使用 USNChanged 检索更改的示例代码

下面的代码示例使用 Active Directory 域服务 中对象的 uSNChanged 属性检索自上一个查询以来的更改。 该代码示例可以执行完全同步或增量更新。 对于完全同步,示例应用程序连接到域控制器的 rootD标准版,并读取存储在下一个增量同步中使用的以下参数:

  • DC 的 DNS 名称。 增量同步必须在与上一次同步相同的 DC 上执行。
  • DC 的调用 ID GUID。 代码示例使用此值检测 DC 是否已从备份还原,在这种情况下,示例必须执行完全同步。
  • 最高CommittedUSN。 此值将成为下一次增量同步上 uSNChanged 筛选器的下限。

该代码示例使用 IDirectorySearch 接口,指定搜索基础的可分辨名称、搜索范围和筛选器。 搜索基础或范围没有限制。 除了指定感兴趣的对象之外,筛选器还必须指定 uSNChanged 比较,例如“uSNChanged >= <下限 USN>”。 对于完全同步,“<下限 USN>”为零。 对于增量同步,它是上一次搜索中 最高的CommittedUSN 值。

请注意,此示例应用程序仅用于演示如何使用 uSNChanged 从 Active Directory 服务器检索更改。 它打印更改,并且实际上不会同步辅助存储中的数据。 因此,它不显示如何处理移动对象或“无父级”条件等问题。 它确实显示如何检索已删除的对象,但它不显示应用程序 如何使用已删除对象的 objectGUID 来确定在存储中删除的相应对象。

此外,示例缓存注册表中的 DC 名称、 invocationIDhighestCommittedUSN 。 在实际同步应用程序中,必须将参数存储在与 Active Directory 服务器保持一致的同一存储中。 这可确保从备份还原数据库时参数和对象数据保持同步。

#include <windows.h>
#include <stdio.h>
#include <activeds.h>
#include <ntdsapi.h>
#include <atlbase.h>

#pragma comment(lib, "activeds")
#pragma comment(lib, "adsiid")

typedef struct _MYUSERDATA
{
    WCHAR objectGUID[40];
    WCHAR distinguishedName[MAX_PATH];
    WCHAR phoneNumber[32];
} MYUSERDATA, *PMYUSERDATA;

#define ARRAYSIZE(__buf__) (sizeof(__buf__)/sizeof(__buf__[0]))

// Forward declaration
VOID BuildGUIDString(WCHAR *szGUID, LPBYTE pGUID); VOID WriteObjectDataToStorage(PMYUSERDATA pUserData, BOOL bUpdate); VOID DeleteObjectDataFromStorage(PMYUSERDATA pUserData);

//********************************************************************
// DoUSNSyncSearch
//********************************************************************
HRESULT DoUSNSyncSearch(
    LPWSTR pszSearchBaseDN,      // Distinguished name of search base
    ULONG ulScope,               // Scope of the search
    LPWSTR *pAttributeNames,     // Attributes to retrieve
    DWORD dwAttributes,          // Number of attributes
    LPWSTR pszPrevInvocationID,  // GUID string for DC's invocationID
    LPWSTR pszPrevHighUSN,       // Highest USN from previous sync
    LPWSTR pszDC)                // Name of DC to bind to
{
    LPWSTR pszServerPath = NULL;
    LPWSTR pszDSPath = NULL;
    IADs *pRootDSE = NULL;
    IADs *pDCService = NULL;
    IADs *pDeletedObj = NULL;
    IDirectorySearch *pSearch = NULL;
    ADS_SEARCH_HANDLE hSearch = NULL;
    ADS_SEARCHPREF_INFO arSearchPrefs[3];
    WCHAR szSearchFilter[256];    // Search filter
    ADS_SEARCH_COLUMN col;
    MYUSERDATA userdata;
    void HUGEP *pArray;
    WCHAR szGUID[40];
    INT64 iLowerBoundUSN;
    HRESULT hr = E_FAIL;
    DWORD dwCount = 0;
    VARIANT var;
    BOOL bUpdate = TRUE;

    // Validate input parameters.
    if (!pszPrevInvocationID || !pszPrevHighUSN || !pszDC)
    {
        wprintf(L"Invalid parameter.\n");
        return E_INVALIDARG;
    }

