Convert CompressionOutputStream to ByteString in scala

Question

There is a JAVA compression API call which gives me CompressionOutputStream and I want to return a ByteString. From what I have seen and tried to do is:

1. Using StreamConverters (https://doc.akka.io/docs/akka/current/stream/operators/StreamConverters/fromOutputStream.html) val sink:

Sink[ByteString, Future[IOResult]] = StreamConverters.fromOutputStream(() => outputStream) <- This returns a Sink but I do not how to convert it to ByteString

2. Using BufferedOutputStream (There is no #getBytes in CompressionInputStream so I wanted to convert it to BufferedOutputStream but its not correct)

val bufferedOutputStream = new BufferedOutputStream()
bufferedOutputStream.writeTo(myOutputStream)
bufferedOutputStream.getBytes()

Any suggestions/help is appreciated.Thanks