cl-flexi-streams binary package in Ubuntu Bionic amd64

 FLEXI-STREAMS implements "virtual" bivalent streams that can be layered
 atop real binary or bivalent streams and that can be used to read and
 write character data in various single- or multi-octet encodings which
 can be changed on the fly. It also supplies in-memory binary streams
 which are similar to string streams.
 .
 FLEXI-STREAMS is currently not optimized towards performance - it is
 rather intended to be easy to use and (if possible) to behave correctly.

Source package