Scala example source code file (Source.scala)

This example Scala source code file (Source.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

array, bufferedsource, char, codec, collection, int, jfile, positioner, source, string, unit

The Source.scala Scala example source code

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

package scala
package io

import scala.collection.AbstractIterator
import java.io.{ FileInputStream, InputStream, PrintStream, File => JFile }
import java.net.{ URI, URL }

/** This object provides convenience methods to create an iterable
 *  representation of a source file.
 *
 *  @author  Burak Emir, Paul Phillips
 *  @version 1.0, 19/08/2004
 */
object Source {
  val DefaultBufSize = 2048

  /** Creates a `Source` from System.in.
   */
  def stdin = fromInputStream(System.in)

  /** Creates a Source from an Iterable.
   *
   *  @param    iterable  the Iterable
   *  @return   the Source
   */
  def fromIterable(iterable: Iterable[Char]): Source = new Source {
    val iter = iterable.iterator
  } withReset(() => fromIterable(iterable))

  /** Creates a Source instance from a single character.
   */
  def fromChar(c: Char): Source = fromIterable(Array(c))

  /** creates Source from array of characters, with empty description.
   */
  def fromChars(chars: Array[Char]): Source = fromIterable(chars)

  /** creates Source from a String, with no description.
   */
  def fromString(s: String): Source = fromIterable(s)

  /** creates Source from file with given name, setting its description to
   *  filename.
   */
  def fromFile(name: String)(implicit codec: Codec): BufferedSource =
    fromFile(new JFile(name))(codec)

  /** creates Source from file with given name, using given encoding, setting
   *  its description to filename.
   */
  def fromFile(name: String, enc: String): BufferedSource =
    fromFile(name)(Codec(enc))

  /** creates `ource` from file with given file `URI`.
   */
  def fromFile(uri: URI)(implicit codec: Codec): BufferedSource =
    fromFile(new JFile(uri))(codec)

  /** creates Source from file with given file: URI
   */
  def fromFile(uri: URI, enc: String): BufferedSource =
    fromFile(uri)(Codec(enc))

  /** creates Source from file, using default character encoding, setting its
   *  description to filename.
   */
  def fromFile(file: JFile)(implicit codec: Codec): BufferedSource =
    fromFile(file, Source.DefaultBufSize)(codec)

  /** same as fromFile(file, enc, Source.DefaultBufSize)
   */
  def fromFile(file: JFile, enc: String): BufferedSource =
    fromFile(file)(Codec(enc))

  def fromFile(file: JFile, enc: String, bufferSize: Int): BufferedSource =
    fromFile(file, bufferSize)(Codec(enc))

  /** Creates Source from `file`, using given character encoding, setting
   *  its description to filename. Input is buffered in a buffer of size
   *  `bufferSize`.
   */
  def fromFile(file: JFile, bufferSize: Int)(implicit codec: Codec): BufferedSource = {
    val inputStream = new FileInputStream(file)

    createBufferedSource(
      inputStream,
      bufferSize,
      () => fromFile(file, bufferSize)(codec),
      () => inputStream.close()
    )(codec) withDescription ("file:" + file.getAbsolutePath)
  }

  /** Create a `Source` from array of bytes, decoding
   *  the bytes according to codec.
   *
   *  @return      the created `Source` instance.
   */
  def fromBytes(bytes: Array[Byte])(implicit codec: Codec): Source =
    fromString(new String(bytes, codec.name))

  def fromBytes(bytes: Array[Byte], enc: String): Source =
    fromBytes(bytes)(Codec(enc))

  /** Create a `Source` from array of bytes, assuming
   *  one byte per character (ISO-8859-1 encoding.)
   */
  def fromRawBytes(bytes: Array[Byte]): Source =
    fromString(new String(bytes, Codec.ISO8859.name))

  /** creates `Source` from file with given file: URI
   */
  def fromURI(uri: URI)(implicit codec: Codec): BufferedSource =
    fromFile(new JFile(uri))(codec)

  /** same as fromURL(new URL(s))(Codec(enc))
   */
  def fromURL(s: String, enc: String): BufferedSource =
    fromURL(s)(Codec(enc))

  /** same as fromURL(new URL(s))
   */
  def fromURL(s: String)(implicit codec: Codec): BufferedSource =
    fromURL(new URL(s))(codec)

  /** same as fromInputStream(url.openStream())(Codec(enc))
   */
  def fromURL(url: URL, enc: String): BufferedSource =
    fromURL(url)(Codec(enc))

  /** same as fromInputStream(url.openStream())(codec)
   */
  def fromURL(url: URL)(implicit codec: Codec): BufferedSource =
    fromInputStream(url.openStream())(codec)

  /** Reads data from inputStream with a buffered reader, using the encoding
   *  in implicit parameter codec.
   *
   *  @param  inputStream  the input stream from which to read
   *  @param  bufferSize   buffer size (defaults to Source.DefaultBufSize)
   *  @param  reset        a () => Source which resets the stream (if unset, reset() will throw an Exception)
   *  @param  close        a () => Unit method which closes the stream (if unset, close() will do nothing)
   *  @param  codec        (implicit) a scala.io.Codec specifying behavior (defaults to Codec.default)
   *  @return              the buffered source
   */
  def createBufferedSource(
    inputStream: InputStream,
    bufferSize: Int = DefaultBufSize,
    reset: () => Source = null,
    close: () => Unit = null
  )(implicit codec: Codec): BufferedSource = {
    // workaround for default arguments being unable to refer to other parameters
    val resetFn = if (reset == null) () => createBufferedSource(inputStream, bufferSize, reset, close)(codec) else reset

    new BufferedSource(inputStream, bufferSize)(codec) withReset resetFn withClose close
  }

  def fromInputStream(is: InputStream, enc: String): BufferedSource =
    fromInputStream(is)(Codec(enc))

  def fromInputStream(is: InputStream)(implicit codec: Codec): BufferedSource =
    createBufferedSource(is, reset = () => fromInputStream(is)(codec), close = () => is.close())(codec)
}

