parity-wasm/examples/interpret.rs

// In this example we execute a contract funciton exported as "_call"
#![allow(deprecated)]

extern crate parity_wasm;

use std::env::args;

use parity_wasm::ModuleInstanceInterface;

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;
	}

	// Intrepreter initialization.
	let program = parity_wasm::ProgramInstance::new();

	// 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 module = program.add_module("main", module, None).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: {:?}", module.execute_export("_call", vec![parity_wasm::RuntimeValue::I32(argument)].into()));
}