如何编组结构的可变大小的数组？ C＃和C ++互操作的帮助

问题描述

我有以下的C ++结构

 结构InnerStruct
{
   诠释A;
   INT B：
};

结构OuterStruct
{
   诠释numberStructs;
   InnerStruct * innerStructs;
};
 

和C ++函数

  OuterStruct getStructs（）;
 

我怎么能这样编组的C＃？当C＃定义为

 结构OuterStruct {
   InnerStruct [] innerStructs;
};
 

解决方案

您需要手动做到这一点，因为没有办法告诉的P / Invoke层有多少数据从C到元帅++返回值。

 结构OuterStruct {
   诠释numberStructs;
   IntPtr的innerStructs;
};

OuterStruct S = getStructs（）; //使用的DllImport
VAR structSize = Marshal.SizeOf（typeof运算（InnerStruct））;
VAR innerStructs =新的名单，其中，InnerStruct＆GT;（）;
VAR PTR = s.innerStructs;

的for（int i = 0; I＆LT; s.numberStructs;我++）
{
    innerStructs.Add（（InnerStruct）Marshal.PtrToStructure（PTR，
        typeof运算（InnerStruct））;
    PTR =（IntPtr的）（（INT）PTR + structSize）;
}
 

请注意，如果你想免费为 innerStructs 内存从C＃code，你必须使用标准分配器 CoTaskMemAlloc来在C ++ code - 那么你可以调用 Marshal.CoTaskMemFree 免费 innerStructs 。

I have the following C++ structs

struct InnerStruct
{
   int A;
   int B;
};

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

And a C++ function

OuterStruct getStructs();

How can I marshal this to C#? Where the C# definitions is

struct OuterStruct {
   InnerStruct[] innerStructs;
};

解决方案

You'll have to do this manually, since there's no way to tell the P/Invoke layer how much data to marshal from your C++ return value.

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 = (IntPtr)((int)ptr + structSize);
}

Note that if you want to free the memory for innerStructs from your C# code, you have to use the standard allocator CoTaskMemAlloc in your C++ code--then you can call Marshal.CoTaskMemFree to free innerStructs.

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