Question

I’m making an unmanaged C++ DLL which uses the C# managed DLL. I’m writting the C++ library as I need to use functions and headers defined in a software for which the C++ library can be added as an addon. But the things I want to make are so complex that my sparse knowledge of C++ would slow me down so I decided to do things in my favourite C# and connect the DLLs via COM and I was successful.

I’m somehow successful in making the code work, but less successful in keeping the code concise as I’m clearly not a professional C++ programmer.

The problem is with converting various string types. BSTR and const char * in particular.

The following code converst const char * to BSTR:

BSTR bstrt;
const char * someChar;

csharpInterfacedClassPointer->get_PropertyForSomeChars(&bstrt);
strcpy_s(nstring, (char *)bstrt);
someChar = nstring;

The problem is, I have plenty of discrete someChars with corresponding discrete interface methods…the property method is generated from the C# interface so I can’t change it. Each of the “someChar” requires the following three lines of code so for 30 discrete variables, I’d need to write 90 lines of code.

csharpInterfacedClassPointer->get_PropertyForSomeCharX(&bstrt);
strcpy_s(nstring, (char *)bstrt);
someCharX = nstring;

The question is: how do write some shortcut for this so it’d fit just in one line?

I tried some sort of function with the “getter” function pointer and the someChar pointer.

typedef HRESULT (__stdcall *get_string_func)(BSTR * str); //getter function pointer

//the converting function
void ConvertAndAssign(get_string_func bstr_get_fx, const char * constCharString) 
{
const size_t nsize = 1000;
char nstring[nsize];

BSTR bstrt;
bstrt = bstr_t(constCharString);
bstr_get_fx(&bstrt);
strcpy_s(nstring, (char *)bstrt);
constCharString = nstring;
}

//calling the function...as I thought that would work
ConvertAndAssign(sPtr->get_DataFile, someChar);

But then the compiler says some weird things aboud bound functions and how they are not allowed as pointers…I googled what does it mean and the solutions given required to alter the function definition but I can’t do that since the definition is generated from the C# code (by regasm.exe).

Important note: I need to get the const char * type in the end because it is the required input type to the functions of the program for which I’m making the C++ DLL.

Answer 1

This question can be deleted if any mod is going to read this. I realized I have a totally different problem. Thanks Vagaus for his effort.