How do I convert an unpaired UTF-16 surrogate to UTF-32?
If an unpaired surrogate is encountered when converting ill-formed UTF-16 data, any conformant converter must treat this as an error. By represented such an unpaired surrogate on its own, the resulting UTF-32 data stream would become ill-formed. While it faithfully reflects the nature of the input, Unicode conformance requires that encoding form conversion always results in valid data stream.
