see also http://unageanu.hatenablog.com/entry/20070827/1188195493

MessageHash.scala

object Main extends App {
  import java.io.FileInputStream
  import java.io.InputStreamReader
  import java.io.BufferedReader
  import java.security.MessageDigest

  val md = MessageDigest.getInstance("SHA-1")
  // val bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream("./hoge.png")))
  val fileInputStream = new FileInputStream("./hoge.png")
  Iterator.continually(fileInputStream.read).takeWhile(_ != -1).foreach(x => md.update(x.toByte))
  val s = md.digest.map("%02x".format(_)).mkString
  println(s)
}