Question

I’m calling a function which is in a ComVisible managed dll from a VC++ code. In the managed dll the function parameter type is string.

In the VC++ code i’ve the variable as PUNICODE_STRING. How can i pass it to the function? How can i convert it into BSTR?

Thank you.

NLV

Answer 1

The first thing to note is that PUNICODE_STRING’s internal string buffer might not be null-terminated. So it would be best to go via a standard null-terminated wide string, that can then be passed straight to SysAllocString.

Try this:

BSTR PUNICODEToBSTR(PUNICODE_STRING pStr)
{
    // create a null-terminated version of the input string
    wchar_t* nullTerminatedString = new wchar_t[pStr->Length + 1];
    memset(nullTerminatedString, 0, sizeof(wchar_t) * (pStr->Length + 1)];
    wcsncpy(nullTerminatedString, pStr->Buffer, pStr->Length);

    // create a BSTR
    BSTR bstrString = ::SysAllocString(nullTerminatedString);

    // tidy-up and return the BSTR
    delete [] nullTerminatedString;
    return bstrString;
}