Question

Is there an direct way to manage C++/CLI Strings in a wrapper to char* parameter for native C++ method?!

example:

void Test::TestFunc(System::String ^%str)
{
    // right conversion to char* and consider the reference
}

native C++ function:

void TestB::Func(char *str)
{
    ...
}

my tricky way:

void Test::TestFunc(System::String ^%szRecvBuffer)
{   
    pin_ptr<const wchar_t> szRecvBufferP = PtrToStringChars(szRecvBuffer);

    // Convert to a char*
    size_t origsize = wcslen(szRecvBufferP) + 1;
    const size_t newsize = 100;
    size_t convertedChars = 0;
    char nstring[newsize];
    wcstombs_s(&convertedChars, nstring, origsize, szRecvBufferP, _TRUNCATE);
    strcat_s(nstring, " (char *)");

    char *szRecvBufferCh = nstring;

    m_object->TestCommand(szRecvBufferCh); // parameter char*
    System::String ^tmp = gcnew System::String(szRecvBufferCh); 
    szRecvBuffer = tmp;
}

greets leon22

Answer 1

You’re doing a lot manually that the runtime will take care of for you.

void Test::TestFunc(String^% szRecvBuffer)
{
    using System::Runtime::InteropServices::Marshal;

    IntPtr memHandle = Marshal::StringToHGlobalAnsi(szRecvBuffer);
    try
    {
        char* const str = static_cast<char*>(memHandle.ToPointer());
        m_object->TestCommand(str);
        szRecvBuffer = gcnew String(str);
    }
    finally
    {
        Marshal::FreeHGlobal(memHandle);
    }
}

If you’re using VC++ 2010, you can use std::unique_ptr<> with a custom deleter to avoid using try..finally, ultimately cutting the number of lines of code in half.