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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: diff3prog.c,v 1.11 2009/10/27 23:59:37 deraadt Exp $	*/

/*
 * Copyright (C) Caldera International Inc.  2001-2002.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code and documentation must retain the above
 *    copyright notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed or owned by Caldera
 *	International, Inc.
 * 4. Neither the name of Caldera International, Inc. nor the names of other
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
 * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
 * INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)diff3.c	8.1 (Berkeley) 6/6/93
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <err.h>

/* diff3 - 3-way differential file comparison */

/* diff3 [-ex3EX] d13 d23 f1 f2 f3 [m1 m3]
 *
 * d13 = diff report on f1 vs f3
 * d23 = diff report on f2 vs f3
 * f1, f2, f3 the 3 files
 * if changes in f1 overlap with changes in f3, m1 and m3 are used
 * to mark the overlaps; otherwise, the file names f1 and f3 are used
 * (only for options E and X).
 */

/*
 * "from" is first in range of changed lines; "to" is last+1
 * from=to=line after point of insertion for added lines.
 */
struct  range {
	int from;
	int to;
};
struct diff {
	struct range old;
	struct range new;
};

size_t szchanges;

struct diff *d13;
struct diff *d23;
/*
 * "de" is used to gather editing scripts.  These are later spewed out in
 * reverse order.  Its first element must be all zero, the "new" component
 * of "de" contains line positions or byte positions depending on when you
 * look (!?).  Array overlap indicates which sections in "de" correspond to
 * lines that are different in all three files.
 */
struct diff *de;
char *overlap;
int  overlapcnt;
FILE *fp[3];
int cline[3];		/* # of the last-read line in each file (0-2) */
/*
 * the latest known correspondence between line numbers of the 3 files
 * is stored in last[1-3];
 */
int last[4];
int eflag;
int oflag;		/* indicates whether to mark overlaps (-E or -X)*/
int debug  = 0;
char f1mark[40], f3mark[40];	/* markers for -E and -X */

int duplicate(struct range *, struct range *);
int edit(struct diff *, int, int);
char *getchange(FILE *);
char *getline(FILE *, size_t *);
int number(char **);
int readin(char *, struct diff **);
int skip(int, int, char *);
void change(int, struct range *, int);
void keep(int, struct range *);
void merge(int, int);
void prange(struct range *);
void repos(int);
void separate(const char *);
__dead void edscript(int);
__dead void trouble(void);
void increase(void);
__dead void usage(void);

int
main(int argc, char **argv)
{
	int ch, i, m, n;

	eflag = 0;
	oflag = 0;
	while ((ch = getopt(argc, argv, "EeXx3")) != -1) {
		switch (ch) {
		case 'E':
			eflag = 3;
			oflag = 1;
			break;
		case 'e':
			eflag = 3;
			break;
		case 'X':
			oflag = eflag = 1;
			break;
		case 'x':
			eflag = 1;
			break;
		case '3':
			eflag = 2;
			break;
		}
	}
	argc -= optind;
	argv += optind;
	/* XXX - argc usage seems wrong here */
	if (argc < 5)
		usage();

	if (oflag) {
		(void)snprintf(f1mark, sizeof(f1mark), "<<<<<<< %s",
		    argc >= 6 ? argv[5] : argv[2]);
		(void)snprintf(f3mark, sizeof(f3mark), ">>>>>>> %s",
		    argc >= 7 ? argv[6] : argv[4]);
	}

	increase();
	m = readin(argv[0], &d13);
	n = readin(argv[1], &d23);
	for (i = 0; i <= 2; i++) {
		if ((fp[i] = fopen(argv[i + 2], "r")) == NULL)
			err(EXIT_FAILURE, "can't open %s", argv[i + 2]);
	}
	merge(m, n);
	exit(EXIT_SUCCESS);
}

/*
 * Pick up the line numbers of all changes from one change file.
 * (This puts the numbers in a vector, which is not strictly necessary,
 * since the vector is processed in one sequential pass.
 * The vector could be optimized out of existence)
 */
int
readin(char *name, struct diff **dd)
{
	int a, b, c, d, i;
	char kind, *p;

	fp[0] = fopen(name, "r");
	if (fp[0] == NULL)
		err(EXIT_FAILURE, "can't open %s", name);
	for (i=0; (p = getchange(fp[0])); i++) {
		if (i >= szchanges - 1)
			increase();
		a = b = number(&p);
		if (*p == ',') {
			p++;
			b = number(&p);
		}
		kind = *p++;
		c = d = number(&p);
		if (*p==',') {
			p++;
			d = number(&p);
		}
		if (kind == 'a')
			a++;
		if (kind == 'd')
			c++;
		b++;
		d++;
		(*dd)[i].old.from = a;
		(*dd)[i].old.to = b;
		(*dd)[i].new.from = c;
		(*dd)[i].new.to = d;
	}
	if (i) {
		(*dd)[i].old.from = (*dd)[i-1].old.to;
		(*dd)[i].new.from = (*dd)[i-1].new.to;
	}
	(void)fclose(fp[0]);
	return (i);
}

