wasm-instrument/tests/overhead.rs

use std::{
	fs::{read, read_dir},
	path::PathBuf,
};
use wasm_instrument::{
	gas_metering, inject_stack_limiter,
	parity_wasm::{deserialize_buffer, elements::Module, serialize},
};

fn fixture_dir() -> PathBuf {
	let mut path = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
	path.push("benches");
	path.push("fixtures");
	path
}

/// Print the overhead of applying gas metering, stack height limiting or both.
///
/// Use `cargo test print_overhead -- --nocapture`.
#[test]
fn print_size_overhead() {
	let mut results: Vec<_> = read_dir(fixture_dir())
		.unwrap()
		.map(|entry| {
			let entry = entry.unwrap();
			let (orig_len, orig_module) = {
				let bytes = read(&entry.path()).unwrap();
				let len = bytes.len();
				let module: Module = deserialize_buffer(&bytes).unwrap();
				(len, module)
			};
			let (gas_metering_len, gas_module) = {
				let module = gas_metering::inject(
					orig_module.clone(),
					&gas_metering::ConstantCostRules::default(),
					"env",
				)
				.unwrap();
				let bytes = serialize(module.clone()).unwrap();
				let len = bytes.len();
				(len, module)
			};
			let stack_height_len = {
				let module = inject_stack_limiter(orig_module, 128).unwrap();
				let bytes = serialize(module).unwrap();
				bytes.len()
			};
			let both_len = {
				let module = inject_stack_limiter(gas_module, 128).unwrap();
				let bytes = serialize(module).unwrap();
				bytes.len()
			};

			let overhead = both_len * 100 / orig_len;

			(
				overhead,
				format!(
					"{:30}: orig = {:4} kb, gas_metering = {} %, stack_limiter = {} %, both = {} %",
					entry.file_name().to_str().unwrap(),
					orig_len / 1024,
					gas_metering_len * 100 / orig_len,
					stack_height_len * 100 / orig_len,
					overhead,
				),
			)
		})
		.collect();
	results.sort_unstable_by(|a, b| b.0.cmp(&a.0));
	for entry in results {
		println!("{}", entry.1);
	}
}