C++ ContextMap::GetContext方法代码示例

/**
 *  This method is called when we receive a WPD_COMMAND_OBJECT_RESOURCES_READ
 *  command.
 *
 *  The parameters sent to us are:
 *  - WPD_PROPERTY_OBJECT_RESOURCES_CONTEXT: the context the driver returned to
 *      the client in OnOpenResource.
 *  - WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_TO_READ: the number of bytes to
 *      read from the resource.
 *
 *  The driver should:
 *  - Read data associated with the resource and return it back to the caller in
 *      WPD_PROPERTY_OBJECT_RESOURCES_DATA.
 *  - Report the number of bytes actually read from the resource in
 *      WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_READ.  This number may be smaller
 *      than WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_TO_READ when reading the last
 *      chunk of data from the resource.
 */
HRESULT WpdObjectResources::OnReadResource(
    _In_ IPortableDeviceValues*  pParams,
    _In_ IPortableDeviceValues*  pResults)
{
    HRESULT                   hr                 = S_OK;
    LPWSTR                    wszResourceContext = NULL;
    DWORD                     dwNumBytesToRead   = 0;
    DWORD                     dwNumBytesRead     = 0;
    BYTE*                     pBuffer            = NULL;
    DWORD                     cbBuffer           = 0;
    WpdObjectResourceContext* pResourceContext   = NULL;
    ContextMap*               pContextMap        = NULL;

    // Get the enumeration context identifier for this enumeration operation.  We will
    // need this to lookup the specific enumeration context in the client context map.
    hr = pParams->GetStringValue(WPD_PROPERTY_OBJECT_RESOURCES_CONTEXT, &wszResourceContext);
    if (hr != S_OK)
    {
        hr = E_INVALIDARG;
        CHECK_HR(hr, "Missing value for WPD_PROPERTY_OBJECT_RESOURCES_CONTEXT");
    }

    // Get the number of bytes to read
    if (hr == S_OK)
    {
        hr = pParams->GetUnsignedIntegerValue(WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_TO_READ, &dwNumBytesToRead);
        CHECK_HR(hr, "Missing value for WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_TO_READ");
    }

    // Get the destination buffer
    if (hr == S_OK)
    {
        hr = pParams->GetBufferValue(WPD_PROPERTY_OBJECT_RESOURCES_DATA, &pBuffer, &cbBuffer);
        CHECK_HR(hr, "Missing value for WPD_PROPERTY_OBJECT_RESOURCES_DATA");
    }

    // Get the client context map so we can retrieve the resource context for this resource
    // operation using the WPD_PROPERTY_OBJECT_RESOURCES_CONTEXT property value obtained above.
    if (hr == S_OK)
    {
        hr = pParams->GetIUnknownValue(PRIVATE_SAMPLE_DRIVER_CLIENT_CONTEXT_MAP, (IUnknown**)&pContextMap);
        CHECK_HR(hr, "Failed to get PRIVATE_SAMPLE_DRIVER_CLIENT_CONTEXT_MAP");
    }

    if (hr == S_OK)
    {
        pResourceContext = (WpdObjectResourceContext*)pContextMap->GetContext(wszResourceContext);
        if (pResourceContext == NULL)
        {
            hr = E_INVALIDARG;
            CHECK_HR(hr, "Missing resource context");
        }
    }

    // Read the next chunk of data for this request
    if (hr == S_OK && pBuffer != NULL)
    {
        hr = ReadDataFromResource(pResourceContext, pBuffer, dwNumBytesToRead, &dwNumBytesRead);
        CHECK_HR(hr, "Failed to read %d bytes from resource", dwNumBytesToRead);
    }

    if (hr == S_OK && pBuffer != NULL)
    {
        hr = pResults->SetBufferValue(WPD_PROPERTY_OBJECT_RESOURCES_DATA, pBuffer, dwNumBytesRead);
        CHECK_HR(hr, "Failed to set WPD_PROPERTY_OBJECT_RESOURCES_DATA");
    }

    if (hr == S_OK)
    {
        hr = pResults->SetUnsignedIntegerValue(WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_READ, dwNumBytesRead);
        CHECK_HR(hr, "Failed to set WPD_PROPERTY_OBJECT_RESOURCES_NUM_BYTES_READ");
    }

    // Free the memory.  CoTaskMemFree ignores NULLs so no need to check.
    CoTaskMemFree(wszResourceContext);

    // Free the memory.  CoTaskMemFree ignores NULLs so no need to check.
    CoTaskMemFree(pBuffer);

    SAFE_RELEASE(pContextMap);

    return hr;
//.........这里部分代码省略.........

