An interface to get parts of a character source.
I'm not using CharSequence because I need the
CharacterSequence.done() method
to cleanup any resource that were used by the sequence.
The IteratingParser uses a FileMappedSequence which used NIO
to read the characters and this implementation needs a cleanup
method to close the file handles, which would not be offered by
the CharSequence interface.
author: support@sql-workbench.net