Example Code

Reading from a file without checking errors

This example function takes the URI of a file and displays the plaintext version of that content on screen. If anything goes wrong, for instance the file does not exist or there are no valid rights that allows the file to be displayed, the function leaves.

It is important to notice the call to ContentAccess::CData::ExecuteIntent(). This must always be called, even if you think it is unlikely to open DRM content.

class CContentViewer : public CBase
        {
public:
        static CContentViewer* NewL();
        static CContentViewer* NewLC();
        
        // Display given content.
        void DisplayContent(const TDesC& aUri, TRequestStatus& aStatus)
                {
                TRAPD(err, DisplayContentL(aUri));
                User::RequestComplete(aStatus, err);
                }
                
private:
        CContentViewer() : CBase() {}
        ~CContentViewer() {} 

        void DisplayContentL(const TDesC& aUri)
                {
                TInt size = 0;
                TInt I = 0;
        
                // Create a CContent object
                // CAF figures out the appropriate agent
                CContent *content = CContent::NewLC(aUri);
        
                // Create a CData object to read the content
                // Tell the agent we are planning to display the content
                CData *data = content->OpenContentLC(EDisplay);
        
                // Don't need content object any more
                CleanupStack::PopAndDestroy(content);
        
                // get the size of the plaintext content
                data->DataSizeL(size);
        
                // Execute the intent, tell the agent that we plan to display the content
                // It is at this point that any stateful rights is decremented
                data->ExecuteIntentL(EDisplay);
        
                // read and display the file until we reach the end of the file
                TBuf <128> buffer;              
                while(I < size)
                        {
                        // read from the file
                        User::LeaveIfError(data->Read(buffer));
                        I += buffer.Length();
        
                        // display on screen
                        printf(buffer);
                        }
        
                // finished with Data object
                CleanupStack::PopAndDestroy(data);
                }
        };

Reading from a file, with error checking

This example is the same as before except it attempts to obtain or wait for rights to become available rather than just leaving if access to the content is restricted.

class CContentViewer : public CActive
        {
public:
        static CContentViewer* NewL();
        static CContentViewer* NewLC();
        
        // Display given content.
        void DisplayContent(const TDesC& aUri, TRequestStatus& aStatus)
                {
                iUri = aUri;
                iClientStatus = &aStatus;
                *iClientStatus = KRequestPending;
                iCurrentState = EOpenFile;
                // trigger our RunL
                iStatus = KRequestPending;
                SetActive();
                User::RequestComplete(iStatus, KErrNone);
                }
        
        void RunL()
                {
                TInt err = iStatus.Int();
                
                switch (iCurrentState)
                        {
                        case EOpenFile:
                                iContent = CContent::NewL(aUri);
                                TRAP(err, iData = iContent->OpenContentL(EDisplay));
                                iCurrentState = EReadAndDisplay;        // follow through...
                        case EReadAndDisplay:
                                if(err == KErrNone)
                                        {
                                        TRAP(err, DisplayFile());
                                        iCurrentState = EFinished;
                                        // tell client iStatus that we have finished
                                        User::RequestComplete(*iClientStatus, err);
                                        return;
                                        }       
                                else if(err == KErrCANoRights)
                                        {
                                        // we don't have rights so we need to wait for them
                                        iCurrentState = EWaitingForRights;
                                        // ask CAF to initiate download of rights
                                        iContent->RequestRights(iStatus);
                                        }
                                else if(err == KErrCAPendingRights)
                                        {
                                        // waiting for rights to arrive, expected any minute now
                                        iCurrentState = EWaitingForRights;
                                        // ask CAF to notify us when they arrive
                                        iContent->NotifyStatusChange(ERightsAvailable , iStatus);
                                        }
                                // wait for CAF to complete our request 
                                iLastError = err;
                                iStatus = KRequestPending;
                                SetActive();
                                break;
                        case EWaitingForRights:
                                if(ret == KErrNone)
                                        {
                                        // change the state to try and display content again
                                        iCurrentState = EReadAndDisplay;
                                        // trigger our RunL
                                        iLastError = err;
                                        iStatus = KRequestPending;
                                        SetActive();
                                        User::RequestComplete(iStatus, KErrNone);
                                        }
                                else
                                        {
                                        // couldn't get rights, tell parent active object we're finished
                                        User::RequestComplete(iClientStatus, err);
                                        return;
                                        }
                                break;
                        }
                }
                
protected:              
        void DoCancel()
                {
                if (iLastError == KErrCAPendingRights)
                        iContent->CancelNotifyStatusChange(iStatus);
                else if (iLastError == KErrCANoRights)
                        iContent->CancelRequestRights(iStatus);
                }

private:
        CContentViewer() : CActive(EPriorityStandard)
                { 
                CActiveScheduler::Add(this); 
                }
        ~CContentViewer() 
                { 
                Cancel();
                if (iData) delete iData; 
                if (iContent) delete iContent;
                }       

