Compute hash in .NET using async await

HashAlgorithmExtensions.cs

public static class HashAlgorithmExtensions
{
    private const int BufferSize = 4096;

    public static async Task<byte[]> ComputeHashAsync(this HashAlgorithm hash, Stream inputStream)
    {
        if (hash == null) throw new ArgumentNullException(nameof(hash));
        if (inputStream == null) throw new ArgumentNullException(nameof(inputStream));

        hash.Initialize();

        var buffer = new byte[BufferSize];
        var streamLength = inputStream.Length;

        while (true)
        {
            var read = await inputStream.ReadAsync(buffer, 0, BufferSize).ConfigureAwait(false);
            if (inputStream.Position == streamLength)
            {
                hash.TransformFinalBlock(buffer, 0, read);
                break;
            }

            hash.TransformBlock(buffer, 0, read, default(byte[]), default(int));
        }

        return hash.Hash;
    }
}