// internal for testing
internal static ImmutableArray <byte> CalculatePublicKeyToken(ImmutableArray <byte> publicKey)
{
var hash = CryptographicHashProvider.ComputeSha1(publicKey);
// SHA1 hash is always 160 bits:
Debug.Assert(hash.Length == CryptographicHashProvider.Sha1HashSize);
// PublicKeyToken is the low 64 bits of the SHA-1 hash of the public key.
int l = hash.Length - 1;
var result = ArrayBuilder <byte> .GetInstance(PublicKeyTokenSize);
for (int i = 0; i < PublicKeyTokenSize; i++)
{
result.Add(hash[l - i]);
}
return(result.ToImmutableAndFree());
}