VC access regedit

#define PATH "HKEY_LOCAL_MACHINE\\Software\\..."

HKEY hk;
if(RegOpenKey(
   HKEY_LOCAL_MACHINE,
   PATH,
  //0,
  //KEY_ALL_ACCESS =>KEY_QUERY_VALUE,
  &hk) != ERROR_SUCCESS)
{
    return FALSE;
}

DWORD dwType = 0;
unsigned char szBuff[1024];
DWORD dwBuffLength = sizeof(szBuff);

if (RegQueryValueEx(hk, "InstallPath", 0, &dwType, szBuff, &dwBuffLength) != ERROR_SUCCESS)
{
return FALSE;
}

if(dwType != REG_SZ)
{
return FALSE;
}

return TRUE;

使用记录：
1)以前RegOpenKeyEx没有试成功，原来是要用KEY_QUERY_VALUE，而不能用KEY_ALL_ACCESS
2)当dwBuffLength传入比获得的字符串长度小的值时，会失败。所以建议传大一些的值，调用后它会将该变量重新设为获得的字符串长度。


-----------------------------------
下面是从wix的wcalog.cpp中的一段：
static BOOL IsVerboseLogging()
{
    static int iVerbose = -1;

    if (0 > iVerbose)
    {
        iVerbose = WcaIsPropertySet("LOGVERBOSE");
        if (0 == iVerbose) // if the property wasn't set, check the registry to see if the logging policy was turned on
        {
            HKEY hkey = NULL;
            WCHAR rgwc[16] = { 0 };
            DWORD cb = sizeof(rgwc);
            if (ERROR_SUCCESS == ::RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"Software\\Policies\\Microsoft\\Windows\\Installer", 0, KEY_QUERY_VALUE, &hkey))
            {
                if (ERROR_SUCCESS == ::RegQueryValueExW(hkey, L"Logging", 0, NULL, reinterpret_cast<BYTE*>(rgwc), &cb))
                {
                    for (LPCWSTR pwc = rgwc; (cb / sizeof(WCHAR)) > static_cast<DWORD>(pwc - rgwc) && *pwc; pwc++)
                    {
                        if (L'v' == *pwc || L'V' == *pwc)
                        {
                            iVerbose = 1;
                            break;
                        }
                    }
                }

                ::RegCloseKey(hkey);
            }
        }
    }

    Assert(iVerbose >= 0);
    return (BOOL)iVerbose;
}