/** The class `Source` implements an iterable representation of source data.
 *  Calling method `reset` returns an identical, resetted source, where
 *  possible.
 *
 *  @author  Burak Emir
 *  @version 1.0
 */
abstract class Source extends Iterator[Char] {
  /** the actual iterator */
  protected val iter: Iterator[Char]

  // ------ public values

  /** description of this source, default empty */
  var descr: String = ""
  var nerrors = 0
  var nwarnings = 0

  private def lineNum(line: Int): String = (getLines() drop (line - 1) take 1).mkString

  class LineIterator extends AbstractIterator[String] with Iterator[String] {
    private[this] val sb = new StringBuilder

    lazy val iter: BufferedIterator[Char] = Source.this.iter.buffered
    def isNewline(ch: Char) = ch == '\r' || ch == '\n'
    def getc() = iter.hasNext && {
      val ch = iter.next()
      if (ch == '\n') false
      else if (ch == '\r') {
        if (iter.hasNext && iter.head == '\n')
          iter.next()

        false
      }
      else {
        sb append ch
        true
      }
    }
    def hasNext = iter.hasNext
    def next = {
      sb.clear()
      while (getc()) { }
      sb.toString
    }
  }

  /** Returns an iterator who returns lines (NOT including newline character(s)).
   *  It will treat any of \r\n, \r, or \n as a line separator (longest match) - if
   *  you need more refined behavior you can subclass Source#LineIterator directly.
   */
  def getLines(): Iterator[String] = new LineIterator()

  /** Returns `'''true'''` if this source has more characters.
   */
  def hasNext = iter.hasNext

  /** Returns next character.
   */
  def next(): Char = positioner.next()

  class Positioner(encoder: Position) {
    def this() = this(RelaxedPosition)
    /** the last character returned by next. */
    var ch: Char = _

    /** position of last character returned by next */
    var pos = 0

    /** current line and column */
    var cline = 1
    var ccol = 1

    /** default col increment for tabs '\t', set to 4 initially */
    var tabinc = 4

    def next(): Char = {
      ch = iter.next()
      pos = encoder.encode(cline, ccol)
      ch match {
        case '\n' =>
          ccol = 1
          cline += 1
        case '\t' =>
          ccol += tabinc
        case _ =>
          ccol += 1
      }
      ch
    }
  }
  /** A Position implementation which ignores errors in
   *  the positions.
   */
  object RelaxedPosition extends Position {
    def checkInput(line: Int, column: Int): Unit = ()
  }
  object RelaxedPositioner extends Positioner(RelaxedPosition) { }
  object NoPositioner extends Positioner(Position) {
    override def next(): Char = iter.next()
  }
  def ch = positioner.ch
  def pos = positioner.pos

  /** Reports an error message to the output stream `out`.
   *
   *  @param pos the source position (line/column)
   *  @param msg the error message to report
   *  @param out PrintStream to use (optional: defaults to `Console.err`)
   */
  def reportError(
    pos: Int,
    msg: String,
    out: PrintStream = Console.err)
  {
    nerrors += 1
    report(pos, msg, out)
  }

  private def spaces(n: Int) = List.fill(n)(' ').mkString
  /**
   *  @param pos the source position (line/column)
   *  @param msg the error message to report
   *  @param out PrintStream to use
   */
  def report(pos: Int, msg: String, out: PrintStream) {
    val line  = Position line pos
    val col   = Position column pos

    out println "%s:%d:%d: %s%s%s^".format(descr, line, col, msg, lineNum(line), spaces(col - 1))
  }

  /**
   *  @param pos the source position (line/column)
   *  @param msg the warning message to report
   *  @param out PrintStream to use (optional: defaults to `Console.out`)
   */
  def reportWarning(
    pos: Int,
    msg: String,
    out: PrintStream = Console.out)
  {
    nwarnings += 1
    report(pos, "warning! " + msg, out)
  }

  private[this] var resetFunction: () => Source = null
  private[this] var closeFunction: () => Unit = null
  private[this] var positioner: Positioner = RelaxedPositioner

  def withReset(f: () => Source): this.type = {
    resetFunction = f
    this
  }
  def withClose(f: () => Unit): this.type = {
    closeFunction = f
    this
  }
  def withDescription(text: String): this.type = {
    descr = text
    this
  }
  /** Change or disable the positioner. */
  def withPositioning(on: Boolean): this.type = {
    positioner = if (on) RelaxedPositioner else NoPositioner
    this
  }
  def withPositioning(pos: Positioner): this.type = {
    positioner = pos
    this
  }

  /** The close() method closes the underlying resource. */
  def close() {
    if (closeFunction != null) closeFunction()
  }

  /** The reset() method creates a fresh copy of this Source. */
  def reset(): Source =
    if (resetFunction != null) resetFunction()
    else throw new UnsupportedOperationException("Source's reset() method was not set.")
}