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/* __ *\
** ________ ___ / / ___ 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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