Custom legacy encoding conversion tools for plain text files

 TECkit is a toolkit for encoding conversions. It offers a simple format for
 describing the mapping between legacy 8-bit encodings and Unicode, and a
 set of utilities based on such descriptions for converting text between 8-bit
 and Unicode encodings.
 .
 It also includes a compiler for a mapping description language that allows for
 bidirectional conversion description (i.e. the same description is used for
 conversion to and from Unicode).