    VariantInit(&var);

    // Allocate the server path string buffer.
    pszServerPath = new WCHAR[7 + wcslen(pszDC) + 1 + 1];
    if(!pszServerPath)
    {
        wprintf(L"failed to allocate memory");
        hr = E_OUTOFMEMORY;
        goto cleanup;
    }

    // If there exists a DC name from the previous USN synchronization,
    // include it in the binding string.
    if (pszDC[0])
    {
        wcscpy_s(pszServerPath, L"LDAP://");
        wcscat_s(pszServerPath, pszDC);
        wcscat_s(pszServerPath, L"/");
    }
    else
    {
        wcscpy_s(pszServerPath, L"LDAP://");
    }

    // Allocate the DS path string buffer.
    pszDSPath = new WCHAR[wcslen(pszServerPath) + 7 + 1];
    if(!pszDSPath)
    {
        wprintf(L"failed to allocate memory");
        hr = E_OUTOFMEMORY;
        goto cleanup;
    }

    // Bind to the root DSE.
    wcscpy_s(pszDSPath, pszServerPath);
    wcscat_s(pszDSPath, L"rootDSE");
    hr = ADsOpenObject(pszDSPath,
                    NULL,
                    NULL,
                    ADS_SECURE_AUTHENTICATION,
                    IID_IADs,
                    (void**)&pRootDSE);
    if (FAILED(hr))
    {
        wprintf(L"failed to bind to root: 0x%x\n", hr);
        goto cleanup;
    }

    // Get the name of the DC connected to.
    hr = pRootDSE->Get(CComBSTR("DnsHostName"), &var);
    if (FAILED(hr))
    {
        wprintf(L"failed to get DnsHostName: 0x%x\n", hr);
        goto cleanup;
    }

    // Compare it to the DC name from the previous USN sync operation.
    // If not the same, perform a full synchronization.
    if (_wcsicmp(pszDC, var.bstrVal) != 0)
    {
        bUpdate = FALSE;
        // This prevents a full sync being performed
        // EVERY time
        wcscpy_s( pszDC, var.bstrVal );

        // Reallocate the string buffer.
        delete[] pszServerPath;
        pszServerPath = new WCHAR[7 + wcslen(var.bstrVal) + 1 + 1];
        if(!pszServerPath)
        {
            wprintf(L"failed to allocate memory");
            hr = E_OUTOFMEMORY;
            goto cleanup;
        }

        // Use the DC name in the bind string prefix.
        wcscpy_s(pszServerPath, L"LDAP://");
        wcscat_s(pszServerPath, var.bstrVal);
        wcscat_s(pszServerPath, L"/");
    }

    // Bind to the DC service object to get the invocationID.
    // The dsServiceName property of root DSE contains the distinguished
    // name of this DC service object.
    VariantClear(&var);
    hr = pRootDSE->Get(CComBSTR("dsServiceName"), &var);
    if (FAILED(hr))
    {
        wprintf(L"failed to get \"dsServiceName\"\n");
        goto cleanup;
    }

    // Reallocate the DS path buffer.
    delete[] pszDSPath;
    pszDSPath = new WCHAR[wcslen(pszServerPath) + wcslen(var.bstrVal) + 1];
    if(!pszDSPath)
    {
        wprintf(L"failed to allocate memory");
        hr = E_OUTOFMEMORY;
        goto cleanup;
    }

    wcscpy_s(pszDSPath, pszServerPath);
    wcscat_s(pszDSPath, var.bstrVal);
    hr = ADsOpenObject(pszDSPath,
                    NULL,
                    NULL,
                    ADS_SECURE_AUTHENTICATION,
                    IID_IADs,
                    (void**)&pDCService);
    VariantClear(&var);
    if (FAILED(hr))
    {
        wprintf(L"failed to bind to the DC service object: 0x%x\n", hr);
        goto cleanup;
    }

