source: MondoRescue/branches/3.2/mindi-busybox/coreutils/cksum.c

/* vi: set sw=4 ts=4: */
/*
 * cksum - calculate the CRC32 checksum of a file
 *
 * Copyright (C) 2006 by Rob Sullivan, with ideas from code by Walter Harms
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

//usage:#define cksum_trivial_usage
//usage:       "FILES..."
//usage:#define cksum_full_usage "\n\n"
//usage:       "Calculate the CRC32 checksums of FILES"

#include "libbb.h"

/* This is a NOEXEC applet. Be very careful! */

int cksum_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int cksum_main(int argc UNUSED_PARAM, char **argv)
{
    uint32_t *crc32_table = crc32_filltable(NULL, 1);
    uint32_t crc;
    off_t length, filesize;
    int bytes_read;
    int exit_code = EXIT_SUCCESS;

#if ENABLE_DESKTOP
    getopt32(argv, ""); /* coreutils 6.9 compat */
    argv += optind;
#else
    argv++;
#endif

    do {
        int fd = open_or_warn_stdin(*argv ? *argv : bb_msg_standard_input);

        if (fd < 0) {
            exit_code = EXIT_FAILURE;
            continue;
        }
        crc = 0;
        length = 0;

#define read_buf bb_common_bufsiz1
        while ((bytes_read = safe_read(fd, read_buf, sizeof(read_buf))) > 0) {
            length += bytes_read;
            crc = crc32_block_endian1(crc, read_buf, bytes_read, crc32_table);
        }
        close(fd);

        filesize = length;

        while (length) {
            crc = (crc << 8) ^ crc32_table[(uint8_t)(crc >> 24) ^ (uint8_t)length];
            /* must ensure that shift is unsigned! */
            if (sizeof(length) <= sizeof(unsigned))
                length = (unsigned)length >> 8;
            else if (sizeof(length) <= sizeof(unsigned long))
                length = (unsigned long)length >> 8;
            else
                length = (unsigned long long)length >> 8;
        }
        crc = ~crc;

        printf((*argv ? "%"PRIu32" %"OFF_FMT"i %s\n" : "%"PRIu32" %"OFF_FMT"i\n"),
                crc, filesize, *argv);
    } while (*argv && *++argv);

    fflush_stdout_and_exit(exit_code);
}