TODO use NativeFinalizer free NativeArray pointer when garbage collected

[wasabia]

https://api.dart.cn/stable/2.17.0/dart-ffi/NativeFinalizer-class.html

[GZGavinZhao]

另：我看不出来你的代码里有没有用，我发现 dart-lang/language#1862 中提出了两个方案能在C和Dart之间传送各种体积大的array的时候减少内存占用并优化性能：

1. How to pass huge objects across isolates and/or ffi, without huge memory and cpu footprint? dart-lang/language#1862 (comment)
2. provide helpers (or samples) for zero-overhead non-leaking bytes transfer between isolates in ffi dart-lang/sdk#47270

[GZGavinZhao]

Hi，我又回来啦~ 以前一直对NativeFinalizer一头雾水，最近花了点时间在自己的代码里试验了一下搞明白它的用法，一些小心得希望能有所帮助：

// filename: lib/src/utils/memory.dart

/// A generic [NativeFinalizer] to free any pointer by calling the C function
/// `free`. It's kind of like a workaround to combat the restriction of
/// [NativeFinalizer] (which only accepts a C function, not a Dart
/// function).
final freenalizer = NativeFinalizer(DynamicLibrary.executable().lookup('free'));

使用方法大概是：

import 'dart:ffi';
import 'package:mypackage/src/utils/memory.dart';

class Foo extends Finalizable {
  Pointer<X> _ptr = calloc();
  Foo() {
    freenalizer.attach(this, _ptr.cast());
  }
}

应用到你这里可能就是将这一行加上一个freenalizer.dispose(this, data.cast())，之后因为PlatformNativeArray的所有child class的constructor里你好像都有用super()，所以理论上dispose()就可以完全丢掉啦。

注：据我所知cast没有任何性能上的影响，使用它仅仅是为了满足静态类型。