我如何马歇尔递归结构到c锋利？

Question

我有一个非托管结构我想编组至c尖锐看起来基本上是这样的：结果

struct MyStruct{  
    /* ... some stuff ... */
    int numChilds;  
    MyStruct *childs;
}

我认为，我必须写一个自定义编组，但我不知道如何继续。

Answer 1

我喜欢用这样的设置时，我并不需要直接指标儿童：

struct MyStruct
{
    /* ... some stuff ... */
    int numChilds;
    IntPtr childData;

    public IEnumerable<MyStruct> Children
    {
        get
        {
            int elementSize = Marshal.SizeOf(typeof(MyStruct));
            for (int i = 0; i < this.numChilds; i++)
            {
                IntPtr data = new IntPtr(this.childData.ToInt64() + elementSize * i);
                MyStruct child = (MyStruct)Marshal.PtrToStructure(data, typeof(MyStruct));
                yield return child;
            }
        }
    }
}

如果您的做的需要直接索引孩子，最简单的办法是创建一个方法GetChild（如下图所示）。更难的方法是创建一个实现IList<MyStruct>一个辅助/包装类。实例将从Children财产归还，其内部会通过调用GetChild方法工作。这是作为练习留给读者自己需要它。

public MyStruct GetChild(int index)
{
    if (index < 0)
        throw new ArgumentOutOfRangeException("index", "The index must be >= 0.");
    if (index >= this.numChilds)
        throw new ArgumentException("The index must be less than the number of children", "index");

    int elementSize = Marshal.SizeOf(typeof(MyStruct));
    IntPtr data = new IntPtr(childData.ToInt64() + elementSize * index);
    MyStruct child = (MyStruct)Marshal.PtrToStructure(data, typeof(MyStruct));
    return child;
}

Answer 2

如果你只想将它传递给一些非托管功能，你可以只使用不安全的代码和stackalloc /修复阵列来获得一个指向对象的数组。

        unsafe struct Foo
        {
            public int value;
            public int fooCount;
            public Foo* foos;
        }

        [DllImport("dll_natv.dll")]
        static extern void PrintFoos(Foo f);

        public unsafe static void Main()
        {
            Foo* foos = stackalloc Foo[10];

            for (int i = 0; i < 10; ++i)
                foos[i].value = i;

            Foo mainFoo = new Foo();
            mainFoo.fooCount = 10;
            mainFoo.value = 100;
            mainFoo.foos = foos;

            PrintFoos(mainFoo);


        }