message box LPCWSTR manipulation and keyword question

I'm trying to implement the string manipulation as shown below:

Code:

---

HRESULT __stdcall
COemUni2::
QueryInterface(
    const IID&  iid,
    void**      ppv
    )
{
    OEMDBG(DBG_VERBOSE, L"COemUni2::QueryInterface() entry.");

        //---------------------------------------------------------------------------
        // adding debugging dialog boxes
        LPCWSTR showtext;

        // I want to show in the body of the dialog box
        // "iid = *value of iid*\nppv = *value of ppv*"

        int msgboxID = MessageBox(
                NULL,
                (LPCWSTR),
                (LPCWSTR) L"Debug Dialog Box",
                MB_OK);
        //---------------------------------------------------------------------------

    if (iid == IID_IUnknown)
    {
        *ppv = static_cast<IUnknown*>(this);
        VERBOSE(DLLTEXT("COemUni2::QueryInterface IUnknown.\r\n"));
    }
    else if (iid == IID_IPrintOemUni2)
    {
        VERBOSE(DLLTEXT("COemUni2::QueryInterface IPrintOemUni2.\r\n"));

        *ppv = static_cast<IPrintOemUni2*>(this);
    }
    else
    {
        WARNING(DLLTEXT("COemUni2::QueryInterface NULL. Returning E_NOINTERFACE.\r\n"));

        *ppv = NULL;
        return E_NOINTERFACE;
    }
    reinterpret_cast<IUnknown*>(*ppv)->AddRef();
    return S_OK;
}

---

I have thought about strcpy() and strcat() functions, however, I'm not sure how well they would work. Does anyone have a more appropriate suggestion?

Secondly, I'm not sure what the keyword void** of the parameter of this function mean. Does this mean pointer to a pointer?

If you don't have access to CString in your code, you can use swprintf to print your values to a wchar_t array:

Code:

---

wchar_t text[100];

swprintf( L"iid = %p\nppv = %p", iid, ppv );

MessageBox( NULL, text, L"Debug Dialog Box", MB_OK);

---

If that is really what you want is up to you. It will be just numbers.

If you want to see the full GUID value of the IID, I use this in a printf-style format specification:

Code:

---

#define GUID_Format L"{%08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X}"
#define GUID_Printf(guid) \
    guid.Data1, guid.Data2, guid.Data3, \
    guid.Data4[0], guid.Data4[1], guid.Data4[2], guid.Data4[3], \
    guid.Data4[4], guid.Data4[5], guid.Data4[6], guid.Data4[7]

...

wchar_t text[100];

swprintf(L"iid = "
        GUID_Format
        L"\nppv = %p", GUID_Printf(iid), ppv);

MessageBoxW(0, text, L"Debug Dialog Box", MB_OK);

---

gg

Thank you for your suggestion. However, I'm getting the following compiling error for this line:

Code:

---

swprintf(L"iid = "
        GUID_Format
        L"\nppv = %p", GUID_Printf(iid), ppv);

---

It's apparently complaining about the blue highlighted parameter about:

Code:

---

e:\research\oemdll\oemuni\intrface.cpp(91) : error C2664: 'swprintf' : cannot co
nvert parameter 2 from 'const unsigned long' to 'const wchar_t *'

---

Does this entail type casting of something like:
(const wchar *) (GUID_Printf(iid)) for the second parameter? Thanks.

Try:

Code:

---

swprintf(text, L"iid = "
        GUID_Format
        L"\nppv = %p", GUID_Printf(iid), ppv);

---

Thanks, Elysia. I guess that's problem solved for now. What would be your general guideline in terms of converting DWORD, PDWORD, and PVOID type parameters of another function?

Are you talking about converting X -> const TCHAR*?
Or X -> Y?
All may require different approaches.
Btw, PDWORD = DWORD* and PVOID = void*
Microsoft evil pointer typedefs.

I'm talking about displaying the parameters of this function in a messagebox in similar fashion as the previous question on the same thread:

Code:

---

HRESULT __stdcall
COemUni2::
GetInfo(
    DWORD      dwMode,
    PVOID      pBuffer,
    DWORD      cbSize,
    PDWORD      pcbNeeded
    )

---

I'm not entirely sure what you mean by converting X -> const TCHAR* or X -> Y.

I meant "any type to const TCHAR*" and "any type to another type."
TCHAR is typically a macro that means either ansi or unicode, btw.
But as for the question, you can display any parameters using (w)sprintf. Look in the manual and you'll find what syntax you should use to convert them into a string.
Any type that begins with P* in windows APIs is a pointer (ie PDWORD = DWORD*).

One last question with respect to windows messagebox and MS typedefs: why are there L's in front of some strings? For example:

Code:

---

swprintf(text, L"iid = "
        GUID_Format
        L"\nppv = %p", GUID_Printf(iid), ppv);

---

L means unicode string.
const wchar_t* p = L"My string";
const char* p2 = "My string";

L means wide characters. Wide character might be unicode, but they might not. On Windows, I think it is.