[tiendc]

Decoding a solid RAR5 archive written by RAR itself spends most of its time in Huffman decoding. Under perf on an x86-64 runner it was 56% of a RAR 7.23 -m3 -s archive. Two things in that path cost more than they need to:

• The decoder was not inlined. HuffmanState::decode was an out-of-line call per symbol, saving and restoring registers each time. It is now #[inline(always)], like decode_peeked inside it.
• peek15 built its word a byte at a time. It matched the remaining input as a slice of at least three bytes and assembled the word one byte at a time. When four or more bytes remain, it now does one four-byte load and shifts out the 15 bits, which start at most 7 bits in. Nearer the end it takes the existing path, so truncation and incremental-input behaviour are unchanged.

rars --threads 1 test on hosted runners, MB/s, with this branch rebased onto 0.12.3 and master at 0.12.3. The archives were written by RAR 7.23 from one folder of ~200 MB (5,500 files: source text, incompressible blocks, mostly-zero files) and timed three rounds in turn:

	master	inline only	this PR	reference
Linux, -m3 -s	264–267	275	307–308	unrar 299–354
Linux, -m5 -s	266–269	277–278	308–310	unrar 351–357
Linux, -m3 (WinRAR's default)	463–468	480–481	506–511	unrar 363–367
Windows, -m3 -s	230–241	239–244	268–269	7-Zip 434–441
Windows, -m5 -s	232–243	236–245	261–269	7-Zip 332–442
Windows, -m3	363–371	377–386	398–401	7-Zip 766–779

Extracting to disk moves less, as writing the files takes most of the time there: Linux -m3 -s goes from 132–133 to 141–142 MB/s; on Windows the change is within noise. The macOS bench job did not get a runner this time.

Solid archives gain most: they keep incompressible data inside the compressed stream, so they have more symbols per byte. Without solid, RAR stores such files instead.

Validation, on top of 0.12.3:

• cargo test -p rars --release: 2633 tests pass; cargo test -p rars-cli: 364 pass.
• clippy -D warnings and fmt are clean.
• CI passes on my fork, except the macOS CLI job, which never got a runner (four attempts were cancelled before any step ran). I ran its step, cargo test -p rars-cli --locked, on an M1 Mac instead, and it passes.
• scripts/reference-corpus.py with RAR 7.23 and 6.24, including the extended cases from CLI extracts RAR 1.5–4 Unix symbolic links as regular files #105 and every damage variant: all 1176 cases agree with UnRAR 7.23.

🤖 Generated with Claude Code