c++ 读写注册表

void RegUpdate(HKEY hRootKey,LPCSTR szSubKey,LPCSTR szValueName,LPCSTR szValue)
{
   HKEY hKey;
   LONG rc;
   int nFile;
   rc = RegCreateKeyEx(hRootKey, szSubKey, NULL, NULL, , KEY_WRITE, NULL, &hKey, NULL);
   if(rc != ERROR_SUCCESS)
      return;
   nFile = strlen(szValue);
   RegSetValueEx(hKey, szValueName, NULL, REG_SZ, (LPBYTE)szValue, nFile);
   RegCloseKey(hKey);
}

string RegGet(HKEY hRootKey,LPCSTR szSubKey,LPCSTR szValueName)
{
    HKEY hKey;
    LONG rc;
    DWORD dwType;
    char szValue[];
    DWORD dwSize;
    rc = RegOpenKey(hRootKey, szSubKey, &hKey);
    if(rc != ERROR_SUCCESS)
        return FALSE;

    rc = RegQueryValueEx(hKey, szValueName, NULL, &dwType, (LPBYTE)szValue, &dwSize);
    if(rc == ERROR_SUCCESS && dwType == REG_SZ)
    {
        RegCloseKey(hKey);
        return (string)szValue;
    }
    RegCloseKey(hKey);
    return NULL;
}