int
number(char **lc)
{
	int nn;
	nn = 0;
	while (isdigit((unsigned char)(**lc)))
		nn = nn*10 + *(*lc)++ - '0';
	return (nn);
}

char *
getchange(FILE *b)
{
	char *line;

	while ((line = getline(b, NULL))) {
		if (isdigit((unsigned char)line[0]))
			return (line);
	}
	return (NULL);
}

char *
getline(FILE *b, size_t *n)
{
	char *cp;
	size_t len;
	static char *buf;
	static size_t bufsize;

	if ((cp = fgetln(b, &len)) == NULL)
		return (NULL);

	if (cp[len - 1] != '\n')
		len++;
	if (len + 1 > bufsize) {
		do {
			bufsize += 1024;
		} while (len + 1 > bufsize);
		if ((buf = realloc(buf, bufsize)) == NULL)
			err(EXIT_FAILURE, NULL);
	}
	memcpy(buf, cp, len - 1);
	buf[len - 1] = '\n';
	buf[len] = '\0';
	if (n != NULL)
		*n = len;
	return (buf);
}

void
merge(int m1, int m2)
{
	struct diff *d1, *d2, *d3;
	int dup, j, t1, t2;

	d1 = d13;
	d2 = d23;
	j = 0;
	while ((t1 = d1 < d13 + m1) | (t2 = d2 < d23 + m2)) {
		if (debug) {
			printf("%d,%d=%d,%d %d,%d=%d,%d\n",
			d1->old.from,d1->old.to,
			d1->new.from,d1->new.to,
			d2->old.from,d2->old.to,
			d2->new.from,d2->new.to);
		}
		/* first file is different from others */
		if (!t2 || (t1 && d1->new.to < d2->new.from)) {
			/* stuff peculiar to 1st file */
			if (eflag==0) {
				separate("1");
				change(1, &d1->old, 0);
				keep(2, &d1->new);
				change(3, &d1->new, 0);
			}
			d1++;
			continue;
		}
		/* second file is different from others */
		if (!t1 || (t2 && d2->new.to < d1->new.from)) {
			if (eflag==0) {
				separate("2");
				keep(1, &d2->new);
				change(2, &d2->old, 0);
				change(3, &d2->new, 0);
			}
			d2++;
			continue;
		}
		/*
		 * Merge overlapping changes in first file
		 * this happens after extension (see below).
		 */
		if (d1 + 1 < d13 + m1 && d1->new.to >= d1[1].new.from) {
			d1[1].old.from = d1->old.from;
			d1[1].new.from = d1->new.from;
			d1++;
			continue;
		}

		/* merge overlapping changes in second */
		if (d2 + 1 < d23 + m2 && d2->new.to >= d2[1].new.from) {
			d2[1].old.from = d2->old.from;
			d2[1].new.from = d2->new.from;
			d2++;
			continue;
		}
		/* stuff peculiar to third file or different in all */
		if (d1->new.from == d2->new.from && d1->new.to == d2->new.to) {
			dup = duplicate(&d1->old,&d2->old);
			/*
			 * dup = 0 means all files differ
			 * dup = 1 means files 1 and 2 identical
			 */
			if (eflag==0) {
				separate(dup ? "3" : "");
				change(1, &d1->old, dup);
				change(2, &d2->old, 0);
				d3 = d1->old.to > d1->old.from ? d1 : d2;
				change(3, &d3->new, 0);
			} else
				j = edit(d1, dup, j);
			d1++;
			d2++;
			continue;
		}
		/*
		 * Overlapping changes from file 1 and 2; extend changes
		 * appropriately to make them coincide.
		 */
		if (d1->new.from < d2->new.from) {
			d2->old.from -= d2->new.from-d1->new.from;
			d2->new.from = d1->new.from;
		} else if (d2->new.from < d1->new.from) {
			d1->old.from -= d1->new.from-d2->new.from;
			d1->new.from = d2->new.from;
		}
		if (d1->new.to > d2->new.to) {
			d2->old.to += d1->new.to - d2->new.to;
			d2->new.to = d1->new.to;
		} else if (d2->new.to > d1->new.to) {
			d1->old.to += d2->new.to - d1->new.to;
			d1->new.to = d2->new.to;
		}
	}
	if (eflag)
		edscript(j);
}

void
separate(const char *s)
{
	printf("====%s\n", s);
}

/*
 * The range of lines rold.from thru rold.to in file i is to be changed.
 * It is to be printed only if it does not duplicate something to be
 * printed later.
 */
void
change(int i, struct range *rold, int dup)
{
	printf("%d:", i);
	last[i] = rold->to;
	prange(rold);
	if (dup || debug)
		return;
	i--;
	(void)skip(i, rold->from, NULL);
	(void)skip(i, rold->to, "  ");
}

