CRC_82_Darc function in C#

Question

I need to calculate the CRC_82_Darc hash in C#. Is there any preexisting Lib for this or did someone already write a function ? I could not find anything on Google.

Answer 1

Here is a simple bit-wise implementation in C:

// CRC-82/DARC Calculation
// Placed into the public domain by Mark Adler, 17 June 2017.

// CRC definition:
// width=82 poly=0x0308c0111011401440411 init=0 refin=true refout=true xorout=0
// check=0x09ea83f625023801fd612 name="CRC-82/DARC"

#include <stddef.h>
#include <stdint.h>

#define POLYHIGH 0x22080
#define POLYLOW 0x8a00a2022200c430

// Update crc[0..1] with the CRC-82/DARC of the len bytes at buf. If buf is
// NULL, then initialize crc[0..1] with the CRC-82/DARC of an empty message.
// The low 64 bits of the CRC are in crc[0], and the high 18 bits of the CRC
// are in the low 18 bits of crc[1]. The remaining bits of crc[1] are always
// zero.
void crc82darc(uint64_t *crc, void const *buf, size_t len) {
    if (buf == NULL) {
        crc[0] = crc[1] = 0;
        return;
    }
    uint64_t cl = crc[0], ch = crc[1] & 0x3ffff;
    for (size_t i = 0; i < len; i++) {
        cl ^= ((unsigned char const *)buf)[i];
        for (int k = 0; k < 8; k++) {
            uint64_t low = cl & 1;
            cl = (cl >> 1) | (ch << 63);
            ch >>= 1;
            if (low) {
                cl ^= POLYLOW;
                ch ^= POLYHIGH;
            }
        }
    }
    crc[0] = cl;
    crc[1] = ch;
}

#ifdef TEST

#include <stdio.h>

int main(void)
{
    uint64_t crc[2];

    crc82darc(crc, NULL, 0);    // initialize crc
    crc82darc(crc, "123456789", 9);
    printf("0x%05llx%016llx\n", crc[1], crc[0]);
    return 0;
}

#endif