How do I implement `BeginRead` in the IMFByteStream interface - c++

Question

I have created ReadByteContainer to store current data and ReadByteAsyncCallback for the callback. Are there alternatives that would work better?
HRESULT MediaByteStream::BeginRead(
BYTE *pb,
ULONG cb,
IMFAsyncCallback *pCallback,
IUnknown *punkState)
{
HRESULT hr = S_OK;
// Create a new read byte container.
ReadByteContainer* readBytes = new ReadByteContainer(pb, cb);
ReadByteAsyncCallback* readCallback = new ReadByteAsyncCallback(this);
// If not created.
if (readBytes == NULL)
{
return E_OUTOFMEMORY;
}
// If not created.
if (readCallback == NULL)
{
return E_OUTOFMEMORY;
}
IMFAsyncResult *pResult = NULL;
readBytes->_readCallback = readCallback;
// Creates an asynchronous result object. Use this function if you are implementing an asynchronous method.
hr = MFCreateAsyncResult(readBytes, pCallback, punkState, &pResult);
if (SUCCEEDED(hr))
{
// Start a new work item thread.
hr = MFPutWorkItem(MFASYNC_CALLBACK_QUEUE_STANDARD, readCallback, pResult);
pResult->Release();
}
// Return the result.
return hr;
}

Answer 1

If pb remains valid until EndRead occurs, you can avoid the copy (new ReadByteContainer), and just keep pb as is.
Normally your MediaByteStream implements IMFAsyncCallback so you should call MFPutWorkItem like this (avoid new ReadByteAsyncCallback) :
hr = MFPutWorkItem(MFASYNC_CALLBACK_QUEUE_STANDARD, this, pResult);
Also, i don't see some lock mechanism inside BeginRead. If you use it in a multithreading environment you should handle this. Close can be call when BeginRead has been called and did not finish, so you will face problems.