    // Get the invocationID GUID from the service object.
    hr = pDCService->Get(CComBSTR("invocationID"), &var);
    if (FAILED(hr))
    {
        wprintf(L"failed to get \"invocationID\"\n");
        goto cleanup;
    }

    hr = SafeArrayAccessData((SAFEARRAY*)(var.pparray), (void HUGEP* FAR*)&pArray);
    if (FAILED(hr))
    {
        wprintf(L"failed to get hugep: 0x%x\n", hr);
        goto cleanup;
    }

    BuildGUIDString(szGUID, (LPBYTE)pArray);
    VariantClear(&var);

    // Compare the invocationID GUID to the GUID string from the previous
    // synchronization. If not the same, this is a different DC or the DC
    // was restored from backup; perform a full synchronization.
    if (_wcsicmp(szGUID, pszPrevInvocationID)!=0)
    {
        bUpdate = FALSE;
        wcscpy_s(pszPrevInvocationID, szGUID);  // Save the invocationID GUID.
    }

    // If previous high USN is an empty string, handle this as a full synchronization.
    bUpdate = (pszPrevHighUSN[0] != '\0');

    // Set the lower bound USN to zero if this is a full synchronization.
    // Otherwise, set it to the previous high USN plus one.
    if (bUpdate == FALSE)
    {
        iLowerBoundUSN = 0;
    }
    else
    {
        iLowerBoundUSN = _wtoi64(pszPrevHighUSN) + 1; // Convert the string to an integer.
    }

    // Get and save the current high USN.
    hr = pRootDSE->Get(CComBSTR("highestCommittedUSN"), &var);
    if (FAILED(hr))
    {
        wprintf(L"failed to get \"highestCommittedUSN\"\n");
        goto cleanup;
    }

    wcscpy_s(pszPrevHighUSN, var.bstrVal);
    wprintf(L"current highestCommittedUSN: %s\n", pszPrevHighUSN);
    VariantClear(&var);

    // Reallocate the DS path buffer.
    delete[] pszDSPath;
    pszDSPath = new WCHAR[wcslen(pszServerPath) + wcslen(pszSearchBaseDN) + 1];
    if(!pszDSPath)
    {
        wprintf(L"failed to allocate memory");
        hr = E_OUTOFMEMORY;
        goto cleanup;
    }

    // Get an IDirectorySearch pointer to the base of the search.
    wcscpy_s(pszDSPath, pszServerPath);
    wcscat_s(pszDSPath, pszSearchBaseDN);
    hr = ADsOpenObject(pszDSPath,
                    NULL,
                    NULL,
                    ADS_SECURE_AUTHENTICATION,
                    IID_IDirectorySearch,
                    (void**)&pSearch);
    if (FAILED(hr))
    {
        wprintf(L"failed to get IDirectorySearch: 0x%x\n", hr);
        goto cleanup;
    }

    // Set up the scope and page size search preferences.
    arSearchPrefs [0].dwSearchPref = ADS_SEARCHPREF_SEARCH_SCOPE;
    arSearchPrefs [0].vValue.dwType = ADSTYPE_INTEGER;
    arSearchPrefs [0].vValue.Integer = ulScope;

    arSearchPrefs [1].dwSearchPref = ADS_SEARCHPREF_PAGESIZE;
    arSearchPrefs [1].vValue.dwType = ADSTYPE_INTEGER;
    arSearchPrefs [1].vValue.Integer = 100;

    hr = pSearch->SetSearchPreference(arSearchPrefs, 2);
    if (FAILED(hr))
    {
        wprintf(L"failed to set search prefs: 0x%x\n", hr);
        goto cleanup;
    }

    // The search filter specifies the objects to monitor
    // and the USNChanged value to exceed.
    swprintf_s(szSearchFilter,

L"(&(objectClass=user)(objectCategory=person)(uSNChanged>=%I64d))",
            iLowerBoundUSN );

    // Search for the objects indicated by the search filter.
    hr = pSearch->ExecuteSearch(szSearchFilter,
                        pAttributeNames, dwAttributes, &hSearch );
    if (FAILED(hr))
    {
        wprintf(L"failed to set execute search: 0x%x\n", hr);
        goto cleanup;
    }

    // Loop through the rows of the search result. Each row is an object
    // with USNChanged greater than or equal to the specified value.
    hr = pSearch->GetNextRow(hSearch);
    while ( SUCCEEDED(hr) && hr != S_ADS_NOMORE_ROWS )
    {
        ZeroMemory(&userdata, sizeof(MYUSERDATA));

