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| 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file |
| 2 // for details. All rights reserved. Use of this source code is governed by a |
| 3 // BSD-style license that can be found in the LICENSE file. |
| 4 |
| 5 library string_scanner.line_scanner; |
| 6 |
| 7 import 'string_scanner.dart'; |
| 8 |
| 9 /// A subclass of [StringScanner] that tracks line and column information. |
| 10 class LineScanner extends StringScanner { |
| 11 /// The scanner's current (zero-based) line number. |
| 12 int get line => _line; |
| 13 int _line = 0; |
| 14 |
| 15 /// The scanner's current (zero-based) column number. |
| 16 int get column => _column; |
| 17 int _column = 0; |
| 18 |
| 19 /// The scanner's state, including line and column information. |
| 20 /// |
| 21 /// This can be used to efficiently save and restore the state of the scanner |
| 22 /// when backtracking. A given [LineScannerState] is only valid for the |
| 23 /// [LineScanner] that created it. |
| 24 LineScannerState get state => |
| 25 new LineScannerState._(this, position, line, column); |
| 26 |
| 27 set state(LineScannerState state) { |
| 28 if (!identical(state._scanner, this)) { |
| 29 throw new ArgumentError("The given LineScannerState was not returned by " |
| 30 "this LineScanner."); |
| 31 } |
| 32 |
| 33 super.position = state.position; |
| 34 _line = state.line; |
| 35 _column = state.column; |
| 36 } |
| 37 |
| 38 set position(int newPosition) { |
| 39 var oldPosition = position; |
| 40 super.position = newPosition; |
| 41 |
| 42 if (newPosition > oldPosition) { |
| 43 var newlines = "\n".allMatches(string.substring(oldPosition, newPosition)) |
| 44 .toList(); |
| 45 _line += newlines.length; |
| 46 if (newlines.isEmpty) { |
| 47 _column += newPosition - oldPosition; |
| 48 } else { |
| 49 _column = newPosition - newlines.last.end; |
| 50 } |
| 51 } else { |
| 52 var newlines = "\n".allMatches(string.substring(newPosition, oldPosition)) |
| 53 .toList(); |
| 54 _line -= newlines.length; |
| 55 if (newlines.isEmpty) { |
| 56 _column -= oldPosition - newPosition; |
| 57 } else { |
| 58 _column = newPosition - string.lastIndexOf("\n", newPosition) - 1; |
| 59 } |
| 60 } |
| 61 } |
| 62 |
| 63 LineScanner(String string, {sourceUrl, int position}) |
| 64 : super(string, sourceUrl: sourceUrl, position: position); |
| 65 |
| 66 int readChar() { |
| 67 var char = super.readChar(); |
| 68 if (char == 0xA) { |
| 69 _line += 1; |
| 70 _column = 0; |
| 71 } else { |
| 72 _column += 1; |
| 73 } |
| 74 return char; |
| 75 } |
| 76 |
| 77 bool scan(Pattern pattern) { |
| 78 var oldPosition = position; |
| 79 if (!super.scan(pattern)) return false; |
| 80 |
| 81 var newlines = "\n".allMatches(lastMatch[0]).toList(); |
| 82 _line += newlines.length; |
| 83 if (newlines.isEmpty) { |
| 84 _column += lastMatch[0].length; |
| 85 } else { |
| 86 _column = lastMatch[0].length - newlines.last.end; |
| 87 } |
| 88 |
| 89 return true; |
| 90 } |
| 91 } |
| 92 |
| 93 /// A class representing the state of a [LineScanner]. |
| 94 class LineScannerState { |
| 95 /// The [LineScanner] that created this. |
| 96 final LineScanner _scanner; |
| 97 |
| 98 /// The position of the scanner in this state. |
| 99 final int position; |
| 100 |
| 101 /// The zero-based line number of the scanner in this state. |
| 102 final int line; |
| 103 |
| 104 /// The zero-based column number of the scanner in this state. |
| 105 final int column; |
| 106 |
| 107 LineScannerState._(this._scanner, this.position, this.line, this.column); |
| 108 } |
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