因为新项目将主要用到CSharp,并同时会涉及Mix programming的问题,与Native C++ and C++ CLI (common language infrastructure),今天迅速的google下,做些初步了解先。
现在的理解:
1. 这里说的mix programming的意思应该是:让CSharp的module,Native C++ module和C++ CLI的module之间可以互相调用。当然不是把这不同语言的code直接写在一起喽。。
2. Csharp的module使用Native C++ module的方法已知的有:
a. 用C++ CLI把native c++ module 包个wrapper module出来,然后,让CSharp的module调用这个wrapper。而且,通过makefile,还可以把这些相关的不同语言写的module打包成一个exe!
b. 直接用C#的语法 + 使用Native C++导出函数的方式来调用(要在C#代码中调用C++函数,大体的思路是这样的:首先将C++函数写成DLL形式的库,然后在C#中导入DLL中的函数进行调用)。
1. 大概的样子如下:
C++代码:
1 int StaticElementNumber = 10;
2 extern "C" AFX_API_EXPORT int GetArrayElementNumber()
3 {
4 return StaticElementNumber;
5 }
C#代码:
(导入函数部分,写在调用函数所在类中)
1 [DllImport("MFCDll.dll")]
2 public static extern int GetArrayElementNumber();
3 int ElementNumber = GetArrayElementNumber();
2. 由于这两种语言中在数据类型上的不同,使得在使用native c++的导出函数时,肯定没法做到fucntion interface一模一样;但是在CLR的帮助下,下面几种类型是可以被有效处理好的:
a. (C++) extern "C" AFX_API_EXPORT HBITMAP GetABitmap(WCHAR *strFileName) =>
(CSharp) public static extern IntPtr GetABitmap([MarshalAs(UnmanagedType.LPWStr)] string strFileName);
b. (C++) extern "C" AFX_API_EXPORT bool GetArray(int ElementNumber, double *BaseAddress) =>
(CSharp) public static extern bool GetArray(int ElementNumber, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 0)] double[] BaseAddress);
3. C# 工程setting中,可以设置是否debug unmanaged code debugging,从而在这种情况下,在运行CSharp module时,直接debug进入C++ module哦!
3. System.Runtime.InteropServices.Marshal
4. 转载一篇Q&A (http://bytes.com/topic/c-sharp/answers/715638-mixing-unmanaged-c-c)
Mixing unmanaged C++ and C#
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How difficult is it for one to integrate unmanaged C++ into C#? I know for functions one can use DLLimport but how does one go about doing it for classes? Do I have to completely reimplement the classes in managed C++ as a wrapper to the unmanaged C++ classes or is there an easier way? Essentially what I have done is written a C++ kernel mode driver and I want to use it from my C# program. Because it requires some setup outside the kernel(because it has to pass buffers back and forth and extract the information out of the buffers) I'd rather keep the that specific code unmanaged because its probably slightly faster. But I don't want to have a huge number of dll imports and write a C# wrapper class over each of the imports because it seems a little excessive. (Not only does the driver internally use a similar class but I'd essentially be implementing the same class 3 times... one in the driver, which is actually slightly different but pretty much with same interface, one in unmanaged C++ to interface with the driver, and some type of managed wrapper.) Is there a better way? Can I just mix unmanaged and managed C++ in the same project to do all the work and not have to end up with a C# wrapper? Basically I think I can get away with just using unsafe code to work with the buffers. I'm mainly worried about the performance hit associated with doing this. From my initial tests C# is anywhere from 2-5 times slower at calling kernel mode drivers than unmanaged C++(not sure if I can get any speed up by indirectly referencing unamanged C++ though so I might take that hit no matter what if I plan on using C#). Of course I don't want to end up with having to change 3 classes every time I make a simple change either. Any ideas? Thanks, Jon |
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re: Mixing unmanaged C++ and C#"Jon Slaughter" <Jon_Slaughter@Hotmail.comwrote in message news:A4kLi.55678$YL5.43177@newssvr29.news.prodigy. net... Quote: How difficult is it for one to integrate unmanaged C++ into C#? I know forfunctions one can use DLLimport but how does one go about doing it for classes? Do I have to completely reimplement the classes in managed C++ as a wrapper to the unmanaged C++ classes or is there an easier way? > called through the PInvoke layer. The only way you can create instances of unmanaged C++ is by wrapping these classes by a managed class that delegates the operations on the unmanaged class. Quote: Essentially what I have done is written a C++ kernel mode driver and Iwant to use it from my C# program. Because it requires