private IEnumerable<CompletionPort> ReadBytesAsync(AsyncMachine<byte[]> machine, long offset, int count)
{
StreamHelper.BeginReadBytes(this.reader.BaseStream, offset, count, machine.CompletionCallback, null);
yield return CompletionPort.SingleOperation;
byte[] values = StreamHelper.EndReadBytes(machine.CompletionResult);
machine.ParameterValue = values;
}