rars

A Rust implementation of RAR.

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• 🦀 crate
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Current Status

rars covers the RAR lineage from early RE~^ archives through RAR 7, compression and decompression. It's not fast, but it works. ish.

CLI

Inspect, test, and extract archives:

rars info archive.rar
rars test archive.rar
rars x archive.rar out/

Create archives with specific RAR generation:

rars a --format rar29 archive.rar files...
rars a --format rar50 --solid --auto-filter archive.rar files...
rars a --format rar70 --store --volume-size 10m archive.part1.rar files...

The writer supports stored and compressed members, split volumes, passwords, header encryption where implemented, comments, RARVM filters, RAR5 quick-open records, and supported recovery records. Run rars --help for the exact option set.

Fast Builds

The optional fast feature enables safe portable SIMD paths for selected hot compression and decompression helpers, including LZ match scanning, x86 filter scanning, and CRC-32 updates. It uses Rust's experimental std::simd API, so it requires a nightly toolchain. Default builds do not enable this feature and remain stable-compatible.

Build or run the CLI with the fast path:

cargo +nightly run -p rars-cli --features fast -- info archive.rar
cargo +nightly build --workspace --features fast

Run the fast test and benchmark paths:

cargo +nightly test --workspace --features fast
cargo +nightly bench -p rars-codec --bench chunk_sizes --features fast

Parallel Builds

The optional parallel feature enables Rayon worker threads for independent archive members. It parallelizes non-solid compression planning for supported writers and buffered extraction of non-solid, non-split single archives while preserving archive order for output. Solid archives and multivolume extraction fall back to the existing sequential stream because their codec state depends on member order.

Build or run the CLI with parallel workers:

cargo run -p rars-cli --features parallel -- --threads 4 a --format rar50 archive.rar files...
cargo run -p rars-cli --features parallel -- x --threads 4 archive.rar out/
cargo test --workspace --features parallel

Measure parallel archive-member work with Criterion:

cargo bench -p rars-format --bench parallel --features parallel
cargo +nightly bench -p rars-format --bench parallel --features fast,parallel

The parallel benchmark reports 1_thread and all_threads_N cases for RAR5 multi-member compression and extraction.

When --threads is omitted, rars uses all available cores. Passing --threads to a CLI built without parallel is rejected.

Development

Run the test suite:

cargo test --workspace --all-targets

Generate a local coverage report:

rustup component add llvm-tools-preview
./scripts/coverage.py

The script prints a line-coverage summary, saves it to target/coverage/summary.txt, and writes HTML output to target/coverage/html/library/index.html and target/coverage/html/cli/index.html.