asked on

From Disk File to IStream through OleSaveToStream

I am trying to convert a disk file to an IStream through the OleSaveToStream function. But I seem to need an IPersistStream object, and I can't figure out how to get one.

Here is my function:

void FileToOleData(HWND hWndParent, LPCTSTR szFileName)
{
CComPtr<IOleObject> pOleObject = NULL;
CComPtr<IStream> pStream = NULL;
CComPtr<IOleClientSite> pClientSite = NULL;

      HRESULT hr;
      WCHAR szWideFileName[255];

#ifdef _UNICODE
      _tcsncpy(szWideFileName, szFileName, 254);
#else
      USES_CONVERSION;
      wcsncpy(szWideFileName, T2W(szFileName), 254);
#endif

      // Open a compound storage document
      IStorage *pStorage = NULL;
      hr = StgOpenStorageEx(
            szWideFileName,
       STGM_READ | STGM_SHARE_DENY_NONE | STGM_TRANSACTED,
       STGFMT_ANY,
       0,
       0, NULL,
       IID_IStorage,
       reinterpret_cast<void**>(&pStorage));

      if (FAILED(hr))
      {
            // error handler here
      }

      hr = OleCreateFromFile(CLSID_NULL,
            szWideFileName, IID_IOleObject, OLERENDER_ASIS, NULL,
            pClientSite, pStorage, (LPVOID*)&pOleObject);
      if (FAILED(hr))
      {
            // error handler here
      }

      // How do I get pOleObject to an IStream?
}

By the end of the function, I have an IOleObject created from the file. I want to convert it to a stream using the OleSaveToStream function, but this requires an IPersistStream interface. So how do I get an IPersistStream interface from IOleObject?

The ultimate goal is to go from a disk file to the OleSaveToStream functions as would be done to insert an OLE Object in a document. Is there some better way to do this?

jkr

You'd use

IPersistStream* pps = NULL;

hr = pOleObject ->QueryInterface(IID_IPersistStream, (void**)&pps);

if (FAILED(hr))
{
// error handler here
}

Baewolfe

ASKER

Yes, that would seem to be the obvious solution, but hr returns with E_NOINTERFACE. The file is a PowerPoint file. Why would a PowerPoint file not support the IPersistStream Interface?

jkr

Hm, another Idea would be to

COleStreamFile osf;

osf.CreateStream(pStorage);

instead...

Baewolfe

ASKER

That creates a stream, but it doesn't take me through the OleSaveToStream, which is a requirement.

You may also want to check out my related question "Problems extracting an OLE Object from a Rich-Text (RTF) File by parsing the file".

Amritpal Singh

have a look at the following article
may be of any help
http://support.microsoft.com/default.aspx?scid=kb;EN-US;242249

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Baewolfe

ASKER

In response to amrit_82...

Borrowing from the MSDN code you referenced, I implement the following function and call it after OleCreateFromFile in my code from the original question. pPersist is NULL so the function returns E_NOINTERFACE.

My main problem from the original question is that my pOleObject is not supporting the IPersistStream interface. I have tested it with both Excel and PowerPoint files.

HRESULT SaveObjectHelper(IOleObject* pObject, IStream* * ppStream)
{
      HRESULT hr=S_OK;
      try
      {
            *ppStream=NULL;

            // QI and return IPersistStream
            IPersistStreamPtr pIPersist(pObject);

// pPersist is NULL here

            if (pIPersist)
            {
                  //Create a standard stream in memory
                  if (FAILED(hr=CreateStreamOnHGlobal(0, TRUE, (IStream **)ppStream)))
                        return hr;

                  // Persist the pRS
                  if (FAILED(hr=OleSaveToStream(pIPersist, *ppStream)))
                        return hr;

            }
            else
                  return E_NOINTERFACE;
      }
      catch (_com_error & e)
      {
            return e.Error();
      }
      return S_OK;

}

Baewolfe

ASKER

In response to YR, pOleObject->GetMoniker returns E_FAIL.