一. 結構體的傳遞
Cpp代碼#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);C#代碼
// 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.
C#代碼[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(平台通用指針))
C#代碼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); //向內存塊裡寫入數值 if (GetVersionPtr(pv)) //直接以非托管內存塊地址為參數 { Console.WriteLine("--osVersion:{0}", Marshal.ReadInt32(pv, 0)); Console.WriteLine("--Major:{0}",Marshal.ReadInt32(pv, 4)); //移動4個字節 Console.WriteLine("--BuildNum: " + Marshal.ReadInt32(pv, 12)); Console.WriteLine("--szVersion: "+Marshal.PtrToStringAnsi((IntPtr)(pv.ToInt32()+20))); } Marshal.FreeHGlobal(pv); //處理完記得釋放內存
二.結構體數組的傳遞
Cpp代碼// 傳遞結構體指針 JNAAPI bool GetVersionArray(OSINFO *info,int nLen);
調用代碼:
C#代碼/** * C#接口,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. 復雜結構體的傳遞
1. 輸出參數,結構體作為指針傳出
Cpp代碼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; // 傳入復雜結構體測試 JNAAPI int GetClass(Class *pClass,int len);C#代碼
// 接口定義 [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 } // 調用復雜結構體測試 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); // 釋放內存
2. 輸入參數, 給復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