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Play Framework/Scala example source code file (TraversableIteratee.scala)

This example Play Framework source code file (TraversableIteratee.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Play Framework (and Scala) source code examples by using tags.

All credit for the original source code belongs to Play Framework; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Play Framework tags/keywords

a, api, concurrent, cont, done, e, enumeratee, input, int, iterate, iteratee, k, library, m, play, play framework

The TraversableIteratee.scala Play Framework example source code

/*
 * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
 */
package play.api.libs.iteratee

import play.api.libs.iteratee.Execution.Implicits.{ defaultExecutionContext => dec }
import scala.concurrent.{ ExecutionContext, Future }

/**
 * @define paramEcSingle @param ec The context to execute the supplied function with. The context is prepared on the calling thread before being used.
 */
object Traversable {

  /**
   * A partially-applied function returned by the `head` method.
   */
  trait Head[E] {
    def apply[A](implicit p: E => scala.collection.TraversableLike[A, E]): Iteratee[E, Option[A]]
  }

  def head[E] = new Head[E] {
    def apply[A](implicit p: E => scala.collection.TraversableLike[A, E]): Iteratee[E, Option[A]] = {

      def step: K[E, Option[A]] = {
        case Input.Empty => Cont(step)
        case Input.EOF => Done(None, Input.EOF)
        case Input.El(xs) if !xs.isEmpty => Done(Some(xs.head), Input.El(xs.tail))
        case Input.El(empty) => Cont(step)
      }
      Cont(step)
    }
  }

  def takeUpTo[M](count: Int)(implicit p: M => scala.collection.TraversableLike[_, M]): Enumeratee[M, M] = new Enumeratee[M, M] {

    def applyOn[A](it: Iteratee[M, A]): Iteratee[M, Iteratee[M, A]] = {

      def step(inner: Iteratee[M, A], leftToTake: Int)(in: Input[M]): Iteratee[M, Iteratee[M, A]] = {
        in match {
          case in @ Input.El(e) =>
            inner.pureFlatFold {
              case Step.Cont(k) => e.splitAt(leftToTake) match {
                case (all, x) if x.isEmpty => Cont(step(k(Input.El(all)), (leftToTake - all.size)))
                case (x, left) if x.isEmpty => Done(inner, Input.El(left))
                case (toPush, left) => Done(k(Input.El(toPush)), Input.El(left))
              }
              case _ => Done(inner, in)
            }

          case Input.EOF => Done(inner, Input.EOF)

          case Input.Empty => Cont(step(inner, leftToTake))
        }

      }
      Cont(step(it, count))
    }
  }

  def take[M](count: Int)(implicit p: M => scala.collection.TraversableLike[_, M]): Enumeratee[M, M] = new Enumeratee[M, M] {

    def applyOn[A](it: Iteratee[M, A]): Iteratee[M, Iteratee[M, A]] = {

      def step(inner: Iteratee[M, A], leftToTake: Int)(in: Input[M]): Iteratee[M, Iteratee[M, A]] = {
        in match {
          case in @ Input.El(e) =>
            e.splitAt(leftToTake) match {
              case (all, x) if x.isEmpty => inner.pureFlatFold {
                case Step.Done(_, _) => Cont(step(inner, (leftToTake - all.size)))
                case Step.Cont(k) => Cont(step(k(Input.El(all)), (leftToTake - all.size)))
                case Step.Error(_, _) => Cont(step(inner, (leftToTake - all.size)))
              }
              case (x, left) if x.isEmpty => Done(inner, Input.El(left))
              case (toPush, left) => Done(inner.pureFlatFold { case Step.Cont(k) => k(Input.El(toPush)); case _ => inner }, Input.El(left))
            }

          case Input.EOF => Done(inner, Input.EOF)

          case Input.Empty => Cont(step(inner, leftToTake))
        }

      }
      Cont(step(it, count))

    }
  }

  import Enumeratee.CheckDone

  /**
   * Splits a stream of traversable input elements on a predicate. Yields all input up until
   * the predicate matches within an input element. The input following a match is unprocessed.
   *
   * @param p The predicate to split input on.
   * $paramEcSingle
   */
  def splitOnceAt[M, E](p: E => Boolean)(implicit traversableLike: M => scala.collection.TraversableLike[E, M], ec: ExecutionContext): Enumeratee[M, M] = new CheckDone[M, M] {
    val pec = ec.prepare()

    def step[A](k: K[M, A]): K[M, Iteratee[M, A]] = {

      case in @ Input.El(e) =>
        Iteratee.flatten(Future(e.span(p))(pec).map {
          case (prefix, suffix) if suffix.isEmpty => new CheckDone[M, M] { def continue[A](k: K[M, A]) = Cont(step(k)) } &> k(Input.El(prefix))
          case (prefix, suffix) => Done(if (prefix.isEmpty) Cont(k) else k(Input.El(prefix)), Input.El(suffix.drop(1)))
        }(dec))

      case Input.Empty =>
        new CheckDone[M, M] { def continue[A](k: K[M, A]) = Cont(step(k)) } &> k(Input.Empty)

      case Input.EOF => Done(Cont(k), Input.EOF)

    }

    def continue[A](k: K[M, A]) = Cont(step(k))

  }

  def drop[M](count: Int)(implicit p: M => scala.collection.TraversableLike[_, M]): Enumeratee[M, M] = new Enumeratee[M, M] {

    def applyOn[A](inner: Iteratee[M, A]): Iteratee[M, Iteratee[M, A]] = {

      def step(it: Iteratee[M, A], leftToDrop: Int)(in: Input[M]): Iteratee[M, Iteratee[M, A]] = {
        in match {
          case in @ Input.El(e) =>
            val left = leftToDrop - e.size
            left match {
              case i if i > 0 => Cont(step(it, left))
              case i =>
                val toPass = if (i < 0) Input.El(e.drop(leftToDrop)) else Input.Empty
                it.pureFlatFold {
                  case Step.Cont(k) => Enumeratee.passAlong.applyOn(k(toPass))
                  case _ => Done(it, toPass)
                }
            }
          case Input.Empty => Cont(step(it, leftToDrop))

          case Input.EOF => Done(it, Input.EOF)
        }
      }

      Cont(step(inner, count))

    }
  }
}

Other Play Framework source code examples

Here is a short list of links related to this Play Framework TraversableIteratee.scala source code file:

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