This is a Python library for parsing and unparsing TeX binary files like DVI, VF, and XDV files.
There are five classes in the external API:
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DVILikeProcessor: This is an abstract class never to be instantiated. It has a class method, process(), that takes an input file and automatically returns an instance of the appropriate class for processing that file presuming the file is correctly formed.
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DVIProcessor, VFProcessor, and XDVProcessor: Classes corresponding to the file types in question. Instantiate a class with FooProcessor(), or use the load() method to load a file into an existing instance. read_file() and write_file() will parse an entire file into memory or unparse an in-memory parse tree into a file; read_bytes() and write_bytes() do the same thing only to an in-memory binary representation of a file. Iterating over any class instance will return the individual packets in the file one at a time. DVIProcessor.pages() will return an iterator over the pages of the DVI file, in reverse order. In the parse tree, each individual packet is represented by a mapping that gives the name of each variable in a packet and the value for that name. The packets themselves or groups of packets, like the pages in a DVI file, are returned as a sequence or an iterator. The write commands take the same kind of parse tree and turn it into a binary representation. PKProcessor exists but is an unimplemented stub at the moment.
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OpcodeCommandsMachine is a skeleton class designed for creating finite state machines that interpret the packets in a TeX binary file. To implement such a machine, subclass OpcodeCommandsMachine and override the methods corresponding to the names of possible commands, create an instance, and then feed it packets one at a time by calling the instance on each packet.
This implementation provides a clean separation of the process of parsing and unparsing TeX binary files and performing other operations on them. By returning a programmatic representation of the parse tree, it's possible to build any kind of TeX binary processor on top of this library. It also handles VF and XDV files, which have no existing implementations in Python at all as far as I know.
The parser itself is a single script, dvilike.py. It requires the Construct binary parsing library (https://pypi.python.org/pypi/construct).
MIT.