Dart/Flutter FFI (外部函数接口)：在Dart中使用FFI调用带有输出参数的本机函数

// sum.c
#include <stdint.h>

int32_t sum_array(int32_t* array, int32_t length) {
    int32_t sum = 0;
    for (int32_t i = 0; i < length; i++) {
        sum += array[i];
    }
    return sum;
}

gcc -shared -o libsum.so sum.c

import 'dart:ffi';
import 'dart:io';

void main() {
  // 加载共享库
  final DynamicLibrary lib = Platform.isAndroid
      ? DynamicLibrary.open("libsum.so")
      : DynamicLibrary.open("libsum.dylib");

  // 定义函数签名
  final int Function(Pointer<Int32>, Int32) sumArray = lib
      .lookup<NativeFunction<Int32 Function(Pointer<Int32>, Int32)>>("sum_array")
      .asFunction();

  // 创建一个整数数组
  final List<int> numbers = [1, 2, 3, 4, 5];
  final Pointer<Int32> arrayPtr = allocate<Int32>(count: numbers.length);
  for (int i = 0; i < numbers.length; i++) {
    arrayPtr[i] = numbers[i];
  }

  // 调用本机函数
  final result = sumArray(arrayPtr, numbers.length);

  print("Sum: $result");

  // 释放内存
  free(arrayPtr);
}