C#调用C/C++动态库 封送结构体,结构体数组

一. 结构体的传递

#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[];
}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);    

// 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 = )]
    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.

[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))

IntPtr pv = Marshal.AllocHGlobal(); //结构体在使用时一定要分配空间(4*sizeof(int)+128)
Marshal.WriteInt32(pv,); //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, ));
    Console.WriteLine("--Major:{0}",Marshal.ReadInt32(pv, )); //移动4个字节
    Console.WriteLine("--BuildNum: " + Marshal.ReadInt32(pv, ));
    Console.WriteLine("--szVersion: "+Marshal.PtrToStringAnsi((IntPtr)(pv.ToInt32()+)));
}
Marshal.FreeHGlobal(pv); //处理完记得释放内存  

二.结构体数组的传递

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

调用代码:

/**
 * 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[];
for (int i = ; i < infos.Length; i++)
{
    infos[i] = new OSINFO();
}  

IntPtr pt = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)) * 2);
GetVersionArray(pt, ); //调用  

//还原成结构体数组
for (int i = ; i < ; 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

typedef struct
{
    char name[];
    int age;
    double scores[];
}Student;  

// Class中包含结构体数组类型
typedef struct
{
    int number;
    Student students[];
}Class;  

// 传入复杂结构体测试
JNAAPI int GetClass(Class *pClass,int len);  

// 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=)]
    public string name;
    public int age;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = )]
    public double[] scores;
}  

// Class
[StructLayout(LayoutKind.Sequential)]
public struct Class
{
    public int number;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = )] // 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)) * ;
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, );  

Class[] pClass = new Class[];
for (int i = ; i < ; 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

　　C#调用C/C++动态库 封送结构体,结构体数组