Valhalla 🤝 🦀

To continue the mythological theme, this project is cheekily named Valinor.

Preface: this project available as-is. We use this code for various purposes internally, and it is probably only useful if you're already a skilled Valhalla hacker.

That said, there are a few reasons we'd like to see such a project exist, so we're open sourcing this code.

Here are a few things that we think are worth exploring:

• Making it easier to build tooling around Valhalla by offering a safe, fast interface
• Improving the ergonomics of routing on mobile (eventually via UniFFI)
• Finding ways to improve graph tile generation with better parallelism, support for alternate data formats (e.g. parquet), and a more understandable mapping system
• Building a safer dynamic costing model system that's plugin-based (ex: via WASM components), which are unlikely to be merged into the upstream codebase anytime soon; as of this writing, C++ is not capable of serving as a WASM Component Host
• Improving the quality and safety of Valhalla (reimplementations tend to identify bugs in the original)
• Simplifying the process of building Valhalla microservices (see valhalla-microservice)

If you're interested in collaborating, please get in touch!

If you check out the repo and build with cargo, all should "just work." However, it's more likely than not that you'd like to use this in a library. At the moment, we rely on an unstable feature of zerocopy due to underspecified behavior of bit copies of unions. See this discussion for details.

TL;DR, you'll need to set a config flag. We do it like this in .cargo/config.toml:

[build]
rustflags = ["--cfg", "zerocopy_derive_union_into_bytes"]

This enables the project to build when checked out directly, but if you're depending on it as a library, you need to do this in your project too!

• Nearly all tests (barring those which use unsupported syscalls) are run under miri to screen for UB.
• Platform support:
  • We test every PR on Linux, macOS, and Windows
  • We also test on a big-endian emulator
  • In theory any platform with Rust std support should work, but some features like the tarball memory mapper require 64-bit atomics.
  • no-std isn't an explicit target yet, but reach out if you're interested.