backroll-rs

Backroll is a pure Rust implementation of GGPO rollback networking library.

Development Status

This is still in an early beta stage. At time of writing, the public facing API is stable, and has undergone limited testing. There may still be notable bugs that have not been found yet.

Differences with the C++ implementation

• (Almost) 100% pure safe Rust. No unsafe pointer manipulation.
• Type safety. backroll-rs heavily utilizes generics and associated types to avoid serialization overhead and potentially unsafe type conversions when saving and loading game state.
• Abstracted transport layer protocols - integrate and use any transport layer library you need. Comes with a raw UDP socket based implementation.
• Configurable at runtime - Many of the hard-coded constants in GGPO are exposed as configuration parameters during session initialization.
• Reduced memory usage - Backroll's use of generics potentially shrinks down the sizes of many data types.
• Vectorized input compression scheme - Backroll utilizes the same XOR + RLE encoding, but it's written to maximize CPU utilization.
• Multithreaded I/O - All network communications run within an async task pool. I/O polling is no longer manual, nor blocks your game's execution.

Repository Structure

This repo contains the following crates:

• backroll - the main Backroll interface, intended to be used as the original GGPO.
• backroll_transport - An isolated set of transport layer abstractions.
• backroll_transport_udp - A transport layer implementation using raw UDP sockets.
• backroll_transport_steam - A transport layer implementation using the Steam provided networking utilities. Enables access to the Steam Datagram Relay service.
• bevy_backroll - a integration plugin for bevy. (Complete, untested).
• lib - third-party linking dependencies (i.e. Steam) for easier local development