Adding a Resource to an Object
In addition to transferring objects to a device, it's also possible to add resources to objects. For example, an application could add a photo to existing information for a given contact.
Resources are added using the interfaces described in the following table.
| Interface | Description |
|---|---|
| IPortableDeviceContent Interface | Provides access to the content-specific methods. |
| IPortableDeviceResources Interface | Used when writing the resource properties and data to the device. |
| IPortableDeviceValues Interface | Used to write properties that describe the resource. |
| IStream Interface | Used to simplify writing the resource to the device. |
The CreateContactPhotoResourceOnDevice function in the sample application's ContentTransfer.cpp module demonstrates how an application could add a photo resource to a contact object. This function prompts the user for the object identifier of the contact on the device, to which the photo resource will be added. Then it displays a FileOpen dialog box so that the user can select the image to be added. Once this data is collected, the application writes the resource to the device.
The first task accomplished by the CreateContactPhotoResourceOnDevice function is to prompt the user to enter an object identifier for the contact to which the photo will be added.
HRESULT hr = S_OK;
WCHAR wszSelection[81] = {0};
WCHAR wszFilePath[MAX_PATH] = {0};
DWORD cbOptimalTransferSize = 0;
CComPtr<IStream> pFileStream;
CComPtr<IStream> pResourceStream;
CComPtr<IPortableDeviceValues> pResourceAttributes;
CComPtr<IPortableDeviceContent> pContent;
CComPtr<IPortableDeviceResources> pResources;
printf("Enter the identifer of the object to which we will add an Audio annotation.\n>");
hr = StringCbGetsW(wszSelection,sizeof(wszSelection));
if (FAILED(hr))
{
printf("An invalid object identifier was specified, aborting resource creation\n");
}do
The next step is the retrieval of an IPortableDeviceContent object, which in turn is used to obtain an IPortableDeviceResources object. (The application uses this latter object to create and write the new resource.)
HRESULT hr = S_OK;
WCHAR wszSelection[81] = {0};
WCHAR wszFilePath[MAX_PATH] = {0};
DWORD cbOptimalTransferSize = 0;
CComPtr<IStream> pFileStream;
CComPtr<IStream> pResourceStream;
CComPtr<IPortableDeviceValues> pResourceAttributes;
CComPtr<IPortableDeviceContent> pContent;
CComPtr<IPortableDeviceResources> pResources;
if (SUCCEEDED(hr))
{
hr = pDevice->Content(&pContent);
if (FAILED(hr))
{
printf("! Failed to get IPortableDeviceContent from IPortableDevice, hr = 0x%lx\n",hr);
}
}
if (SUCCEEDED(hr))
{
hr = pContent->Transfer(&pResources);
if (FAILED(hr))
{
printf("! Failed to get IPortableDeviceResources from IPortableDeviceContent, hr = 0x%lx\n",hr);
}
}
After this, the sample displays the FileOpen dialog box, which allows the user to specify the name of the image file that contains the photo they want to add to the contact information.
HRESULT hr = S_OK;
WCHAR wszSelection[81] = {0};
WCHAR wszFilePath[MAX_PATH] = {0};
DWORD cbOptimalTransferSize = 0;
CComPtr<IStream> pFileStream;
CComPtr<IStream> pResourceStream;
CComPtr<IPortableDeviceValues> pResourceAttributes;
CComPtr<IPortableDeviceContent> pContent;
CComPtr<IPortableDeviceResources> pResources;
if (SUCCEEDED(hr))
{
OPENFILENAME OpenFileNameInfo = {0};
OpenFileNameInfo.lStructSize = sizeof(OPENFILENAME);
OpenFileNameInfo.hwndOwner = NULL;
OpenFileNameInfo.lpstrFile = wszFilePath;
OpenFileNameInfo.nMaxFile = ARRAYSIZE(wszFilePath);
OpenFileNameInfo.lpstrFilter = L"JPEG (*.JPG)\0*.JPG\0JPEG (*.JPEG)\0*.JPEG\0JPG (*.JPE)\0*.JPE\0JPG (*.JFIF)\0*.JFIF\0\0";;
OpenFileNameInfo.nFilterIndex = 1;
OpenFileNameInfo.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
OpenFileNameInfo.lpstrDefExt = L"JPG";
if (GetOpenFileName(&OpenFileNameInfo) == FALSE)
{
printf("The transfer operation was cancelled.\n");
hr = E_ABORT;
}
}
Once the sample has an IPortableDeviceResources object and the name of the image file, it does the following in preparation for actually transferring data to the device.
- It opens an IStream object on the selected file for read operations.
- It creates an IPortableDeviceValues object, which will contain information such as the image size and format.
