source: MondoRescue/branches/2.2.5/mindi-busybox/coreutils/cksum.c@ 1765

/* 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 tarball for details. */

#include "libbb.h"

int cksum_main(int argc, char **argv);
int cksum_main(int argc, char **argv)
{
    uint32_t *crc32_table = crc32_filltable(NULL, 1);

    FILE *fp;
    uint32_t crc;
    long length, filesize;
    int bytes_read;
    char *cp;

    int inp_stdin = (argc == optind) ? 1 : 0;

    do {
        fp = fopen_or_warn_stdin((inp_stdin) ? bb_msg_standard_input : *++argv);

        crc = 0;
        length = 0;

#define read_buf bb_common_bufsiz1
        while ((bytes_read = fread(read_buf, 1, BUFSIZ, fp)) > 0) {
            cp = read_buf;
            length += bytes_read;
            while (bytes_read--)
                crc = (crc << 8) ^ crc32_table[((crc >> 24) ^ (*cp++)) & 0xffL];
        }

        filesize = length;

        for (; length; length >>= 8)
            crc = (crc << 8) ^ crc32_table[((crc >> 24) ^ length) & 0xffL];
        crc ^= 0xffffffffL;

        if (inp_stdin) {
            printf("%" PRIu32 " %li\n", crc, filesize);
            break;
        }

        printf("%" PRIu32 " %li %s\n", crc, filesize, *argv);
        fclose(fp);
    } while (*(argv + 1));

    fflush_stdout_and_exit(EXIT_SUCCESS);
}