Scala example source code file (BufferedSource.scala)

This example Scala source code file (BufferedSource.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, bufferedlineiterator, bufferedreader, codec, collection, inputstream, int, io, iterator, mutable, pushbackreader, source, string

The BufferedSource.scala Scala example source code

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

package scala.io

import java.util.Arrays
import java.io.{ InputStream, BufferedReader, InputStreamReader, PushbackReader }
import Source.DefaultBufSize
import scala.collection.{ Iterator, AbstractIterator }
import scala.collection.mutable.ArrayBuffer

/** This object provides convenience methods to create an iterable
 *  representation of a source file.
 *
 *  @author  Burak Emir, Paul Phillips
 */
class BufferedSource(inputStream: InputStream, bufferSize: Int)(implicit val codec: Codec) extends Source {
  def this(inputStream: InputStream)(implicit codec: Codec) = this(inputStream, DefaultBufSize)(codec)
  def reader() = new InputStreamReader(inputStream, codec.decoder)
  def bufferedReader() = new BufferedReader(reader(), bufferSize)

  // The same reader has to be shared between the iterators produced
  // by iter and getLines. This is because calling hasNext can cause a
  // block of data to be read from the stream, which will then be lost
  // to getLines if it creates a new reader, even though next() was
  // never called on the original.
  private var charReaderCreated = false
  private lazy val charReader = {
    charReaderCreated = true
    bufferedReader()
  }

  override lazy val iter = (
    Iterator
    continually (codec wrap charReader.read())
    takeWhile (_ != -1)
    map (_.toChar)
  )

  private def decachedReader: BufferedReader = {
    // Don't want to lose a buffered char sitting in iter either. Yes,
    // this is ridiculous, but if I can't get rid of Source, and all the
    // Iterator bits are designed into Source, and people create Sources
    // in the repl, and the repl calls toString for the result line, and
    // that calls hasNext to find out if they're empty, and that leads
    // to chars being buffered, and no, I don't work here, they left a
    // door unlocked.
    // To avoid inflicting this silliness indiscriminately, we can
    // skip it if the char reader was never created: and almost always
    // it will not have been created, since getLines will be called
    // immediately on the source.
    if (charReaderCreated && iter.hasNext) {
      val pb = new PushbackReader(charReader)
      pb unread iter.next().toInt
      new BufferedReader(pb, bufferSize)
    }
    else charReader
  }


  class BufferedLineIterator extends AbstractIterator[String] with Iterator[String] {
    private val lineReader = decachedReader
    var nextLine: String = null

    override def hasNext = {
      if (nextLine == null)
        nextLine = lineReader.readLine

      nextLine != null
    }
    override def next(): String = {
      val result = {
        if (nextLine == null) lineReader.readLine
        else try nextLine finally nextLine = null
      }
      if (result == null) Iterator.empty.next()
      else result
    }
  }

  override def getLines(): Iterator[String] = new BufferedLineIterator

  /** Efficiently converts the entire remaining input into a string. */
  override def mkString = {
    // Speed up slurping of whole data set in the simplest cases.
    val allReader = decachedReader
    val sb = new StringBuilder
    val buf = new Array[Char](bufferSize)
    var n = 0
    while (n != -1) {
      n = charReader.read(buf)
      if (n>0) sb.appendAll(buf, 0, n)
    }
    sb.result
  }
}