| // 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. |
| |
| import 'package:charcode/ascii.dart'; |
| |
| import 'string_scanner.dart'; |
| |
| // Note that much of this code is duplicated in eager_span_scanner.dart. |
| |
| /// A regular expression matching newlines across platforms. |
| final _newlineRegExp = RegExp(r'\r\n?|\n'); |
| |
| /// 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. |
| /// |
| /// This does not include the scanner's match information. |
| LineScannerState get state => |
| LineScannerState._(this, position, line, column); |
| |
| /// Whether the current position is between a CR character and an LF |
| /// charactet. |
| bool get _betweenCRLF => peekChar(-1) == $cr && peekChar() == $lf; |
| |
| set state(LineScannerState state) { |
| if (!identical(state._scanner, this)) { |
| throw ArgumentError('The given LineScannerState was not returned by ' |
| 'this LineScanner.'); |
| } |
| |
| super.position = state.position; |
| _line = state.line; |
| _column = state.column; |
| } |
| |
| @override |
| set position(int newPosition) { |
| final oldPosition = position; |
| super.position = newPosition; |
| |
| if (newPosition > oldPosition) { |
| final newlines = _newlinesIn(string.substring(oldPosition, newPosition)); |
| _line += newlines.length; |
| if (newlines.isEmpty) { |
| _column += newPosition - oldPosition; |
| } else { |
| _column = newPosition - newlines.last.end; |
| } |
| } else { |
| final newlines = _newlinesIn(string.substring(newPosition, oldPosition)); |
| if (_betweenCRLF) newlines.removeLast(); |
| |
| _line -= newlines.length; |
| if (newlines.isEmpty) { |
| _column -= oldPosition - newPosition; |
| } else { |
| _column = |
| newPosition - string.lastIndexOf(_newlineRegExp, newPosition) - 1; |
| } |
| } |
| } |
| |
| LineScanner(String string, {sourceUrl, int? position}) |
| : super(string, sourceUrl: sourceUrl, position: position); |
| |
| @override |
| bool scanChar(int character) { |
| if (!super.scanChar(character)) return false; |
| _adjustLineAndColumn(character); |
| return true; |
| } |
| |
| @override |
| int readChar() { |
| final character = super.readChar(); |
| _adjustLineAndColumn(character); |
| return character; |
| } |
| |
| /// Adjusts [_line] and [_column] after having consumed [character]. |
| void _adjustLineAndColumn(int character) { |
| if (character == $lf || (character == $cr && peekChar() != $lf)) { |
| _line += 1; |
| _column = 0; |
| } else { |
| _column += 1; |
| } |
| } |
| |
| @override |
| bool scan(Pattern pattern) { |
| if (!super.scan(pattern)) return false; |
| |
| final newlines = _newlinesIn(lastMatch![0]!); |
| _line += newlines.length; |
| if (newlines.isEmpty) { |
| _column += (lastMatch![0])!.length; |
| } else { |
| _column = (lastMatch![0])!.length - newlines.last.end; |
| } |
| |
| return true; |
| } |
| |
| /// Returns a list of [Match]es describing all the newlines in [text], which |
| /// is assumed to end at [position]. |
| List<Match> _newlinesIn(String text) { |
| final newlines = _newlineRegExp.allMatches(text).toList(); |
| if (_betweenCRLF) newlines.removeLast(); |
| return newlines; |
| } |
| } |
| |
| /// 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); |
| } |