一、结构体传递
-
#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[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);
可以通过二种方式进行调用:
-
// 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;
-
}
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(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
-
// 传递结构体指针
-
JNAAPI bool GetVersionArray(OSINFO *info,int nLen);
调用:
-
/**
-
* 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[] ptArr = new IntPtr[1];
-
ptArr[0] = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)) * 2); //分配包含两个元素的数组
-
IntPtr pt = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(OSINFO)));
-
Marshal.Copy(ptArr, 0, pt, 1); //拷贝指针数组
-
GetVersionArray(pt, 2); //调用
-
//还原成结构体数组
-
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. 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[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);
-
// 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)