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
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;
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
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()
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
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
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
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
EnumWindows(WNDENUMPROC IpEnumFunc,LPARAM lPararm)
.NET 程序可以通过P/Invoke调用 EnumWindows API
CLR能够将Delegate 转换为函数指针，EnumWindows 来回调这个函数指针
[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();
NativeMethods.GetWindowText(hwnd, text, );
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,);
Console.Read();
} } -
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。
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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
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MDA报错StackImbalanceMDA
VS提示报错，参数错位调用协定不对
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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 * -;
}
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, , sizeof(int)* length);
}
void TestArray(int *a, int length)
{
for (int i = ; i < length; i++)
{
a[i]++;
}
} void TestCallback(void(*pf)())
{
pf();
}
int TestCharWidth(char *s)
{
return strlen(s);
} 文件名 Source.cppLIBRARY "PInvoke"
EXPORTS
TestInt
TestIntPtr
TestCharPtr
TestStructPtr
TestPtrPtr
TestArray
TestCallback
TestCharWidth
文件名 Source.def - C#
class Program
{ [StructLayoutAttribute(LayoutKind.Sequential)]
public struct Mytype
{ /// int
public int i; /// char*
[MarshalAsAttribute(UnmanagedType.LPStr)]
public string s; /// double
public 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(, )); // TestIntPtr
int i = ;
TestIntPtr(ref i);
Console.WriteLine("TestIntPtr:" + i); // TestCharPtr
IntPtr 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 // TestCharWidth
string a = "a的";
IntPtr aPtr = Marshal.StringToHGlobalAnsi(a); // Ansi
int len = TestCharWidth(aPtr);
Console.WriteLine("TestCharWidth:" + len);
a = Marshal.PtrToStringAnsi(aPtr);
Marshal.FreeHGlobal(aPtr); aPtr = Marshal.StringToHGlobalUni(a); // Unicode
len = 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); // TestStructPtr
Mytype myType = new Mytype { i = , d = 1.1, s = a, p = IntPtr.Zero };
TestStructPtr(ref myType);
Console.WriteLine("Mytype->i:" + myType.i);
Console.WriteLine("Mytype->d:" + myType.d); // TestArray
int[] array = new int[] { , , };
TestArray(array, array.Length); for (int z = ; z < array.Length; z++)
{
Console.WriteLine("array[{0}]" + array[z], z);
} // TestCallback
TestCallback(CallbackFunction); Console.Read();
} }
- c++