使用列舉物件

[從 Windows 8 和 Windows Server 2012 開始， 虛擬磁碟服務 COM 介面已由 Windows 記憶體管理 API 取代。

下列程式代碼範例示範呼叫端如何使用 IEnumVdsObject 介面搭配列舉對象運作。 請注意，列舉對象傳回的資訊是靜態的。 您必須再次查詢 物件，才能看到新的組態變更。

GetControllerById 函式會採用由 pSubsystem 參數指定的 IVdsSubSystem 介面，並查詢子系統中的控制器，然後逐一查看傳回的列舉，搜尋具有符合 pControllerId 參數所指定之 GUID 的控制器。 如果找到相符的控制器，則會由 ppController 參數連同 S_OK HRESULT 傳回。

//
// Simple macro to release non-null interfaces.
//
#include <windows.h>
#include "vds.h"
#include <stdio.h>

#define _SafeRelease(x) {if (NULL != x) { x->Release(); x = NULL; } }

HRESULT GetControllerById(
         IN IVdsSubSystem       *pSubsystem,
         IN CONST VDS_OBJECT_ID *pControllerId,
         OUT IVdsController     **ppController)
{
    VDS_CONTROLLER_PROP vdsControllerProperties;
    IEnumVdsObject      *pEnumController = NULL;
    IVdsController      *pController     = NULL;
    IUnknown            *pUnknown        = NULL;
    HRESULT             hResult          = S_OK;
    ULONG               ulFetched        = 0;
    BOOL                bDone            = FALSE;

    ZeroMemory(&vdsControllerProperties, sizeof(VDS_CONTROLLER_PROP));

    // Query for the enumeration of controllers belonging
    // to the given subsystem.
    hResult = pSubsystem->QueryControllers(&pEnumController);

    if (SUCCEEDED(hResult) && (!pEnumController)) 
    {
        hResult = E_UNEXPECTED; // Errant provider, 
        // returned S_OK 
        // with a NULL pointer.
    }

    if (SUCCEEDED(hResult)) 
    {
        // Enumerate through all the controllers this subsystem 
        // contains to find the controller of interest.
        while (!bDone) 
        {
            ulFetched = 0;
            hResult = pEnumController->Next(1, &pUnknown, &ulFetched);

            if (hResult == S_FALSE) 
            {
                hResult = E_INVALIDARG;
                break;
            }

            if (SUCCEEDED(hResult) && (!pUnknown)) 
            {
                hResult = E_UNEXPECTED; // Errant provider, 
                // returned S_OK with
                // a NULL pointer 
            }

            // Use an IVdsController interface to get the controller 
            // properties and check for the desired GUID.
            if (SUCCEEDED(hResult)) 
            {
                hResult = pUnknown->QueryInterface(IID_IVdsController,  
                    (void **) &pController);
            }

            if (SUCCEEDED(hResult) && (!pController)) 
            {
                hResult = E_UNEXPECTED; // Errant provider, 
                // returned S_OK 
                // with a NULL pointer
            }

            if (SUCCEEDED(hResult)) 
            {
                hResult = pController->  
                GetProperties( &vdsControllerProperties);
            }

            if (SUCCEEDED(hResult) 
                && IsEqualGUID(*pControllerId, vdsControllerProperties.id)) 
            {
                bDone = TRUE;
            } 
            else 
            {
                _SafeRelease(pController);
            }

            _SafeRelease(pUnknown);

            //Free the strings in the properties structure.
            if (NULL != vdsControllerProperties.pwszIdentification) 
            {
                CoTaskMemFree(vdsControllerProperties.pwszIdentification);
            }

            ZeroMemory(&vdsControllerProperties, sizeof(VDS_CONTROLLER_PROP));
        }
    }

    if (SUCCEEDED(hResult)) 
    {
        *ppController = pController;
    }

    _SafeRelease(pEnumController);
    return hResult;
}

相關主題

使用 VDS

協助程序物件

IEnumVdsObject

IVdsSubSystem