AsynchronousIo

The following readAll is a Task to read file content with the help of AsynchronousIo.ReadFile

        import java.nio._, file._, channels._
        import com.thoughtworks.dsl.domains.Task
        import com.thoughtworks.dsl.keywords._
        import com.thoughtworks.dsl.keywords.Shift._
        import com.thoughtworks.dsl.keywords.AsynchronousIo.ReadFile
        import scala.collection.mutable.ArrayBuffer
        import scala.io.Codec
        def readAll(channel: AsynchronousFileChannel, temporaryBufferSize: Int = 4096): Task[ArrayBuffer[CharBuffer]] = Task {
          val charBuffers = ArrayBuffer.empty[CharBuffer]
          val decoder = Codec.UTF8.decoder
          val byteBuffer = ByteBuffer.allocate(temporaryBufferSize)
          var position: Long = 0L
          while (!ReadFile(channel, byteBuffer, position) != -1) {
            position += byteBuffer.position()
            byteBuffer.flip()
            charBuffers += decoder.decode(byteBuffer)
            byteBuffer.clear()
          }
          charBuffers
        }

    `Task`s created from !-notation can be used in `for`-comprehension,
    and other keywords can be used together in the same `for` block.
    For example, the following `cat` function contains a single `for` block to concatenate file contents.
    It asynchronously iterates elements `Seq`, `ArrayBuffer` and `String` with the help of [[keywords.Each]],
    managed native resources with the help of [[keywords.Using]],
    performs previously created `readAll` task with the help of [[keywords.Shift]],
    and finally converts the return type [[comprehension.ComprehensionOps.as as]] a `Task[Vector[Char]]`.

        import com.thoughtworks.dsl._
        import com.thoughtworks.dsl.keywords._
        import com.thoughtworks.dsl.domains.Task
        import com.thoughtworks.dsl.Dsl.to
        import java.net.URL
        def cat(paths: Path*) = ToView {
          for {
            path <- Each(paths)
            channel <- Using(AsynchronousFileChannel.open(path))
            charBuffers <- Shift(readAll(channel))
            charBuffer <- Each(charBuffers)
            char <- Each(charBuffer.toString)
          } yield char
        }.to[Task]

    Then the `cat` function is used to concatenate files from this project, as shown below:

        Task.toFuture(Task {
          val filesToRead = for (fileName <- Seq(".sbtopts", ".scalafmt.conf")) yield {
            Paths.get(sourcecode.File()).getParent.resolve("../../../../../..").resolve(fileName)
          }
          (!Shift(cat(filesToRead: _*))).mkString should be(
            filesToRead.map { fileToRead =>
              new String(Files.readAllBytes(fileToRead), io.Codec.UTF8.charSet)
            }.mkString
          )
        })