Adler32 hash in C#

adler32.cs

private static uint Adler32(string str)
{
    const int mod = 65521;
    uint a = 1, b = 0;
    foreach (char c in str) {
        a = (a + c) % mod;
        b = (b + a) % mod;
    }
    return (b << 16) | a;
}

you could probably implement this with Span<byte> to be encoding agnostic, but ty for putting this up in a gist!