/*
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1987, 1990, 1993, 1994
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 * $FreeBSD: head/usr.bin/cmp/cmp.c 216370 2010-12-11 08:32:16Z joel $
 *
 * @(#) Copyright (c) 1987, 1990, 1993, 1994 The Regents of the University of California.  All rights reserved.
 * @(#)cmp.c    8.3 (Berkeley) 4/2/94
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <nl_types.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "extern.h"

bool    lflag, sflag, xflag, zflag;

static const struct option long_opts[] =
{
        {"verbose",     no_argument,            NULL, 'l'},
        {"silent",      no_argument,            NULL, 's'},
        {"quiet",       no_argument,            NULL, 's'},
        {NULL,          no_argument,            NULL, 0}
};

static void usage(void);

int
main(int argc, char *argv[])
{
        struct stat sb1, sb2;
        off_t skip1, skip2;
        int ch, fd1, fd2, oflag;
        bool special;
        const char *file1, *file2;

        oflag = O_RDONLY;
        while ((ch = getopt_long(argc, argv, "+hlsxz", long_opts, NULL)) != -1)
                switch (ch) {
                case 'h':               /* Don't follow symlinks */
                        oflag |= O_NOFOLLOW;
                        break;
                case 'l':               /* print all differences */
                        lflag = true;
                        break;
                case 's':               /* silent run */
                        sflag = true;
                        break;
                case 'x':               /* hex output */
                        lflag = true;
                        xflag = true;
                        break;
                case 'z':               /* compare size first */
                        zflag = true;
                        break;
                case '?':
                default:
                        usage();
                }
        argv += optind;
        argc -= optind;

        if (lflag && sflag)
                errx(ERR_EXIT, "specifying -s with -l or -x is not permitted");

        if (argc < 2 || argc > 4)
                usage();

        /* Backward compatibility -- handle "-" meaning stdin. */
        special = false;
        if (strcmp(file1 = argv[0], "-") == 0) {
                special = true;
                fd1 = STDIN_FILENO;
                file1 = "stdin";
        } else if ((fd1 = open(file1, oflag, 0)) < 0 && errno != EMLINK) {
                if (!sflag)
                        err(ERR_EXIT, "%s", file1);
                else
                        exit(ERR_EXIT);
        }
        if (strcmp(file2 = argv[1], "-") == 0) {
                if (special)
                        errx(ERR_EXIT,
                                "standard input may only be specified once");
                special = true;
                fd2 = STDIN_FILENO;
                file2 = "stdin";
        } else if ((fd2 = open(file2, oflag, 0)) < 0 && errno != EMLINK) {
                if (!sflag)
                        err(ERR_EXIT, "%s", file2);
                else
                        exit(ERR_EXIT);
        }

        skip1 = argc > 2 ? strtol(argv[2], NULL, 0) : 0;
        skip2 = argc == 4 ? strtol(argv[3], NULL, 0) : 0;

        if (sflag && skip1 == 0 && skip2 == 0)
                zflag = true;

        if (fd1 == -1) {
                if (fd2 == -1) {
                        c_link(file1, skip1, file2, skip2);
                        exit(0);
                } else if (!sflag)
                        errx(ERR_EXIT, "%s: Not a symbolic link", file2);
                else
                        exit(ERR_EXIT);
        } else if (fd2 == -1) {
                if (!sflag)
                        errx(ERR_EXIT, "%s: Not a symbolic link", file1);
                else
                        exit(ERR_EXIT);
        }

        if (!special) {
                if (fstat(fd1, &sb1)) {
                        if (!sflag)
                                err(ERR_EXIT, "%s", file1);
                        else
                                exit(ERR_EXIT);
                }
                if (!S_ISREG(sb1.st_mode))
                        special = true;
                else {
                        if (fstat(fd2, &sb2)) {
                                if (!sflag)
                                        err(ERR_EXIT, "%s", file2);
                                else
                                        exit(ERR_EXIT);
                        }
                        if (!S_ISREG(sb2.st_mode))
                                special = true;
                }
        }

        if (special)
                c_special(fd1, file1, skip1, fd2, file2, skip2);
        else {
                if (zflag && sb1.st_size != sb2.st_size) {
                        if (!sflag)
                                (void) printf("%s %s differ: size\n",
                                    file1, file2);
                        exit(DIFF_EXIT);
                }
                c_regular(fd1, file1, skip1, sb1.st_size,
                    fd2, file2, skip2, sb2.st_size);
        }
        exit(0);
}

static void
usage(void)
{

        (void)fprintf(stderr,
            "usage: cmp [-l | -s | -x] [-hz] file1 file2 [skip1 [skip2]]\n");
        exit(ERR_EXIT);
}