source: MondoRescue/branches/2.2.2/mindi-busybox/coreutils/cksum.c@ 1247

/* 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 <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include "busybox.h"

int cksum_main(int argc, char **argv) {
    
    uint32_t *crc32_table = bb_crc32_filltable(1);

    FILE *fp;
    uint32_t crc;
    long length, filesize;
    int bytes_read;
    char *cp;
    RESERVE_CONFIG_BUFFER(buf, BUFSIZ);
    int inp_stdin = (argc == optind) ? 1 : 0;
    
    do {
        fp = bb_wfopen_input((inp_stdin) ? bb_msg_standard_input : *++argv);
            
        crc = 0;
        length = 0;
        
        while ((bytes_read = fread(buf, 1, BUFSIZ, fp)) > 0) {
            cp = 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));
    
    return EXIT_SUCCESS;
}