Simple Dart example to demonstrate shared memory for Isolates

iso_ffi.dart

import 'dart:ffi';
import 'dart:isolate';
import 'dart:io';
import 'package:ffi/ffi.dart';

void newIsolate(SendPort sendPort) {
  final ptr = calloc.allocate<Int>(100);
  ptr[0] = 42;
  sendPort.send(ptr.address);
  sleep(const Duration(seconds: 1));
  ptr[0] = 43;
  sleep(const Duration(seconds: 1));
  print("Isolate terminating");
  sendPort.send("end");
}

void mainIsolate() async {
  ReceivePort recvPort = ReceivePort();
  Isolate.spawn(newIsolate, recvPort.sendPort); // Starting myIsolate
  recvPort.listen((message) {
    if (message is int) {
      // when message is an int, it must be the array address
      final ptr = Pointer<Int>.fromAddress(message);
      // we know have an array located at exactly the same address
      // as in the isolate, poll [0] for a while
      for (var i = 0; i < 15; i++) {
        final val = ptr[0];
        print("Value = $val");
        sleep(const Duration(milliseconds: 100));
      }
    } else {
      // when message is not int, it must be the "end" message
      print("main terminating");
      exit(0);
    }
  });
}