HRESULT WpdObjectEnumerator::OnFindNext(IPortableDeviceValues*  pParams,
                                            IPortableDeviceValues*  pResults)
{
    HRESULT                     hr                    = S_OK;
    LPWSTR                      wszEnumContext        = NULL;
    DWORD                       dwNumObjectsRequested = 0;
    ContextMap*                 pContextMap           = NULL;
    WpdObjectEnumeratorContext* pEnumeratorContext    = NULL;
    DWORD                       NumObjectsEnumerated  = 0;

    CComPtr<IPortableDevicePropVariantCollection> pObjectIDCollection;

    // First get ALL parameters for this command.  If we cannot get ALL parameters
    // then E_INVALIDARG should be returned and no further processing should occur.

    // Get the enumeration context identifier for this enumeration operation.
    // The enumeration context identifier is needed to lookup the specific
    // enumeration context in the client context map for this enumeration operation.
    // NOTE that more than one enumeration may be in progress.
    hr = pParams->GetStringValue(WPD_PROPERTY_OBJECT_ENUMERATION_CONTEXT, &wszEnumContext);
    if (hr != S_OK)
    {
        hr = E_INVALIDARG;
        CHECK_HR(hr, "Missing value for WPD_PROPERTY_OBJECT_ENUMERATION_CONTEXT");
    }

    // Get the number of objects requested for this enumeration call.
    // The driver should always attempt to meet this requested value.
    // If there are fewer children than requested, the driver should return the remaining
    // children and a return code of S_FALSE.
    hr = pParams->GetUnsignedIntegerValue(WPD_PROPERTY_OBJECT_ENUMERATION_NUM_OBJECTS_REQUESTED, &dwNumObjectsRequested);
    if (hr != S_OK)
    {
        hr = E_INVALIDARG;
        CHECK_HR(hr, "Missing value for WPD_PROPERTY_OBJECT_ENUMERATION_NUM_OBJECTS_REQUESTED");
    }

    // Get the client context map so we can retrieve the enumeration context for this enumeration
    // operation.
    if (hr == S_OK)
    {
        hr = pParams->GetIUnknownValue(PRIVATE_SAMPLE_DRIVER_CLIENT_CONTEXT_MAP, (IUnknown**)&pContextMap);
        CHECK_HR(hr, "Failed to get PRIVATE_SAMPLE_DRIVER_CLIENT_CONTEXT_MAP");
    }

    if (hr == S_OK)
    {
        pEnumeratorContext = (WpdObjectEnumeratorContext*)pContextMap->GetContext(wszEnumContext);
        if (pEnumeratorContext == NULL)
        {
            hr = E_INVALIDARG;
            CHECK_HR(hr, "Missing enumeration context");
        }
    }

    // CoCreate a collection to store the object identifiers being returned for this enumeration call.
    if (hr == S_OK)
    {
        hr = CoCreateInstance(CLSID_PortableDevicePropVariantCollection,
                              NULL,
                              CLSCTX_INPROC_SERVER,
                              IID_IPortableDevicePropVariantCollection,
                              (VOID**) &pObjectIDCollection);
        CHECK_HR(hr, "Failed to CoCreate CLSID_PortableDevicePropVariantCollection");
    }

    // If the enumeration context reports that their are more objects to return, then continue, if not,
    // return an empty results set.
    if ((hr == S_OK) && (pEnumeratorContext != NULL) && (pEnumeratorContext->HasMoreChildrenToEnumerate() == TRUE))
    {
        if (pEnumeratorContext->m_strParentObjectID.CompareNoCase(L"") == 0)
        {
            // We are being asked for the WPD_DEVICE_OBJECT_ID
            hr = AddStringValueToPropVariantCollection(pObjectIDCollection, WPD_DEVICE_OBJECT_ID);
            CHECK_HR(hr, "Failed to add 'DEVICE' object ID to enumeration collection");

            // Update the the number of children we are returning for this enumeration call
            NumObjectsEnumerated++;
        }
        else if (pEnumeratorContext->m_strParentObjectID.CompareNoCase(WPD_DEVICE_OBJECT_ID) == 0)
        {
    
            // We are being asked for direct children of the WPD_DEVICE_OBJECT_ID
            switch (m_pBaseDriver->m_SensorType)
            {
                case WpdBaseDriver::UNKNOWN:
                    hr = AddStringValueToPropVariantCollection(pObjectIDCollection, SENSOR_OBJECT_ID);
                    break;
                case WpdBaseDriver::COMPASS:
                    hr = AddStringValueToPropVariantCollection(pObjectIDCollection, COMPASS_SENSOR_OBJECT_ID);
                    break;
                case WpdBaseDriver::SENSIRON:
                    hr = AddStringValueToPropVariantCollection(pObjectIDCollection, TEMP_SENSOR_OBJECT_ID);
                    break;
                case WpdBaseDriver::FLEX:
                    hr = AddStringValueToPropVariantCollection(pObjectIDCollection, FLEX_SENSOR_OBJECT_ID);
                    break;
                case WpdBaseDriver::PING:
                    hr = AddStringValueToPropVariantCollection(pObjectIDCollection, PING_SENSOR_OBJECT_ID);
                    break;
//.........这里部分代码省略.........