c# - 如何将递归结构编组为 c 锐利？

Question

我有一个非托管结构，我想编组为 c sharp，它看起来基本上像这样：

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

我相信我必须编写一个自定义编组器，但我不确定如何进行。

Answer 1

当我不需要直接索引孩子时，我喜欢使用这样的设置：

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;
            }
        }
    }
}

如果您确实需要直接索引子项，最简单的方法是创建一个方法GetChild（如下所示）。更难的方法是创建一个实现IList<MyStruct>. 将从Children属性返回一个实例，其内部将通过调用该GetChild方法来工作。如果需要，这将作为练习留给读者。

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

如果您只想将它​​传递给一些非托管函数，您可以使用不安全代码和 stackalloc / 修复数组来获取指向对象数组的指针。

        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);


        }