I have this c++ header:
// BRepPrimAPI_MakeSphere.hxx file
#include <Standard.hxx>
#include <Standard_DefineAlloc.hxx>
#include <BRepPrim_Sphere.hxx>
#include <BRepPrimAPI_MakeOneAxis.hxx>
class gp_Pnt;
class gp_Ax2;
class BRepPrimAPI_MakeSphere : public BRepPrimAPI_MakeOneAxis
{
public:
DEFINE_STANDARD_ALLOC
Standard_EXPORT BRepPrimAPI_MakeSphere(const Standard_Real R);
Standard_EXPORT Standard_Address OneAxis();
Standard_EXPORT BRepPrim_Sphere& Sphere();
protected:
private:
BRepPrim_Sphere mySphere;
};
and this c++ source:
// BRepPrimAPI_MakeSphere.cxx file
#include <BRepBuilderAPI.hxx>
#include <BRepPrimAPI_MakeSphere.hxx>
#include <gp.hxx>
#include <gp_Ax2.hxx>
#include <gp_Dir.hxx>
#include <gp_Pnt.hxx>
BRepPrimAPI_MakeSphere::BRepPrimAPI_MakeSphere(const Standard_Real R) :
mySphere(gp::XOY(),R)
{
}
Standard_Address BRepPrimAPI_MakeSphere::OneAxis()
{
return &mySphere;
}
BRepPrim_Sphere& BRepPrimAPI_MakeSphere::Sphere()
{
return mySphere;
}
Standard_EXPORT is defined as follows:
# define Standard_EXPORT __declspec( dllexport )
DEFINE_STANDARD_ALLOC is defined as follows:
# define DEFINE_STANDARD_ALLOC
void* operator new (size_t theSize)
{
return Standard::Allocate (theSize);
}
void operator delete (void* theAddress)
{
Standard::Free (theAddress);
}
void* operator new[] (size_t theSize)
{
return Standard::Allocate (theSize);
}
void operator delete[] (void* theAddress)
{
Standard::Free (theAddress);
}
void* operator new (size_t, void* theAddress)
{
return theAddress;
}
void operator delete (void*, void*)
{
}
I want to use them in my c# code.
I have tried three methods that didn't work for me:
Wrapping the c++ code with CLR to manage it and then use it in the c# code.
SWIG
P/Invoke
Now the issue is that this is one class in a huge c++ library. What I am trying to do is automatically generate the warppers for every single class so I can have the library's full functionality.
The main problem I'm having is handling return types and arguments.
This is what I'm trying right now:
extern "C" __declspec(dllexport) void Call_BRepPrimAPI_MakeSphere(BRepPrimAPI_MakeSphere* p, const Standard_Real R) {
p->BRepPrimAPI_MakeSphere::BRepPrimAPI_MakeSphere(R);
}
But I obviously can't use this in c# because the two argument types don't exist in c# right?
Basically my question is how and what would be the best way to wrap this class?
Basically my question is how and what would be the best way to wrap this class?
I would use c++/cli, that should let you define .Net wrappers that can interact directly with native c++ objects.
What I am trying to do is automatically generate the warppers for every single class so I can have the library's full functionality.
I do not think this can be done in general, at least not without extra knowledge about resource management and other details not expressed in the c++ source. Just consider if a C# object is disposed, should you delete the underlying C++ object? To decide this you need to know if the object is shared or not, and there is no general way to know this.
But creating and using c++/cli code is kind of a pain. You need to have a fair bit of in depth knowledge of c#, c++ and c++/cli. In some cases there are just no alternative, but I would consider other solutions first, like .Net native libraries, or rewriting the required functions in C#.
Related
I have a dll that was written in c++, I need to use this dll in my c# code. After searching I found that using P/Invoke would give me access to the function I need, but these functions are defined with in a class and use non-static private member variables. So I need to be able to create an instance of this class to properly use the functions. How can I gain access to this class so that I can create an instance? I have been unable to find a way to do this.
I guess I should note that the c++ dll is not my code.
There is no way to directly use a C++ class in C# code. You can use PInvoke in an indirect fashion to access your type.