        // Display the content, if any error occurs then leave
        void DisplayContentL();
                {
                TInt size = 0;
                TInt I = 0;
                TBuf <128> buffer;
        
                // Execute the intent, tell the agent that we plan to display the content
                // It is at this point that any stateful rights is decremented
                iData->ExecuteIntentL(EDisplay);
        
                // get the size of the plaintext content
                iData->DataSizeL(size);
        
                // read and display the file until we reach the end of the file
                while(I < size)
                        {
                        // read from the file
                        User::LeaveIfError(iData->Read(buffer));
                        I += buffer.Length();
                
                        // Display on screen
                        printf(buffer);
                        }
                }

private:
        enum TState
                {
                EOpenFile = 0,
                EReadAndDisplay,
                EWaitingForRights,
                EFinished
                };

        CContent*       iContent;
        CData*          iData;
        TDesC           iUri;

        TState                  iCurrentState;
        TInt                    iLastError;
        TRequestStatus*         iClientStatus;
        }; 

Preventing access to DRM content

Some servers may wish to prevent access to DRM content by untrusted clients, even if the server itself has DRM capability.

To achieve this, the server must use the ContentAccess::TIntent::EUnknown intent when accessing content. Content files that are not DRM protected still work normally, but access to DRM protected content is blocked.

// Tell the agent we have no idea what the application plans to do 
CData *data = content->OpenContentL(EUnknown); 

// Execute the intent, tell the agent that we have no idea what the content is used for 
data->ExecuteIntentL(EUnknown);

File containing several content objects

When reading from a particular content object within a file, the application must supply the UniqueId of the object when calling ContentAccess::CContent::OpenContentL().

void DisplayTextFileL(const TDesC& aUri)
        {
        TInt size = 0;
        TInt I = 0;

        TBuf <128> buffer;

        // Create a CContent object
        // CAF figures out the appropriate agent
        CContent *content = CContent::NewLC(aUri);

        // Find the objects in the file with MIME type image/jpeg
        RStreamablePtrArray<CEmbeddedObject> myArray;
        CleanupClosePushL(myArray);

        User::LeaveIfError(content->Search(myArray, _L("image/jpeg"), EFalse));

        // Get the virtual path of the first image/jpeg we find
        TVirtualPathPtr picture = *myArray[0];

        // Tell the agent to open the object with the given UniqueId
        CData *data = content->OpenContentLC(EDisplay, picture.UniqueId());
        
        // Don't need content object or array any more
        CleanupStack::PopAndDestroy(2); // content, myArray

        // get the size of the plaintext content
        data->DataSizeL(size);

        // Execute the intent, tell the agent that we plan to display the content
        // It is at this point that any stateful rights is decremented
        data->ExecuteIntentL(EDisplay);

        // read and display the file until we reach the end of the file
        while(I < size)
                {
                // read from the file
                User::LeaveIfError(data->Read(buffer));
                I += buffer.Length();

                // display on screen
                printf(buffer);
                }

        // finished with Data object
        CleanupStack::PopAndDestroy(data);
        }

Importing a content file, agent provides output files

This example shows how a messaging application that has just received a message attachment from a mail server can offer the attachment to CAF for processing. The output files is saved in C:\files\.

void CMyApp::ReceiveMessageAttachment(const TDesC8& aContentType, const TDesC8& aMessageAttachment)
        {
        // Create supplier object
        CSupplier* supplier = CSupplier::NewLC();

        // Tell the agent where we would like the output files to be written
        supplier->SetOutputDirectoryL(_L("C:\\files"));

        // Check if CAF can import this attachment we just received
        if(supplier->IsImportSupported(aContentType))
                {
                ProcessAttachmentL(supplier, aContentType, aMessageAttachment); 
                }
        else
                {
                // just save the message to a file in its current form
                RFile theFile;
                theFile.Open(iFs, "myFile");
                theFile.Write(aMessageAttachment);
                theFile.Close();
                
                // Add the file to the list of attachments
                AddAttachment("myFile");
                }
        }


void CMyApp::ProcessAttachmentL(CSupplier* aSupplier, const TDesC8& aContentType, const TDesC8& aMessageAttachment)
        {
        TInt err = KErrNone;
        TBuf <128> buf;

        // Create meta-data array
        CMetaDataArray* metaDataArray = new (ELeave) CMetaDataArray();
        CleanupStack::PushL(metaDataArray);

        // Add any useful information we can think of....
        // Obviously these would not be hardcoded this way in a real import
        metaDataArray->AddL(_L("Content Type"), _L("application/vnd.oma.drm.dm"));
        metaDataArray->AddL(_L("Content Length"), _L("1201"));
        metaDataArray->AddL(_L("X-Oma-Drm-Separate-Delivery"), _L("6"));

        // Create the import object
        CImportFile* import = aSupplier->ImportFileL(aContentType, *metaDataArray, _L("myfile"));
        CleanupStack::PushL(import);

        // import the attachment
        err = import->WriteData(aMessageText);

