uptown_funk is a crate that lets you elegantly define Wasm host functions that are compatible with both Wasmtime and Wasmer runtimes.

It consists of a macro and a few structs/traits that let you translate from Wasm primitive types to higher level Rust types, and back.

Lets look at an example of a host function definition using uptown_funk:

```rust

[hostfunctions(namespace = "wasisnapshot_preview1")]

impl WasiState { async fn fdpread(&mut self, fd: u32, iovs: &mut [IoSliceMut<'>], offset: Filesize) -> (Status, u32) { // ... }

// .. Other functions depending on the WasiState struct.

} ```

The host_function macro lets us grab any host side struct and use it as state for the Wasm instances. Instead of dealing with low level pointers + lengths passed from the WebAssembly guests, we can pretend to receive higher level Rust type (e.g. &mut [IoSliceMut<'_>]) and the macro is going to create appropriate wrappers for us. And of course, it correctly works with async functions on Lunatic.