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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2006, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.io;
/** convenience methods to encode line and column number in one
* single integer. The encode line (column)
* numbers range from 0 to LINE_MASK (COLUMN_MASK), where 0 indicates
* that the line (column) is the 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 Zengers 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 )
error(line+" < 0");
if(( line == 0 )&&(column != 0))
error(line+","+column+" not allowed");
if( column < 0 )
error(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 StringBuffer();
sb.append(line(pos));
sb.append(':');
sb.append(column(pos));
sb.toString();
}
}
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