/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005 Brian Somers <brian@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>

#include <err.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "extern.h"

int
c_link(const char *file1, off_t skip1, const char *file2, off_t skip2,
    off_t limit)
{
        char buf1[PATH_MAX], *p1;
        char buf2[PATH_MAX], *p2;
        ssize_t len1, len2;
        int dfound;
        off_t byte;
        u_char ch;

        if ((len1 = readlink(file1, buf1, sizeof(buf1) - 1)) < 0) {
                if (!sflag)
                        err(ERR_EXIT, "%s", file1);
                else
                        exit(ERR_EXIT);
        }

        if ((len2 = readlink(file2, buf2, sizeof(buf2) - 1)) < 0) {
                if (!sflag)
                        err(ERR_EXIT, "%s", file2);
                else
                        exit(ERR_EXIT);
        }

        if (skip1 > len1)
                skip1 = len1;
        buf1[len1] = '\0';

        if (skip2 > len2)
                skip2 = len2;
        buf2[len2] = '\0';

        dfound = 0;
        byte = 1;
        for (p1 = buf1 + skip1, p2 = buf2 + skip2;
            *p1 && *p2 && (limit == 0 || byte <= limit); p1++, p2++) {
                if ((ch = *p1) != *p2) {
                        if (xflag) {
                                dfound = 1;
                                (void)printf("%08llx %02x %02x\n",
                                    (long long)byte - 1, ch, *p2);
                        } else if (lflag) {
                                dfound = 1;
                                if (bflag)
                                        (void)printf("%6lld %3o %c %3o %c\n",
                                            (long long)byte, ch, ch, *p2, *p2);
                                else
                                        (void)printf("%6lld %3o %3o\n",
                                            (long long)byte, ch, *p2);
                        } else {
                                diffmsg(file1, file2, byte, 1, ch, *p2);
                                return (DIFF_EXIT);
                        }
                }
                byte++;
        }

        if (*p1 || *p2) {
                eofmsg (*p1 ? file2 : file1);
                return (DIFF_EXIT);
        }
        return (dfound ? DIFF_EXIT : 0);
}