88 lines
3.1 KiB
Scala
88 lines
3.1 KiB
Scala
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package docs.stream.cookbook
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import akka.stream.scaladsl.{ Sink, Source }
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import akka.util.ByteString
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import scala.annotation.tailrec
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import scala.concurrent.Await
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import scala.concurrent.duration._
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class RecipeParseLines extends RecipeSpec {
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"Recipe for parsing line from bytes" must {
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"work" in {
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val rawData = Source(List(
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ByteString("Hello World"),
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ByteString("\r"),
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ByteString("!\r"),
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ByteString("\nHello Akka!\r\nHello Streams!"),
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ByteString("\r\n\r\n")))
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import akka.stream.stage._
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//#parse-lines
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def parseLines(separator: String, maximumLineBytes: Int) =
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new StatefulStage[ByteString, String] {
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private val separatorBytes = ByteString(separator)
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private val firstSeparatorByte = separatorBytes.head
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private var buffer = ByteString.empty
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private var nextPossibleMatch = 0
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def initial = new State {
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override def onPush(chunk: ByteString, ctx: Context[String]): Directive = {
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buffer ++= chunk
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if (buffer.size > maximumLineBytes)
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ctx.fail(new IllegalStateException(s"Read ${buffer.size} bytes " +
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s"which is more than $maximumLineBytes without seeing a line terminator"))
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else emit(doParse(Vector.empty).iterator, ctx)
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}
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@tailrec
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private def doParse(parsedLinesSoFar: Vector[String]): Vector[String] = {
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val possibleMatchPos = buffer.indexOf(firstSeparatorByte, from = nextPossibleMatch)
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if (possibleMatchPos == -1) {
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// No matching character, we need to accumulate more bytes into the buffer
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nextPossibleMatch = buffer.size
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parsedLinesSoFar
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} else {
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if (possibleMatchPos + separatorBytes.size > buffer.size) {
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// We have found a possible match (we found the first character of the terminator
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// sequence) but we don't have yet enough bytes. We remember the position to
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// retry from next time.
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nextPossibleMatch = possibleMatchPos
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parsedLinesSoFar
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} else {
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if (buffer.slice(possibleMatchPos, possibleMatchPos + separatorBytes.size)
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== separatorBytes) {
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// Found a match
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val parsedLine = buffer.slice(0, possibleMatchPos).utf8String
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buffer = buffer.drop(possibleMatchPos + separatorBytes.size)
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nextPossibleMatch -= possibleMatchPos + separatorBytes.size
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doParse(parsedLinesSoFar :+ parsedLine)
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} else {
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nextPossibleMatch += 1
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doParse(parsedLinesSoFar)
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}
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}
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}
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}
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}
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}
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val linesStream = rawData.transform(() => parseLines("\r\n", 100))
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//#parse-lines
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Await.result(linesStream.grouped(10).runWith(Sink.head), 3.seconds) should be(List(
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"Hello World\r!",
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"Hello Akka!",
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"Hello Streams!",
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""))
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}
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}
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}
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