...
> The checksums for the randomly-generated test cases were calculated
> using a reference implementation [1] and this test compares them against
> the values yielded by the kernel's implementation.

I'd just use a naïve implementation - doesn't really matter
if it is a bit slow.

Slow is relative - this code only takes 35ms to crc-64 over 5MB of data.

{
    volatile const uint32_t *r = (const void *)buf;
    for (crc = 0; r < (const uint32_t *)buf_end; r++) {
        uint64_t val = le32toh(*r);
        crc ^= bswap64(val);
        for (i = 0; i < 32; i++) {
            if (crc & (1ull << 63))
                crc = (crc << 1) ^ 0x42f0e1eba9ea3693ull;
            else
                crc = crc << 1;
        }
    }
}

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Hi David,

On 9/26/24 13:21, David Laight wrote:
> ...
>> The checksums for the randomly-generated test cases were calculated
>> using a reference implementation [1] and this test compares them against
>> the values yielded by the kernel's implementation.
> 
> I'd just use a naïve implementation - doesn't really matter
> if it is a bit slow.

Thanks for the feedback. I agree that it makes more sense to use a naive 
implementation to validate the results from the kernel's crc16 instead 
of having a table of pre-computed results. I will include in v2 a 
bog-standard implementation of crc16 similar to yours (using a loop 
instead of a lookup table) to validate the results.

Thanks,
Vinicius

> 
> Slow is relative - this code only takes 35ms to crc-64 over 5MB of data.
> 
> {
>      volatile const uint32_t *r = (const void *)buf;
>      for (crc = 0; r < (const uint32_t *)buf_end; r++) {
>          uint64_t val = le32toh(*r);
>          crc ^= bswap64(val);
>          for (i = 0; i < 32; i++) {
>              if (crc & (1ull << 63))
>                  crc = (crc << 1) ^ 0x42f0e1eba9ea3693ull;
>              else
>                  crc = crc << 1;
>          }
>      }
> }
> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)