Scala example source code file (Position.scala)

This example Scala source code file (Position.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

column_bits, column_mask, illegalargumentexception, int, line_bits, line_mask, position, string, this, unit

The Position.scala Scala example source code

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

package scala
package io

/** The object Position provides convenience methods to encode
 *  line and column number in one single integer.  The encoded line
 *  (column) numbers range from 0 to `LINE_MASK` (`COLUMN_MASK`),
 *  where `0` indicates that the line (column) is undefined and
 *  `1` represents the first line (column).
 *
 *  Line (Column) numbers greater than `LINE_MASK` (`COLUMN_MASK`) are
 *  replaced by `LINE_MASK` (`COLUMN_MASK`). Furthermore, if the encoded
 *  line number is `LINE_MASK`, the column number is always set to 0.
 *
 *  The following properties hold:
 *
 *  the undefined position is 0:   `encode(0,0) == 0`
 *  encodings are non-negative :   `encode(line,column) >= 0`
 *  position order is preserved:
 *  {{{
 *  (line1 <= line2) || (line1 == line2 && column1 <= column2)
 *  }}}
 *  implies
 *  {{{
 *  encode(line1,column1) <= encode(line2,column2)
 *  }}}
 *  @author Burak Emir (translated from work by Matthias Zenger and others)
 */
@deprecated("This class will be removed.", "2.10.0")
private[scala] abstract class Position {
  /** Definable behavior for overflow conditions.
   */
  def checkInput(line: Int, column: Int): Unit

  /** Number of bits used to encode the line number */
  final val LINE_BITS   = 20
  /** Number of bits used to encode the column number */
  final val COLUMN_BITS = 31 - LINE_BITS // no negatives => 31
  /** Mask to decode the line number */
  final val LINE_MASK   = (1 << LINE_BITS) - 1
  /** Mask to decode the column number */
  final val COLUMN_MASK = (1 << COLUMN_BITS) - 1

  /** Encodes a position into a single integer. */
  final def encode(line: Int, column: Int): Int = {
    checkInput(line, column)

    if (line >= LINE_MASK)
      LINE_MASK << COLUMN_BITS
    else
      (line << COLUMN_BITS) | scala.math.min(COLUMN_MASK, column)
  }

  /** Returns the line number of the encoded position. */
  final def line(pos: Int): Int = (pos >> COLUMN_BITS) & LINE_MASK

  /** Returns the column number of the encoded position. */
  final def column(pos: Int): Int = pos & COLUMN_MASK

  /** Returns a string representation of the encoded position. */
  def toString(pos: Int): String = line(pos) + ":" + column(pos)
}

private[scala] object Position extends Position {
  def checkInput(line: Int, column: Int) {
    if (line < 0)
      throw new IllegalArgumentException(line + " < 0")
    if ((line == 0) && (column != 0))
      throw new IllegalArgumentException(line + "," + column + " not allowed")
    if (column < 0)
      throw new IllegalArgumentException(line + "," + column + " not allowed")
  }
}