source: src/router/busybox/editors/cmp.c @ 8864

/* vi: set sw=4 ts=4: */
/*
 * Mini cmp implementation for busybox
 *
 * Copyright (C) 2000,2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/* BB_AUDIT SUSv3 (virtually) compliant -- uses nicer GNU format for -l. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/cmp.html */

/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
 *
 * Original version majorly reworked for SUSv3 compliance, bug fixes, and
 * size optimizations.  Changes include:
 * 1) Now correctly distinguishes between errors and actual file differences.
 * 2) Proper handling of '-' args.
 * 3) Actual error checking of i/o.
 * 4) Accept SUSv3 -l option.  Note that we use the slightly nicer gnu format
 *    in the '-l' case.
 */

#include "libbb.h"

static FILE *cmp_xfopen_input(const char *filename)
{
        FILE *fp;

        fp = fopen_or_warn_stdin(filename);
        if (fp)
                return fp;
        xfunc_die();    /* We already output an error message. */
}

static const char fmt_eof[] ALIGN1 = "cmp: EOF on %s\n";
static const char fmt_differ[] ALIGN1 = "%s %s differ: char %"OFF_FMT"d, line %d\n";
// This fmt_l_opt uses gnu-isms.  SUSv3 would be "%.0s%.0s%"OFF_FMT"d %o %o\n"
static const char fmt_l_opt[] ALIGN1 = "%.0s%.0s%"OFF_FMT"d %3o %3o\n";

static const char opt_chars[] ALIGN1 = "sl";
#define CMP_OPT_s (1<<0)
#define CMP_OPT_l (1<<1)

int cmp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int cmp_main(int argc, char **argv)
{
        FILE *fp1, *fp2, *outfile = stdout;
        const char *filename1, *filename2 = "-";
        USE_DESKTOP(off_t skip1 = 0, skip2 = 0;)
        off_t char_pos = 0;
        int line_pos = 1; /* Hopefully won't overflow... */
        const char *fmt;
        int c1, c2;
        unsigned opt;
        int retval = 0;

        xfunc_error_retval = 2; /* 1 is returned if files are different. */

        opt_complementary = "-1"
                        USE_DESKTOP(":?4")
                        SKIP_DESKTOP(":?2")
                        ":l--s:s--l";
        opt = getopt32(argv, opt_chars);
        argv += optind;

        filename1 = *argv;
        fp1 = cmp_xfopen_input(filename1);

        if (*++argv) {
                filename2 = *argv;
#if ENABLE_DESKTOP
                if (*++argv) {
                        skip1 = XATOOFF(*argv);
                        if (*++argv) {
                                skip2 = XATOOFF(*argv);
                        }
                }
#endif
        }

        fp2 = cmp_xfopen_input(filename2);
        if (fp1 == fp2) {               /* Paranoia check... stdin == stdin? */
                /* Note that we don't bother reading stdin.  Neither does gnu wc.
                 * But perhaps we should, so that other apps down the chain don't
                 * get the input.  Consider 'echo hello | (cmp - - && cat -)'.
                 */
                return 0;
        }

        if (opt & CMP_OPT_l)
                fmt = fmt_l_opt;
        else
                fmt = fmt_differ;

#if ENABLE_DESKTOP
        while (skip1) { getc(fp1); skip1--; }
        while (skip2) { getc(fp2); skip2--; }
#endif
        do {
                c1 = getc(fp1);
                c2 = getc(fp2);
                ++char_pos;
                if (c1 != c2) {                 /* Remember: a read error may have occurred. */
                        retval = 1;             /* But assume the files are different for now. */
                        if (c2 == EOF) {
                                /* We know that fp1 isn't at EOF or in an error state.  But to
                                 * save space below, things are setup to expect an EOF in fp1
                                 * if an EOF occurred.  So, swap things around.
                                 */
                                fp1 = fp2;
                                filename1 = filename2;
                                c1 = c2;
                        }
                        if (c1 == EOF) {
                                die_if_ferror(fp1, filename1);
                                fmt = fmt_eof;  /* Well, no error, so it must really be EOF. */
                                outfile = stderr;
                                /* There may have been output to stdout (option -l), so
                                 * make sure we fflush before writing to stderr. */
                                xfflush_stdout();
                        }
                        if (!(opt & CMP_OPT_s)) {
                                if (opt & CMP_OPT_l) {
                                        line_pos = c1;  /* line_pos is unused in the -l case. */
                                }
                                fprintf(outfile, fmt, filename1, filename2, char_pos, line_pos, c2);
                                if (opt) {      /* This must be -l since not -s. */
                                        /* If we encountered an EOF,
                                         * the while check will catch it. */
                                        continue;
                                }
                        }
                        break;
                }
                if (c1 == '\n') {
                        ++line_pos;
                }
        } while (c1 != EOF);

        die_if_ferror(fp1, filename1);
        die_if_ferror(fp2, filename2);

        fflush_stdout_and_exit(retval);
}