        // Get the distinguishedName.
        hr = pSearch->GetColumn(hSearch, L"distinguishedName", &col);
        if ( SUCCEEDED(hr) )
        {
            if (col.dwADsType == ADSTYPE_DN_STRING && col.pADsValues)
            {
                wcscpy_s(userdata.distinguishedName,
col.pADsValues->DNString);
            }

            pSearch->FreeColumn( &col );
        }

        // Get the telephone number.
        hr = pSearch->GetColumn( hSearch, L"telephoneNumber", &col );
        if ( SUCCEEDED(hr) )
        {
            if (col.dwADsType == ADSTYPE_CASE_IGNORE_STRING &&
col.pADsValues)
            {
                wcscpy_s(userdata.phoneNumber, col.pADsValues->CaseIgnoreString);
            }

            pSearch->FreeColumn( &col );
        }

        // Get the objectGUID.
        hr = pSearch->GetColumn( hSearch, L"objectGUID", &col );
        if ( SUCCEEDED(hr) )
        {
            if ((col.dwADsType == ADSTYPE_OCTET_STRING) && col.pADsValues &&
                (col.pADsValues->OctetString.lpValue))
            {
                BuildGUIDString(szGUID, (LPBYTE) col.pADsValues->OctetString.lpValue);
                wcscpy_s(userdata.objectGUID, szGUID);
            }

            pSearch->FreeColumn( &col );
        }

        // Write the data from Active Directory to the secondary storage.
        WriteObjectDataToStorage(&userdata, bUpdate);
        dwCount++;
        hr = pSearch->GetNextRow( hSearch);
    }

    wprintf(L"dwCount: %d\n", dwCount);

    // If this is a full synchronization, the operation is complete.
    if (!bUpdate)
    {
        goto cleanup;
    }

    // If it is an update, search for deleted objects.

    // Release the search handle and pointer to reuse them.
    wprintf(L"Searching for deleted objects\n");
    if (hSearch)
    {
        pSearch->CloseSearchHandle(hSearch);
        hSearch = NULL;
    }
    if (pSearch)
    {
        pSearch->Release();
        pSearch = NULL;
    }

    // Bind to the Deleted Objects container.
    hr = pRootDSE->Get(CComBSTR("defaultNamingContext"), &var);
    if (FAILED(hr))
    {
        wprintf(L"failed to get \"defaultNamingContext\"\n");
        goto cleanup;
    }

    LPWSTR pwszFilter = L"%s<WKGUID=%s,%s>";

    // Reallocate the DS path buffer.
    delete[] pszDSPath;
    pszDSPath = new WCHAR[  wcslen(pwszFilter) +
                            wcslen(pszServerPath) +
                            wcslen(GUID_DELETED_OBJECTS_CONTAINER_W) +
                            wcslen(var.bstrVal) +
                            1];
    if(!pszDSPath)
    {
        wprintf(L"failed to allocate memory");
        hr = E_OUTOFMEMORY;
        goto cleanup;
    }

    swprintf_s(   pszDSPath, pwszFilter,
                pszServerPath,
                GUID_DELETED_OBJECTS_CONTAINER_W,
                var.bstrVal);
    VariantClear(&var);

    hr = ADsOpenObject(pszDSPath,
                    NULL,
                    NULL,
                    ADS_SECURE_AUTHENTICATION | ADS_FAST_BIND,
                    IID_IDirectorySearch,
                    (void**)&pSearch);
    if (FAILED(hr))
    {
        wprintf(L"failed to get IDirectorySearch: 0x%x\n", hr);
        goto cleanup;
    }

