README.md

November 3, 2025 ยท View on GitHub

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The MOO File Format

MOO is a simple chunked binary format used to encode x86 CPU SingleStepTests.

MOO stands for Machine Opcode Operation.

Parser implementations

  • Rust: A Rust crate for working with MOO files, moo-rs, is available in /crates/moo.
  • C++: A single-header MOO parser is available in /cpp

MOO Utilities (Mootilities?)

  • A general utility for working with MOO files called moo_util is available under /crates/moo_util.

    • See its README for more information on how to use it.

  • A python script moo2json.py is available under /python. This script can be used to convert a single MOO file or an entire set of MOO files into the more traditional SingleStepTest JSON format.

Note


If you end up writing a MOO parser in another language, or expand the capabilities of one of the parsers above, please consider contributing your parser via a PR so that others can benefit from your work.

MOO Format Specification

See the documentation for the current MOO specification, v1.1