.
527  * (This puts the numbers in a vector, which is not strictly necessary,
528  * since the vector is processed in one sequential pass.
529  * The vector could be optimized out of existence)
530  */
531 static ssize_t
532 readin(char *name, struct diff **dd)
533 {
534 	int a, b, c, d;
535 	char kind, *p;
536 	size_t i;
537 
538 	fp[0] = fopen(name, "r");
539 	if (fp[0] == NULL)
540 		return (-1);
541 	for (i = 0; (p = getchange(fp[0])); i++) {
542 		if (i >= szchanges - 1)
543 			increase();
544 		a = b = number(&p);
545 		if (*p == ',') {
546 			p++;
547 			b = number(&p);
548 		}
549 		kind = *p++;
550 		c = d = number(&p);
551 		if (*p==',') {
552 			p++;
553 			d = number(&p);
554 		}
555 		if (kind == 'a')
556 			a++;
557 		if (kind == 'd')
558 			c++;
559 		b++;
560 		d++;
561 		(*dd)[i].old.from = a;
562 		(*dd)[i].old.to = b;
563 		(*dd)[i].new.from = c;
564 		(*dd)[i].new.to = d;
565 	}
566 
567 	if (i) {
568 		(*dd)[i].old.from = (*dd)[i-1].old.to;
569 		(*dd)[i].new.from = (*dd)[i-1].new.to;
570 	}
571 
572 	(void)fclose(fp[0]);
573 
574 	return (i);
575 }
576 
577 static int
578 number(char **lc)
579 {
580 	int nn;
581 
582 	nn = 0;
583 	while (isdigit((unsigned char)(**lc)))
584 		nn = nn*10 + *(*lc)++ - '0';
585 
586 	return (nn);
587 }
588 
589 static char *
590 getchange(FILE *b)
591 {
592 	char *line;
593 
594 	while ((line = get_line(b, NULL))) {
595 		if (isdigit((unsigned char)line[0]))
596 			return (line);
597 	}
598 
599 	return (NULL);
600 }
601 
602 static char *
603 get_line(FILE *b, size_t *n)
604 {
605 	char *cp;
606 	size_t len;
607 	static char *buf;
608 	static size_t bufsize;
609 
610 	if ((cp = fgetln(b, &len)) == NULL)
611 		return (NULL);
612 
613 	if (cp[len - 1] != '\n')
614 		len++;
615 	if (len + 1 > bufsize) {
616 		do {
617 			bufsize += 1024;
618 		} while (len + 1 > bufsize);
619 		buf = xreallocarray(buf, 1, bufsize);
620 	}
621 	memcpy(buf, cp, len - 1);
622 	buf[len - 1] = '\n';
623 	buf[len] = '\0';
624 	if (n != NULL)
625 		*n = len;
626 
627 	return (buf);
628 }
629 
630 static int
631 merge(size_t m1, size_t m2)
632 {
633 	struct diff *d1, *d2, *d3;
634 	int dpl, j, t1, t2;
635 
636 	d1 = d13;
637 	d2 = d23;
638 	j = 0;
639 	for (;;) {
640 		t1 = (d1 < d13 + m1);
641 		t2 = (d2 < d23 + m2);
642 		if (!t1 && !t2)
643 			break;
644 
645 		if (debug) {
646 			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
647 			d1->old.from, d1->old.to,
648 			d1->new.from, d1->new.to,
649 			d2->old.from, d2->old.to,
650 			d2->new.from, d2->new.to);
651 		}
652 
653 		/* first file is different from others */
654 		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
655 			/* stuff peculiar to 1st file */
656 			if (eflag==0) {
657 				separate("1");
658 				change(1, &d1->old, 0);
659 				keep(2, &d1->new);
660 				change(3, &d1->new, 0);
661 			}
662 			d1++;
663 			continue;
664 		}
665 
666 		/* second file is different from others */
667 		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
668 			if (eflag==0) {
669 				separate("2");
670 				keep(1, &d2->new);
671 				change(2, &d2->old, 0);
672 				change(3, &d2->new, 0);
673 			}
674 			d2++;
675 			continue;
676 		}
677 
678 		/*
679 		 * Merge overlapping changes in first file
680 		 * this happens after extension (see below).