    // Specify the scope, pagesize, and tombstone search preferences.
    arSearchPrefs[0].dwSearchPref = ADS_SEARCHPREF_SEARCH_SCOPE;
    arSearchPrefs[0].vValue.dwType = ADSTYPE_INTEGER;
    arSearchPrefs[0].vValue.Integer = ADS_SCOPE_SUBTREE;

    arSearchPrefs[1].dwSearchPref = ADS_SEARCHPREF_PAGESIZE;
    arSearchPrefs[1].vValue.dwType = ADSTYPE_INTEGER;
    arSearchPrefs[1].vValue.Integer = 100;

    arSearchPrefs[2].dwSearchPref = ADS_SEARCHPREF_TOMBSTONE;
    arSearchPrefs[2].vValue.dwType = ADSTYPE_BOOLEAN;
    arSearchPrefs[2].vValue.Boolean = TRUE;

    hr = pSearch->SetSearchPreference(arSearchPrefs, 3);
    if (FAILED(hr))
    {
        wprintf(L"failed to set search prefs: 0x%x\n", hr);
        goto cleanup;
    }

    // Set up the search filter.
    swprintf_s(szSearchFilter,
            L"(&(isDeleted=TRUE)(uSNChanged>=%I64d))",
            iLowerBoundUSN );

    // Execute the search.
    hr = pSearch->ExecuteSearch(szSearchFilter,
                        pAttributeNames, dwAttributes, &hSearch );
    if (FAILED(hr))
    {
        wprintf(L"failed to set execute search: 0x%x\n", hr);
        goto cleanup;
    }
    wprintf(L"Started search for deleted objects.\n");

    // Loop through the rows of the search result.
    // Each row is an object deleted since the previous call.
    dwCount = 0;
    hr = pSearch->GetNextRow(hSearch);
    while ( SUCCEEDED(hr) && hr != S_ADS_NOMORE_ROWS )
    {
        ZeroMemory(&userdata, sizeof(MYUSERDATA) );

        // Get the distinguishedName.
        hr = pSearch->GetColumn(hSearch, L"distinguishedName", &col);
        if ( SUCCEEDED(hr) )
        {
            if (col.dwADsType == ADSTYPE_DN_STRING && col.pADsValues)
            {
                wcscpy_s(userdata.distinguishedName,
col.pADsValues->DNString);
            }

            pSearch->FreeColumn( &col );
        }

        // Get the objectGUID number.
        hr = pSearch->GetColumn( hSearch, L"objectGUID", &col );
        if ( SUCCEEDED(hr) )
        {
            if ((col.dwADsType == ADSTYPE_OCTET_STRING) && col.pADsValues &&
                (col.pADsValues->OctetString.lpValue))
            {
                BuildGUIDString(szGUID, (LPBYTE) col.pADsValues->OctetString.lpValue);
                wcscpy_s(userdata.objectGUID, szGUID);
            }

            pSearch->FreeColumn( &col );
        }

        // If the objectGUID of a deleted object matches an objectGUID in
        // the secondary storage, delete the object from storage.
        DeleteObjectDataFromStorage(&userdata);
        dwCount++;
        hr = pSearch->GetNextRow(hSearch);
    }

    wprintf(L"deleted dwCount: %d\n", dwCount);

cleanup:

    if (pszServerPath)
      {
        delete[] pszServerPath;
            pszServerPath = NULL;
      }
    if (pszDSPath)
      {
        delete[] pszDSPath;
            pszDSPath = NULL;
      }
    if (pRootDSE)
      {
        pRootDSE->Release();
            pRootDSE = NULL;
      }
    if (pDCService)
      {
        pDCService->Release();
            pDCService = NULL;
      }
    if (pDeletedObj)
      {
        pDeletedObj->Release();
            pDeletedObj = NULL;
      }
    if (hSearch)
      {
        pSearch->CloseSearchHandle(hSearch);
            hSearch = NULL;
      }
    if (pSearch)
      {
        pSearch->Release();
            pSearch = NULL;
      }
    VariantClear(&var);

    return hr;
}

//********************************************************************
// DeleteObjectDataFromStorage routine
//********************************************************************
VOID DeleteObjectDataFromStorage(PMYUSERDATA pUserData) {
    wprintf(L"DELETED OBJECT:\n");
    wprintf(L"   objectGUID: %s\n", pUserData->objectGUID);
    wprintf(L"   distinguishedName: %s\n", pUserData->distinguishedName);
    wprintf(L"---------------------------------------------\n");

