| // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| library string_scanner.line_scanner; |
| |
| import 'string_scanner.dart'; |
| |
| /// A subclass of [StringScanner] that tracks line and column information. |
| class LineScanner extends StringScanner { |
| /// The scanner's current (zero-based) line number. |
| int get line => _line; |
| int _line = 0; |
| |
| /// The scanner's current (zero-based) column number. |
| int get column => _column; |
| int _column = 0; |
| |
| /// The scanner's state, including line and column information. |
| /// |
| /// This can be used to efficiently save and restore the state of the scanner |
| /// when backtracking. A given [LineScannerState] is only valid for the |
| /// [LineScanner] that created it. |
| LineScannerState get state => |
| new LineScannerState._(this, position, line, column); |
| |
| set state(LineScannerState state) { |
| if (!identical(state._scanner, this)) { |
| throw new ArgumentError("The given LineScannerState was not returned by " |
| "this LineScanner."); |
| } |
| |
| super.position = state.position; |
| _line = state.line; |
| _column = state.column; |
| } |
| |
| set position(int newPosition) { |
| var oldPosition = position; |
| super.position = newPosition; |
| |
| if (newPosition > oldPosition) { |
| var newlines = "\n".allMatches(string.substring(oldPosition, newPosition)) |
| .toList(); |
| _line += newlines.length; |
| if (newlines.isEmpty) { |
| _column += newPosition - oldPosition; |
| } else { |
| _column = newPosition - newlines.last.end; |
| } |
| } else { |
| var newlines = "\n".allMatches(string.substring(newPosition, oldPosition)) |
| .toList(); |
| _line -= newlines.length; |
| if (newlines.isEmpty) { |
| _column -= oldPosition - newPosition; |
| } else { |
| _column = newPosition - string.lastIndexOf("\n", newPosition) - 1; |
| } |
| } |
| } |
| |
| LineScanner(String string, {sourceUrl, int position}) |
| : super(string, sourceUrl: sourceUrl, position: position); |
| |
| int readChar() { |
| var char = super.readChar(); |
| if (char == 0xA) { |
| _line += 1; |
| _column = 0; |
| } else { |
| _column += 1; |
| } |
| return char; |
| } |
| |
| bool scan(Pattern pattern) { |
| var oldPosition = position; |
| if (!super.scan(pattern)) return false; |
| |
| var newlines = "\n".allMatches(lastMatch[0]).toList(); |
| _line += newlines.length; |
| if (newlines.isEmpty) { |
| _column += lastMatch[0].length; |
| } else { |
| _column = lastMatch[0].length - newlines.last.end; |
| } |
| |
| return true; |
| } |
| } |
| |
| /// A class representing the state of a [LineScanner]. |
| class LineScannerState { |
| /// The [LineScanner] that created this. |
| final LineScanner _scanner; |
| |
| /// The position of the scanner in this state. |
| final int position; |
| |
| /// The zero-based line number of the scanner in this state. |
| final int line; |
| |
| /// The zero-based column number of the scanner in this state. |
| final int column; |
| |
| LineScannerState._(this._scanner, this.position, this.line, this.column); |
| } |