681 		 */
682 		if (d1 + 1 < d13 + m1 && d1->new.to >= d1[1].new.from) {
683 			d1[1].old.from = d1->old.from;
684 			d1[1].new.from = d1->new.from;
685 			d1++;
686 			continue;
687 		}
688 
689 		/* merge overlapping changes in second */
690 		if (d2 + 1 < d23 + m2 && d2->new.to >= d2[1].new.from) {
691 			d2[1].old.from = d2->old.from;
692 			d2[1].new.from = d2->new.from;
693 			d2++;
694 			continue;
695 		}
696 		/* stuff peculiar to third file or different in all */
697 		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
698 			dpl = duplicate(&d1->old,&d2->old);
699 			if (dpl == -1)
700 				return (-1);
701 
702 			/*
703 			 * dpl = 0 means all files differ
704 			 * dpl = 1 means files 1 and 2 identical
705 			 */
706 			if (eflag==0) {
707 				separate(dpl ? "3" : "");
708 				change(1, &d1->old, dpl);
709 				change(2, &d2->old, 0);
710 				d3 = d1->old.to > d1->old.from ? d1 : d2;
711 				change(3, &d3->new, 0);
712 			} else
713 				j = edit(d1, dpl, j);
714 			d1++;
715 			d2++;
716 			continue;
717 		}
718 
719 		/*
720 		 * Overlapping changes from file 1 and 2; extend changes
721 		 * appropriately to make them coincide.
722 		 */
723 		if (d1->new.from < d2->new.from) {
724 			d2->old.from -= d2->new.from-d1->new.from;
725 			d2->new.from = d1->new.from;
726 		} else if (d2->new.from < d1->new.from) {
727 			d1->old.from -= d1->new.from-d2->new.from;
728 			d1->new.from = d2->new.from;
729 		}
730 		if (d1->new.to > d2->new.to) {
731 			d2->old.to += d1->new.to - d2->new.to;
732 			d2->new.to = d1->new.to;
733 		} else if (d2->new.to > d1->new.to) {
734 			d1->old.to += d2->new.to - d1->new.to;
735 			d1->new.to = d2->new.to;
736 		}
737 	}
738 
739 	return (edscript(j));
740 }
741 
742 static void
743 separate(const char *s)
744 {
745 	diff_output("====%s\n", s);
746 }
747 
748 /*
749  * The range of lines rold.from thru rold.to in file i is to be changed.
750  * It is to be printed only if it does not duplicate something to be
751  * printed later.
752  */
753 static void
754 change(int i, struct range *rold, int fdup)
755 {
756 	diff_output("%d:", i);
757 	last[i] = rold->to;
758 	prange(rold);
759 	if (fdup || debug)
760 		return;
761 	i--;
762 	(void)skip(i, rold->from, NULL);
763 	(void)skip(i, rold->to, "  ");
764 }
765 
766 /*
767  * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
768  */
769 static void
770 prange(struct range *rold)
771 {
772 	if (rold->to <= rold->from)
773 		diff_output("%da\n", rold->from - 1);
774 	else {
775 		diff_output("%d", rold->from);
776 		if (rold->to > rold->from+1)
777 			diff_output(",%d", rold->to - 1);
778 		diff_output("c\n");
779 	}
780 }
781 
782 /*
783  * No difference was reported by diff between file 1 (or 2) and file 3,
784  * and an artificial dummy difference (trange) must be ginned up to
785  * correspond to the change reported in the other file.
786  */
787 static void
788 keep(int i, struct range *rnew)
789 {
790 	int delta;
791 	struct range trange;
792 
793 	delta = last[3] - last[i];
794 	trange.from = rnew->from - delta;
795 	trange.to = rnew->to - delta;
796 	change(i, &trange, 1);
797 }
798 
799 /*
800  * skip to just before line number from in file "i".  If "pr" is non-NULL,
801  * print all skipped stuff with string pr as a prefix.
