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/* ____ ____ ____ ____ ______ *\
** / __// __ \/ __// __ \/ ____/ SOcos COmpiles Scala **
** __\_ \/ /_/ / /__/ /_/ /\_ \ (c) 2002, LAMP/EPFL **
** /_____/\____/\___/\____/____/ **
\* */
// $Id$
package ch.epfl.lamp.util;
/**
* This class represents a position in a source file. Such a position
* is defined by a source file (mandatory), a line number (optional)
* and a column number (optional, may be specified only if the line
* number is defined).
*
* Line (Column) numbers range from 0 to Integer.MAX_VALUE. A value of
* 0 indicates that the line (column) is undefined, 1 represents the
* first line (column). Negative values are prohibited.
*
* The class provides also functions to encode a line number and a
* column number into 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)
*/
public class Position {
//########################################################################
// Public Constants
/** Number of bits used to encode the line number */
public static final int LINE_BITS = 20;
/** Number of bits used to encode the column number */
public static final int COLUMN_BITS = 31 - LINE_BITS; // no negatives => 31
/** Mask to decode the line number */
public static final int LINE_MASK = (1 << LINE_BITS) - 1;
/** Mask to decode the column number */
public static final int COLUMN_MASK = (1 << COLUMN_BITS) - 1;
/** The undefined position */
public static final int NOPOS = 0;
/** The first position in a source file */
public static final int FIRSTPOS = encode(1, 1);
//########################################################################
// Public Functions
/** Encodes a position into a single integer. */
public static int encode(int line, int column) {
assert line >= 0 : line;
assert line == 0 ? column == 0 : column >= 0 : line + "," + column;
if (line >= LINE_MASK) { line = LINE_MASK; column = 0; }
if (column > COLUMN_MASK) column = COLUMN_MASK;
return (line << COLUMN_BITS) | column;
}
/** Returns the line number of the encoded position. */
public static int line(int position) {
return (position >> COLUMN_BITS) & LINE_MASK;
}
/** Returns the column number of the encoded position. */
public static int column(int position) {
return position & COLUMN_MASK;
}
//########################################################################
// Private Fields
/** The position's file */
private final SourceFile file;
/** The position's line number */
private final int line;
/** The position's column number */
private final int column;
//########################################################################
// Public Constructors
/** Initializes a new instance. */
public Position(String source) {
this(new SourceFile(source, new byte[0]));
}
/** Initializes a new instance. */
public Position(SourceFile file) {
this(file, 0, 0);
}
/** Initializes a new instance. */
public Position(SourceFile file, int position) {
this(file, line(position), column(position));
}
/** Initializes a new instance. */
public Position(SourceFile file, int line, int column) {
this.file = file;
this.line = line;
this.column = column;
assert file != null;
assert line >= 0 : line;
assert line == 0 ? column == 0 : column >= 0 : line + "," + column;
}
//########################################################################
// Public Methods
/** Returns the file of this position. */
public SourceFile file() {
return file;
}
/** Returns the line number of this position. */
public int line() {
return line;
}
/** Returns the column number of this position. */
public int column() {
return column;
}
/** Returns an int encoding the line and column of this position. */
public int encodedLineColumn() {
return encode(line, column);
}
/** Returns a string representation of this position. */
public String toString() {
StringBuffer buffer = new StringBuffer(file.name());
if (line > 0) buffer.append(":").append(line);
if (line > 0 && column > 0) buffer.append(":").append(column);
return buffer.toString();
}
/** Returns the hash code of this position. */
public int hashCode() {
return file.hashCode() ^ encodedLineColumn();
}
/** Returns true iff the given object represents the same position. */
public boolean equals(Object object) {
if (!(object instanceof Position)) return false;
Position that = (Position)object;
return file == that.file && line == that.line && column == that.column;
}
//########################################################################
}
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