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/*

 * efone - Distributed internet phone system.

 *

 * (c) 1999,2000 Krzysztof Dabrowski

 * (c) 1999,2000 ElysiuM deeZine

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version

 * 2 of the License, or (at your option) any later version.

 *

 */

/* based on implementation by Finn Yannick Jacobs */

#include <stdio.h>

#include <stdlib.h>

#include <systemc.h>

/* crc_tab[] -- this crcTable is being build by chksum_crc32GenTab().

 *              so make sure, you call it before using the other

 *              functions!

 */

u_int32_t crc_tab[256];

/* chksum_crc() -- to a given block, this one calculates the

 *                              crc32-checksum until the length is

 *                              reached. the crc32-checksum will be

 *                              the result.

 */

u_int32_t chksum_crc32 (sc_uint<8> *block, unsigned int length)

{

    register unsigned long crc;

    unsigned long i;

    crc = 0xFFFFFFFF;

    for (i = 0; i < length; i++)

        {

            crc = ((crc >> 8) & 0x00FFFFFF) ^ crc_tab[(crc ^ *block++) & 0xFF];

        }

    return (crc ^ 0xFFFFFFFF);

}

/* chksum_crc32gentab() --      to a global crc_tab[256], this one will

 *                              calculate the crcTable for crc32-checksums.

 *                              it is generated to the polynom [..]

 */

void chksum_crc32gentab ()

{

    unsigned long crc, poly;

    int i, j;

    poly = 0xEDB88320L;

    for (i = 0; i < 256; i++)

        {

            crc = i;

            for (j = 8; j > 0; j--)

                {

                    if (crc & 1)

                        {

                            crc = (crc >> 1) ^ poly;

                        }

                    else

                        {

                            crc >>= 1;

                        }

                }

            crc_tab[i] = crc;

        }

}