[Pyparsing] Using pyparsing to implement a matching engine for a regexp-like matching language?

[Andrew W. <and...@gm...>]

I am trying to write a matching engine for a matching language for a 
filtering proxy compatible with that of The Proxomitron. The matching 
language is basically an extended superset of shell-style globs, with 
functionality comparable to regexps (see 
http://www.proxomitron.info/45/help/Matching%20Rules.html).

I think that I can implement the parser for the match and replace
patterns themselves using pyparsing, but I am not exactly sure of how to
implement the "core" of the matching engine - the part that takes an
input string, finds a match, and extracts any parts specified in the
pattern.

I could almost use pyparsing as a matching engine as well, by
dynamically generating a parser from the pattern and parsing the data to
be filtered with it, but pyparsing appears to be a pull parser (one that
takes all its input at once), as opposed to a push parser (which can be
fed multiple chunks of input). Also, non-matching input might cause
parse errors.

A matching engine for a filtering proxy has to be able to handle partial
input and "hold" data until enough is received to determine whether
there is a match (or else the entire document would have to be held
until the end is reached, filtered, and then sent all at once to the
remote client, and that would make it appear much less responsive and
possibly break some applications).

Is there a way to use pyparsing as a push parser, or can anyone
recommend any other Python libraries that would be suitable for my 
purposes? I don't want to reinvent the wheel unless no suitable library 
exists.