write-compressor

Design encoders as exact mathematical inverses of decoders by documenting the decoder's state machine, deriving encoder operations algebraically, and verifying perfect reversibility. This ensures compatibility in arithmetic coding, entropy encoding, and compression systems through side-by-side state verification and round-trip testing.

Build verification harnesses that perform end-to-end round-trip testing: encode data, then decode it, and confirm the output matches the original input. Implement side-by-side state checks during phased development to catch inverse relationship violations early.

Yes. This Skill applies directly to arithmetic coders and other entropy encoders where the encoder must be the precise inverse of an existing decoder. Derive the encoder's state transitions from the decoder's documented behavior and verify through bitstream-level round-trip testing.

Document the decoder's state variables and transitions, then algebraically invert each operation to construct the encoder. Implement in phases, starting with the minimal case that round-trips perfectly, then expand coverage with unit tests and robust debugging strategies.

Mismatched inverses cause bitstream decode failures or data corruption. Use side-by-side state verification to identify where encoder and decoder diverge, then refine the mathematical inverse relationship. End-to-end round-trip testing detects these failures before production use.

This Skill has no external dependencies. You need the decoder's specification or source code, encoding theory knowledge, and a testing framework for verification. The approach works with any compression or entropy-coding system where decoder behavior is documented.