The basic pattern is that for every member function in class Foo, create an associated non-member function which calls into the member function.
class Foo {
public:
int Bar();
};
extern "C" Foo* Foo_Create() { return new Foo(); }
extern "C" int Foo_Bar(Foo* pFoo) { return pFoo->Bar(); }
extern "C" void Foo_Delete(Foo* pFoo) { delete pFoo; }
Now it's a matter of PInvoking these methods into your C# code
[DllImport("Foo.dll")]
public static extern IntPtr Foo_Create();
[DllImport("Foo.dll")]
public static extern int Foo_Bar(IntPtr value);
[DllImport("Foo.dll")]
public static extern void Foo_Delete(IntPtr value);
The downside is you'll have an awkward IntPtr to pass around but it's a somewhat simple matter to create a C# wrapper class around this pointer to create a more usable model.
Even if you don't own this code, you can create another DLL which wraps the original DLL and provides a small PInvoke layer.
Marshal C++ Class and use the PInvoke
C++ Code ,ClassName.h
class __declspec(dllexport) CClassName
{
public:
CClassName();
~CClassName();
void function();
};
C++ Code, ClassName.cpp
CClassName::CClassName()
{
}
CClassName::~CClassName()
{
}
void CClassName::function()
{
std::cout << "Bla bla bla" << std::endl;
}
C++ Code, ClassNameCaller.h file for the caller function
#include "ClassName.h"
#ifdef __cplusplus
extern "C" {
#endif
extern __declspec(dllexport) CClassName* CreateClassName();
extern __declspec(dllexport) void DisposeClassName(CClassName* a_pObject);
extern __declspec(dllexport) void function(CClassName* a_pObject);
#ifdef __cplusplus
}
#endif
C++ Code, ClassNameCaller.cpp file for the caller function
#include "ClassNameCaller.h"
CClassName* CreateClassName()
{
return new CClassName();
}
void DisposeClassName(CClassName* a_pObject)
{
if(a_pObject!= NULL)
{
delete a_pObject;
a_pObject= NULL;
}
}
void function(CClassName* a_pObject)
{
if(a_pObject!= NULL)
{
a_pObject->function();
}
}
C# code
[DllImport("ClassNameDll.dll")]
static public extern IntPtr CreateClassName();
[DllImport("ClassNameDll.dll")]
static public extern void DisposeClassName(IntPtr pClassNameObject);
[DllImport("ClassNameDll.dll")]
static public extern void CallFunction(IntPtr pClassNameObject);
//use the functions
IntPtr pClassName = CreateClassName();
CallFunction(pClassName);
DisposeClassName(pClassName);
pClassName = IntPtr.Zero;
Here is a sample how to call C++ class method from VB - for C# you only have to rewrite the sample program in Step 4.
You may need to write an intermediary DLL (in C++, perhaps) that handles this for you and exposes the interface you need. Your DLL would be in charge of loading the 3rd party DLL, creating an instance of this C++ object, and exposing its member functions as needed via whatever API you design. You would then use P/Invoke to get at your API and cleanly manipulate the object.
Note: For the API of your DLL, try keeping the data types limited to primitives (long, int, char*, etc.) to prevent module boundary issues.
The way I've done this is by creating a thin Managed C++ wrapper around my unmanaged C++ DLL. The managed wrapper contains "proxy" classes that wrap around the unmanaged code exposing the interface that's needed by the .NET application.
This is a bit of double work but it allows quite seamless operation in normal environments. Things do get trickier with dependencies in some circumstances (such as ASP.NET) but you will probably not run into that.
I agree with JaredPar.
Creating instances of unmanaged classes in managed code should not be possible.
Another thing is - if you could recompile the DLL in managed C++ or make a COM component out of it, it would be much easier/
I am new to C# but have worked extensively with C++. I have a C++ function that needs to be called from C#. After reading some answers from SO and some googling, I conclude that I need to make a pure C interface to the function. I have done this, but am still confused about how to call it from C#.
