CRC32 code

CONST unsigned int crc32_table[256]={
    0x00000000L, 0x04c11db7L, 0x09823b6eL, 0x0d4326d9L,
    0x130476dcL, 0x17c56b6bL, 0x1a864db2L, 0x1e475005L,
    0x2608edb8L, 0x22c9f00fL, 0x2f8ad6d6L, 0x2b4bcb61L,
    0x350c9b64L, 0x31cd86d3L, 0x3c8ea00aL, 0x384fbdbdL,
    0x4c11db70L, 0x48d0c6c7L, 0x4593e01eL, 0x4152fda9L,
    0x5f15adacL, 0x5bd4b01bL, 0x569796c2L, 0x52568b75L,
    0x6a1936c8L, 0x6ed82b7fL, 0x639b0da6L, 0x675a1011L,
    0x791d4014L, 0x7ddc5da3L, 0x709f7b7aL, 0x745e66cdL,
    0x9823b6e0L, 0x9ce2ab57L, 0x91a18d8eL, 0x95609039L,
    0x8b27c03cL, 0x8fe6dd8bL, 0x82a5fb52L, 0x8664e6e5L,
    0xbe2b5b58L, 0xbaea46efL, 0xb7a96036L, 0xb3687d81L,
    0xad2f2d84L, 0xa9ee3033L, 0xa4ad16eaL, 0xa06c0b5dL,
    0xd4326d90L, 0xd0f37027L, 0xddb056feL, 0xd9714b49L,
    0xc7361b4cL, 0xc3f706fbL, 0xceb42022L, 0xca753d95L,
    0xf23a8028L, 0xf6fb9d9fL, 0xfbb8bb46L, 0xff79a6f1L,
    0xe13ef6f4L, 0xe5ffeb43L, 0xe8bccd9aL, 0xec7dd02dL,
    0x34867077L, 0x30476dc0L, 0x3d044b19L, 0x39c556aeL,
    0x278206abL, 0x23431b1cL, 0x2e003dc5L, 0x2ac12072L,
    0x128e9dcfL, 0x164f8078L, 0x1b0ca6a1L, 0x1fcdbb16L,
    0x018aeb13L, 0x054bf6a4L, 0x0808d07dL, 0x0cc9cdcaL,
    0x7897ab07L, 0x7c56b6b0L, 0x71159069L, 0x75d48ddeL,
    0x6b93dddbL, 0x6f52c06cL, 0x6211e6b5L, 0x66d0fb02L,
    0x5e9f46bfL, 0x5a5e5b08L, 0x571d7dd1L, 0x53dc6066L,
    0x4d9b3063L, 0x495a2dd4L, 0x44190b0dL, 0x40d816baL,
    0xaca5c697L, 0xa864db20L, 0xa527fdf9L, 0xa1e6e04eL,
    0xbfa1b04bL, 0xbb60adfcL, 0xb6238b25L, 0xb2e29692L,
    0x8aad2b2fL, 0x8e6c3698L, 0x832f1041L, 0x87ee0df6L,
    0x99a95df3L, 0x9d684044L, 0x902b669dL, 0x94ea7b2aL,
    0xe0b41de7L, 0xe4750050L, 0xe9362689L, 0xedf73b3eL,
    0xf3b06b3bL, 0xf771768cL, 0xfa325055L, 0xfef34de2L,
    0xc6bcf05fL, 0xc27dede8L, 0xcf3ecb31L, 0xcbffd686L,
    0xd5b88683L, 0xd1799b34L, 0xdc3abdedL, 0xd8fba05aL,
    0x690ce0eeL, 0x6dcdfd59L, 0x608edb80L, 0x644fc637L,
    0x7a089632L, 0x7ec98b85L, 0x738aad5cL, 0x774bb0ebL,
    0x4f040d56L, 0x4bc510e1L, 0x46863638L, 0x42472b8fL,
    0x5c007b8aL, 0x58c1663dL, 0x558240e4L, 0x51435d53L,
    0x251d3b9eL, 0x21dc2629L, 0x2c9f00f0L, 0x285e1d47L,
    0x36194d42L, 0x32d850f5L, 0x3f9b762cL, 0x3b5a6b9bL,
    0x0315d626L, 0x07d4cb91L, 0x0a97ed48L, 0x0e56f0ffL,
    0x1011a0faL, 0x14d0bd4dL, 0x19939b94L, 0x1d528623L,
    0xf12f560eL, 0xf5ee4bb9L, 0xf8ad6d60L, 0xfc6c70d7L,
    0xe22b20d2L, 0xe6ea3d65L, 0xeba91bbcL, 0xef68060bL,
    0xd727bbb6L, 0xd3e6a601L, 0xdea580d8L, 0xda649d6fL,
    0xc423cd6aL, 0xc0e2d0ddL, 0xcda1f604L, 0xc960ebb3L,
    0xbd3e8d7eL, 0xb9ff90c9L, 0xb4bcb610L, 0xb07daba7L,
    0xae3afba2L, 0xaafbe615L, 0xa7b8c0ccL, 0xa379dd7bL,
    0x9b3660c6L, 0x9ff77d71L, 0x92b45ba8L, 0x9675461fL,
    0x8832161aL, 0x8cf30badL, 0x81b02d74L, 0x857130c3L,
    0x5d8a9099L, 0x594b8d2eL, 0x5408abf7L, 0x50c9b640L,
    0x4e8ee645L, 0x4a4ffbf2L, 0x470cdd2bL, 0x43cdc09cL,
    0x7b827d21L, 0x7f436096L, 0x7200464fL, 0x76c15bf8L,
    0x68860bfdL, 0x6c47164aL, 0x61043093L, 0x65c52d24L,
    0x119b4be9L, 0x155a565eL, 0x18197087L, 0x1cd86d30L,
    0x029f3d35L, 0x065e2082L, 0x0b1d065bL, 0x0fdc1becL,
    0x3793a651L, 0x3352bbe6L, 0x3e119d3fL, 0x3ad08088L,
    0x2497d08dL, 0x2056cd3aL, 0x2d15ebe3L, 0x29d4f654L,
    0xc5a92679L, 0xc1683bceL, 0xcc2b1d17L, 0xc8ea00a0L,
    0xd6ad50a5L, 0xd26c4d12L, 0xdf2f6bcbL, 0xdbee767cL,
    0xe3a1cbc1L, 0xe760d676L, 0xea23f0afL, 0xeee2ed18L,
    0xf0a5bd1dL, 0xf464a0aaL, 0xf9278673L, 0xfde69bc4L,
    0x89b8fd09L, 0x8d79e0beL, 0x803ac667L, 0x84fbdbd0L,
    0x9abc8bd5L, 0x9e7d9662L, 0x933eb0bbL, 0x97ffad0cL,
    0xafb010b1L, 0xab710d06L, 0xa6322bdfL, 0xa2f33668L,
    0xbcb4666dL, 0xb8757bdaL, 0xb5365d03L, 0xb1f740b4L
};


