appimageupdate

A Rust implementation of AppImageUpdate - a tool for updating AppImages using efficient delta updates.

Features

• Delta Updates - Only download the changed portions of the AppImage, saving bandwidth and time
• Decentralized - No central repository required; updates come directly from the source
• Checksum Verification - SHA1 verification ensures downloaded files are valid
• Permission Preservation - Maintains executable permissions from the original AppImage
• Skip Unnecessary Updates - Automatically skips update if the target file already exists with the correct checksum

Installation

From Source

git clone https://github.com/qaidvoid/appimageupdate.git
cd appimageupdate
cargo install --path .

Usage

Update an AppImage

appimageupdate update ./myapp.AppImage

Output:

Source:   ./myapp.AppImage (85.3 MB)
Target:   ./myapp-2.0.AppImage (92.1 MB)

Performing delta update...

Reused:        42.1 MB  (1247 blocks)
Downloaded:    50.0 MB  (1482 blocks)
Saved:         42.1 MB  (45%)

Updated: ./myapp-2.0.AppImage

Check for Updates

appimageupdate check ./myapp.AppImage

Output:

Source:   ./myapp.AppImage (85.3 MB)
Target:   ./myapp-2.0.AppImage (92.1 MB)

Status: Update available

Options

appimageupdate update [OPTIONS] <APPIMAGE>

Arguments:
  <APPIMAGE>  Path to the AppImage to update

Options:
  -o, --output <DIR>   Output directory for the updated AppImage
  -w, --overwrite      Overwrite existing target file
  -h, --help           Print help

How It Works

1. Reads Update Information - Extracts embedded update info from the AppImage's .upd-info ELF section
2. Fetches Zsync Metadata - Downloads the .zsync control file which contains block checksums and file metadata
3. Calculates Delta - Compares local file blocks against remote blocks using rolling checksums
4. Downloads Only Changes - Fetches only the blocks that differ from the local copy
5. Assembles & Verifies - Reconstructs the file and verifies SHA1 checksum

Supported Update Formats

• zsync|<url> - Direct zsync URL
• gh-releases-zsync|<user>|<repo>|<tag>|<filename> - GitHub releases with glob pattern matching

Comparison with Upstream

This is a Rust rewrite of the upstream AppImageUpdate (C++/Qt).

Advantages:

• Single binary with no runtime dependencies
• Cleaner, more maintainable codebase
• URL caching to avoid redundant API calls
• Better error messages

Differences:

• No GPG signature verification (not implemented)
• No pling integration (not implemented)

Library Usage

use appimageupdate::{Updater, Error};

fn main() -> Result<(), Error> {
    let updater = Updater::new("./myapp.AppImage")?;

    if updater.check_for_update()? {
        let (path, stats) = updater.perform_update()?;
        println!("Updated to: {}", path.display());
        println!("Saved {}% bandwidth", stats.saved_percentage());
    } else {
        println!("Already up to date!");
    }

    Ok(())
}