Roll Observatory packages and add a roll script

string_scanner/lib/src/line_scanner.dart

-// 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 '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 = new 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.
-  LineScannerState get state =>
-      new 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 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 = _newlinesIn(string.substring(oldPosition, newPosition));
-      _line += newlines.length;
-      if (newlines.isEmpty) {
-        _column += newPosition - oldPosition;
-      } else {
-        _column = newPosition - newlines.last.end;
-      }
-    } else {
-      var 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);
-
-  int readChar() {
-    var char = super.readChar();
-    if (char == $lf || (char == $cr && peekChar() != $lf)) {
-      _line += 1;
-      _column = 0;
-    } else {
-      _column += 1;
-    }
-    return char;
-  }
-
-  bool scan(Pattern pattern) {
-    if (!super.scan(pattern)) return false;
-
-    var 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) {
-    var 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);
-}