bool CheckCRC(unsigned char *str, unsigned int slen, unsigned char *crcstr)
{
    unsigned int i;
    unsigned int iCRC = 0xFFFFFFFF;
    unsigned int crcvalue;

    for (i=0; i<slen; i++)
    {
        iCRC = (iCRC << 8) ^ crc32_table[(iCRC >> 24) ^ str[i]];
    }

    //source crc value   
    crcvalue = *crcstr++;
    crcvalue <<= 8;
    crcvalue += *crcstr++;
    crcvalue <<= 8;
    crcvalue += *crcstr++;
    crcvalue <<= 8;
    crcvalue += *crcstr;

    if (crcvalue == iCRC)
        return TRUE;
    else
        return FALSE;
}


#pragma warning(disable:4701)
bool CHECK_CRC32(int length, unsigned char *pData) const
{
#if 1
    unsigned char tmp8;
    unsigned int tmp,n,m=0,z=0xffffffff,gx=0x82608edb;
    int i;
    for (i=0;i<length*8;i++)
    {
        if (i%8==0)
            tmp8=pData[i/8];
        m=z&0x80000000;
        m=m>>31;
        n=tmp8&0x80;
        n=n>>7;
        tmp=n^m;
        if (tmp==1)
            z=z^gx;
        z=z<<1;
        z+=tmp;
        tmp8=tmp8<<1;
    }

    return 0 == z;
#else
    return CheckCRC(pData, length - 4, pData + length - 4);
#endif
}