zarchive

Simple Rust bindings to ZArchive.

Overview

ZArchive is yet another file archive format. Think of zip, tar, 7z, etc. but with the requirement of allowing random-access reads and supporting compression.

Features / Specifications

• Supports random-access reads within stored files
• Uses zstd compression (64KiB blocks)
• Scales reasonably well up to multiple terabytes with millions of files
• The theoretical size limit per-file is 2^48-1 (256 Terabyte)
• The encoding for paths within the archive is Windows-1252 (case-insensitive)
• Contains a SHA256 hash of the whole archive for integrity checks
• Endian-independent. The format always uses big-endian internally
• Stateless file and directory iterator handles which don't require memory allocation (not entirely true of the Rust bindings)

Rust Bindings

The zarchive crate provides Rust bindings to the C++ library. The API is intentionally limited. While most of the reader API is implemented, only a basic archive packing function is exposed for writing, due to complex safety considerations. The Rust bindings add some slight overhead to the reader's directory iteration API, but hopefully with a sufficient benefit of convenience.

Example - Pack and extract an archive

use zarchive::{pack, extract};
pack("/path/to/stuff/to/pack", "/path/to/archive.zar")?;
extract("/path/to/archive.zar", "/path/to/extract")?;

Limitations

• Not designed for adding, removing or modifying files after the archive has been created

No-seek creation

When creating new archives only byte append operations are used. No file seeking is necessary. This makes it possible to create archives on storage which is write-once. It also simplifies streaming ZArchive creation over network.

UTF8 paths

UTF8 for file and folder paths is theoretically supported as paths are just binary blobs. But the case-insensitive comparison only applies to latin letters (a-z). The Rust bindings use the primitive &str type, which means that all paths passed through this API are UTF8.

Wii U specifics

Originally this format was created to store Wii U games dumps. These use the file extension .wua (Wii U Archive) but are otherwise regular ZArchive files. To allow multiple Wii U titles to be stored inside a single archive, each title must be placed in a subfolder following the naming scheme: 16-digit titleId followed by _v and then the version as decimal. For example: 0005000e10102000_v32

License

The zarchive crate is licensed under the GPL 3+. The original ZArchive library is licensed under MIT No Attribution, with the exception of sha_256.c and sha_256.h which are public domain, see: https://github.com/amosnier/sha-2.