The function in C++ looks like this:
int processImages(
std::string& inputFilePath, // An input file
const std::vector<std::string>& inputListOfDirs, // Input list of dirs
std::vector<InternalStruct>& vecInternalStruct, // Input/Output struct
std::vector<std::vector< int > >& OutputIntsForEachFile,
std::vector< std::vector<SmallStruct> >& vecVecSmallStruct, // Output
int verboseLevel
);
The same function, converted in C, looks like this:
int processImagesC(
char* p_inputFilePath, // An input file
char** p_inputListOfDirs, // Input list of dirs
size_t* p_numInputDirs, // Indicating number of elements
InternalStruct* p_vecInternalStruct, // Input/Output struct
size_t* p_numInternalStructs,
int** p_OutputIntsForEachFile, // a 2d array each row ending with -1
size_t* p_numOutputIntsForEachFile //one number indicating its number of rows
SmallStruct** p_vecVecSmallStruct, // Output
size_t* p_numInVecSmallStruct,
int verboseLevel
);
This is based on this advice.
Now I need to call this from C#, which is where the confusion is. I have tried my best to convert the structures.
The C# code looks like this:
[DllImport(
#"C:\path\to\cppdll.dll", CallingConvention=CallingConvention.Cdecl,
EntryPoint="processImagesC", SetLastError=true)]
[return: MarshalAs(UnmanagedType.I4)]
unsafe public static extern int processImagesC(
String inputFilePath,
String[] inputListOfDirs,
ref uint numInputListOfDirs,
// Should I use ref InternalStruct * vecInternalStruct?
ref InternalStruct[] vecInternalStruct,
ref uint numInternalStruct,
// Or ref int[] or ref int[][] or int[][]?
ref int[][] OutputIntsForEachFile,
ref uint numOutputIntsForEachFile,
// again, ref ..[], [][], or ref [][]?
ref SmallStruct[][] vecVecSmallStruct,
int verboseLevel
);
There are memory allocations for all the output variables (pointers) done within the C/C++ code. This likely means we need to declare the code as unsafe, correct?
How do we handle memory deallocation? Should I write another API (function) that does the deallocation of objects/arrays allocated by C/C++?
The C++ code needs to be standard compliant and platform independent, so I cannot insert any windows-specific things in it.
I hope someone could make sense of this and provide an answer or at least point me in the right direction.
Since there seems to be some interest in using It Just Works (IJW) with C++/CLI, I'll post some info about that, further google searches and research will need to be done to figure it all. C++/CLI can be enabled with a single compiler flag (/CLI, enabled through Property Page->General->Common Language Runtime Support). C++/cli is NOT c++, but rather just another managed language. C++/CLI classes can be compiled into dll's and called directly from other .NET projects (C#, VB.NET, ect). However, unlike the other .NET languages it can directly interact with C++ code.
This is an ok start to learning C++/CLI. The big thing to learn is the decorations that tell you the class is managed (.NET class) and not Vanila C++. The "ref" keyword decalres the definition as a .NET definition:
public ref class Foo{ public: void bar();};//Managed class, visible to C#
public ref struct Foo{};//Managed struct, visible to C#
All reference classes are referred to with Handles rather than pointers or references. A handle is denoted by the ^ operator. To make a new handle, you use gcnew, and to access functions/members of the handle, use the -> operator.
//in main
Foo^ a = gcnew Foo();
a->bar();
You often have to move structures common from C# to native types and back again. (such as managed Array^ or String^ to void* or std::string). This process is called Marshaling. This handy table is pretty useful for figuring that out.
A common task is to create a wrapper for a native class, done like this:
//Foo.h
#include <string>
namespace nativeFoo
{
class Foo
{
private:
std::string fooHeader;
public:
Foo() {fooHeader = "asdf";}
std::string Bar(std::string& b) {return fooHeader+b;}
};
}
//ManagedFoo.h
#include "foo.h"
namespace managedFoo
{
public ref class Foo
{
private:
nativeFoo::Foo* _ptr;
public:
Foo(){_ptr = new nativeFoo::Foo();}
~Foo(){!Foo();}
!Foo(){if (_ptr){delete ptr;ptr = NULL;}}
String^ bar(String^ b)
{
return marshal_as<String^>(_ptr->bar(marshal_as<std::string>(b)));
}
};
}
Warning: I am totally missing a bunch of #include and #using statements, this is just to give a general gist of how to use this.
