source: mainline/uspace/app/bdsh/cmds/modules/cmp/cmp.c@ c4f7bf6

/*
 * Copyright (c) 2012 Sean Bartell
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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 <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <mem.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <vfs/vfs.h>

#include "cmds.h"
#include "cmp.h"
#include "config.h"
#include "entry.h"
#include "errors.h"
#include "util.h"

static const char *cmdname = "cmp";
#define CMP_VERSION "0.0.1"
#define CMP_BUFLEN 1024

static struct option const long_options[] = {
        { "help", no_argument, 0, 'h' },
        { "version", no_argument, 0, 'v' },
        { 0, 0, 0, 0 }
};

/* Dispays help for cat in various levels */
void help_cmd_cmp(unsigned int level)
{
        if (level == HELP_SHORT) {
                printf("`%s' compares the contents of two files\n", cmdname);
        } else {
                help_cmd_cmp(HELP_SHORT);
                printf(
                "Usage:  %s [options] <file1> <file2>\n"
                "Options:\n"
                "  -h, --help       A short option summary\n"
                "  -v, --version    Print version information and exit\n"
                "No output is printed; the return code is 1 if the files differ.\n",
                cmdname);
        }

        return;
}

static int cmp_files(const char *fn0, const char *fn1)
{
        int rc = 0;
        const char *fn[2] = {fn0, fn1};
        int fd[2] = {-1, -1};
        char buffer[2][CMP_BUFLEN];
        ssize_t offset[2];

        for (int i = 0; i < 2; i++) {
                fd[i] = open(fn[i], O_RDONLY);
                if (fd[i] < 0) {
                        rc = errno;
                        printf("Unable to open %s\n", fn[i]);
                        goto end;
                }
        }

        do {
                for (int i = 0; i < 2; i++) {
                        offset[i] = 0;
                        ssize_t size;
                        do {
                                size = read(fd[i], buffer[i] + offset[i],
                                    CMP_BUFLEN - offset[i]);
                                if (size < 0) {
                                        rc = errno;
                                        printf("Error reading from %s\n",
                                            fn[i]);
                                        goto end;
                                }
                                offset[i] += size;
                        } while (size && offset[i] < CMP_BUFLEN);
                }

                if (offset[0] != offset[1] ||
                    bcmp(buffer[0], buffer[1], offset[0])) {
                        rc = 1;
                        goto end;
                }
        } while (offset[0] == CMP_BUFLEN);

end:
        if (fd[0] >= 0)
                close(fd[0]);
        if (fd[1] >= 0)
                close(fd[1]);
        return rc;
}

/* Main entry point for cmd, accepts an array of arguments */
int cmd_cmp(char **argv)
{
        int rc;
        unsigned int argc;
        int c, opt_ind;
        
        argc = cli_count_args(argv);

        for (c = 0, optind = 0, opt_ind = 0; c != -1;) {
                c = getopt_long(argc, argv, "hv", long_options, &opt_ind);
                switch (c) {
                case 'h':
                        help_cmd_cmp(HELP_LONG);
                        return CMD_SUCCESS;
                case 'v':
                        printf("%s\n", CMP_VERSION);
                        return CMD_SUCCESS;
                }
        }

        if (argc - optind != 2) {
                printf("%s - incorrect number of arguments. Try `%s --help'\n",
                        cmdname, cmdname);
                return CMD_FAILURE;
        }

        rc = cmp_files(argv[optind], argv[optind + 1]);
        if (rc)
                return CMD_FAILURE;
        else
                return CMD_SUCCESS;
}