1/* vi: set sw=4 ts=4: */
2/*
3 * Mini cmp implementation for busybox
4 *
5 * Copyright (C) 2000,2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
6 *
7 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
8 */
9
10/* BB_AUDIT SUSv3 (virtually) compliant -- uses nicer GNU format for -l. */
11/* http://www.opengroup.org/onlinepubs/007904975/utilities/cmp.html */
12
13/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
14 *
15 * Original version majorly reworked for SUSv3 compliance, bug fixes, and
16 * size optimizations.  Changes include:
17 * 1) Now correctly distinguishes between errors and actual file differences.
18 * 2) Proper handling of '-' args.
19 * 3) Actual error checking of i/o.
20 * 4) Accept SUSv3 -l option.  Note that we use the slightly nicer gnu format
21 *    in the '-l' case.
22 */
23
24#include "libbb.h"
25
26static FILE *cmp_xfopen_input(const char *filename)
27{
28	FILE *fp;
29
30	fp = fopen_or_warn_stdin(filename);
31	if (fp)
32		return fp;
33	xfunc_die();	/* We already output an error message. */
34}
35
36static const char fmt_eof[] ALIGN1 = "cmp: EOF on %s\n";
37static const char fmt_differ[] ALIGN1 = "%s %s differ: char %"OFF_FMT"d, line %d\n";
38// This fmt_l_opt uses gnu-isms.  SUSv3 would be "%.0s%.0s%"OFF_FMT"d %o %o\n"
39static const char fmt_l_opt[] ALIGN1 = "%.0s%.0s%"OFF_FMT"d %3o %3o\n";
40
41static const char opt_chars[] ALIGN1 = "sl";
42#define CMP_OPT_s (1<<0)
43#define CMP_OPT_l (1<<1)
44
45int cmp_main(int argc, char **argv);
46int cmp_main(int argc, char **argv)
47{
48	FILE *fp1, *fp2, *outfile = stdout;
49	const char *filename1, *filename2 = "-";
50	USE_DESKTOP(off_t skip1 = 0, skip2 = 0;)
51	off_t char_pos = 0;
52	int line_pos = 1; /* Hopefully won't overflow... */
53	const char *fmt;
54	int c1, c2;
55	unsigned opt;
56	int retval = 0;
57
58	xfunc_error_retval = 2;	/* 1 is returned if files are different. */
59
60	opt_complementary = "-1"
61			USE_DESKTOP(":?4")
62			SKIP_DESKTOP(":?2")
63			":l--s:s--l";
64	opt = getopt32(argv, opt_chars);
65	argv += optind;
66
67	filename1 = *argv;
68	fp1 = cmp_xfopen_input(filename1);
69
70	if (*++argv) {
71		filename2 = *argv;
72#if ENABLE_DESKTOP
73		if (*++argv) {
74			skip1 = XATOOFF(*argv);
75			if (*++argv) {
76				skip2 = XATOOFF(*argv);
77			}
78		}
79#endif
80	}
81
82	fp2 = cmp_xfopen_input(filename2);
83	if (fp1 == fp2) {		/* Paranoia check... stdin == stdin? */
84		/* Note that we don't bother reading stdin.  Neither does gnu wc.
85		 * But perhaps we should, so that other apps down the chain don't
86		 * get the input.  Consider 'echo hello | (cmp - - && cat -)'.
87		 */
88		return 0;
89	}
90
91	if (opt & CMP_OPT_l)
92		fmt = fmt_l_opt;
93	else
94		fmt = fmt_differ;
95
96#if ENABLE_DESKTOP
97	while (skip1) { getc(fp1); skip1--; }
98	while (skip2) { getc(fp2); skip2--; }
99#endif
100	do {
101		c1 = getc(fp1);
102		c2 = getc(fp2);
103		++char_pos;
104		if (c1 != c2) {			/* Remember: a read error may have occurred. */
105			retval = 1;		/* But assume the files are different for now. */
106			if (c2 == EOF) {
107				/* We know that fp1 isn't at EOF or in an error state.  But to
108				 * save space below, things are setup to expect an EOF in fp1
109				 * if an EOF occurred.  So, swap things around.
110				 */
111				fp1 = fp2;
112				filename1 = filename2;
113				c1 = c2;
114			}
115			if (c1 == EOF) {
116				die_if_ferror(fp1, filename1);
117				fmt = fmt_eof;	/* Well, no error, so it must really be EOF. */
118				outfile = stderr;
119				/* There may have been output to stdout (option -l), so
120				 * make sure we fflush before writing to stderr. */
121				xfflush_stdout();
122			}
123			if (!(opt & CMP_OPT_s)) {
124				if (opt & CMP_OPT_l) {
125					line_pos = c1;	/* line_pos is unused in the -l case. */
126				}
127				fprintf(outfile, fmt, filename1, filename2, char_pos, line_pos, c2);
128				if (opt) {	/* This must be -l since not -s. */
129					/* If we encountered an EOF,
130					 * the while check will catch it. */
131					continue;
132				}
133			}
134			break;
135		}
136		if (c1 == '\n') {
137			++line_pos;
138		}
139	} while (c1 != EOF);
140
141	die_if_ferror(fp1, filename1);
142	die_if_ferror(fp2, filename2);
143
144	fflush_stdout_and_exit(retval);
145}
146