# lznt1
[](https://crates.io/crates/lznt1)
[](https://docs.rs/lznt1)
[](https://spdx.org/licenses/MIT)
A safe, pure-Rust, `no_std` implementation of the **LZNT1** compression algorithm.
LZNT1 is the standard compression algorithm used by the Windows NT kernel, notably in **NTFS filesystem compression**, Active Directory replication, and various Windows API functions (`RtlCompressBuffer`). This crate allows you to read and write LZNT1 streams on any platform without linking to system libraries.
## ✨ Features
* **Pure Rust**: No C dependencies or bindings.
* **Safe**: Enforced via `#![forbid(unsafe_code)]`.
* **`no_std` Compatible**: only requires the `alloc` crate.
* **Robust**: Extensively fuzz-tested to ensure resilience against malformed inputs.
* **Simple API**: Straightforward `compress` and `decompress` functions operating on byte slices and vectors.
## 📦 Installation
Add this to your `Cargo.toml`:
```toml
[dependencies]
lznt1 = "0.1.0" # Use the latest version
````
## 🚀 Usage
### Decompression
```rust
use lznt1::decompress;
fn main() -> Result<(), lznt1::DecompressionError> {
// Example: "Hello world" compressed
let compressed_data = [
0x0c, 0xb0, 0x00,
b'H', b'e', b'l', b'l', b'o', b' ', b'w', b'o',
0x00,
b'r', b'l', b'd',
];
let mut buffer = Vec::new();
decompress(&compressed_data, &mut buffer)?;
assert_eq!(buffer, b"Hello world");
Ok(())
}
```
### Compression
```rust
use lznt1::compress;
fn main() {
let input = b"The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog.";
let mut compressed_output = Vec::new();
compress(input, &mut compressed_output);
println!("Original size: {}", input.len());
println!("Compressed size: {}", compressed_output.len());
}
```
## 🛠️ Technical Details
LZNT1 works by splitting data into **4KB chunks**. Each chunk is stored either:
1. **Compressed**: A header (`0xB000` + size) followed by LZ77 sequences (literals and offset/length tuples).
2. **Uncompressed**: A header (`0x3000` + size) followed by raw data (used when compression doesn't save space).
This implementation handles the adaptive window splitting logic and the "Tag Group" format (1 tag byte per 8 items) defined by the algorithm.
## 🧪 Testing & Fuzzing
This crate prioritizes correctness and safety.
* **Unit Tests**: Comprehensive suite covering edge cases, boundary conditions, and RLE patterns.
* **Fuzzing**: Integration with `cargo-fuzz` to verify that the decompressor never panics or crashes, even on malicious/random input.
* **Benchmarks**: Performance tracked via `criterion`.
To run the tests:
```bash
cargo test
```
To run benchmarks:
```bash
cargo bench
```
## ⚖️ License
This project is licensed under the [MIT License](https://www.google.com/search?q=LICENSE).