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, NopExternals, RuntimeValue, ImportsBuilder};
use parity_wasm::validation::validate_module;

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");

    let validated_module = validate_module(module).expect("Failed to validate 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(&validated_module, &ImportsBuilder::default())
        .expect("Failed to instantiate module")
        .run_start(&mut NopExternals)
        .expect("Failed to run start function in 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", &[RuntimeValue::I32(argument)], &mut NopExternals));
}