source: MondoRescue/trunk/mindi-busybox/coreutils/cmp.c@ 956

/* vi: set sw=4 ts=4: */
/*
 * Mini cmp implementation for busybox
 *
 * Copyright (C) 2000,2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

/* 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 <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "busybox.h"

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

    if ((fp = bb_wfopen_input(filename)) != NULL) {
        return fp;
    }

    exit(bb_default_error_retval);  /* We already output an error message. */
}

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

static const char opt_chars[] = "sl";

enum {
    OPT_s = 1,
    OPT_l = 2
};

int cmp_main(int argc, char **argv)
{
    FILE *fp1, *fp2, *outfile = stdout;
    const char *filename1, *filename2;
    const char *fmt;
    int c1, c2, char_pos, line_pos;
    int opt_flags;
    int exit_val = 0;

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

    opt_flags = bb_getopt_ulflags(argc, argv, opt_chars);

    if ((opt_flags == 3) || (((unsigned int)(--argc - optind)) > 1)) {
        bb_show_usage();
    }

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

    filename2 = "-";
    if (*++argv) {
        filename2 = *argv;
    }
    fp2 = cmp_xfopen_input(filename2);

    if (fp1 == fp2) {           /* Paranioa 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;
    }

    fmt = fmt_differ;
    if (opt_flags == OPT_l) {
        fmt = fmt_l_opt;
    }

    char_pos = 0;
    line_pos = 1;
    do {
        c1 = getc(fp1);
        c2 = getc(fp2);
        ++char_pos;
        if (c1 != c2) {         /* Remember -- a read error may have occurred. */
            exit_val = 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) {
                bb_xferror(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. */
                bb_xfflush_stdout();
            }
            if (opt_flags != OPT_s) {
                if (opt_flags == OPT_l) {
                    line_pos = c1;  /* line_pos is unused in the -l case. */
                }
                bb_fprintf(outfile, fmt, filename1, filename2, char_pos, line_pos, c2);
                if (opt_flags) {    /* This must be -l since not -s. */
                    /* If we encountered and EOF, the while check will catch it. */
                    continue;
                }
            }
            break;
        }
        if (c1 == '\n') {
            ++line_pos;
        }
    } while (c1 != EOF);

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

    bb_fflush_stdout_and_exit(exit_val);
}