Provides a stream-based approach to decoding Unicode data. Each function below works the same way: you give it a chunk of data, and it gives back a DecodeResult. If the parse was a success, then you get a chunk of Text (possibly empty) and a continuation parsing function. If the parse was a failure, you get a chunk of successfully decoded Text (possibly empty) and the unconsumed bytes.

In order to indicate end of stream, you pass an empty ByteString to the decode function. This call may result in a failure, if there were unused bytes left over from a previous step which formed part of a code sequence.