如何編組一個可變大小的結構數組？ C＃和C ++互操作幫助

Question

我有以下C ++結構

struct InnerStruct
{
   int A;
   int B;
};

struct OuterStruct
{
   int numberStructs;
   InnerStruct* innerStructs;
};

還有一個C ++函數

OuterStruct getStructs();

我如何將其編組為C＃？ C＃定義的位置

struct OuterStruct {
   InnerStruct[] innerStructs;
};

Answer 1

您必須手動執行此操作，因為無法告訴P / Invoke層要從C ++返回值編組多少數據。

struct OuterStruct {
   int numberStructs;
   IntPtr innerStructs;
};

OuterStruct s = getStructs(); // using DllImport
var structSize = Marshal.SizeOf(typeof(InnerStruct));
var innerStructs = new List<InnerStruct>();
var ptr = s.innerStructs;

for (int i = 0; i < s.numberStructs; i++)
{
    innerStructs.Add((InnerStruct)Marshal.PtrToStructure(ptr, 
        typeof(InnerStruct));
    ptr = ptr + structSize;
}

請注意，如果要從C＃代碼中innerStructs的內存， innerStructs必須在C ++代碼中使用標准分配器CoTaskMemAlloc - 然后可以調用Marshal.CoTaskMemFree來釋放innerStructs 。