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# udif
**Cross-platform Rust library for Apple DMG disk images (aka Universal Disk Image Format)**
[](https://crates.io/crates/udif)
[](https://docs.rs/udif)
[](LICENSE)
Read, write, and manipulate Apple DMG files on any platform.
**Full LZFSE support** — works with modern macOS disk images that other libraries can't read.
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## Why udif?
**udif is the only cross-platform Rust crate that can both read AND write DMGs with modern compression.**
| Read | ✓ | ✓ | ✓ | ✓ |
| **Write** | ✓ | ❌ | ❌ | ✓ |
| LZFSE | ✓ | ✓ | ❌ | ❌ |
| XZ | ✓ | ❌ | ❌ | ❌ |
| Bzip2 | ✓ | ✓ | ❌ | ❌ |
| Zlib | ✓ | ✓ | ✓ | ✓ |
| **Checksum** | ✓ | ❌ | ❌ | ❌ |
> **Example:** A typical macOS Kernel Debug Kit DMG uses 100% LZFSE compression.
> Only udif and dmgwiz can read it — but only udif can write new DMGs with LZFSE.
## Features
| **List partitions** | Parse DMG structure, show partition table |
| **Extract data** | Decompress partitions to raw disk images |
| **Create DMG** | Build DMG files with multiple compression options |
| **Checksum verification** | CRC32 integrity validation on read and write |
| **Cross-platform** | Works on Windows, Linux, and macOS |
### Compression Support
| LZFSE | | | Apple's native compression |
| XZ | | | XZ (LZMA2) compression |
| Zlib | | | Best compatibility |
| Bzip2 | | | Better ratio, slower |
| Raw | | | No compression |
## Quick Start
### Read DMG
```rust
use udif::DmgArchive;
// Open and list partitions
let mut archive = DmgArchive::open("image.dmg")?;
for p in archive.partitions() {
println!("{}: {} bytes", p.name, p.size);
}
// Extract main HFS+/APFS partition
let data = archive.extract_main_partition()?;
std::fs::write("disk.raw", &data)?;
```
### Create DMG
```rust
use udif::{DmgBuilder, CompressionMethod};
let disk_data = std::fs::read("disk.raw")?;
DmgBuilder::new()
.compression(CompressionMethod::Zlib)
.add_partition("Macintosh HD", disk_data)
.build("output.dmg")?;
```
### Checksum Verification
By default, checksums are verified when opening a DMG. To skip verification (e.g., for corrupted files):
```rust
use udif::{DmgArchive, DmgReaderOptions};
// Default: checksums verified
let archive = DmgArchive::open("image.dmg")?;
// Skip verification for corrupted/legacy files
let options = DmgReaderOptions { verify_checksums: false };
let archive = DmgArchive::open_with_options("image.dmg", options)?;
```
## Documentation
| [Format Specification](docs/FORMATS.md) | DMG binary format details |
| [CLI Tool](docs/CLI.md) | Command-line tool usage |
| [Implementation Notes](docs/IMPLEMENTATION.md) | Tricky parts and gotchas |
## Example Output
```
$ udif-tool info Kernel_Debug_Kit.dmg
DMG Information: Kernel_Debug_Kit.dmg
============================================================
Header:
Version: 4
Sector count: 2351263
Data fork length: 1023271318 bytes
Segment: 1/1
Size:
Uncompressed: 1203845632 bytes (1148.08 MB)
Compressed: 1023271318 bytes (975.87 MB)
Compression: 15.0%
Partitions: 7
Block types used:
LZFSE: 988 blocks
```
```
$ udif-tool list Kernel_Debug_Kit.dmg
Partitions in Kernel_Debug_Kit.dmg:
================================================================================
ID Sectors Size Ratio Name
--------------------------------------------------------------------------------
-1 1 512 B 89.6% Protective Master Boot Record (MBR : 0)
0 1 512 B 78.9% GPT Header (Primary GPT Header : 1)
1 32 16.00 KB 98.7% GPT Partition Data (Primary GPT Table : 2)
2 2089050 1020.04 MB 4.3% Untitled 1 (Apple_HFSX : 3)
3 262144 128.00 MB 100.0% (Apple_Free : 4)
```
## Alternatives
| **udif** | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ❌ | Full featured |
| [dmgwiz](https://crates.io/crates/dmgwiz) | ✓ | ❌ | ✓ | ❌ | ✓ | ✓ | ❌ | ✓ | Read-only |
| [apple-dmg](https://crates.io/crates/apple-dmg) | ✓ | ❌ | ❌ | ❌ | ❌ | ✓ | ❌ | ❌ | Zlib only |
| [dmg-oxide](https://crates.io/crates/dmg-oxide) | ✓ | ✓ | ❌ | ❌ | ❌ | ✓ | ❌ | ❌ | Zlib only |
| [dmg](https://crates.io/crates/dmg) | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | macOS only (hdiutil) |
**Choose udif if you need:**
- Write/create DMG support AND modern compression (LZFSE/XZ)
- Cross-platform support (Windows, Linux, macOS)
- XZ compression (no other cross-platform crate supports it)
- Ensure integrity (no other cross-platform crate have checksum generation / validation)
**Choose dmgwiz if you need:**
- Encrypted DMG support (we don't have this yet)
- Read-only access is sufficient
See [Comparison](docs/COMPARISON.md) for detailed analysis.
## Next Steps
- [ ] **Encrypted DMG support** — FileVault / AES-128 / AES-256 encrypted disk images
- [ ] **ADC compression** — Apple Data Compression for legacy DMGs
- [ ] **Streaming decompression** — decompress partitions without buffering entire output
- [ ] **Parallel block decompression** — decompress blocks across multiple threads
- [ ] **LZFSE write optimization** — tunable compression levels for LZFSE output
- [ ] **APFS partition detection** — identify APFS containers within DMGs
- [ ] **Partition resizing** — create DMGs with custom partition layouts
- [ ] **Progress callbacks** — report compression/decompression progress for UI integration
## License
MIT