Scala example source code file (Codec.scala)

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

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

Scala tags/keywords

action, annotation, array, charset, charsetdecoder, codec, converts, handler, int, string, t

The Codec.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package io

import java.nio.charset.{ Charset, CharsetDecoder, CharsetEncoder, CharacterCodingException, CodingErrorAction => Action }
import scala.annotation.migration
import scala.language.implicitConversions

// Some notes about encodings for use in refining this implementation.
//
// Emails: encoding recorded in header, e.g. Content-Type: charset= "iso-8859-1"
// HTML: optional content-type meta tag.
//   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
// XML: optional encoding parameter.
//   <?xml version="1.0" encoding="ISO8859-1" ?>
//
// MacRoman vs. UTF-8: see http://jira.codehaus.org/browse/JRUBY-3576
// -Dfile.encoding: see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4375816

/** A class for character encoding/decoding preferences.
 *
 */
class Codec(val charSet: Charset) {
  type Configure[T] = (T => T, Boolean)
  type Handler      = CharacterCodingException => Int

  // these variables allow configuring the Codec object, and then
  // all decoders and encoders retrieved from it will use these settings.
  private[this] var _onMalformedInput: Action         = null
  private[this] var _onUnmappableCharacter: Action    = null
  private[this] var _encodingReplacement: Array[Byte] = null
  private[this] var _decodingReplacement: String      = null
  private[this] var _onCodingException: Handler       = e => throw e

  /** The name of the Codec. */
  override def toString = name

  // these methods can be chained to configure the variables above
  def onMalformedInput(newAction: Action): this.type              = { _onMalformedInput = newAction ; this }
  def onUnmappableCharacter(newAction: Action): this.type         = { _onUnmappableCharacter = newAction ; this }
  def decodingReplaceWith(newReplacement: String): this.type      = { _decodingReplacement = newReplacement ; this }
  def encodingReplaceWith(newReplacement: Array[Byte]): this.type = { _encodingReplacement = newReplacement ; this }
  def onCodingException(handler: Handler): this.type              = { _onCodingException = handler ; this }

  def name = charSet.name
  def encoder: CharsetEncoder = {
    val enc = charSet.newEncoder()
    if (_onMalformedInput ne null) enc onMalformedInput _onMalformedInput
    if (_onUnmappableCharacter ne null) enc onUnmappableCharacter _onUnmappableCharacter
    if (_encodingReplacement ne null) enc replaceWith _encodingReplacement
    enc
  }
  def decoder: CharsetDecoder = {
    val dec = charSet.newDecoder()
    if (_onMalformedInput ne null) dec onMalformedInput _onMalformedInput
    if (_onUnmappableCharacter ne null) dec onUnmappableCharacter _onUnmappableCharacter
    if (_decodingReplacement ne null) dec replaceWith _decodingReplacement
    dec
  }

  def wrap(body: => Int): Int =
    try body catch { case e: CharacterCodingException => _onCodingException(e) }
}

trait LowPriorityCodecImplicits {
  self: Codec.type =>

  /** The Codec of Last Resort. */
  implicit lazy val fallbackSystemCodec: Codec = defaultCharsetCodec
}

object Codec extends LowPriorityCodecImplicits {
  final val ISO8859: Codec = new Codec(Charset forName "ISO-8859-1")
  final val UTF8: Codec    = new Codec(Charset forName "UTF-8")

  /** Optimistically these two possible defaults will be the same thing.
   *  In practice this is not necessarily true, and in fact Sun classifies
   *  the fact that you can influence anything at all via -Dfile.encoding
   *  as an accident, with any anomalies considered "not a bug".
   */
  def defaultCharsetCodec = apply(Charset.defaultCharset)
  def fileEncodingCodec   = apply(scala.util.Properties.encodingString)
  def default             = defaultCharsetCodec

  def apply(encoding: String): Codec        = new Codec(Charset forName encoding)
  def apply(charSet: Charset): Codec        = new Codec(charSet)
  def apply(decoder: CharsetDecoder): Codec = {
    val _decoder = decoder
    new Codec(decoder.charset()) { override def decoder = _decoder }
  }

  @migration("This method was previously misnamed `toUTF8`. Converts from Array[Byte] to Array[Char].", "2.9.0")
  def fromUTF8(bytes: Array[Byte]): Array[Char] = fromUTF8(bytes, 0, bytes.length)
  def fromUTF8(bytes: Array[Byte], offset: Int, len: Int): Array[Char] = {
    val bbuffer = java.nio.ByteBuffer.wrap(bytes, offset, len)
    val cbuffer = UTF8.charSet decode bbuffer
    val chars   = new Array[Char](cbuffer.remaining())
    cbuffer get chars

    chars
  }

  @migration("This method was previously misnamed `fromUTF8`. Converts from character sequence to Array[Byte].", "2.9.0")
  def toUTF8(cs: CharSequence): Array[Byte] = {
    val cbuffer = java.nio.CharBuffer.wrap(cs, 0, cs.length)
    val bbuffer = UTF8.charSet encode cbuffer
    val bytes = new Array[Byte](bbuffer.remaining())
    bbuffer get bytes

    bytes
  }
  def toUTF8(chars: Array[Char], offset: Int, len: Int): Array[Byte] = {
    val cbuffer = java.nio.CharBuffer.wrap(chars, offset, len)
    val bbuffer = UTF8.charSet encode cbuffer
    val bytes = new Array[Byte](bbuffer.remaining())
    bbuffer get bytes

    bytes
  }

  implicit def string2codec(s: String): Codec           = apply(s)
  implicit def charset2codec(c: Charset): Codec         = apply(c)
  implicit def decoder2codec(cd: CharsetDecoder): Codec = apply(cd)
}