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Scala example source code file (Position.scala)

This example Scala source code file (Position.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

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

The Scala Position.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.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)
 */
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) | 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)
}

object Position extends Position {
  /** The undefined position */
  @deprecated("This will be removed", "2.9.0")
  final val NOPOS = 0

  /** The first position in a source file */
  @deprecated("This will be removed", "2.9.0")
  final val FIRSTPOS = encode(1, 1)

  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")
  }
}

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