C#調用C/C++動態庫 封送結構體,結構體數組

一. 結構體的傳遞

#define JNAAPI extern "C" __declspec(dllexport) // C方式導出函數  
  
typedef struct      
{    
    int osVersion;    
    int majorVersion;    
    int minorVersion;    
    int buildNum;    
    int platFormId;    
    char szVersion[128];    
}OSINFO;    
  
// 1. 獲取版本信息(傳遞結構體指針)    
JNAAPI bool GetVersionPtr( OSINFO *info );    
// 2.獲取版本信息(傳遞結構體引用)    
JNAAPI bool GetVersionRef(OSINFO &info);    

// OSINFO定義  
[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;  
}  

可以通過二種方式來調用:

  1. 方式一(傳入結構體引用),在C#中,結構體是以傳值方式傳遞,類才是以傳地址方式傳遞,加關鍵字ref即可. C端傳遞了兩種不同類型的參數,都可以通過引用來解決.

[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(傳入IntPtr(平臺通用指針))

IntPtr pv = Marshal.AllocHGlobal(148); //結構體在使用時一定要分配空間(4*sizeof(int)+128)  
Marshal.WriteInt32(pv,148); //向記憶體塊里寫入數值  
if (GetVersionPtr(pv)) //直接以非托管記憶體塊地址為參數  
{  
    Console.WriteLine("--osVersion:{0}", Marshal.ReadInt32(pv, 0));  
    Console.WriteLine("--Major:{0}",Marshal.ReadInt32(pv, 4)); //移動4個位元組  
    Console.WriteLine("--BuildNum: " + Marshal.ReadInt32(pv, 12));  
    Console.WriteLine("--szVersion: "+Marshal.PtrToStringAnsi((IntPtr)(pv.ToInt32()+20)));  
}  
Marshal.FreeHGlobal(pv); //處理完記得釋放記憶體  

二.結構體數組的傳遞

// 傳遞結構體指針  
JNAAPI bool GetVersionArray(OSINFO *info,int nLen);  

   調用代碼:

/** 
 * C#介面,對於包含數組類型,只能傳遞IntPtr 
 */   
[DllImport("jnalib.dll", EntryPoint = "GetVersionArray")]  
public static extern bool GetVersionArray(IntPtr p, int nLen);    
  
// 源目標參數  
OSINFO[] infos = new OSINFO[2];  
for (int i = 0; i < infos.Length; i++)  
{  
    infos[i] = new OSINFO();  
}  
  
IntPtr[] ptArr = new IntPtr[1];  
ptArr[0] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)) * 2); //分配包含兩個元素的數組  
IntPtr pt = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)));   
Marshal.Copy(ptArr, 0, pt, 1); //拷貝指針數組  
GetVersionArray(pt, 2); //調用  
  
//還原成結構體數組  
for (int i = 0; i < 2; i++)    
{  
    infos[i]=(OSINFO)Marshal.PtrToStructure((IntPtr)(pt.ToInt32()+i*Marshal.SizeOf(typeof(OSINFO))),typeof(OSINFO));  
    Console.WriteLine("OsVersion:{0} szVersion:{1}", infos[i].osVersion, infos[i].szVersion);  
}  

三. 複雜結構體的傳遞

   1. 輸出參數,結構體作為指針傳出

typedef struct  
{  
    char name[20];  
    int age;  
    double scores[30];  
}Student;  
  
// Class中包含結構體數組類型  
typedef struct  
{  
    int number;  
    Student students[50];  
}Class;  
  
// 傳入複雜結構體測試  
JNAAPI int GetClass(Class *pClass,int len);  

// 介面定義   
[DllImport("jnalib.dll", EntryPoint = "GetClass")]  
public static extern int GetClass(IntPtr pv,int len);  
  
// 結構體定義  
// 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)] // 指定數組尺寸   
    public Student[] students; // 結構體數組定義  
}  
  
// 調用複雜結構體測試  
int size = Marshal.SizeOf(typeof(Class)) * 50;  
IntPtr pBuff = Marshal.AllocHGlobal(size); // 直接分配50個元素的空間,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); // 釋放記憶體  

   2. 輸入參數, 給複雜結構體賦值後作為輸入參數傳入

   對於比較大的結構體指針,無法直接應用結構體類型,轉化成IntPtr類型, 此時需要將原生類型轉化為指針,並給指針賦值

   調用方法: 

Marshal.StructureToPtr(stu, ptr1, true) 

轉摘自

　　C#調用C/C++動態庫 封送結構體,結構體數組