Benchmark ffi calls

ffi_benchmark.dart

import 'dart:core';
import 'dart:ffi';

final _libc = DynamicLibrary.open('libc.so.6');

typedef abs_t = Int32 Function(Int32);
typedef abs_d = int Function(int);

final _abs = _libc.lookupFunction<abs_t, abs_d>('abs');

void main() {
	print('_libc $_libc');
	print('_abs $_abs');

	int a = -1337;
	int b = 0;
	int n = 10000000;

	int ms = 0;
	int us = 0;

	
	print('start benchmark ..');
	Stopwatch sw = Stopwatch()..start();
	
	for (int i = 1; i < n; i++) {
		
		sw.reset();
		b = _abs(a);
		sw.stop();
		us += sw.elapsedMicroseconds;
		ms += sw.elapsedMilliseconds;
		
	}

	print('$n iterations took ${ms}ms (${us}us)');
	print('average : ${ms / n}ms (${us / n}us)');

	print('a = $a');
	print('b = $b');
}