libaaruformat

libaaruformat is a C library for reading and writing AaruFormat disk images — the native image format of the Aaru Data Preservation Suite.

What is Aaru?

Aaru is an open-source application for managing and preserving digital storage media. It can create, convert, compare, and analyze disk images from a wide variety of physical formats — floppy disks, hard drives, optical discs, tapes, memory cards, and more. Aaru is written in C# and runs on Windows, macOS, and Linux.

What is AaruFormat?

AaruFormat is Aaru's own disk image file format, designed from the ground up for long-term archival and data preservation. Unlike most existing image formats, which target a single media family or prioritize emulation speed, AaruFormat aims to be a single, universal, extensible standard capable of faithfully representing any kind of digital or analog storage media — from punch cards to Blu-ray discs to magnetic flux captures.

Key design goals of the format include:

• Universality: one format for all media types, eliminating the need for a different format per storage technology.
• Completeness: stores not just raw sector data, but also per-sector metadata (subchannel data, error flags, tags), per-media metadata (TOCs, catalog numbers, serial numbers), dump hardware information, and CHS geometry.
• Compression: blocks of sectors are compressed individually (LZMA, Zstd, or FLAC for audio), allowing random access without decompressing the entire image.
• Deduplication: a Deduplication Table (DDT) maps each sector to a content-addressed block via xxHash, so identical sectors across the image are stored only once.
• Integrity: every block carries a CRC64 checksum. Hashes (MD5, SHA1, SHA256, SpamSum, BLAKE3) are computed during writing and stored in the image.
• Resilience: optional Reed-Solomon erasure coding protects data blocks, deduplication tables, metadata, and the index against corruption, with transparent recovery on read.
• Openness: the format specification is freely available in docs/spec/ and is published under the same terms as the library.

What is libaaruformat?

libaaruformat is the reference implementation of AaruFormat, written in C. Aaru itself uses libaaruformat via P/Invoke, having replaced its earlier C# implementation. The library can also be used independently by other projects — emulators, forensic tools, archival systems, or anything written in C or a language with C FFI — to read and write AaruFormat images without depending on the .NET runtime.

The library is written in C99, has no external runtime dependencies (all third-party code is statically linked from the 3rdparty/ directory), and builds on macOS, Linux, and Windows. It is licensed under the LGPL-2.1.

Features

Core

• AaruFormat V1 images reading (writing will never be implemented)
• AaruFormat V2 images reading and writing
• Image identification and verification
• LRU block cache for read performance
• Large file (>2 GiB) I/O support
• Feature parity with the C# implementation

Compression

• LZMA
• Zstandard (Zstd)
• FLAC (for CD audio tracks)
• Claunia Subchannel Transform (for CD subchannel data)

Checksums & Hashing

• Hashing while writing: MD5, SHA1, SHA256, SpamSum, BLAKE3
• CRC64 with SIMD acceleration (CLMUL on x86, VMULL on ARM)
• ECC CD checksums

Erasure Coding & Data Recovery

• Reed-Solomon error correction with configurable K,M parameters
• GF(2^8) arithmetic with 4-path SIMD dispatch (AVX2, SSSE3, ARM NEON, scalar fallback)
• Five protection groups: data blocks, DDT-primary, DDT-secondary, metadata, index
• Transparent recovery on read
• Recovery footer at EOF with backup header

Console Disc Encryption/Decryption

• PS3: Per-sector AES-128-CBC encryption/decryption, encryption map support, IRD file parsing
• Wii U: Two-tier encryption (disc key + per-title keys), WUD/WUX format support
• NGC/Wii: Wii partition encryption, GameCube/Wii LFG PRNG junk detection and generation

Media & Metadata

• Optical disc tracks
• Tape files and partitions
• Raw flux transition captures (Kryoflux, Pauline, Applesauce)
• Apple Lisa tag handling
• Dump hardware lists
• CHS geometry retrieval and setting
• XML metadata retrieval (writing will never be implemented)
• JSON metadata retrieval and writing
• Deduplication (xxHash-based with hash maps)
• Media type list in sync with Aaru

CLI Tool (aaruformattool)

Optional command-line tool built with -DBUILD_TOOL=ON. Commands include:

• identify — Identify AaruFormat version
• info — Display detailed image information
• read / read_long — Read sectors
• verify / verify_sectors — Verify image and sector integrity
• compare — Compare images
• convert — Convert between image formats
• convert-ps3 — Convert PS3 disc images
• convert-wiiu — Convert Wii U disc images (WUD/WUX)
• convert-ngcw — Convert GameCube/Wii disc images
• inject-media-tag — Add media tags to images

Platform Support

• macOS (x86_64, arm64)
• Linux (x86_64, aarch64, armv7, mips, riscv64)
• Windows (MSVC, MinGW — x86, x64, ARM, ARM64)

Developer

• Unit testing (Google Test)
• Automatic API documentation generation (Doxygen)
• Format specification in AsciiDoc (docs/spec/)

Things still to be implemented

• Automatic media type generation from C# enumeration
• NuGet package for linking with Aaru
• Snapshots
• Parent images
• Data positioning measurements

Building and Testing

Standard Build

mkdir build
cd build
cmake ..
cmake --build .

Running Tests

cd build
ctest --verbose

Building with Address Sanitizer

For debugging memory issues, you can build with Address Sanitizer enabled:

mkdir build-asan
cd build-asan
cmake -DUSE_ASAN=ON -DCMAKE_BUILD_TYPE=Debug ..
cmake --build .
ctest --verbose

For detailed information on using Address Sanitizer to detect memory issues, see docs/ASAN_USAGE.md.

Build Options

• -DBUILD_SHARED_LIBS=OFF — Build as static library (default: shared)
• -DBUILD_TOOL=ON — Build the CLI tool (requires Argtable3, ICU, curses)
• -DUSE_SLOG=ON — Enable slog logging for debugging
• -DUSE_ASAN=ON — Enable Address Sanitizer for memory error detection