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上一章地址
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API版本
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具有字符串参数的API通常有两种版本
- GetWindowText
- GetWindowTextA
- GetWindowTextW
- GetWindowText
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缺省情况下CLR会自动寻找合适的匹配
- CharSet=Ansi时寻找A版本
- CharSet=Unicode寻找W版本
- CharSet=Auto和平台相关
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DLLImportAttribute（ExactSpelling=true）会关掉这种行为
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Ref/Out参数 （C#关键字）
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out=[Out]&
- C#:out int a
- IL:[Out] int &a
- C++:int *pa;
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ref=[In,Out]&
- C#:ref int a
- IL:[In,Out] int &a
- C++:int *pa;
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个人感觉 使用Ref/Out 参数P/Invoke CRL会对根据对应关键字添加对应IL特性 System.Runtime.InteropServices下面的InAttribute、OutAttribute
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引用类型和值类型
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非托管C/C++ 代码：struct A{int a;}
托管代码:struct A{int a;} class A{int a;} -
非托管C/C++代码 A A* A** A为值类型 A ref A IntPtr a A为引用类型 N/A A ref A
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自定义参数转换
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托管类型和非托管类型之间是一对多关系
- String
- char */wchar_t *
- char[N]/wchar_t[N] 固定长度的字符串
- BSTR, Ansi BSTR
- String
- MarshalAsAttribute(UnmanagedType)
- UnmanagedType 枚举指定对应非托管类型
- [MarshalAsAttribute(UnmanagedType.LPWSTR)] string A
- 非托管函数：void Func(wchar_t *)
- 托管函数：Public static extern void Func([MarshalAs(UnmanagdType.LPWSTR)] string);
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内存管理
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在数据转换中需要进行内存分配
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举例：
- C#调用Func(string) Marshal.StringToHGlobalAnsi("balabala")
- C#调用Func(ref string)
- C#调用string Func()
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CoTaskMemAlloc / CoTaskMemFree (分配/释放 内存) 内存交换才使用
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实例分析CreateProcess
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API原型
BOOL WINAPI CreateProcess(_In_opt_ LPCTSTR lpApplicationName,_Inout_opt_ LPTSTR lpCommandLine,_In_opt_ LPSECURITY_ATTRIBUTES lpProcessAttributes,_In_opt_ LPSECURITY_ATTRIBUTES lpThreadAttributes,_In_ BOOL bInheritHandles,_In_ DWORD dwCreationFlags,_In_opt_ LPVOID lpEnvironment,_In_opt_ LPCTSTR lpCurrentDirectory,_In_ LPSTARTUPINFO lpStartupInfo,_Out_ LPPROCESS_INFORMATION lpProcessInformation );
（opt 可选的输入参数）
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C#
Public static extern bool CreateProcess(
[In] string applicationName,
[In,Out] StringBuilder commandName,
[In] ref SECURITY_ATTRIBUTES processAttributes,
[In] ref SECURITY_ATTRIBUTES threadAttributes,
[In] bool inheritHandles,
[In] uint creationFlags,
[In] IntPtr lpEnvironment,
[In] string currentDirectory,
[In] ref STARTUP_INFO startupInfo,
[Out] out PROCESS_INFORMATION processInformation
);
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DLL生命周期
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Dll在第一次调用的时候自动加载，不会自动被释放，加载不到或者找不到函数就会抛出异常
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Dll不会自动被卸载,建议做法生命一个外部调用类 DLL会伴随外部调用类一起被清理卸载
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如果需要手段管理DLL生命周期，只能手动调用LoadLibrary/GetProcAddress