Begin from this:
How to pass structure as pointer in C dll from C#
And something about marshalling in this:
Deep copying an array c# without serialization
Note that Marshal.Copy also overloads for arrays use. With marshalling you can get rid of ref excepting that you do want to. Just write C/C++ in their way.
And following is a little bit complicated:
Physical disk size not correct (IoCtlDiskGetDriveGeometry)
The 2 ways I've often seen this handled is to either have a 'FreeResource' style API, or specify in the function the size of output buffers.
Method 1
C++
void GetName(char ** _str)
{
if (!_str)
return; // error
*_str = new char[20];
strcpy(*str, "my name");
}
void FreeString(char * _str)
{
delete str;
}
Client (any language)
char * name;
GetName(&name);
...
FreeString(name);
Method 2
C++
void GetName(char * _str, size_t _len)
{
if (_len < 20)
return; // error
strcpy(str, "my name");
}
Client (any language)
char * name = new char[20];
GetName(name, 20);
...
If you are willing to use third party tool, there is a tool named C#/.NET PInvoke Interop SDK may be helpful to you. But you can do it yourself as well. For simple classes with a few methods, you can write your own code in managed C# code.
The basic idea of instantiating a C++ object from .NET world is to allocate exact size of the C++ object from .NET, then call the constructor which is exported from the C++ DLL to initialize the object, then you will be able to call any of the functions to access that C++ object, if any of the method involves other C++ classes, you will need to wrap them in a C# class as well, for methods with primitive types, you can simply P/Invoke them. If you have only a few methods to call, it would be simple, manual coding won't take long. When you are done with the C++ object, you call the destructor method of the C++ object, which is a export function as well. if it does not have one, then you just need to free your memory from .NET.
Here is an example.
public class SampleClass : IDisposable
{
[DllImport("YourDll.dll", EntryPoint="ConstructorOfYourClass", CharSet=CharSet.Ansi, CallingConvention=CallingConvention.ThisCall)]
public extern static void SampleClassConstructor(IntPtr thisObject);
[DllImport("YourDll.dll", EntryPoint="DoSomething", CharSet=CharSet.Ansi, CallingConvention=CallingConvention.ThisCall)]
public extern static void DoSomething(IntPtr thisObject);
[DllImport("YourDll.dll", EntryPoint="DoSomethingElse", CharSet=CharSet.Ansi, CallingConvention=CallingConvention.ThisCall)]
public extern static void DoSomething(IntPtr thisObject, int x);
IntPtr ptr;
public SampleClass(int sizeOfYourCppClass)
{
this.ptr = Marshal.AllocHGlobal(sizeOfYourCppClass);
SampleClassConstructor(this.ptr);
}
public void DoSomething()
{
DoSomething(this.ptr);
}
public void DoSomethingElse(int x)
{
DoSomethingElse(this.ptr, x);
}
public void Dispose()
{
Marshal.FreeHGlobal(this.ptr);
}
}
For the detail, please see the below link,
C#/.NET PInvoke Interop SDK
The tool, xInterop NGen++ 2.0 has been released. Please check it out if you are interested in creating C# wrapper for native C++ DLL.
(I am the author of the SDK tool)
I have defined in C++ function for external calls:
template<typename T>
void __declspec(dllexport) SwapMe(T *fisrt, T *second)
{
std::cout << typeid(T).name() << std::endl;
T temp = *first;
*first = *second;
*second = temp;
}
I want to use it in C# program. I've tried in this way:
unsafe class Program
{
[DllImport("lib1.dll", EntryPoint = "SwapMe")]
static extern void SwapMe<T>(T first, T second);
...
}
But, I'm getting such error:
Generic method or method in generic class is internal call, PInvoke, or is defined in a COM Import class.
Seems to be, that Generic in C# is managed type and it's rather different stuff by architecture with unmanaged template in C++.
How can I use template method in my C# program?
