/*
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1987 Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* !lint */

#ifndef lint
static	char sccsid[] = "@(#)cmp.c 1.1 94/10/31 SMI"; /* from UCB 4.5 11/18/87 */
#endif /* !lint */

#include <sys/param.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <stdio.h>
#include <ctype.h>
#include <errno.h>

#define DIFF	1			/* found differences */
#define ERR	2			/* error during run */
#define NO	0			/* no/false */
#define OK	0			/* didn't find differences */
#define YES	1			/* yes/true */

static int	fd1,			/* descriptor, file 1 */
		fd2,			/* descriptor, file 2 */
		silent = NO;		/* if silent run */
static short	all = NO;		/* if report all differences */
static	u_char	buf1[MAXBSIZE],		/* read buffers */
		buf2[MAXBSIZE];
static char	*file1,			/* name, file 1 */
		*file2;			/* name, file 2 */

main(argc,argv)
int	argc;
char	**argv;
{
	extern char	*optarg;	/* getopt externals */
	extern int	optind;
	int	ch;			/* arguments */
	u_long	otoi();

	while ((ch = getopt(argc,argv,"ls")) != EOF)
		switch(ch) {
			case 'l':		/* print all differences */
				all = YES;
				break;
			case 's':		/* silent run */
				silent = YES;
				break;
			case '?':
			default:
				usage();
		}
	argv += optind;
	argc -= optind;

	if (argc < 2 || argc > 4)
		usage();

	/* open up files; "-" is stdin */
	file1 = argv[0];
	if (strcmp(file1,"-") != 0 && (fd1 = open(file1,O_RDONLY)) < 0)
		cantopen(file1);
	file2 = argv[1];
	if ((fd2 = open(file2,O_RDONLY)) < 0)
		cantopen(file2);

	/* handle skip arguments */
	if (argc > 2) {
		skip(otoi(argv[2]),fd1,file1);
		if (argc == 4)
			skip(otoi(argv[3]),fd2,file2);
	}
	cmp();
	/*NOTREACHED*/
}

/*
 * skip --
 *	skip first part of file
 */
static
skip(dist,fd,fname)
register u_long	dist;			/* length in bytes, to skip */
register int	fd;			/* file descriptor */
char	*fname;				/* file name for error */
{
	register int	rlen;		/* read length */
	register int	nread;

	for (;dist;dist -= rlen) {
		rlen = MIN(dist,sizeof(buf1));
		if ((nread = read(fd,buf1,rlen)) != rlen) {
			if (nread < 0)
				ioerror(fname);
			else
				endoffile(fname);
		}
	}
}

static
cmp()
{
	register u_char	*C1,		/* traveling pointers */
			*C2;
	register int	cnt,		/* counter */
			len1,		/* read length 1 */
			len2;		/* read length 2 */
	register long	byte,		/* byte count */
			line;		/* line count */
	short	dfound = NO;		/* if difference found */

	for (byte = 0,line = 1;;) {
		switch(len1 = read(fd1,buf1,MAXBSIZE)) {
			case -1:
				ioerror(file1);
			case 0:
				/*
				 * read of file 1 just failed, find out
				 * if there's anything left in file 2
				 */
				switch(read(fd2,buf2,1)) {
					case -1:
						ioerror(file2);
					case 0:
						exit(dfound ? DIFF : OK);
					default:
						endoffile(file1);
				}
		}
		/*
		 * file1 might be stdio, which means that a read of less than
		 * MAXBSIZE might not mean an EOF.  So, read whatever we read
		 * from file1 from file2.
		 */
		if ((len2 = read(fd2,buf2,len1)) == -1)
			ioerror(file2);
		if (len2 == 0)
			endoffile(file2);
		if (bcmp(buf1,buf2,len2)) {
			if (silent)
				exit(DIFF);
			if (all) {
				dfound = YES;
				for (C1 = buf1,C2 = buf2,cnt = len2;cnt--;++C1,++C2) {
					++byte;
					if (*C1 != *C2)
						printf("%6ld %3o %3o\n",byte,*C1,*C2);
				}
			}
			else for (C1 = buf1,C2 = buf2;;++C1,++C2) {
				++byte;
				if (*C1 != *C2) {
					printf("%s %s differ: char %ld, line %ld\n",file1,file2,byte,line);
					exit(DIFF);
				}
				if (*C1 == '\n')
					++line;
			}
		}
		else {
			byte += len2;
			/*
			 * here's the real performance problem, we've got to
			 * count the stupid lines, which means that -l is a
			 * *much* faster version, i.e., unless you really
			 * *want* to know the line number, run -s or -l.
			 */
			if (!silent && !all)
				for (C1 = buf1,cnt = len2;cnt--;)
					if (*C1++ == '\n')
						++line;
		}
		/*
		 * couldn't read as much from file2 as from file1; checked
		 * here because there might be a difference before we got
		 * to this point, which would have precedence.
		 */
		if (len2 < len1)
			endoffile(file2);
	}
}

/*
 * otoi --
 *	octal/decimal string to u_long
 */
static u_long
otoi(C)
register char	*C;		/* argument string */
{
	register u_long	val;	/* return value */
	register int	base;	/* number base */

	base = (*C == '0') ? 8 : 10;
	for (val = 0;isdigit(*C);++C)
		val = val * base + *C - '0';
	return(val);
}

/*
 * usage --
 *	print usage and die
 */
static
usage()
{
	fputs("usage: cmp [-ls] file1 file2 [skip1] [skip2]\n",stderr);
	exit(ERR);
}

/*
 * cantopen --
 *	print open error message and die
 */
cantopen(filename)
char *filename;
{
	register int sverrno;

	if (!silent) {
		sverrno = errno;
		(void) fprintf(stderr, "cmp: Can't open %s: ", filename);
		errno = sverrno;
		perror("");
	}
	exit(ERR);
}

/*
 * ioerror --
 *	print I/O error message and die
 */
ioerror(filename)
char *filename;
{
	register int sverrno;

	if (!silent) {
		sverrno = errno;
		(void) fprintf(stderr, "cmp: I/O error on %s: ", filename);
		errno = sverrno;
		perror("");
	}
	exit(ERR);
}

/*
 * endofffile --
 *	print end-of-file message and exit indicating the files were different
 */
endoffile(filename)
char *filename;
{
	if (!silent)
		(void) fprintf(stderr, "cmp: EOF on %s\n", filename);
	exit(DIFF);
}