🚀 go-pugleaf

> Do I have to take care of freeing that memory, or is someone else taking 
> care of freeing the STRRET.pOleStr (e.g. pDesktopFolder) ?

Yes you do as stated in documentation.

> 
> Please feel free to mention any other (clean-up) issues that you might 
> notice with the code sample below.
> 
> Thanks,
> 
> Kris


First of all if your app is VCL CoInitialize is not needed. By default 
COM is initialized in VCL app.

I would never assume anything in API. You should always check uType to 
see what is the appropriate action. Also for safety reasons it would be 
good to use RAII idiom to handle resource cleanup properly.

Here is my version of the same thing. It is longer and uses only 
standard C and C++ library together with Windows API hence it is console 
app.

The only thing that can be removed in VCL app is use of ole_init.

//---------------------------------------------------------------------------
#include <windows.h>
#include <shlobj.h>
#include <cstdlib>
#include <string>
#include <vector>
#include <iostream>

#pragma comment(lib,"shell32.lib")

//---------------------------------------------------------------------------
struct ole_init {
   ole_init(void) : _isinit(false) {
     _isinit = SUCCEEDED(::CoInitialize(NULL));
   }
   ~ole_init(void) {
     if (_isinit) {
       _isinit = false;
       ::CoUninitialize();
     }
   }
   bool init_ok(void) const { return _isinit; }
private:
   bool _isinit;
};

std::wstring string2wstring (const std::string& str) {
   std::wstring result;
   if (!str.empty()) {
     std::vector<wchar_t> buffer(str.size());
     std::size_t res = std::mbstowcs(&buffer[0],str.c_str(),str.size());
     if (res > 0) {
      result.assign(buffer.begin(),buffer.end());
     }
   }
   return result;
}

struct pidl_holder {
  explicit pidl_holder(int folder) : _pidl(NULL) {
     LPITEMIDLIST ppidl = NULL;
     HRESULT hr = ::SHGetSpecialFolderLocation(NULL,folder,&ppidl);
     if (SUCCEEDED(hr)) {
       _pidl = ppidl;
     }
  }
  ~pidl_holder(void) { release(); }
  LPITEMIDLIST ptr(void) {return _pidl;}
private:
   LPITEMIDLIST _pidl;
   void release(void) {
     if (NULL != _pidl) {
        ::CoTaskMemFree(_pidl);
        _pidl = NULL;
     }
   }
};

struct shdesktop_folder {
   shdesktop_folder(void) : _desktop_folder(NULL) {
     LPSHELLFOLDER df = NULL;
     if (SUCCEEDED(::SHGetDesktopFolder(&df))) {
       _desktop_folder = df;
     }
   }
   ~shdesktop_folder(void) {
     if (NULL != _desktop_folder) {
      _desktop_folder->Release();
      _desktop_folder = NULL;
     }
   }
   LPSHELLFOLDER ptr(void) { return _desktop_folder; }
private:
   LPSHELLFOLDER _desktop_folder;
};

std::wstring get_display_name(void) {
   ole_init ol;
   std::wstring result;
   if (ol.init_ok()) {
     pidl_holder pidlobj(CSIDL_PERSONAL);
     LPITEMIDLIST pidl = pidlobj.ptr();
     if (NULL != pidl) {
         shdesktop_folder deskFolder;
         LPSHELLFOLDER pDesktopFolder = deskFolder.ptr();
         if (NULL != pDesktopFolder) {
            STRRET sname = {};
            HRESULT hr = pDesktopFolder->GetDisplayNameOf(  pidl
                                                           ,SHGDN_INFOLDER
                                                           ,&sname);
            if (SUCCEEDED(hr)) {
              if (sname.uType == STRRET_WSTR) {
                result = sname.pOleStr;
                ::CoTaskMemFree(sname.pOleStr);
                sname.pOleStr = NULL;
              } else if (sname.uType == STRRET_CSTR) {
                result = string2wstring(sname.cStr);
              } //else here add the third case code
            }
         }
     }
   }
   return result;
}

int main(int /*argc*/, char** /*argv[]*/)
{
  std::wcout << get_display_name() << std::endl;
  return EXIT_SUCCESS;
}
//---------------------------------------------------------------------------

"Darko Miletic" <kiklop@fibertel.com.ar> wrote in message 
news:47d92ad2@newsgroups.borland.com...

> First of all if your app is VCL CoInitialize is not needed.
> By default COM is initialized in VCL app.

There is no harm in doing it yourself, though.  The COM library is reference 
counted.  As long as all calls to CoInitialize() have balanced calls to 
CoUnitialize(), you will be fine.


Gambit 

"Kris" <x@x.com> wrote in message news:47d8ec90$1@newsgroups.borland.com...

> Do I have to take care of freeing that memory

Yes.

> is someone else taking care of freeing the STRRET.pOleStr
> (e.g. pDesktopFolder) ?

No.

> Probably safe to assume STRRET_WSTR is set in this specific case
> So simply use the pOleStr member without any additional checks

You cannot assume that.  You need to look at the STRRET's uType parameter to 
know exactly how to interpret the STRRET's contents properly, for example:

    switch( sName.uType )
    {
        case STRRET_CSTR
            DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%s]", sName.cStr);
            break;
        case STRRET_OFFSET:
        {
            char *pName = (char*)(((LPBYTE)pidl) + sName.uOffset);
            DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%s]", pName);
            break;
        }
        case STRRET_WSTR:
        {
            // assuming DEBUG() is based on printf() or similar function...
            DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%ls]", sName.pOleStr);
            CoTaskMemFree(sName.pOleStr);
            break;
        }
    }

Alternatively, you can use one of the StrRetTo...() functions instead, which 
also handle freeing the STRRET_WSTR memory for you, ie:


    TCHAR szBuf[MAX_PATH+1] = {0};
    StrRetToBuf(&sName, pidl, szBuf, MAX_PATH+1);

    #ifdef UNICODE
    DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%ls]", szBuf);
    #else
    DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%s]", szBuf);
    #endif

Or:

    LPTSTR pName;
    StrRetToStr(&sName, pidl, &pName);

    #ifdef UNICODE
    DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%ls]", szBuf);
    #else
    DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%s]", szBuf);
    #endif

    CoTaskMemFree(pName);

Or:

    WideString wName;
    StrRetToBSTR(&sName, pidl, &wName);

    DEBUG("DisplayNameof(CSIDL_PERSONAL)=[%ls]", wName.c_bstr());


Gambit 

Remy Lebeau (TeamB) wrote:
> "Darko Miletic" <kiklop@fibertel.com.ar> wrote in message 
> news:47d92ad2@newsgroups.borland.com...
> 
>> First of all if your app is VCL CoInitialize is not needed.
>> By default COM is initialized in VCL app.
> 
> There is no harm in doing it yourself, though.  The COM library is reference 
> counted.  As long as all calls to CoInitialize() have balanced calls to 
> CoUnitialize(), you will be fine.

You are right but I was just saying that if it is already there no need 
to add more code than needed.

"Darko Miletic" <kiklop@fibertel.com.ar> wrote in message 
news:47d96258$1@newsgroups.borland.com...

> You are right but I was just saying that if it is already
> there no need to add more code than needed.

On the other hand, it is not good practice to assume what the framework does 
internally.  The VCL calls CoInitialize/Ex() at startup only when certain 
units (namely - ComObj, DBTables, HTTPIntr, ScktMain, SConnect, and VCLCom) 
are being used by the project.


Gambit 

Thank you once again for a very comprehensive and complete answer. And 
yes, simply assuming STRRET_WSTR was quite lazy on my part :-)

Regards,

Kris