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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2008, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.io
/** <p>
* The object <code>Position</code> provides convenience methods to encode
* line and column number in one single integer. The encode line (column)
* numbers range from 0 to <code>LINE_MASK</code>
* (<code>COLUMN_MASK</code>), where 0 indicates that the line (column) is
* the undefined and 1 represents the first line (column). Line (Column)
* numbers greater than <code>LINE_MASK</code>
* (<code>COLUMN_MASK</code>) are replaced by <code>LINE_MASK</code>
* (<code>COLUMN_MASK</code>). Furthermore, if the encoded line number is
* <code>LINE_MASK</code>, the column number is always set to 0.
* </p>
* <p>
* The following properties hold:
* </p>
* <ul>
* <li>
* the undefined position is 0: <code>encode(0,0) == 0</code>
* </li>
* <li>
* encodings are non-negative : <code>encode(line,column) >= 0</code>
* </li>
* <li>
* position order is preserved:
* <code>(line1 < line2) || (line1 == line2 && column1 < column2)</code>
* <div>implies</div>
* <code>encode(line1,column1) <= encode(line2,column2)</code>
* </li>
* </ul>
*
* @author Burak Emir (translated from work by Matthias Zenger and others)
*/
object Position {
/** 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
/** The undefined position */
final val NOPOS = 0
/** The first position in a source file */
final val FIRSTPOS = encode(1, 1)
//########################################################################
// Public Functions
/** Encodes a position into a single integer. */
final def encode(line: Int, column: Int): Int = {
var line1, column1 = 0
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")
{if (line >= LINE_MASK) {
line1 = LINE_MASK
column1 = 0
} else {
line1 = line
if (column > COLUMN_MASK)
column1 = COLUMN_MASK
else
column1 = column
}}
{(line1 << COLUMN_BITS) | column1;}
}
/** 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 = {
val sb = new StringBuilder()
sb.append(line(pos))
sb.append(':')
sb.append(column(pos))
sb.toString()
}
}
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