some setup outside the kernel(because it has to pass buffers back and forth and extract the information out of the buffers) I'd rather keep the that specific code unmanaged because its probably slightly faster. > are extending the path to the final code. .. Quote: But I don't want to have a huge number of dll imports and write a C#wrapper class over each of the imports because it seems a little excessive. (Not only does the driver internally use a similar class but I'd essentially be implementing the same class 3 times... one in the driver, which is actually slightly different but pretty much with same interface, one in unmanaged C++ to interface with the driver, and some type of managed wrapper.) > Is there a better way? Can I just mix unmanaged and managed C++ in the same project to do all the work and not have to end up with a C# wrapper? the same assembly. C++/CLI can mix native and managed code in a single DLL. Quote: Basically I think I can get away with just using unsafe code to work withthe buffers. I'm mainly worried about the performance hit associated with doing this. From my initial tests C# is anywhere from 2-5 times slower at calling kernel mode drivers than unmanaged C++(not sure if I can get any speed up by indirectly referencing unamanged C++ though so I might take that hit no matter what if I plan on using C#). Of course I don't want to end up with having to change 3 classes every time I make a simple change either. > PInvoke signature (DllImport), what function are you actually calling, what are you measuring and how did you measure this? The first time you call into unmanaged from managed you'll incur a serious call overhead, this is because the CLR has to synthesize and JIT a (marshaling) thunk, but once the thunk is created the overhead is very low, all depends on the argument types, the number of arguments and the security attribute set on the invoked function. For instance, calling a function that takes no or only blittable type arguments and which has the SuppressUnmanagedCodeSecurity attribute set [1], the overhead is only 4 instructions. This is the minimal overhead taken to signal the GC that the thread has transitioned into unmanaged or returned from unmanaged. Functions that take arrays or structures of blit-able types only, take an overhead of ~50 instructions, while functions that take string arguments [3], incur the highest overhead 50-xxx instructions depending on the type unmanaged char (wide char or MBCS), the reason for this is that the marshaler needs to convert the managed String representation into the unmanaged char or wchar_t representation. [1] 4 instructions overhead [DllImport("lib.dll"), SuppressUnmanagedCodeSecurity] extern static int F(int i); [2] ~50 instructions overhead [DllImport("lib.dll"), SuppressUnmanagedCodeSecurity] extern static void F(int[] ia); [3] ~55instructions overhead [DllImport("lib.dll"), SuppressUnmanagedCodeSecurity] extern static int FS([MarshalAs(UnmanagedType.LPWStr)] string s); extern "C" __declspec(dllexport) int __stdcall FS(wchar_t *s){....} a minimum of several hundred instruction depending on the string length. [DllImport("lib.dll"), SuppressUnmanagedCodeSecurity] extern static int FS(string s); extern "C" __declspec(dllexport) int __stdcall FS(char *s){....} The managed/unmanaged transition is low when compared to a kernel transition (+ 4000 instruction), add to that that you will probably execute several thousands instruction in the driver, and it becomes apparent that the managed/unmanaged overhead becomes negligible. After all, this is the overhead the you'll take when using the IO, Socket etc... classes from managed code. Performing disk IO from managed code is not measurable slower than from unmanaged code. Willy. |
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re: Mixing unmanaged C++ and C#I would write a wrapper assembly in managed C++ using IJW (It Just works). Following is a link to a Code Project sample that shows how easy it is to mix managed and unmanaged C++ I used it and it works great. http://www.codeproject.com/managedcpp/ijw_unmanaged.asp Hope it works for you. Leon Lambert |
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