third_party/parity-wasm/examples/inject.rs

extern crate parity_wasm;

use std::env;

use parity_wasm::elements;
use parity_wasm::builder;

pub fn inject_nop(opcodes: &mut elements::Opcodes) {
	use parity_wasm::elements::Opcode::*;
	let opcodes = opcodes.elements_mut();
	let mut position = 0;
	loop {
		let need_inject = match &opcodes[position] {
			&Block(_) | &If(_) => true,
			_ => false,
		};
		if need_inject {
			opcodes.insert(position + 1, Nop);
		}

		position += 1;
		if position >= opcodes.len() {
			break;
		}
	}
}

fn main() {
	let args = env::args().collect::<Vec<_>>();
	if args.len() != 3 {
		println!("Usage: {} input_file.wasm output_file.wasm", args[0]);
		return;
	}

	let mut module = parity_wasm::deserialize_file(&args[1]).unwrap();

	for section in module.sections_mut() {
		match section {
			&mut elements::Section::Code(ref mut code_section) => {
				for ref mut func_body in code_section.bodies_mut() {
					inject_nop(func_body.code_mut());
				}
			},
			_ => { }
		}
	}

	let mut build = builder::from_module(module);
	let import_sig = build.push_signature(
		builder::signature()
			.param().i32()
			.param().i32()
			.return_type().i32()
			.build_sig()
	);
	let build = build.import()
		.module("env")
		.field("log")
		.external().func(import_sig)
		.build();

	parity_wasm::serialize_to_file(&args[2], build.build()).unwrap();
}