A_walk_in_the_park/lib/main.dart

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

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:path_provider/path_provider.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

typedef GetHelloFunc = Pointer<Utf8> Function();
typedef GetHello = Pointer<Utf8> Function();

typedef MmapNative = Pointer<Void> Function(Pointer<Void>, IntPtr, Int32, Int32, Int32, IntPtr);
typedef MmapDart = Pointer<Void> Function(Pointer<Void>, int, int, int, int, int);

final DynamicLibrary libc = DynamicLibrary.open("libc.so");
final dlopen = libc.lookupFunction<
    Pointer<Void> Function(Pointer<Utf8>, Int32),
    Pointer<Void> Function(Pointer<Utf8>, int)>('dlopen');

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  Future _incrementCounter() async {
    print("Running on ${Platform.operatingSystem} (${Platform.version}) | IsAndroid: ${Platform.isAndroid}");

    ByteData data = await rootBundle.load("assets/files/libnative.so");
    var soData = data.buffer.asUint8List();
    final int length = soData.length;

    //this works as quick and dirt way but we want from memory
    // final String tempLibPath = "${Directory.systemTemp.path}/libnative.so";
    // final File libFile = File(tempLibPath);
    // libFile.createSync(recursive: true);
    // libFile.writeAsBytesSync(soData, flush: true);
    // Process.runSync("chmod", ["777", tempLibPath]);
    // final DynamicLibrary dylib = DynamicLibrary.open(tempLibPath);

    final MmapDart mmap = libc.lookupFunction<MmapNative, MmapDart>("mmap");
    const int PROT_READ = 0x1;
    const int PROT_WRITE = 0x2;
    const int PROT_EXEC = 0x4;
    const int MAP_PRIVATE = 0x02;
    const int MAP_ANONYMOUS = 0x20;
    final Pointer<Void> mem = mmap(nullptr, length, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

    if (mem.address == 0) {
      print("Failed to allocate executable memory!");
      return;
    }

    final Pointer<Uint8> memBytes = mem.cast<Uint8>();
    for (int i = 0; i < length; i++) {
      memBytes[i] = soData[i];
    }

    Pointer<Utf8> cPath = "/proc/self/mem".toNativeUtf8();
    Pointer<Void> handle = dlopen(cPath, 2); // RTLD_LAZY
    malloc.free(cPath);

    if (handle.address == 0) {
      print("Failed to load ELF!");
      return;
    }

    print("Library successfully loaded!");

    final DynamicLibrary dylib = DynamicLibrary.process();
    final GetHello getHello = dylib.lookupFunction<GetHelloFunc, GetHello>("get_hello");
    print(getHello().toDartString()); // Prints "Hello from native C!"

    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(

        child: Column(

          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: const Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}