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#include "libbb.h"
14
15static const char fmt_eof[] ALIGN1 = "cmp: EOF on %s\n";
16static const char fmt_differ[] ALIGN1 = "%s %s differ: char %"OFF_FMT"u, line %u\n";
17// This fmt_l_opt uses gnu-isms.  SUSv3 would be "%.0s%.0s%"OFF_FMT"u %o %o\n"
18static const char fmt_l_opt[] ALIGN1 = "%.0s%.0s%"OFF_FMT"u %3o %3o\n";
19
20static const char opt_chars[] ALIGN1 = "sl";
21#define CMP_OPT_s (1<<0)
22#define CMP_OPT_l (1<<1)
23
24int cmp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
25int cmp_main(int argc UNUSED_PARAM, char **argv)
26{
27	FILE *fp1, *fp2, *outfile = stdout;
28	const char *filename1, *filename2 = "-";
29	off_t skip1 = 0, skip2 = 0, char_pos = 0;
30	int line_pos = 1; /* Hopefully won't overflow... */
31	const char *fmt;
32	int c1, c2;
33	unsigned opt;
34	int retval = 0;
35
36	xfunc_error_retval = 2;	/* 1 is returned if files are different. */
37
38	opt_complementary = "-1"
39			IF_DESKTOP(":?4")
40			IF_NOT_DESKTOP(":?2")
41			":l--s:s--l";
42	opt = getopt32(argv, opt_chars);
43	argv += optind;
44
45	filename1 = *argv;
46	fp1 = xfopen_stdin(filename1);
47
48	if (*++argv) {
49		filename2 = *argv;
50		if (ENABLE_DESKTOP && *++argv) {
51			skip1 = XATOOFF(*argv);
52			if (*++argv) {
53				skip2 = XATOOFF(*argv);
54			}
55		}
56	}
57
58	fp2 = xfopen_stdin(filename2);
59	if (fp1 == fp2) {		/* Paranoia check... stdin == stdin? */
60		/* Note that we don't bother reading stdin.  Neither does gnu wc.
61		 * But perhaps we should, so that other apps down the chain don't
62		 * get the input.  Consider 'echo hello | (cmp - - && cat -)'.
63		 */
64		return 0;
65	}
66
67	if (opt & CMP_OPT_l)
68		fmt = fmt_l_opt;
69	else
70		fmt = fmt_differ;
71
72	if (ENABLE_DESKTOP) {
73		while (skip1) { getc(fp1); skip1--; }
74		while (skip2) { getc(fp2); skip2--; }
75	}
76	do {
77		c1 = getc(fp1);
78		c2 = getc(fp2);
79		++char_pos;
80		if (c1 != c2) {			/* Remember: a read error may have occurred. */
81			retval = 1;		/* But assume the files are different for now. */
82			if (c2 == EOF) {
83				/* We know that fp1 isn't at EOF or in an error state.  But to
84				 * save space below, things are setup to expect an EOF in fp1
85				 * if an EOF occurred.  So, swap things around.
86				 */
87				fp1 = fp2;
88				filename1 = filename2;
89				c1 = c2;
90			}
91			if (c1 == EOF) {
92				die_if_ferror(fp1, filename1);
93				fmt = fmt_eof;	/* Well, no error, so it must really be EOF. */
94				outfile = stderr;
95				/* There may have been output to stdout (option -l), so
96				 * make sure we fflush before writing to stderr. */
97				fflush_all();
98			}
99			if (!(opt & CMP_OPT_s)) {
100				if (opt & CMP_OPT_l) {
101					line_pos = c1;	/* line_pos is unused in the -l case. */
102				}
103				fprintf(outfile, fmt, filename1, filename2, char_pos, line_pos, c2);
104				if (opt) {	/* This must be -l since not -s. */
105					/* If we encountered an EOF,
106					 * the while check will catch it. */
107					continue;
108				}
109			}
110			break;
111		}
112		if (c1 == '\n') {
113			++line_pos;
114		}
115	} while (c1 != EOF);
116
117	die_if_ferror(fp1, filename1);
118	die_if_ferror(fp2, filename2);
119
120	fflush_stdout_and_exit(retval);
121}
122