Template functions are not burnt into the binary by the C++ compiler. Only specialized versions are ever emitted. The C++ compiler logically clones the template definition and replaces T with whatever concrete type is wanted.
This means that you must create a specialized wrapper:
void __declspec(dllexport) SwapMe(int *fisrt, int *second) { //example
{ SwapMe(first, second); }
You can call this one from C#, But you cannot call the template version.
C++ templates and C# generics work very differently.
To add to the above, we recently went through this and used T4 (TextTransform.exe) to generate templates for the wrappers in C++.
To do this, we included a T4 file in the C++ project and for each combination of type args, generated a wrapper method around the C++ template method. The wrapper method was then exported.
Finally in C# we did the same, using T4 to generate a generic wrapper around the exported methods. This way you bridge the divide between .NET Generics and C++ templates while harnessing the full awesomeness of C++ Templates
I've got an existing application written in Borland C++ Builder. My client wants it rewritten in C#/WPF. This requires a lot of work and is a complex task because I need to rewrite the whole (huge) algorithm. I was thinking of a way to reuse the code and to be able to create only GUI in C#/WPF. Is this possible? Would that be easy? How can I make C++ classes visible to .NET ?
If you could give me brief answers with some links/examples I would be grateful.
You can wrap your old C++ code in a C++/CLI wrapper and build it into a DLL file. It should then be visible in any .NET project.
Depending on your algorithm/function structure, this may change a little, but the basic form, and the way I did this, is the following. Keep in mind this is a VERY basic example, but I tried to include the key points:
1. Define the CLI wrapper
using namespace System;
#include "myAlgorithmClass"
public ref class MyCLIWrapperClass //the 'ref' keyword specifies that this is a managed class
{
public:
MyCLIWrapperClass(); //Constructor
//function definitions are the same, though some types,
//like string, change a little. Here's an example:
String ^ GetAString(); //the "String" is the .NET "System.String" and the ^ is sort of a pointer for managed classes
//int, double, long, char, etc do not need to be specified as managed.
//.NET code will know how to handle these types.
//Here you want to define some functions in the wrapper that will call
//the functions from your un-managed class. Here are some examples:
//Say that your functions in the Algorithm class are int Func1, double Func2, and std::string Func3:
int Func1();
double Func2();
String ^ Func3();
private:
//All private functions and members here
myAlgorithmClass algor;
};
2. Implement the wrapper class
using namespace System;
#include <string> //For the string function ex. below
#include "myAlgorithmClass"
MyCLIWrapperClass::MyCLIWrapperClass()
{
algor = myAlgorithmClass(); //create instance of your un-managed class
}
int MyCLIWrapperClass::Func1()
{
return algor.Func1(); //Call the un-managed class function.
}
double MyCLIWrapperClass::Func2()
{
return algor.Func2(); //Call the un-managed class function.
}
String ^ MyCLIWrapperClass::Func3()
{
//Converting a std::string to a System.String requires some conversion
//but I'm sure you can find that somewhere on Google or here on SO
String ^ myString = "";
std::string myUnmanagedString = algor.Func3(); //Call the un-managed class function.
//Convert myUnmanagedString from std::string to System.String here
return myString;
}
After you write the wrapper class and compile it into a class library you can create a reference to the .DLL file in a C# project and C# should see the managed wrapper class and all its public functions.
Another thing to note is that if you are creating new managed objects in C++ you use the keyword "gcnew" instead of "new". So a new string would be String ^ someString = gcnew String();
Finally, here are some links to some things about CLI that may help:
CLI - Wikipedia
CLI - Code Project
CLI - FunctionX
Well, As far as i can remember by head, you can use interops for that matter.
It is in fact better to continue using a code that was for a long time tested, and is stable. With net Interop Services you can create a very good bridge between the new app and the old one.
examples:
http://www.daniweb.com/forums/thread136041.html
http://msdn.microsoft.com/en-us/library/aa645736%28v=vs.71%29.aspx
http://www.codeguru.com/cpp/cpp/cpp_managed/interop/article.php/c6867
I have a dll that was written in c++, I need to use this dll in my c# code. After searching I found that using P/Invoke would give me access to the function I need, but these functions are defined with in a class and use non-static private member variables. So I need to be able to create an instance of this class to properly use the functions. How can I gain access to this class so that I can create an instance? I have been unable to find a way to do this.
