libchm

Pure-Rust reader for CHM (Compiled HTML Help) archives, including LZX decompression. No unsafe code, no C dependencies.

Installation

cargo add libchm

Requires Rust 1.87 or newer.

Usage

use libchm::{ChmFile, EntrySel};

fn main() -> libchm::Result<()> {
    let mut chm = ChmFile::open("docs.chm")?;
    for entry in chm.entries(EntrySel::ALL)? {
        println!("{}", entry.path);
    }
    let bytes = chm.read_path("/index.html")?;
    println!("index size: {}", bytes.len());
    Ok(())
}

Paths are absolute within the archive and matched case-insensitively; directory entries end with /.

Use find and read separately when you want the entry's metadata before reading it:

let entry = chm.find("/index.html")?;
println!("{} is {} bytes", entry.path, entry.length);
let bytes = chm.read(&entry)?;

Selecting entries

EntrySel is a bitflag that filters by category (NORMAL, SPECIAL, META) and kind (FILES, DIRS). An entry matches only when the selector names both its category and its kind, so EntrySel::NORMAL alone yields nothing. Use EntrySel::ALL to get everything, or combine flags:

// Ordinary content files, skipping directories and CHM-internal metadata.
let pages = chm.entries(EntrySel::NORMAL | EntrySel::FILES)?;
// Everything under one directory.
let images = chm.entries_in("/images", EntrySel::NORMAL | EntrySel::FILES)?;

Robustness

CHM archives are untrusted input. Every header field that feeds an allocation, an index, or a divisor is validated before use, so a malformed or hostile file is reported as a ChmError rather than panicking or attempting a huge allocation.

Bindings

• pychmrs: Python wrapper

License

MIT