Thanks Viktor. That certainly looks more succinct. My actual use case
(this one was intentionally simplified to make the example easier) is that
I have messages coming in in protobuf format, each one preceded by a length
indicator. So my Transformer basically toggles back and forth between two
states; looking for the length of the next message or reading the current
message. I got the code working correctly but it's definitely verbose.
It's recursive (and tail recursive at that) but it still needs
improvement. I want to add sufficient unit testing to it and then I want
to start to tighten up the internals of the code. I will use this code
here as a guideline. Thanks.
On Wednesday, September 3, 2014 8:15:33 AM UTC-4, Chris Baxter wrote:
>
> Posted this on Stackoverflow but haven't seen any activity on it so I
> figured I'd post it here as well.
>
> I've been playing around with the experimental Akka Streams API a bit and
> I have a use case that I wanted to see how to implement. For my use case,
> I have a `StreamTcp` based `Flow` that is being fed from binding the input
> stream of connections to my server socket. The Flow that I have is based
> on `ByteString` data coming into it. The data that is coming in is going
> to have a delimiter in it that means I should treat everything before the
> delimiter as one message and everything after and up to the next delimiter
> as the next message. So playing around with a simpler example, using no
> sockets and just static text, this is what I came up with:
>
> import akka.actor.ActorSystem
> import akka.stream.{ FlowMaterializer, MaterializerSettings }
> import akka.stream.scaladsl.Flow
> import scala.util.{ Failure, Success }
> import akka.util.ByteString
> object BasicTransformation {
> def main(args: Array[String]): Unit = {
> implicit val system = ActorSystem("Sys")
> val data = ByteString("Lorem Ipsum is simply.Dummy text of the
> printing.And typesetting industry.")
> Flow(data).
> splitWhen(c => c == '.').
> foreach{producer =>
> Flow(producer).
> filter(c => c != '.').
> fold(new StringBuilder)((sb, c) => sb.append(c.toChar)).
> map(_.toString).
> filter(!_.isEmpty).
> foreach(println(_)).
> consume(FlowMaterializer(MaterializerSettings()))
> }.
> onComplete(FlowMaterializer(MaterializerSettings())) {
> case any =>
> system.shutdown
> }
> }
> }
>
> The main function on the `Flow` that I found to accomplish my goal was
> `splitWhen`, which then produces additional sub-flows, one for each message
> per that `.` delimiter. I then process each sub-flow with another pipeline
> of steps, finally printing the individual messages at the end.
>
> This all seems a bit verbose, to accomplish what I thought to be a pretty
> simple and common use case. So my question is, is there a cleaner and less
> verbose way to do this or is this the correct and preferred way to split a
> stream up by a delimiter?
>
> The link to the SO question is:
> http://stackoverflow.com/questions/25631099/how-to-split-an-inbound-stream-on-a-delimiter-character-using-akka-streams
>
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