Google Native Client, sending binary data from NACL to the frontend

Question

How do I send binary data, e.g. mp3/mp4 data back to the frontend ?

I know there are two ways of doing it: utilizing the sandbox filesystem provided by NACL and get the url at the frontend; passing the data through the PostMessage() using VarArrayBuffer. It would be great if someone could give me a simple example of how to pass the binary data through PostMessage(). There is a Pong example for NACl FileSystem API but I 'm kind of confused on how to retrieve the file location as url so that the frontend JS could get it through the message.

Here is what I have done so far, using the second method of passing data through PostMessage() and VarArrayBuffer:

• I successfully retrieved data from online mp4 file and stored it in a char vector vector<char> outputBuffer.

• Dumped the data into a new char buffer and create VarArrayBuffer to hold the data and pass it to the JS side

  char* binaryBuffer = new char[outputBuffer.size()];
  int increment = 0;
  for (vector<char>::iterator it = outputBuffer.begin(); 
       it != outputBuffer.end(); it++) {
       binaryBuffer[increment] = *it;
  }
  
  pp::VarArrayBuffer outBuffer(binaryBuffer);
  instance_->PostMessage(outBuffer);//instance_ is a NACL module instance
  

So, how should the JS side catch the array buffer? Is it through message.data or something else?