New library (uc2_rans.h / uc2_rans.c) — table-based range Asymmetric
Numeral Systems (rANS) entropy coder:
- 32-bit state with 12-bit probability precision
- Supports up to 344 symbols (matching UC2's LZ77 alphabet)
- Frequency table normalization with minimum-frequency guarantee
- Reverse-order encoding with automatic renormalization
- Fast O(1) decoding via cumulative frequency lookup table
Performance: <5% overhead vs Shannon entropy on tested distributions.
Single-symbol streams compress to ~4 bytes (near-zero information).
Skewed distributions (90% one symbol) achieve sub-bit-per-symbol rates.
6 unit tests:
- Table construction with frequency normalization
- Round-trip: uniform, skewed, 344-symbol alphabet, single-symbol
- Comparison vs Shannon entropy (verified <5% overhead)
Eremey Valetov
db94be6043