This is code that we used.  It is quite old as we no longer use oo4o and prefer to use OCI directly.

 

The method is taken from a class that encapsulated this kind of functionallity.  m_pDatabase is a member pointer to an ODatabase object.

 

 

BOOL CBlobHander::CreateFileFromBlob(LPCSTR pszTableName, LPCTSTR pszBlobField, LPCTSTR pszWhereClause, LPCTSTR pszFilename)
{
#ifdef _DEBUG
 if (m_pDatabase && !m_pDatabase->m_Database.IsOpen())
 {
  MessageBox(NULL, "Can not Create File - Database Not Connected", "Error", MB_ICONINFORMATION | MB_OK);
  return FALSE;
 }
#endif

 

 ODynaset dyn;
 CString strSQL;

 

 strSQL.Format("SELECT %s FROM %s WHERE %s", pszBlobField, pszTableName, pszWhereClause);
 
 if (_BOOL(dyn.Open(m_pDatabase->m_Database, strSQL)))
 {

 

#ifdef _DEBUG
  if (dyn.GetRecordCount() == 0)
  {
   MessageBox(NULL, "Can not find Object Record.", "Error", MB_ICONINFORMATION | MB_OK);
   return FALSE;
  }
  else if (dyn.GetRecordCount() > 1)
  {
   MessageBox(NULL, "Query returned more than one record.  Can not update.", "Error", MB_ICONINFORMATION | MB_OK);
   return FALSE;
  }
#endif

 

  OBlob oblob;
  dyn.GetFieldValue(0, &oblob);

 

#ifdef _DEBUG
  if (oblob.IsNull() || (oblob.GetSize() == 0))
  {
   MessageBox(NULL, "Can not Create File - Blob is Empty.", "Error", MB_ICONINFORMATION | MB_OK);
   return FALSE;
  }
#endif

 

  unsigned char *buffer = 0;

 

  try
  {
   fstream fs;

 

   fs.open(pszFilename, ios::out);
   fs.setmode(filebuf::binary);

 

   unsigned long size = oblob.GetSize();

 

   // calculate an optimum buffersize of approximately 32k bytes
   unsigned long optchunk = oblob.GetOptimumChunkSize();
   unsigned int bufsize = ((int)(32768/optchunk)) *optchunk;
   
   if (bufsize > size)
    bufsize = size;

 

   buffer = (unsigned char *)malloc(bufsize);

 

   //By taking advantage of streaming we get the best performance
   //and do not need to allocate a large buffer

 

   oblob.EnableStreaming(size);

 

   short status= OLOB_NEED_DATA;
   unsigned long amtread=0;

 

   while(status == OLOB_NEED_DATA)
   {
    amtread = oblob.Read(&status, buffer, bufsize);
    
    //if (status != OLOB_NODATA)
     if (amtread == 0)
      fs.write(buffer, bufsize);
     else
      fs.write(buffer, amtread);
   }

 

   oblob.DisableStreaming();

 

   fs.close();
  }
  catch(OException E)
  {
   CString strMsg;
   strMsg.Format("%s Error: %s", E.GetFailedMethodName(), E.GetErrorText());
   MessageBox(NULL, strMsg, "Error", MB_ICONINFORMATION | MB_OK);
  }

 

  if (buffer)
   free(buffer);   
  
  return TRUE;
 }
 else
 {
  int n = dyn.ErrorNumber();
  MessageBox(NULL, dyn.GetErrorText(), "Failed To Open Object Record", MB_ICONINFORMATION | MB_OK);

 

  return FALSE;
 }
}

---

From: Alaa Mostafa [mailto:alaa210@...]
Sent: 22 June 2004 06:04
To: oo4ole@yahoogroups.com
Subject: [oo4ole] How to use oo4o to save BLob ?[Scanned]

Hi all

used oo4ole with Visual C++ ,

How to save image (stored in BLOB data type ) Using OO4O ;

 

thanks

 

alaa

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