z7z

A cleanroom 7z archive implementation in Zig. Creates and extracts 7z archives that are fully interoperable with the reference 7-Zip implementation.

Features

• LZMA2 compression — BT4+HC2/HC3 match finder, forward optimal parser, parallel compression
• AES-256-CBC encryption — password-protected archives with -p/--password
• BCJ x86 filter — executable pre-processing for better compression
• MIME-grouped solid blocks — content-based file type detection via libmagic (--solid/--no-solid overrides)
• Full metadata — mtime, birthtime (fixes 7zz's long-standing bug of storing ctime instead), atime, POSIX permissions
• Extended attributes — xattrs preserved on macOS and Linux, including com.apple.ResourceFork (resource forks); stored as custom property 0x7A, invisible to 7zz (7zz t validates clean). Ephemeral xattrs (com.apple.quarantine, etc.) are excluded. Use --no-xattr to skip
• Symlink support — with path-traversal security
• Progress reporting — rate/ETA on interactive terminals
• stdin/stdout — pipe support via -/@stdin/@stdout
• i18n groundwork — --lang flag, Z7Z_LANG env var (30-language translation ready)
• Cross-platform — macOS aarch64, Linux x86_64/aarch64, Windows x86_64/aarch64

Architecture

CLI (C) ──► C FFI boundary ──► Zig core (pure logic, no I/O)

All business logic lives in the Zig core with no I/O. The C FFI is the public API — the CLI itself calls through it, dogfooding the same interface that external consumers use.

Performance

Compared against 7zz at -mx=5 on macOS/ARM64 (Apple M4):

Workload	z7z	7zz -mmt=1	z7z vs 7zz-st
1.16MB text	12.3ms	23.1ms	1.88x faster
4MB text	19.5ms	73.2ms	3.76x faster
1MB random	8.5ms	54.3ms	6.43x faster

Compression ratios within 1-2% of 7zz at -mx=5. Full bidirectional interop verified.

Building

Requires Zig 0.15+:

zig build                          # ReleaseFast by default
zig build -Doptimize=Debug         # debug build
zig build test                     # run all tests

Or with Nix:

nix develop                        # enter dev shell
nix build                          # build package
nix flake check                    # run checks

Usage

z7z create archive.7z file1.txt file2.txt dir/   # create archive
z7z create -p secret enc.7z file1.txt             # encrypted archive
z7z extract archive.7z                            # extract to current dir
z7z extract archive.7z -o outdir/                 # extract to specific dir
z7z list archive.7z                               # list contents
z7z --help                                        # full usage

Status

This is an active work in progress. See PLAN.md for the roadmap.

License

MIT