WUW4.dll - The Software Update Wizard Dynamic Link Library

The wuw4.dll file is a Windows dynamic link library, which your application uses to communicate with the Software Update Wizard Service application. If you are instead calling wuwstub.exe from your application then wuwstub.exe uses wuw4.dll to communicate with the Software Update Wizard service (WebUpdateSvc.exe) and launches the Software Update Wizard User Interface component (WuWUI.exe).

Wuw4.dll is normally installed into the Windows folder. If you use wuwinstaller.exe to install the Software Update Wizard it will locate wuw4.dll there.

Wuw4.dll contains 2 exported functions:

WebUpdate(URL)

and

WebUpdateWait(URL, TimeOut)

The first function, WebUpdate(), passes the URL of the update script to the Software Update Wizard and returns immediately. It therefore causes the Software Update Wizard to work asynchronously (i.e. in parallel) with your application.

The WebUpdateWait() function passes the URL and a timeout in milliseconds ('000ths of a second) to wuw4.dll. However, the WebUpdateWait() function in wuw4.dll does not return until the Software Update Wizard has completely finished processing the call. It therefore causes the Software Update Wizard to work synchronously (i.e. sequentially) with your application. Note that the milliseconds argument causes control to return to your program either when the specified time is up or when the Software Update Wizard has finished, whichever occurs earlier.

When the DLL receives the URL of the update script it then either sends the URL through a named pipe to the Software Update Wizard Service.

The declaration of the WebUpdate() function from the (supplied) WebUpdate.h file is shown here:

//////////////////////////////////////////////////////////////////
// Software Update Wizard DLL Header File
// © Peter Boulton, Data Perceptions / PowerProgrammer - 2002-2005
//////////////////////////////////////////////////////////////////
// The one and only function - WebUpdate(LPCTSTR szURL) where
// szURL is the URL of the server update script file.
// Function returns 1 if successful, else 0.
// Note __stdcall calling convention for use in VB
// Example call:
//
//       WebUpdate("http://www.myserver.com/update.txt");
//
// Here is an example VBA call:
// --------------------------------------------------------------------------------------------------------------
//   Private Declare Function WebUpdate Lib "D:\MSDEV\Projects\wuw\Release\wuw4.dll" (ByVal URL As String) As Long
// --------------------------------------------------------------------------------------------------------------
//   Private Sub CommandButton1_Click()
//
//   Dim myURL As String
//   myURL = "http://localhost/prophecy/prophecyupdate.txt"
//   Call WebUpdate(myURL)
//
//   End Sub

/////////////////////////////////////////////////////////////////////////////////////////
// Implementation 1: Returns immediately on launching Software Update Wizard
int __stdcall WebUpdate(LPCTSTR URL);
/////////////////////////////////////////////////////////////////////////////////////////
// Implementation 2: Returns after Software Update Wizard has finished parsing script file and,
//                   if necessary, downloading the updates, or after nTimeOut milliseconds,
//                   whichever occurs earlier.
int __stdcall WebUpdateWait(LPCTSTR szURL, UINT nTimeOut);
/////////////////////////////////////////////////////////////////////////////////////////

Notes

The DLL is a simple Windows dll. It does not need to be registered with Windows as a COM dll.
The "http://" part of the URL must be included in the URL passed as an argument to the WebUpdate() function.
VB users should note that the "ByVal" part of the function declaration highlighted in the example above is required.
C/C++ users should include the WebUpdate.h header file in their projects and within the source code file which contains the call to WebUpdate() / WebUpdateWait(). This file is installed in the Developer Edition Software Update Wizard installation folder. Also, the wuw4.lib file supplied in the Software Update Wizard installation folder should be specified in the Link / Object /library modules section of your projects build settings. (Alternatively, your application can dynamically link to wuw4.dll using the LoadLibrary() API.)
The WebUpdate() function returns 1 if successful and 0 if unsuccessful. However, success means that the DLL successfully communicated with the Software Update Wizard Service, NOT whether an update was successfully processed. If your application needs to know whether an update was successfully processed you need to use WebUpdateWait() in conjunction with one of the following 4 options:
1. It must check the "Counter=" line of the appropriate section of the user's WebUpdateSvc4.ini file before the call to WebUpdate() and then again afterwards. If the before and after values are different then an update was successfully processed. (Note: this option will not work if your script uses the RunAlways keyword.)
2. The Software Update Wizard also maintains a registry value of the number of successful updates processed at HKEY_LOCAL_MACHINE\SOFTWARE\WUW\UpdateCounter. If you capture the value of this key both before and after the Software Update Wizard has finished processing you can detect whether an update has been made.
3. Parsing the end of the WebUpdateSvc4.log file to check for a successful update.
4. Checking the before and after version numbers/date stamps of the updated files from within your own application.
If you would rather not use the wuw4.dll Dynamic Link Library for a synchronous update (i.e. via the WebUpdateWait() exported function), an alternative approach is to launch the wuwstub.exe application, using the Windows ShellExecute() API. This performs exactly the same function as wuw4.dll, except that the WebUpdateWait() function is not supported. However, your application can simulate the behaviour of WebUpdateWait() by obtaining the current value of the following (type REG_DWORD ) registry key prior to launching the Software Update Wizard update check with wuwstub.exe:

HKEY_LOCAL_MACHINE\SOFTWARE\WUW\UsageCounter

Once wuwstub.exe has been launched your application must intermittently inspect the registry key value until it has changed, which must mean that the Software Update Wizard has finished updating. Note that the registry value is incremented when updates have been processed, if no updates are required or even if no internet connection was found. Its purpose is simply to count the number of calls to the Software Update Wizard.