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逆向P/Invoke
非托管代码到托管代码这种叫逆向P/Invoke-
部分API接收函数指针作为参数
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EnumWindows(WNDENUMPROC IpEnumFunc,LPARAM lPararm)
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.NET 程序可以通过P/Invoke调用 EnumWindows API
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CLR能够将Delegate 转换为函数指针，EnumWindows 来回调这个函数指针
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[UnmanagedFunctionPointer(CallingConvention.Winapi)] delegate bool EnumWindowProc(IntPtr hwnd, IntPtr lParam); EnumWindow(new EnumWindowProc(MyEnumWindow), IntPtr.Zero);
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DEMO
class Program{ /// Return Type: BOOL->int///hwnd: HWND->HWND__*///lParam: LPARAM->LONG_PTR->int [UnmanagedFunctionPointerAttribute(CallingConvention.Winapi)]public delegate bool WNDENUMPROC(IntPtr hwnd, IntPtr lParam);class NativeMethods {[DllImport("User32.dll",CallingConvention=CallingConvention.Winapi)]public static extern int GetWindowText(IntPtr hwnd, StringBuilder text, int count);/// Return Type: BOOL->int///lpEnumFunc: WNDENUMPROC///lParam: LPARAM->LONG_PTR->int[DllImportAttribute("user32.dll", EntryPoint = "EnumWindows")][return: MarshalAsAttribute(UnmanagedType.Bool)]public static extern bool EnumWindows(WNDENUMPROC lpEnumFunc, int lParam); }private static bool WNDENUMPROC_Callback(IntPtr hwnd, IntPtr lParam) {StringBuilder text = new StringBuilder(255);NativeMethods.GetWindowText(hwnd, text, 255);Console.WriteLine("窗口名：" + text + ",id=" + hwnd.ToInt32() + ",lParam=" + lParam);return true;}static void Main(string[] args){WNDENUMPROC myWNDENUMPROC = new WNDENUMPROC(WNDENUMPROC_Callback); NativeMethods.EnumWindows(myWNDENUMPROC,22);Console.Read(); }}
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常见问题
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抛出DllNotFoundException
找不到DLL一般他会到当前目录去找 或者系统目录去找 DLL如果实在无法差错可以使用全路径+dll名不推荐最好是放相对路径
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抛出AccessViolationException
访问违规，一般是内存不可以读不可以写或者一起读一起写造成的，通常原因参数转换错误，类型不对应，长度问题。 -
抛出EntryPointNotFoundException
API方法入口找不到一般都是方法名写错或者调用协定不对 -
MDA报错StackImbalanceMDA
VS提示报错，参数错位调用协定不对 -
返回数据错误
参数是否正确，MarshalAs转换是否成功，开启非托管调试查看。
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进阶DEMO
- c++
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <Windows.h> /*自定义*/ typedef struct Mytype {int i;char *s;double d;struct Mytype *p; }Mytype;int TestInt(int a,int b) {return a + b; } void TestIntPtr(int *i) {*i = *i * -1; } char * TestCharPtr(char *a,char *b) {return strcat(a, b); } void TestStructPtr(Mytype *p) {p->i++;p->d++; } void TestPtrPtr(int **a,int length) {*a = (int*)malloc(sizeof(int)*length);memset(*a, 0, sizeof(int)* length); } void TestArray(int *a, int length) {for (int i = 0; i < length; i++){a[i]++;} }void TestCallback(void(*pf)()) {pf(); } int TestCharWidth(char *s) {return strlen(s); }
文件名 Source.cppLIBRARY "PInvoke"EXPORTSTestIntTestIntPtrTestCharPtrTestStructPtrTestPtrPtrTestArrayTestCallbackTestCharWidth
文件名 Source.def - C#
