I am working on C++/CLI wrapper for C static libary that is eventually used in C# application.
I have function like this in C Library.
long SubscriveEvent(void* handle,device name ,....);
long StartCaptureViceo(handle,...,...);
Here StartCaptureViceo () will use the handle from SubscriveEvent()
I nee to maintain some variable in C# for this void
Now what data type i should use in C++/CLI to Retain.
Please help me for this.
System::IntPtr
Related
I am working on refactoring a large amount of code from an unmanaged C++ assembly into a C# assembly. There is currently a mixed-mode assembly going between the two with, of course, a mix of managed and unmanaged code. There is a function I am trying to call in the unmanaged C++ which relies on FILE*s (as defined in stdio.h). This function ties into a much larger process which cannot be refactored into the C# code yet, but which now needs to be called from the managed code.
I have searched but cannot find a definitive answer to what kind of underlying system pointer the System::IO::FileStream class uses. Is this just applied on top of a FILE*? Or is there some other way to convert a FileStream^ to a FILE*? I found FileStream::SafeFileHandle, on which I can call DangerousGetHandle().ToPointer() to get a native void*, but I'm just trying to be certain that if I cast this to FILE* that I'm doing the right thing...?
void Write(FILE *out)
{
Data->Write(out); // huge bulk of code, writing the data
}
virtual void __clrcall Write(System::IO::FileStream ^out)
{
// is this right??
FILE *pout = (FILE*)out->SafeFileHandle->DangerousGetHandle().ToPointer();
Write(pout);
}
You'll need _open_osfhandle followed by _fdopen.
Casting is not magic. Just because the input and types output are right for your situation doesn't mean the values are.
I want to pass a managed array from VB.NET to a function in a VC++ project. How would I declare my C++ function and how would I use the array when I'm inside it? Specifically, I want to make VB compatible functions like the one below, which is written in plain old C.
void Vcopy(double *A, double *B)
{
int n;
for(n=0;n<3;n++)
{
B[n]=A[n];
}
}
Maybe some kind soul could convert this to something that would play nicer with VB. Thanks!
Can the C++ method be managed, e.g., C++/CLI ?
If so, then:
void Vcopy(array<double> ^A, array<double> ^B)
By the way, the rest of the method should be identical, provided that the size is 3 - otherwise use A->Length and B->Length.
How can i accomplish this interop between c and vb.net?
In my vb.net code i need to call some c functions from a .dll,
the c function looks like
int __stdcall foo (someStruct* myStructure, char* myString )
The myString gets filled in the c function, and i need the text from myString on the vb.net side
best regards
The typical way to pass a string back would be to use a pre-allocated StringBuilder on the .NET side. Structures work fine too, generally speaking, you just have to define them in .NET. If you post your structure definition we may be able to assist with that.
I building Wrapper in C++/CLI for C Static library to be used in .NET application through C#
I have function like this in C
long My_COM_Interface( PVOID hDevice,IUnknown **pUnknown);
How to declare IUnknown ** in C++/CLI
for first argument I am using IntPtr but Not able to find out the Replacement for IUknown.
I have another COM Data type GUID in another function this is also an issue for me.
Please Help me find the relacement for data type IUnknown and GUID.
There is no replacement.
C++/CLI understands native types just fine. Include the right header files, and you can use IUnknown* like always.
I'd refer to the APIs, e.g.
public static IntPtr GetIUnknownForObject(Object o);
This API can simply be used from C++/CLR and suggests you should use IntPtr^
try using parameter like;
ref object pUnknown
and use it like
MyObject o = pUnknown as MyObject
I am trying to use a C# class in a C++-CLI project, but Visual Studio will only let me declare a handle (^) to a C# object in a local scope, just inside a function. The only way I got it working was declaring a global pointer to a handle:
SUTAdapter::Form1^ *ptForm1;
But if then I create an object inside a function and give its address to the global pointer:
SUTAdapter::Form1^ form1;
form1 = gcnew SUTAdapter::Form1();
ptForm1 = &form1;
(*ptForm1)->incCounter(0);
When the function exits and I try to use the incCounter function inside some other C++-CLI function, the object seems gone (debugger says this == null). Is there a way to have a global handle of a C# code in C++-CLI? I guess global handles are forbidden for some reason I don't understand but I am out of ideas and I need this done. Thank you.
edit:
*ptForm1 = gcnew SUTAdapter::Form1();
Gives a null reference exception. Why?
This restriction seems consistent with the other CLR-based languages. C# has no concept of a static, function-scoped variable for example. The lack of such functionality in C++/CLI suggests that is the way the CLR works - static objects must be defined at the class scope.
The CLR is object based, so this is just a case of that object-oriented nature influencing the design of languages that run on top of it.
From an OO view point, I like the C# way better anyway.
Ok thanks for your answers but I finally solved it, I found it googling:
http://bytes.com/groups/net-vc/473036-how-define-global-com-object-vc-8-a
It seems that VS doesn't let global handles or static handles inside functions. I am puzzled about this because sometimes it is necessary to access managed objects globally.
The solution is to declare a "GlobalObjects" class with static handles inside it:
ref class GlobalObjects
{
public:
static SUTAdapter::Form1^ hndForm1;
};
This way I can access the C# form/class globally. The error code of the previoous error is C3145, I am still wondering why does not VS allow the declaration of global handles.
Will Visual Studio let you declare a static handle to a C# object in a local scope?
SUTAdapter::Form1^ theForm() {
static SUTAdapter::Form1^ form1 = gcnew SUTAdapter::Form1();
return form1;
}
*ptForm1 = gcnew SUTAdapter::Form1();
Gives a null reference exception because you are dereferncing a null pointer - it is just like a pointer to any other type in that regard.
I think - and that's without testing it - that the problem you're having is because you're storing a pointer to a local handle, which might confuse the garbage collector a little due to the fact that you're taking a pointer to an automatic object.
Have you tried to replace the above assignment with
*ptForm1 = gcnew SUTAdapter::Form1();
instead of the detour via the local object reference?