C#调用C++ 平台调用P/Invoke 结构体--内存对齐方式、union封装【七】

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【1】内存对齐方式

C++代码：

#pragma pack(push)#pragma pack(1)typedef struct _testStru2{intiVal;charcVal;__int64 llVal;}testStru2;#pragma pack(pop)

EXPORTDLL_API void Struct_PackN( testStru2 *pStru ){if (NULL == pStru){return;}pStru->iVal = 1;pStru->cVal = 'a';pStru->llVal = 2;wprintf(L"Struct_PackN \n");}

C#代码，指定Pack即可：

[StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Unicode)]public struct testStru2{    public int iVal;    public sbyte cVal;    public long  llVal;};[DllImport("ExportDll.dll", CharSet = CharSet.Unicode)]public static extern void Struct_PackN(ref testStru2 pStru);

测试：

CExportDll.testStru2 stru2 = new CExportDll.testStru2();CExportDll.Struct_PackN(ref stru2);

【2】Union中含有结构体

C++代码：

typedef union _testStru4{intiValLower;intiValUpper;struct {__int64 llLocation;};}testStru4;

EXPORTDLL_API void Struct_Union( testStru4 *pStru ){if (NULL == pStru){return;}pStru->llLocation = 1024;wprintf(L"Struct_Union \n");}

C#代码：定义成Explict，并显示通过FieldOffset指定内存偏移

[StructLayout(LayoutKind.Explicit, CharSet=CharSet.Unicode)]public struct testStru4{    [FieldOffset(0)]    intiValLower;    [FieldOffset(4)]    intiValUpper;    [FieldOffset(0)]           long    llLocation;        };[DllImport("ExportDll.dll", CharSet = CharSet.Unicode)]public static extern void Struct_Union(ref testStru4 pStru);

测试：

CExportDll.testStru4 stru4 = new CExportDll.testStru4();CExportDll.Struct_Union(ref stru4);

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