I guess I should note that the c++ dll is not my code.
There is no way to directly use a C++ class in C# code. You can use PInvoke in an indirect fashion to access your type.
The basic pattern is that for every member function in class Foo, create an associated non-member function which calls into the member function.
class Foo {
public:
int Bar();
};
extern "C" Foo* Foo_Create() { return new Foo(); }
extern "C" int Foo_Bar(Foo* pFoo) { return pFoo->Bar(); }
extern "C" void Foo_Delete(Foo* pFoo) { delete pFoo; }
Now it's a matter of PInvoking these methods into your C# code
[DllImport("Foo.dll")]
public static extern IntPtr Foo_Create();
[DllImport("Foo.dll")]
public static extern int Foo_Bar(IntPtr value);
[DllImport("Foo.dll")]
public static extern void Foo_Delete(IntPtr value);
The downside is you'll have an awkward IntPtr to pass around but it's a somewhat simple matter to create a C# wrapper class around this pointer to create a more usable model.
Even if you don't own this code, you can create another DLL which wraps the original DLL and provides a small PInvoke layer.
Marshal C++ Class and use the PInvoke
C++ Code ,ClassName.h
class __declspec(dllexport) CClassName
{
public:
CClassName();
~CClassName();
void function();
};
C++ Code, ClassName.cpp
CClassName::CClassName()
{
}
CClassName::~CClassName()
{
}
void CClassName::function()
{
std::cout << "Bla bla bla" << std::endl;
}
C++ Code, ClassNameCaller.h file for the caller function
#include "ClassName.h"
#ifdef __cplusplus
extern "C" {
#endif
extern __declspec(dllexport) CClassName* CreateClassName();
extern __declspec(dllexport) void DisposeClassName(CClassName* a_pObject);
extern __declspec(dllexport) void function(CClassName* a_pObject);
#ifdef __cplusplus
}
#endif
C++ Code, ClassNameCaller.cpp file for the caller function
#include "ClassNameCaller.h"
CClassName* CreateClassName()
{
return new CClassName();
}
void DisposeClassName(CClassName* a_pObject)
{
if(a_pObject!= NULL)
{
delete a_pObject;
a_pObject= NULL;
}
}
void function(CClassName* a_pObject)
{
if(a_pObject!= NULL)
{
a_pObject->function();
}
}
C# code
[DllImport("ClassNameDll.dll")]
static public extern IntPtr CreateClassName();
[DllImport("ClassNameDll.dll")]
static public extern void DisposeClassName(IntPtr pClassNameObject);
[DllImport("ClassNameDll.dll")]
static public extern void CallFunction(IntPtr pClassNameObject);
//use the functions
IntPtr pClassName = CreateClassName();
CallFunction(pClassName);
DisposeClassName(pClassName);
pClassName = IntPtr.Zero;
Here is a sample how to call C++ class method from VB - for C# you only have to rewrite the sample program in Step 4.
You may need to write an intermediary DLL (in C++, perhaps) that handles this for you and exposes the interface you need. Your DLL would be in charge of loading the 3rd party DLL, creating an instance of this C++ object, and exposing its member functions as needed via whatever API you design. You would then use P/Invoke to get at your API and cleanly manipulate the object.
Note: For the API of your DLL, try keeping the data types limited to primitives (long, int, char*, etc.) to prevent module boundary issues.
The way I've done this is by creating a thin Managed C++ wrapper around my unmanaged C++ DLL. The managed wrapper contains "proxy" classes that wrap around the unmanaged code exposing the interface that's needed by the .NET application.
This is a bit of double work but it allows quite seamless operation in normal environments. Things do get trickier with dependencies in some circumstances (such as ASP.NET) but you will probably not run into that.
I agree with JaredPar.
Creating instances of unmanaged classes in managed code should not be possible.
Another thing is - if you could recompile the DLL in managed C++ or make a COM component out of it, it would be much easier/