gistfile1.scala

trait InputStreamRenderable extends Renderable {
  def in: InputStream

  def writeTo(out: OutputStream, cs: Charset) {
    val in = this.in // it's a def, and we only want one
    streamCopy(Channels.newChannel(in), Channels.newChannel(out))
    in.close()
  }

  private def streamCopy(src: ReadableByteChannel, dest: WritableByteChannel) {
    val buffer = getByteBuffer(4 * 1024)
    @tailrec
    def loop() {
      if(src.read(buffer) > 0) {
        buffer.flip
        dest.write(buffer)
        buffer.compact
        loop
      }
    }
    loop

    buffer.flip
    while(buffer.hasRemaining) {
      dest.write(buffer)
    }
  }

  protected def getByteBuffer(size: Int) = ByteBuffer.allocate(size)
}

/**
 * Extension for types that exist as a File.  This is useful primarily for zero-copy optimizations.
 */
trait FileRenderable extends InputStreamRenderable {
  def file: File

  def in: InputStream = new FileInputStream(file)

  override protected def getByteBuffer(size: Int) = ByteBuffer.allocateDirect(size) // zero-copy byte buffer
}