        // tell CAF (and hence the agent) it's now got the entire file
        if (err == KErrNone)
                {
                err = import->WriteDataComplete();
                if (err == KErrNone)
                        {
                        // Look at the output of the import operation
                        for(TInt I = 0; I < import->OutputFileCountL(); I++)
                                {
                                // for this example only add content output files
                                // (absorb any rights in the original attachment 'silently')
                                if(import->OutputFilesL(I).OutputType == EContent)
                                        {
                                        // Add file to list of attachments for this message
                                        AddAttachment(import->OutputFilesL(I).FileName());
                                        }               
                                }
                        }
                }

        // Error handling
        if (err != KErrNone)
                {
                if (err == KErrNotReady)        
                        {
                        DisplayErrorMsg("Agent not ready for import");
                        }
                else if (err == KErrCACorruptContent)
                        {
                        DisplayErrorMsg("Content data is corrupt");
                        }
                else
                        {       
                        DisplayErrorMsg("Unexpected error: %d", err);
                        }
                }

        // Finished
        CleanupStack::PopAndDestroy(2);         // metaDataArray, import
        }

Importing a content file (application provides output files)

This example shows how a messaging application that has just received a message attachment from a mail server can offer the attachment to CAF for processing and store the file in its own private directory.

void CMyApp::ReceiveMessageAttachment(const TDesC8& aContentType, const TDesC8& aMessageAttachment)
        {
        // Create supplier object
        CSupplier* supplier = CSupplier::NewLC();

        // Check if CAF can import this attachment we just received
        if(supplier->IsImportSupported(aContentType))
                {
                ProcessAttachmentL(supplier, aContentType, aMessageAttachment); 
                }
        else
                {
                // just save the message to a file in its current form
                RFile theFile;
                theFile.Open(iFs, "myFile");
                theFile.Write(aMessageAttachment);
                theFile.Close();
                
                // Add the file to the list of attachments
                AddAttachment("myFile");
                }
        }


void CMyApp::ProcessAttachmentL(CSupplier* aSupplier, const TDesC8& aContentType, const TDesC8& aMessageAttachment)
        {
        TInt err = KErrNone;
        TBuf <128> buf;
        TBuf <4> fileExtension;

        _LIT(KOutputFileName, "\\private\\12345678\\outputfile.");
        TFileName fileName(KOutputFileExtension);

        RFile file;
        
        // Create meta-data array
        CMetaDataArray* metaDataArray = CMetaDataArray::NewLC();

        // Add any useful information we can think of....
        // Obviously these would not be hardcoded this way in a real import
        metaDataArray->AddL(_L("Content Type"), _L("application/vnd.oma.drm.dm"));
        metaDataArray->AddL(_L("Content Length"), _L("1201"));
        metaDataArray->AddL(_L("X-Oma-Drm-Separate-Delivery"), _L("6"));

        // Create the import object, no suggested file name implies the application supplies output files
        CImportFile* import = aSupplier->ImportFileL(aContentType, *metaDataArray);
        CleanupStack::PushL(import);

        // Start importing the attachment
        // (if the agent needs one or more output files, continue looping until 
        // the agent finishes the previous)
        TInt err = import->WriteData(aMessageText);
        while(err == KErrCANewFileHandleRequired)
                {
                import->GetSuggestedOutputFileExtension(fileExtension);
                filName.Append(fileExtension);

                User::LeaveIfError(file.Open(iFs, fileName));
                err = import->ContinueWithNewOutputFile(file);
                file.Close();
                }
        
        if (err == KErrNone)
                {
                // Complete the import process
                err = import->WriteDataComplete();
                while(err == KErrCANewFileHandleRequired)
                        {
                        import->GetSuggestedOutputFileExtension(fileExtension);
                        filName.Append(fileExtension);
        
                        User::LeaveIfError(file.Open(iFs, fileName));
                        err = import->ContinueWithNewOutputFile(file);
                        file.Close();
                        }
                
                if (err == KErrNone)
                        {
                        // Look at the output of the import operation
                        for(TInt I = 0; I < import->OutputFileCountL(); I++)
                                {
                                // for this example only add content output files
                                // (absorb any rights in the original attachment 'silently')
                                if(import->OutputFilesL(I).OutputType == EContent)
                                        {
                                        // Add file to list of attachments for this message
                                        AddAttachment(import->OutputFilesL(I).FileName());
                                        }               
                                }
                        }
                }
                
        // Error handling
        if (err != KErrNone)
                {
                if (err == KErrNotReady)        
                        {
                        DisplayErrorMsg("Agent not ready for import");
                        }
                else if (err == KErrCACorruptContent)
                        {
                        DisplayErrorMsg("Content data is corrupt");
                        }
                else
                        {       
                        DisplayErrorMsg("Unexpected error: %d", err);
                        }
                }

        // Finshed
        CleanupStack::PopAndDestroy(2);         // metaDataArray, import
        }