Okay so maybe
JITInputGroup can instead have a kind of iterable for zip
entries using some kind of basic interface of sorts to obtain entries.
Basically, the block reader and the stream reader can be used in either
case as needed. The only issue is that
InputStream is needed for the
base class. But since they are now both merged, I can instead have the
block be able to create a ZIP entry stream from a given block. So that
would work regardless.