windows registry read - c++

Question

Using this code snippet:
TCHAR buf[255] = {0};
DWORD dwBufSize = sizeof(buf);
HKEY hKey = 0;
DWORD dwType = REG_DWORD;
if ( RegOpenKeyEx( HKEY_CURRENT_USER, TEXT("Software\\Developer\\KGReader"), 0, KEY_QUERY_VALUE, &hKey) == ERROR_SUCCESS)
{
if( RegQueryValueEx( HKEY_CURRENT_USER, TEXT("Software\\Developer\\KGReader\\ComPort"), 0, &dwType, (LPBYTE)buf, &dwBufSize ) == ERROR_SUCCESS )
{
nrPort = _wtoi(buf);
}
if( RegQueryValueEx( HKEY_CURRENT_USER, TEXT("Software\\Developer\\KGReader\\KGID"), 0, &dwType, (LPBYTE)buf, &dwBufSize ) == ERROR_SUCCESS )
{
nrCentrala = _wtoi(buf);
}
}
No value is passed to hKey using RegOpenKeyEx method.
Although RegOpenKeyEx returns an ERROR_SUCCES, RegQueryValueEx returns 2 (ERROR_FILE_NOT_FOUND). KGID and ComPort do exist,i added them myself, i double checked the paths.

Answer 1

Pass the hKey obtained from the RegOpenKeyEx() call to the RegQueryValueEx() functions instead of HKEY_CURRENT_USER. The second argument to RegQueryValueEx() is the name of the value, not a path.
For example:
if( RegQueryValueEx(hKey,
TEXT("ComPort"),
0,
&dwType,
(LPBYTE)buf,
&dwBufSize ) == ERROR_SUCCESS )
Remember to reset buf and dwBufSize before the second call to RegQueryValueEx:
memset(buf, 0, sizeof(buf));
dwBufSize = sizeof(buf);
For error reporting purposes you should save the return value of the RegOpenKeyEx() and RegQueryValueEx() functions so the failure reason can be made known.
The posted code may be incomplete but ensure RegCloseKey(hKey) is called if the call to RegOpenKeyEx() was successful.

Answer 2

The first argument to RegQueryValueEx should be the HKEY opened by RegOpenKeyEx. In addition, the second argument should just be a value name, not the full path:
if( RegQueryValueEx( hKey, TEXT("ComPort"), 0, &dwType,
(LPBYTE)buf, &dwBufSize ) == ERROR_SUCCESS )