rust-gzip#

A GNU gzip-compatible compression tool written in Rust.

Passes 30/30 tests from the upstream GNU gzip 1.14 test suite, run unmodified against the rust-gzip binary in a Nix sandbox.

Usage#

The binary is gzip from pkgs.rust-gzip (release) or pkgs.rust-gzip-dev (debug, faster compile). gunzip and zcat are installed as symlinks.

# Compress / decompress
echo "hello" | gzip | gunzip

# From a Nix shell
nix run .#rust-gzip -- -d file.gz

Features#

Compress / decompress / test / list with stdin, single file, multiple files, and directory recursion (-r).
Suffix handling: -S <suffix> / --suffix, default .gz, canonical alternates (.tgz, .z, .Z, -gz, -z, _z).
Exit-code semantics: 0 success, 2 warning (out-of-range mtime), 1 hard error. Multi-file runs keep the worst code.
--help / --version write to stdout; exit 1 on write failure (e.g. /dev/full), matching coreutils conventions.
--synchronous, ---presume-input-tty accepted as no-ops.
Multi-member gzip streams; trailing NUL padding silently tolerated.
Legacy format decompression:
- Pack (magic 1f 1e) — static Huffman, ported from unpack.c.
- LZW / compress (magic 1f 9d) — variable-width codes, ported from unlzw.c.

Architecture#

Multi-module src/ layout:

Module	Purpose
`main.rs`	Entry point
`cli.rs`	Argument parsing, `Mode` / `Options`, `--help` / `--version`
`compress.rs`	Gzip compression with hand-rolled framing (OS=3, exact mtime)
`decompress.rs`	Multi-format decompression (gzip, pack, LZW) with CRC32 + ISIZE trailer verification
`ops.rs`	File operations — compress / decompress / test / list for files and stdio
`unpack.rs`	Pack format decoder (magic `1f 1e`, static Huffman)
`unlzw.rs`	LZW / compress decoder (magic `1f 9d`, variable-width codes)
`util.rs`	`CountingReader`, suffix handling, output file creation

Implementation notes#

zlib-rs backend — flate2 is configured with the zlib-rs feature (pure Rust zlib rewrite) instead of the default miniz_oxide. This gives deflate validation strictness matching GNU gzip's own inflate (e.g. rejecting corrupt bitstreams that miniz_oxide silently accepts) while keeping the dependency tree C-free.
Hand-rolled gzip framing — compress_stream writes the 10-byte header directly (OS=3, source mtime or 0), delegates deflate to flate2::write::DeflateEncoder, then appends the CRC32 + ISIZE trailer. This byte-exact control is what passes the reference and reproducible tests.
Member-by-member decoding — decompress_stream buffers the full input and walks member boundaries using flate2::Decompress with a flag-aware header parser, rather than using MultiGzDecoder. This handles multi-member archives, trailing NUL padding, legacy format dispatch, and -cdf cat-style pass-through.
Deflate no-progress → format violated — when zlib-rs consumes all input without reaching StreamEnd, the error is reported as invalid compressed data--format violated to match GNU gzip's own inflate.c behavior (structural Huffman errors, not premature EOF).

Testing#

Each of the 30 upstream test scripts runs as its own Nix check:

# Single test
nix build .#checks.x86_64-linux.rust-gzip-test-keep

# View a failure log
nix log .#checks.x86_64-linux.rust-gzip-test-keep

# All tests (keep going on failures)
nix build .#checks.x86_64-linux.rust-gzip-test-* --keep-going --no-link

Test harness#

The harness (testsuite.nix) extracts pkgs.gzip.src, builds a shadow $PATH with gzip / gunzip / zcat pointing at rust-gzip-dev and companion scripts (zdiff, zgrep, znew, …) from the upstream tarball, exports the environment variables the gnulib init.sh framework expects (LC_ALL=C, srcdir, VERSION, etc.), then runs each test script and propagates its exit code. Exit 77 (automake "skip") is treated as pass.

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