HRESULT hr = S_OK;
WCHAR wszSelection[81] = {0};
WCHAR wszFilePath[MAX_PATH] = {0};
DWORD cbOptimalTransferSize = 0;
CComPtr<IStream> pFileStream;
CComPtr<IStream> pResourceStream;
CComPtr<IPortableDeviceValues> pResourceAttributes;
CComPtr<IPortableDeviceContent> pContent;
CComPtr<IPortableDeviceResources> pResources;
if (SUCCEEDED(hr))
{
// Open the selected file as an IStream. This will simplify reading the
// data and writing to the device.
hr = SHCreateStreamOnFile(wszFilePath, STGM_READ, &pFileStream);
if (SUCCEEDED(hr))
{
// CoCreate the IPortableDeviceValues to hold the resource attributes
hr = CoCreateInstance(CLSID_PortableDeviceValues,
NULL,
CLSCTX_INPROC_SERVER,
IID_IPortableDeviceValues,
(VOID**) &pResourceAttributes);
if (SUCCEEDED(hr))
{
// Fill in the necessary information regarding this resource
// Set the WPD_OBJECT_ID. This informs the driver which object this request is intended for.
hr = pResourceAttributes->SetStringValue(WPD_OBJECT_ID, wszSelection);
if (FAILED(hr))
{
printf("! Failed to set WPD_OBJECT_ID when creating a resource, hr = 0x%lx\n",hr);
}
// Set the WPD_RESOURCE_ATTRIBUTE_RESOURCE_KEY to WPD_RESOURCE_CONTACT_PHOTO
if (SUCCEEDED(hr))
{
hr = pResourceAttributes->SetKeyValue(WPD_RESOURCE_ATTRIBUTE_RESOURCE_KEY, WPD_RESOURCE_CONTACT_PHOTO);
if (FAILED(hr))
{
printf("! Failed to set WPD_RESOURCE_ATTRIBUTE_RESOURCE_KEY to WPD_RESOURCE_CONTACT_PHOTO, hr = 0x%lx\n",hr);
}
}
// Set the WPD_RESOURCE_ATTRIBUTE_TOTAL_SIZE by requesting the total size of the
// data stream.
if (SUCCEEDED(hr))
{
STATSTG statstg = {0};
hr = pFileStream->Stat(&statstg, STATFLAG_NONAME);
if (SUCCEEDED(hr))
{
hr = pResourceAttributes->SetUnsignedLargeIntegerValue(WPD_RESOURCE_ATTRIBUTE_TOTAL_SIZE, statstg.cbSize.QuadPart);
if (FAILED(hr))
{
printf("! Failed to set WPD_RESOURCE_ATTRIBUTE_TOTAL_SIZE, hr = 0x%lx\n",hr);
}
}
else
{
printf("! Failed to get file's total size, hr = 0x%lx\n",hr);
}
}
// Set the WPD_RESOURCE_ATTRIBUTE_FORMAT to WPD_OBJECT_FORMAT_JFIF because we are
// creating a contact photo resource with JPG image data.
if (SUCCEEDED(hr))
{
hr = pResourceAttributes->SetGuidValue(WPD_RESOURCE_ATTRIBUTE_FORMAT, WPD_OBJECT_FORMAT_JFIF);
if (FAILED(hr))
{
printf("! Failed to set WPD_RESOURCE_ATTRIBUTE_FORMAT to WPD_OBJECT_FORMAT_JFIF, hr = 0x%lx\n",hr);
}
}
}
}
if (FAILED(hr))
{
printf("! Failed to open file named (%ws) to transfer to device, hr = 0x%lx\n",wszFilePath, hr);
}
}
After preparing the IStream and IPortableDeviceValues objects for the write operation, the sample transfers the image to the device. The sample completes the transfer in three steps, as follows:
- It creates the resource on the device by calling the IPortableDeviceResources::CreateResource method.
- It calls a StreamCopy helper function to copy the source stream to the destination stream.
- It informs the device driver that the transfer is complete by calling the IPortableDeviceDataStream::Commit method.
HRESULT hr = S_OK;
WCHAR wszSelection[81] = {0};
WCHAR wszFilePath[MAX_PATH] = {0};
DWORD cbOptimalTransferSize = 0;
CComPtr<IStream> pFileStream;
CComPtr<IStream> pResourceStream;
CComPtr<IPortableDeviceValues> pResourceAttributes;
CComPtr<IPortableDeviceContent> pContent;
CComPtr<IPortableDeviceResources> pResources;
if (SUCCEEDED(hr))
{
hr = pResources->CreateResource(pResourceAttributes, // Properties describing this resource
&pResourceStream, // Returned resource data stream (to transfer the data to)
&cbOptimalTransferSize, // Returned optimal buffer size to use during transfer
NULL);
// Since we have IStream-compatible interfaces, call our helper function
// that copies the contents of a source stream into a destination stream.
if (SUCCEEDED(hr))
{
DWORD cbTotalBytesWritten = 0;
hr = StreamCopy(pResourceStream, // Destination (The resource to transfer to)
pFileStream, // Source (The File data to transfer from)
cbOptimalTransferSize, // The driver specified optimal transfer buffer size
&cbTotalBytesWritten); // The total number of bytes transferred from file to the device
if (FAILED(hr))
{
printf("! Failed to transfer object to device, hr = 0x%lx\n",hr);
}
}
else
{
printf("! Failed to get IStream (representing destination object data on the device) from IPortableDeviceContent, hr = 0x%lx\n",hr);
}
// After transferring content to the device, the client is responsible for letting the
// driver know that the transfer is complete by calling the Commit() method
// on the IPortableDeviceDataStream interface.
if (SUCCEEDED(hr))
{
hr = pResourceStream->Commit(0);
if (FAILED(hr))
{
printf("! Failed to commit resource to device, hr = 0x%lx\n",hr);
}
}
}
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