Calculating the GCD - Wasmtime

# Calculating the GCD

You can also browse this source code online and clone the wasmtime repository to run the example locally.

This example shows off how run a wasm program which calculates the GCD of two numbers.

## `gcd.wat`

    (module
      (func $gcd (param i32 i32) (result i32)
        (local i32)
        block  ;; label = @1
          block  ;; label = @2
            local.get 0
            br_if 0 (;@2;)
            local.get 1
            local.set 2
            br 1 (;@1;)
          end
          loop  ;; label = @2
            local.get 1
            local.get 0
            local.tee 2
            i32.rem_u
            local.set 0
            local.get 2
            local.set 1
            local.get 0
            br_if 0 (;@2;)
          end
        end
        local.get 2
      )
      (export "gcd" (func $gcd))
    )

## `gcd.rs`

    //! Example of instantiating of the WebAssembly module and invoking its exported
    //! function.

    // You can execute this example with `cargo run --example gcd`

    use wasmtime::*;

    fn main() -> Result<()> {
        // Load our WebAssembly (parsed WAT in our case), and then load it into a
        // `Module` which is attached to a `Store` cache. After we've got that we
        // can instantiate it.
        let mut store = Store::<()>::default();
        let module = Module::from_file(store.engine(), "examples/gcd.wat")?;
        let instance = Instance::new(&mut store, &module, &[])?;

        // Invoke `gcd` export
        let gcd = instance.get_typed_func::<(i32, i32), i32>(&mut store, "gcd")?;

        println!("gcd(6, 27) = {}", gcd.call(&mut store, (6, 27))?);
        Ok(())
    }