class Program{[StructLayoutAttribute(LayoutKind.Sequential)]public struct Mytype{/// intpublic int i;/// char* [MarshalAsAttribute(UnmanagedType.LPStr)]public string s;/// doublepublic double d;/// Mytype*public System.IntPtr p;}/// Return Type: void public delegate void Callback();static void CallbackFunction(){Console.WriteLine("callback invoked");}/// Return Type: int///a: int///b: int[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestInt", CallingConvention = CallingConvention.Cdecl)]public static extern int TestInt(int a, int b);/// Return Type: void///i: int*[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestIntPtr", CallingConvention = CallingConvention.Cdecl)]public static extern void TestIntPtr(ref int i);/// Return Type: char*///a: char*///b: char*[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestCharPtr", CallingConvention = CallingConvention.Cdecl)]public static extern System.IntPtr TestCharPtr(System.IntPtr a, System.IntPtr b);/// Return Type: void///p: Mytype*[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestStructPtr", CallingConvention = CallingConvention.Cdecl)]public static extern void TestStructPtr(ref Mytype p);/// Return Type: void///a: int**///length: int[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestPtrPtr", CallingConvention = CallingConvention.Cdecl)]public static extern void TestPtrPtr(ref System.IntPtr a, int length);/// Return Type: void///a: int*///length: int[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestArray", CallingConvention = CallingConvention.Cdecl)]public static extern void TestArray(int[] a, int length);/// Return Type: void///pf: Anonymous_5afb5371_1680_4be9_99a9_ab5bd7ded029[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestCallback", CallingConvention = CallingConvention.Cdecl )]public static extern void TestCallback(Callback pf);/// Return Type: int///s: char*[DllImportAttribute("Pinvoke.dll", EntryPoint = "TestCharWidth", CallingConvention = CallingConvention.Cdecl)]public static extern int TestCharWidth( IntPtr s);static void Main(string[] args){Console.WriteLine("TestInt:" + TestInt(11, 2));// TestIntPtrint i = 22;TestIntPtr(ref i);Console.WriteLine("TestIntPtr:" + i);// TestCharPtrIntPtr helloPtr = Marshal.StringToHGlobalAnsi("啊阿斯达斯的阿萨德+");IntPtr worldPtr = Marshal.StringToHGlobalAnsi("+阿萨德阿萨德");IntPtr helloWorldPtr = TestCharPtr(helloPtr, worldPtr);string helloWorld = Marshal.PtrToStringAnsi(helloWorldPtr);Console.WriteLine("TestCharPtr:" + helloWorld);//helloPtr = Marshal.StringToHGlobalUni("啊阿斯蒂芬a");//worldPtr = Marshal.StringToHGlobalUni("阿萨德阿萨德");//helloWorldPtr = TestCharPtr(helloPtr, worldPtr);//helloWorld = Marshal.PtrToStringUni(helloWorldPtr);//Console.WriteLine("TestCharPtr01:" + helloWorld);// Marshal.FreeCoTaskMem() Marshal.FreeHGlobal(helloPtr);Marshal.FreeHGlobal(worldPtr);// Marshal.FreeHGlobal(helloWorldPtr); // 因为helloWorldPtr和helloPtr指向的是同一地址，所以再次释放会报错// TestCharWidthstring a = "a的";IntPtr aPtr = Marshal.StringToHGlobalAnsi(a); // Ansiint len = TestCharWidth(aPtr);Console.WriteLine("TestCharWidth:" + len);a = Marshal.PtrToStringAnsi(aPtr);Marshal.FreeHGlobal(aPtr);aPtr = Marshal.StringToHGlobalUni(a); // Unicodelen = TestCharWidth(aPtr); // 值是1，strlen没有正确处理unicode，所以不要使用strlen测量unicode字符串的长度Console.WriteLine("TestCharWidth:" + len);a = Marshal.PtrToStringUni(aPtr);Marshal.FreeHGlobal(aPtr);// TestStructPtrMytype myType = new Mytype { i = 0, d = 1.1, s = a, p = IntPtr.Zero };TestStructPtr(ref myType);Console.WriteLine("Mytype->i:" + myType.i);Console.WriteLine("Mytype->d:" + myType.d);// TestArrayint[] array = new int[] { 1, 2, 3 };TestArray(array, array.Length);for (int z = 0; z < array.Length; z++){Console.WriteLine("array[{0}]" + array[z], z);}// TestCallback TestCallback(CallbackFunction);Console.Read();}}
- c++