    return;
}

//********************************************************************
// WriteObjectDataToStorage routine
//********************************************************************
VOID WriteObjectDataToStorage(PMYUSERDATA pUserData, BOOL bUpdate) {
    if (bUpdate)
    {
        wprintf(L"UPDATE:\n");
    }
    else
    {
        wprintf(L"INITIAL DATA:\n");
    }

    wprintf(L"   objectGUID: %s\n", pUserData->objectGUID);
    wprintf(L"   distinguishedName: %s\n", pUserData->distinguishedName);
    wprintf(L"   phoneNumber: %s\n", pUserData->phoneNumber);
    wprintf(L"---------------------------------------------\n");

    return;
}

//********************************************************************
// WriteSyncParamsToStorage routine
// This example caches the parameters in the registry. In a real // synchronization application, store the parameters in the same // storage that you are keeping consistent with Active Directory.
// This ensures that the parameters and object data remain synchronized // if the storage is ever restored from a backup.
//********************************************************************
DWORD WriteSyncParamsToStorage(
    LPWSTR pszPrevInvocationID, // Receives invocation ID
    LPWSTR pszPrevHighUSN,      // Receives previous high USN
    LPWSTR pszDCName)           // Receives name of DC to bind to
{
    HKEY hReg = NULL;
    DWORD dwStat = NO_ERROR;

    // Create a registry key under
    // HKEY_CURRENT_USER\SOFTWARE\Vendor\Product.
    dwStat = RegCreateKeyExW(HKEY_CURRENT_USER,
        L"Software\\Microsoft\\Windows 2000 AD-Synchro-USN",
        0,
        NULL,
        REG_OPTION_NON_VOLATILE,
        KEY_WRITE,
        NULL,
        &hReg,
        NULL);
    if (NO_ERROR == dwStat)
    {
        // Cache the invocationID as a value under the registry key.
        dwStat = RegSetValueExW(hReg,
            L"InvocationID",
            0,
            REG_SZ,
            (LPBYTE)pszPrevInvocationID,
            (lstrlenW(pszPrevInvocationID) + 1) * sizeof(WCHAR));

        // Cache the previous high USN as a value under the registry key.
        dwStat = RegSetValueExW(hReg,
            L"PreviousHighUSN",
            0,
            REG_SZ,
            (LPBYTE)pszPrevHighUSN,
            (lstrlenW(pszPrevHighUSN) + 1) * sizeof(WCHAR));

        // Cache the DC name as a value under the registry key.
        dwStat = RegSetValueExW(hReg,
            L"DC name",
            0,
            REG_SZ,
            (LPBYTE)pszDCName,
            (lstrlenW(pszDCName) + 1) * sizeof(WCHAR));

        RegCloseKey(hReg);
    }

    return dwStat;
}

//********************************************************************
// GetSyncParamsFromStorage routine
// This example reads the parameters from the registry. In a real // synchronization application, store the parameters in the // same storage that you are keeping consistent with Active Directory.
//********************************************************************
DWORD GetSyncParamsFromStorage(
    LPWSTR pszPrevInvocationID, // Receives invocation ID
    DWORD dwPrevInvocationSize, // size of the buffer, in WCHARS
    LPWSTR pszPreviousHighUSN,  // Receives previous high USN
    DWORD dwPrevHighUSNSize,    // size of the buffer, in WCHARS
    LPWSTR pszDCName,           // Receives name of DC to bind to
    DWORD dwDCNameSize)         // size of the buffer, in WCHARS
{
    HKEY hReg = NULL;
    DWORD dwStat;

    // Open the registry key.
    dwStat = RegOpenKeyExW(
                HKEY_CURRENT_USER,
                L"Software\\Microsoft\\Windows 2000 AD-Synchro-USN",
                0,
                KEY_QUERY_VALUE,
                &hReg);
    if (NO_ERROR == dwStat)
    {
        // Get the previous invocationID from the registry.
        dwPrevInvocationSize = dwPrevInvocationSize * sizeof(WCHAR);
        dwStat = RegQueryValueExW(hReg,
            L"InvocationID",
            NULL,
            NULL,
            (LPBYTE)pszPrevInvocationID,
            &dwPrevInvocationSize);
        if (dwStat != NO_ERROR)
        {
            wprintf(L"RegQueryValueEx failed to get invocationID: 0x%x\n", dwStat);
        }