802  */
803 static int
804 skip(int i, int from, char *pr)
805 {
806 	size_t j, n;
807 	char *line;
808 
809 	for (n = 0; cline[i] < from - 1; n += j) {
810 		if ((line = get_line(fp[i], &j)) == NULL)
811 			return (-1);
812 		if (pr != NULL)
813 			diff_output("%s%s", pr, line);
814 		cline[i]++;
815 	}
816 	return ((int) n);
817 }
818 
819 /*
820  * Return 1 or 0 according as the old range (in file 1) contains exactly
821  * the same data as the new range (in file 2).
822  */
823 static int
824 duplicate(struct range *r1, struct range *r2)
825 {
826 	int c,d;
827 	int nchar;
828 	int nline;
829 
830 	if (r1->to-r1->from != r2->to-r2->from)
831 		return (0);
832 	(void)skip(0, r1->from, NULL);
833 	(void)skip(1, r2->from, NULL);
834 	nchar = 0;
835 	for (nline=0; nline < r1->to - r1->from; nline++) {
836 		do {
837 			c = getc(fp[0]);
838 			d = getc(fp[1]);
839 			if (c == -1 || d== -1)
840 				return (-1);
841 			nchar++;
842 			if (c != d) {
843 				repos(nchar);
844 				return (0);
845 			}
846 		} while (c != '\n');
847 	}
848 	repos(nchar);
849 	return (1);
850 }
851 
852 static void
853 repos(int nchar)
854 {
855 	int i;
856 
857 	for (i = 0; i < 2; i++)
858 		(void)fseek(fp[i], (long)-nchar, SEEK_CUR);
859 }
860 
861 /*
862  * collect an editing script for later regurgitation
863  */
864 static int
865 edit(struct diff *diff, int fdup, int j)
866 {
867 	if (((fdup + 1) & eflag) == 0)
868 		return (j);
869 	j++;
870 	overlap[j] = !fdup;
871 	if (!fdup)
872 		overlapcnt++;
873 	de[j].old.from = diff->old.from;
874 	de[j].old.to = diff->old.to;
875 	de[j].new.from = de[j-1].new.to + skip(2, diff->new.from, NULL);
876 	de[j].new.to = de[j].new.from + skip(2, diff->new.to, NULL);
877 	return (j);
878 }
879 
880 /* regurgitate */
881 static int
882 edscript(int n)
883 {
884 	int j, k;
885 	char block[BUFSIZ+1];
886 
887 	for (; n > 0; n--) {
888 		if (!oflag || !overlap[n])
889 			prange(&de[n].old);
890 		else
891 			diff_output("%da\n=======\n", de[n].old.to -1);
892 		(void)fseek(fp[2], (long)de[n].new.from, SEEK_SET);
893 		for (k = de[n].new.to-de[n].new.from; k > 0; k-= j) {
894 			j = k > BUFSIZ ? BUFSIZ : k;
895 			if (fread(block, 1, j, fp[2]) != (size_t)j)
896 				return (-1);
897 			block[j] = '\0';
898 			diff_output("%s", block);
899 		}
900 
901 		if (!oflag || !overlap[n])
902 			diff_output(".\n");
903 		else {
904 			diff_output("%s\n.\n", f3mark);
905 			diff_output("%da\n%s\n.\n", de[n].old.from - 1, f1mark);
906 		}
907 	}
908 
909 	return (overlapcnt);
910 }
911 
912 static void
913 increase(void)
914 {
915 	size_t newsz, incr;
916 
917 	/* are the memset(3) calls needed? */
918 	newsz = szchanges == 0 ? 64 : 2 * szchanges;
919 	incr = newsz - szchanges;
920 
921 	d13 = xreallocarray(d13, newsz, sizeof(*d13));
922 	memset(d13 + szchanges, 0, incr * sizeof(*d13));
923 	d23 = xreallocarray(d23, newsz, sizeof(*d23));
924 	memset(d23 + szchanges, 0, incr * sizeof(*d23));
925 	de = xreallocarray(de, newsz, sizeof(*de));
926 	memset(de + szchanges, 0, incr * sizeof(*de));
927 	overlap = xreallocarray(overlap, newsz, sizeof(*overlap));
928 	memset(overlap + szchanges, 0, incr * sizeof(*overlap));
929 	szchanges = newsz;
930 }