/*
 * print the range of line numbers, rold.from thru rold.to, as n1,n2 or n1
 */
void
prange(struct range *rold)
{
	if (rold->to <= rold->from)
		printf("%da\n", rold->from - 1);
	else {
		printf("%d", rold->from);
		if (rold->to > rold->from+1)
			printf(",%d", rold->to - 1);
		printf("c\n");
	}
}

/*
 * No difference was reported by diff between file 1 (or 2) and file 3,
 * and an artificial dummy difference (trange) must be ginned up to
 * correspond to the change reported in the other file.
 */
void
keep(int i, struct range *rnew)
{
	int delta;
	struct range trange;

	delta = last[3] - last[i];
	trange.from = rnew->from - delta;
	trange.to = rnew->to - delta;
	change(i, &trange, 1);
}

/*
 * skip to just before line number from in file "i".  If "pr" is non-NULL,
 * print all skipped stuff with string pr as a prefix.
 */
int
skip(int i, int from, char *pr)
{
	size_t j, n;
	char *line;

	for (n = 0; cline[i] < from - 1; n += j) {
		if ((line = getline(fp[i], &j)) == NULL)
			trouble();
		if (pr != NULL)
			printf("%s%s", pr, line);
		cline[i]++;
	}
	return ((int) n);
}

/*
 * Return 1 or 0 according as the old range (in file 1) contains exactly
 * the same data as the new range (in file 2).
 */
int
duplicate(struct range *r1, struct range *r2)
{
	int c,d;
	int nchar;
	int nline;

	if (r1->to-r1->from != r2->to-r2->from)
		return (0);
	(void)skip(0, r1->from, NULL);
	(void)skip(1, r2->from, NULL);
	nchar = 0;
	for (nline=0; nline < r1->to - r1->from; nline++) {
		do {
			c = getc(fp[0]);
			d = getc(fp[1]);
			if (c == -1 || d== -1)
				trouble();
			nchar++;
			if (c != d) {
				repos(nchar);
				return (0);
			}
		} while (c != '\n');
	}
	repos(nchar);
	return (1);
}

void
repos(int nchar)
{
	int i;

	for (i = 0; i < 2; i++)
		(void)fseek(fp[i], (long)-nchar, SEEK_CUR);
}

__dead void
trouble(void)
{
	errx(EXIT_FAILURE, "logic error");
}

/*
 * collect an editing script for later regurgitation
 */
int
edit(struct diff *diff, int dup, int j)
{
	if (((dup + 1) & eflag) == 0)
		return (j);
	j++;
	overlap[j] = !dup;
	if (!dup)
		overlapcnt++;
	de[j].old.from = diff->old.from;
	de[j].old.to = diff->old.to;
	de[j].new.from = de[j-1].new.to + skip(2, diff->new.from, NULL);
	de[j].new.to = de[j].new.from + skip(2, diff->new.to, NULL);
	return (j);
}

/* regurgitate */
__dead void
edscript(int n)
{
	int j,k;
	char block[BUFSIZ];

	for (n = n; n > 0; n--) {
		if (!oflag || !overlap[n])
			prange(&de[n].old);
		else
			printf("%da\n=======\n", de[n].old.to -1);
		(void)fseek(fp[2], (long)de[n].new.from, SEEK_SET);
		for (k = de[n].new.to-de[n].new.from; k > 0; k-= j) {
			j = k > BUFSIZ ? BUFSIZ : k;
			if (fread(block, 1, j, fp[2]) != j)
				trouble();
			(void)fwrite(block, 1, j, stdout);
		}
		if (!oflag || !overlap[n])
			printf(".\n");
		else {
			printf("%s\n.\n", f3mark);
			printf("%da\n%s\n.\n", de[n].old.from - 1, f1mark);
		}
	}
	exit(overlapcnt);
}

void
increase(void)
{
	struct diff *p;
	char *q;
	size_t newsz, incr;

	/* are the memset(3) calls needed? */
	newsz = szchanges == 0 ? 64 : 2 * szchanges;
	incr = newsz - szchanges;

	p = realloc(d13, newsz * sizeof(struct diff));
	if (p == NULL)
		err(1, NULL);
	memset(p + szchanges, 0, incr * sizeof(struct diff));
	d13 = p;
	p = realloc(d23, newsz * sizeof(struct diff));
	if (p == NULL)
		err(1, NULL);
	memset(p + szchanges, 0, incr * sizeof(struct diff));
	d23 = p;
	p = realloc(de, newsz * sizeof(struct diff));
	if (p == NULL)
		err(1, NULL);
	memset(p + szchanges, 0, incr * sizeof(struct diff));
	de = p;
	q = realloc(overlap, newsz * sizeof(char));
	if (q == NULL)
		err(1, NULL);
	memset(q + szchanges, 0, incr * sizeof(char));
	overlap = q;
	szchanges = newsz;
}


__dead void
usage(void)
{
	extern char *__progname;

	fprintf(stderr, "usage: %s [-exEX3] /tmp/d3a.?????????? "
	    "/tmp/d3b.?????????? file1 file2 file3\n", __progname);
	exit(EXIT_FAILURE);
}