Crate zlib_bitexact_rs 

zlib-bitexact-rs — a pure-Rust, bit-exact port of stock zlib 1.3.1’s deflate.

Its raw DEFLATE output is byte-identical to the C deflate() for the configuration MAME’s CHD codec uses: deflateInit2(Z_BEST_COMPRESSION, Z_DEFLATED, -15, 8, Z_DEFAULT_STRATEGY) followed by a single deflate(Z_FINISH). It exists for consumers that must recreate the exact bytes zlib/chdman produce (e.g. chd-rs reproducing MAME CHD hunks), not merely emit valid DEFLATE — every encoded byte is continuously differential-tested against the real zlib 1.3.1, compiled from source as a dev-only oracle.

⚠️ This is NOT zlib-rs / miniz_oxide / flate2 — those are valid DEFLATE encoders but their compressed bytes differ from stock zlib (zlib-ng-style improvements). This crate reproduces stock zlib 1.3.1 exactly.

Decode is out of scope: inflate is unambiguous, so any zlib-compatible inflater reads this crate’s output.

Example

// `raw` is byte-identical to zlib 1.3.1 deflateInit2(9, Z_DEFLATED, -15, 8, default)
// + deflate(Z_FINISH) over the same input.
let raw = zlib_bitexact_rs::deflate_raw(b"the quick brown fox jumps over the lazy dog");
assert!(!raw.is_empty());

See ROADMAP.md for the build plan and CLAUDE.md for the architecture + bit-exactness hazards.

Functions

deflate_raw

Compress input into a raw DEFLATE stream (no zlib header, no adler32 trailer), byte-identical to stock zlib 1.3.1 with deflateInit2(9, Z_DEFLATED, -15, 8, Z_DEFAULT_STRATEGY) + a single deflate(Z_FINISH).