        // Get the previous high USN from the registry.
        dwPrevHighUSNSize = dwPrevHighUSNSize * sizeof(WCHAR);
        dwStat = RegQueryValueExW(hReg,
            L"PreviousHighUSN",
            NULL,
            NULL,
            (LPBYTE)pszPreviousHighUSN,
            &dwPrevHighUSNSize);
        if (dwStat != NO_ERROR)
        {
            wprintf(L"RegQueryValueEx failed to get previous high USN:
0x%x\n", dwStat);
        }

        // Get the DC name from the registry.
        dwDCNameSize = dwDCNameSize * sizeof(WCHAR);
        dwStat = RegQueryValueExW(hReg,
            L"DC name",
            NULL,
            NULL,
            (LPBYTE)pszDCName,
            &dwDCNameSize);
        if (dwStat != NO_ERROR)
        {
            wprintf(L"RegQueryValueEx failed to get DC name: 0x%x\n", dwStat);
        }

        RegCloseKey(hReg);
    }

    return dwStat;
}

//********************************************************************
// BuildGUIDString
// Routine that makes the GUID a string in directory service bind form.
//********************************************************************
VOID BuildGUIDString(WCHAR *szGUID, LPBYTE pGUID) {
    DWORD i;
    DWORD dwlen = sizeof(GUID);
    WCHAR buf[4];

    wcscpy_s(szGUID, L"");
    for(i = 0; i < dwlen; i++)
    {
        swprintf_s(buf, L"%02x", pGUID[i]);
        wcscat_s(szGUID, buf);
    }
}

//********************************************************************
// Main
//********************************************************************
int main(int argc, char* argv[])
{
    DWORD dwStat;
    HRESULT hr;

    // Attributes to retrieve
    LPWSTR szAttribs[] =
    {
        {L"telephoneNumber"},
        {L"distinguishedName"},
        {L"uSNChanged"},
        {L"objectGUID"},
        {L"isDeleted"}
    };
    LPWSTR *pszAttribs=szAttribs;
    DWORD dwAttribs = sizeof(szAttribs)/sizeof(LPWSTR);

    // DC properties to cache for next synchronization.
    WCHAR szPrevInvocationID[40];
    WCHAR szPrevHighUSN[40];
    WCHAR szDCName[MAX_PATH];

    CoInitialize(NULL);

    if (argc > 1)
    {
        // Perform a full synchronization.
        // Initialize synchronization parameters to empty strings.
        wprintf(L"Performing a full read.\n");
        szPrevInvocationID[0] = '\0';
        szPrevHighUSN[0] = '\0';
        szDCName[0] = '\0';
    }
    else
    {
        // Perform a synchronization update.
        // Initialize synchronization parameters from storage.
        wprintf(L"Retrieving changes only.\n");
        dwStat = GetSyncParamsFromStorage(
            szPrevInvocationID,
            ARRAYSIZE(szPrevInvocationID),
            szPrevHighUSN,
            ARRAYSIZE(szPrevHighUSN),
            szDCName,
            ARRAYSIZE(szDCName));
        if (dwStat != NO_ERROR)
        {
            wprintf(L"Could not get synchronization parameters: %u\n", dwStat);
            goto cleanup;
        }
    }

    // Perform the search and update the synchronization parameters.
    hr = DoUSNSyncSearch(L"OU=UK,DC=xapac,DC=xnet,DC=intra",
                        ADS_SCOPE_SUBTREE,
                        pszAttribs, dwAttribs,
                        szPrevInvocationID, szPrevHighUSN, szDCName);
    if (FAILED(hr))
    {
        wprintf(L"DoUSNSyncSearch failed: 0x%x\n", hr);
        goto cleanup;
    }

    // Cache the synchronization parameters in storage for the next synchronization.
    wprintf(L"Caching the synchronization parameters.\n");
    dwStat = WriteSyncParamsToStorage(
                szPrevInvocationID, szPrevHighUSN, szDCName);
    if (dwStat != NO_ERROR)
    {
        wprintf(L"Error caching the synchronization parameters: %u\n", dwStat);
        goto cleanup;
    }

cleanup:

    CoUninitialize();

    return 1;
}