README.md

Rust Host Application for Example Components

This is a native Rust CLI application that can run WebAssembly Components of the adder world, defined in examples/tutorial/wit/adder/world.wit, using WebAssembly Interface Types ("WIT").

The adder world exports an interface called add which defines an function that takes two unsigned and adds them:

package docs:adder@0.1.0;

interface add {
    add: func(x: u32, y: u32) -> u32;
}

world adder {
    export add;
}

The application uses WebAssembly ecosystem crates (e.g. wasmtime) to generate Rust bindings, instantiate WASI worlds, and executes the exported add function (docs:adder/add.add) of a provided component.

This host binary takes in two unsigned 32bit integers (u32) operands and a path to a component. This host then:

1. Loads the component from the given path
2. Instantiates it as an implementer of the adder world
3. Executes the add function exported by the component
4. Prints the result

If running with cargo (part of the Rust toolchain), then you should see output like the following:

$ cargo run --release -- 1 2 add.wasm
1 + 2 = 3

Note

add.wasm is available in this folder, but can be replaced with your own built WebAssembly component at any time (written in any language that supports WebAssembly Components), given that it satisfies the adder world described above.