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Understanding Mobile Data Synchronization: Utilizing MS ActiveSync Capabilities at a High Level

  • August 17, 2005
  • By Alex Gusev
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Windows CE Services

As you probably very well aware, a whole bunch of data synchronization methods and techniques are bound around one common basis: Windows CE Services. This term combines ActiveSync custom service providers, file filters, connection notifications, and the CeUtil API. An upcoming article will be dedicated to the last two topics. ActiveSync service provider's development will be described later. Most of the discussed topics below are related to the desktop side only.

So, you can start with CeUtil. This DLL exports about a dozen functions that allow you to manage ActiveSync's Registry values. Obviously enough, you can do the same job using regular RegXXX calls. A benefit you get with CeUtil API is that it provides an abstract layer over ActiveSync registry settings, so you don't need to bother with their exact names, which in turn may vary a bit between different OS versions and localizations. Thus far, here is what you can use:


HRESULT __stdcall CeSvcOpen( UINT uSvc, LPTSTR pszPath,
                             BOOL fCreate, PHCESVC phSvc );
HRESULT __stdcall CeSvcOpenEx( HCESVC hSvcRoot, LPTSTR pszPath,
                               BOOL fCreate, PHCESVC phSvc );
HRESULT __stdcall CeSvcClose( HCESVC hSvc );
HRESULT __stdcall CeSvcGetString( HCESVC hSvc, LPCTSTR pszValName,
                                  LPTSTR pszVal, DWORD cbVal );
HRESULT __stdcall CeSvcSetString( HCESVC hSvc, LPCTSTR pszValName,
                                  LPCTSTR pszVal );
HRESULT __stdcall CeSvcGetDword( HCESVC hSvc, LPCTSTR pszValName,
                                 LPDWORD pdwVal );
HRESULT __stdcall CeSvcSetDword( HCESVC hSvc, LPCTSTR pszValName,
                                 DWORD dwVal );
HRESULT __stdcall CeSvcGetBinary( HCESVC hSvc, LPCTSTR pszValName,
                                  LPBYTE pszVal, LPDWORD pcbVal );
HRESULT __stdcall CeSvcSetBinary( HCESVC hSvc, LPCTSTR pszValName,
                                  LPBYTE pszVal, DWORD cbVal );
HRESULT __stdcall CeSvcDeleteVal( HCESVC hSvc, LPCTSTR pszValName );
DEVICEID __stdcall CeGetDeviceId( void );
DEVICEID __stdcall CeGetSelectedDeviceId( void );
HRESULT __stdcall CeSvcEnumProfiles(PHCESVC phSvc,
                                    DWORD lProfileIndex,
                                    PDWORD plProfile);

As you see, there are three logical functional groups:

  • To access Registry keys
  • To manipulate values
  • To obtain device info

CeUtil offers you a lot of predefined keys touching different aspects of ActiveSync programming. You will find an excerpt from the SDK help in the following table. But prior to this, let me highlight the following point. CeUtil Registry keys are mirrored at several locations. There is "MACHINE_ROOT":

HKEY_LOCAL_MACHINESoftwareMicrosoftWindows CE Services—Used to address settings in general;

There is also "LOCAL_ROOT":

HKEY_CURRENT_USERSoftwareMicrosoftWindows CE Services—Addresses specific device configuration.

So, you have some freedom to configure Windows CE Services at different levels. Having said this all, here is a table:

Registry Key CEUTIL Constants Description
MACHINE_ROOT CESVC_ROOT_MACHINE Windows CE Services root hierarchy under HKEY_LOCAL_MACHINE
MACHINE_ROOTFilters CESVC_FILTERS The Filters Registry root. New filters should register themselves here
MACHINE_ROOTCustomMenus CESVC_CUSTOM_MENUS Custom menus Registry root
MACHINE_ROOTServices CESVC_SERVICES_COMMON Services Registry root
MACHINE_ROOTServices Synchronization CESVC_SYNC_COMMON Synchronization Registry root. New sync services should register here
LOCAL_ROOT CESVC_ROOT_USER Windows CE Services root hierarchy under HKEY_CURRENT_USER
LOCAL_ROOTPartners CESVC_DEVICES Individual device subkeys are created under this key
LOCAL_ROOTPartners<device id> CESVC_DEVICEX Particular device root subkey
LOCAL_ROOTPartners<selected device id> CESVC_DEVICE_SELECTED Root subkey for the currently selected device
LOCAL_ROOTPartners<device id>Services CESVC_SERVICES_USER Root Services subkey for a particular device
LOCAL_ROOTPartners<device id>ServicesSynchronization CESVC_SYNC Synchronization reg root for a particular device

Thus far, you're getting access to desired Registry key by calling CeSvcOpen. A deeper hierarchy is achieved by subsequent CeSvcOpenEx calls. By playing with their parameters, you can control key access and creation policy.

I will skip a second group of functions dealing with key values themselves due to their simplicity and move forward to a device-related one. It isn't complicated in usage but nevertheless may be pretty helpfull. A code snippet below shows just one simple case of it:


HCESVC hSvc;
DWORD dwProfile = 0;
DWORD dwProfileInx = 0;
TCHAR szDevName[255] = { 0 } , szDevType[255] = { 0 };
HRESULT hr = S_OK;
HCESVC hDevice;
do
{
   hr = CeSvcEnumProfiles(&hSvc,dwProfileInx,&dwProfile);
   if ( hr == ERROR_NO_MORE_ITEMS )
      break;
   if ( hr != S_OK )
   {
      // handle an error as needed
      break;
   }
   
   if ( S_OK == CeSvcOpen(CESVC_DEVICEX, (LPTSTR)dwProfile,
        FALSE, &hDevice) )
   {
      CeSvcGetString(hDevice,_T("DisplayName"),szDevName,
                     sizeof(szDevName)/sizeof(TCHAR));
      CeSvcGetString(hDevice,_T("DeviceType"),szDevType,
                     sizeof(szDevType)/sizeof(TCHAR));
      // do whatever you want with this info
      
      CeSvcClose(hDevice);
   }
   
   dwProfileInx++;
}
while ( hr == S_OK );

This is actually all the story about CeUtil. Use it wisely, and leave it in peace for now.





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