parity-wasm/examples/interpret.rs

// In this example we execute a contract funciton exported as "_call"

extern crate parity_wasm;

use std::env::args;
use parity_wasm::interpreter::{ModuleInstance, HostState};

fn main() {
    let args: Vec<_> = args().collect();
    if args.len() != 3 {
        println!("Usage: {} <wasm file> <arg>", args[0]);
        println!("    wasm file should contain exported `_call` function with single I32 argument");
        return;
    }

    // Here we load module using dedicated for this purpose
    // `deserialize_file` function (which works only with modules)
    let module = parity_wasm::deserialize_file(&args[1]).expect("Failed to load module");

    // Intialize deserialized module. It adds module into It expects 3 parameters:
     // - a name for the module
     // - a module declaration
     // - "main" module doesn't import native module(s) this is why we don't need to provide external native modules here
     // This test shows how to implement native module https://github.com/NikVolf/parity-wasm/blob/master/src/interpreter/tests/basics.rs#L197
    let main = ModuleInstance::new(&module)
        .run_start(&mut HostState::default())
        .expect("Failed to initialize module");

    // The argument should be parsable as a valid integer
    let argument: i32 = args[2].parse().expect("Integer argument required");

    // "_call" export of function to be executed with an i32 argument and prints the result of execution
    println!("Result: {:?}", main.invoke_export("_call", &[parity_wasm::RuntimeValue::I32(argument)], &mut HostState::default()));
}