Registry RegQueryKeyEx

Registry RegQueryKeyEx

• Lawrence Parker

  Thanks goes well .
  Is buffer like a character array
  
  e.g char bob[5] = "hello"
  
  

• Stephan Smetsers

  Thanks for the quick reply. I am still getting the following errors:
  Main.cpp(44) : error C2664: 'MessageBoxA' : cannot convert parameter 2 from 'char' to 'const char *'
  Conversion from integral type to pointer type requires reinterpret_cast, C-style cast or function-style cast
  
  
  error C2440: 'initializing' : cannot convert from 'char *' to 'char'
  This conversion requires a reinterpret_cast, a C-style cast or function-style cast
  (This is for the line TCHAR buffer = new TCHAR[bufSize];)
  
  error C2541: delete : cannot delete objects that are not pointers
  
  

• ScoobySue

  If you are stuck at the concept of a buffer, I'd suggest you buy or lend a good book on C++ before diving much more. That will surely save you some time later.

  With regard to RegQueryValueEx, what you'd generally want to do is call it once to get the type and size of the data stored at it, and also get a sign if it even exists.

  DWORD bufSize = 0;
  DWORD valueType = 0;
  LONG result;
  
  result = RegQueryValueEx(hkey, _T("valuename"), NULL, &valueType, NULL, &bufSize);
  
  if (result != ERROR_SUCCESS)
  {
   // the value may not exist, or the key is invalid
   return;
  }

  Next, you would like to confirm that the value is actually of a proper type, and that it has a sane size. If everything is ok, RegQueryValueEx will be called a second time to actually get the value. If this call also succeeds, show the result in a message box.

  if ((valueType == REG_SZ || valueType == REG_EXPAND_SZ) && 
    (bufSize > 0))
  {
   TCHAR* buffer = new TCHAR[bufSize / sizeof(TCHAR)];
   
   result = RegQueryValueEx(hkey, _T("valuename"), NULL, NULL, (LPBYTE)buffer, &bufSize);
   
   if (result == ERROR_SUCCESS)
   {
    MessageBox(0, buffer, _T("The value"), MB_SETFOREGROUND);
   }
   
   delete [] buffer;
  }

  Last but not least, free the memory allocated to hold the data.

  One thing I havent touched here, is the fact that strings located in the registry aren't guaranteed to have a terminating null character -- that part is left for you to figure out. An alternative would be to use RegGetValue, which is certain to return null-terminated strings.

  
  
  

• Matt Stum

  Sorry, a missing * in that would-be pointer declaration. That's what I get from relying on my built-in compiler

  I've updated the previous post now.

  
  
  
• Registry RegQueryKeyEx