一. 结构体的传递

Cpp代码

#define JNAAPI extern "C" __declspec(dllexport) // C方式导出函数    typedef struct      {        int osVersion;        int majorVersion;        int minorVersion;        int buildNum;        int platFormId;        char szVersion[128];    }OSINFO;      // 1. 获取版本信息(传递结构体指针)    JNAAPI bool GetVersionPtr( OSINFO *info );    // 2.获取版本信息(传递结构体引用)    JNAAPI bool GetVersionRef(OSINFO &info);

C#代码

// OSINFO定义  [StructLayout(LayoutKind.Sequential)]  public struct OSINFO  {      public int osVersion;      public int majorVersion;      public int minorVersion;      public int buildNum;      public int platFormId;      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]      public string szVersion;  }

 

可以通过二种方式来调用:

  1. 方式一(传入结构体引用),在C#中,结构体是以传值方式传递,类才是以传地址方式传递,加关键字ref即可. C端传递了两种不同类型的参数,都可以通过引用来解决.

C#代码

[DllImport("jnalib.dll", EntryPoint = "GetVersionPtr")]  public static extern bool GetVersionPtr(ref OSINFO info);  public static extern bool GetVersionRef(ref OSINFO info);

  2. 方式二(传入IntPtr(平台通用指针))

C#代码

IntPtr pv = Marshal.AllocHGlobal(148); //结构体在使用时一定要分配空间(4*sizeof(int)+128)  Marshal.WriteInt32(pv,148); //向内存块里写入数值  if (GetVersionPtr(pv)) //直接以非托管内存块地址为参数  {      Console.WriteLine("--osVersion:{0}", Marshal.ReadInt32(pv, 0));      Console.WriteLine("--Major:{0}",Marshal.ReadInt32(pv, 4)); //移动4个字节      Console.WriteLine("--BuildNum: " + Marshal.ReadInt32(pv, 12));      Console.WriteLine("--szVersion: "+Marshal.PtrToStringAnsi((IntPtr)(pv.ToInt32()+20)));  }  Marshal.FreeHGlobal(pv); //处理完记得释放内存

  

二.结构体数组的传递

Cpp代码

// 传递结构体指针  JNAAPI bool GetVersionArray(OSINFO *info,int nLen);

   调用代码:

C#代码

/**  * C#接口,对于包含数组类型,只能传递IntPtr  */   [DllImport("jnalib.dll", EntryPoint = "GetVersionArray")]  public static extern bool GetVersionArray(IntPtr p, int nLen);      // 源目标参数  OSINFO[] infos = new OSINFO[2];  for (int i = 0; i < infos.Length; i++)  {      infos[i] = new OSINFO();  }    IntPtr pt = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)) * 2);   GetVersionArray(pt, 2); //调用    //还原成结构体数组  for (int i = 0; i < 2; i++)    {      IntPtr ptr = (IntPtr)((UInt32)pt + i * Marshal.SizeOf(typeof(OSINFO)));    infos[i]=(OSINFO)Marshal.PtrToStructure(ptr,typeof(OSINFO));      Console.WriteLine("OsVersion:{0} szVersion:{1}", infos[i].osVersion, infos[i].szVersion);  }  Marshal.FreeHGlobal (pt);

 

三. 复杂结构体的传递

   1. 输出参数,结构体作为指针传出

Cpp代码

typedef struct  {      char name[20];      int age;      double scores[30];  }Student;    // Class中包含结构体数组类型  typedef struct  {      int number;      Student students[50];  }Class;    // 传入复杂结构体测试  JNAAPI int GetClass(Class *pClass,int len);

C#代码

// 接口定义   [DllImport("jnalib.dll", EntryPoint = "GetClass")]  public static extern int GetClass(IntPtr pv,int len);    // 结构体定义  // Student  [StructLayout(LayoutKind.Sequential)]  public struct Student  {      [MarshalAs(UnmanagedType.ByValTStr,SizeConst=20)]      public string name;      public int age;      [MarshalAs(UnmanagedType.ByValArray, SizeConst = 30)]      public double[] scores;  }    // Class  [StructLayout(LayoutKind.Sequential)]  public struct Class  {      public int number;      [MarshalAs(UnmanagedType.ByValArray, SizeConst = 50)] // 指定数组尺寸       public Student[] students; // 结构体数组定义  }    // 调用复杂结构体测试  int size = Marshal.SizeOf(typeof(Class)) * 50;  IntPtr pBuff = Marshal.AllocHGlobal(size); // 直接分配50个元素的空间,比Marshal.copy方便多了  GetClass(pBuff, 50);    Class[] pClass = new Class[50];  for (int i = 0; i < 50; i++)  {      IntPtr ptr = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(Class)) * i);      pClass[i] = (Class)Marshal.PtrToStructure(ptr, typeof(Class));  }  Marshal.FreeHGlobal(pBuff); // 释放内存

   2. 输入参数, 给复杂结构体赋值后作为输入参数传入

   对于比较大的结构体指针,无法直接应用结构体类型,转化成IntPtr类型, 此时需要将原生类型转化为指针,并给指针赋值

   调用方法: 

Marshal.StructureToPtr(stu, ptr1, true)

 

转摘自