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runtime/observatory/lib/src/service/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.
+
+part of service;
+
+/// A text scanner that keeps track of token position, line, and column.
+class Scanner {
+  final String string;
+
+  /// The current position of the scanner in the string, in characters.
+  int get tokenPos => _tokenPos;
+  set tokenPos(int newTokenPos) {
+    if (newTokenPos < 0 || newTokenPos > string.length) {
+      throw new ArgumentError("Invalid tokenPos $tokenPos");
+    }
+
+    var oldTokenPos = _tokenPos;
+    _tokenPos = newTokenPos;
+
+    if (newTokenPos > oldTokenPos) {
+      var newlines =
+      "\n".allMatches(string.substring(oldTokenPos, newTokenPos)).toList();
+      _line += newlines.length;
+      if (newlines.isEmpty) {
+        _column += newTokenPos - oldTokenPos;
+      } else {
+        _column = newTokenPos - newlines.last.end;
+      }
+    } else {
+      var newlines =
+      "\n".allMatches(string.substring(newTokenPos, oldTokenPos)).toList();
+      _line -= newlines.length;
+      if (newlines.isEmpty) {
+        _column -= oldTokenPos - newTokenPos;
+      } else {
+        _column = newTokenPos - string.lastIndexOf("\n", newTokenPos) - 1;
+      }
+    }
+  }
+  int _tokenPos = 0;
+
+  /// 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 [ScannerState] is only valid for the
+  /// [Scanner] that created it.
+  ScannerState get state => new ScannerState._(this, tokenPos, line, column);
+  set state(ScannerState state) {
+    if (!identical(state._scanner, this)) {
+      throw new ArgumentError("The given LineScannerState was not returned by "
+      "this LineScanner.");
+    }
+
+    _tokenPos = state.tokenPos;
+    _line = state.line;
+    _column = state.column;
+  }
+
+  /// The data about the previous match made by the scanner.
+  ///
+  /// If the last match failed, this will be `null`.
+  Match get lastMatch => _lastMatch;
+  Match _lastMatch;
+
+  /// Whether the scanner has completely consumed [string].
+  bool get isDone => tokenPos == string.length;
+
+  Scanner(this.string, {int tokenPos: 0, int line: 0, int column: 0}) {
+    this._tokenPos = tokenPos;
+    this._line = line;
+    this._column = column;
+  }
+
+  /// Consumes a single character and returns its character code.
+  ///
+  /// This throws a [FormatException] if the string has been fully consumed. It
+  /// doesn't affect [lastMatch].
+  int readChar() {
+    if (isDone) {
+      throw new FormatException('no more input');
+    }
+    var char = string.codeUnitAt(_tokenPos++);
+    if (char == 0xA) {
+      _line += 1;
+      _column = 0;
+    } else {
+      _column += 1;
+    }
+    return char;
+  }
+
+  /// Returns the character code of the character [offset] away from [tokenPos].
+  ///
+  /// [offset] defaults to zero, and may be negative to inspect already-consumed
+  /// characters.
+  ///
+  /// This returns `null` if [offset] points outside the string. It doesn't
+  /// affect [lastMatch].
+  int peekChar([int offset = 0]) {
+    var index = tokenPos + offset;
+    if (index < 0 || index >= string.length) {
+      return null;
+    }
+    return string.codeUnitAt(index);
+  }
+
+  /// If [pattern] matches at the current tokenPos of the string, scans forward
+  /// until the end of the match.
+  ///
+  /// Returns whether or not [pattern] matched.
+  bool scan(Pattern pattern) {
+    var success = matches(pattern);
+    if (!success) {
+      return success;
+    }
+    _tokenPos = _lastMatch.end;
+    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;
+  }
+
+  /// If [pattern] matches at the current tokenPos of the string, scans forward
+  /// until the end of the match.
+  ///
+  /// If [pattern] did not match, throws a [FormatException] describing the
+  /// tokenPos of the failure.
+  void expect(Pattern pattern, {String name}) {
+    if (scan(pattern)) {
+      return;
+    }
+    throw new FormatException('expect($pattern) failed.');
+  }
+
+  /// If the string has not been fully consumed, this throws a
+  /// [FormatException].
+  void expectDone() {
+    if (isDone) {
+      return;
+    }
+    throw new FormatException('not done');
+  }
+
+  /// Returns whether or not [pattern] matches at the current tokenPos of the
+  /// string.
+  ///
+  /// This doesn't move the scan pointer forward.
+  bool matches(Pattern pattern) {
+    _lastMatch = pattern.matchAsPrefix(string, tokenPos);
+    return _lastMatch != null;
+  }
+
+  /// Returns the substring of [string] between [start] and [end].
+  ///
+  /// Unlike [String.substring], [end] defaults to [tokenPos] rather than the
+  /// end of the string.
+  String substring(int start, [int end]) {
+    if (end == null) end = tokenPos;
+    return string.substring(start, end);
+  }
+}
+
+/// A class representing the state of a [LineScanner].
+class ScannerState {
+  /// The [LineScanner] that created this.
+  final Scanner _scanner;
+
+  /// The position of the scanner in this state.
+  final int tokenPos;
+
+  /// 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;
+
+  ScannerState._(this._scanner, this.tokenPos, this.line, this.column);
+}
+
+class ScannedRegion {
+  final ScannerState start;
+  final ScannerState end;
+  ScannedRegion(this.start, this.end);
+
+  bool contained(int line, int column) {
+    // TODO(johnmccutchan): Fix.
+    return false;
+  }
+}
+
+/// Computes a list of source regions that are Dart source code comments.
+/// Handles comments that span multiple lines.
+class CommentScanner {
+  Scanner _scanner;
+
+  CommentScanner(String source, {int tokenPos: 0, int line: 0, int column: 0}) {
+    _scanner =
+        new Scanner(source, tokenPos: tokenPos, line: line, column: column);
+  }
+
+  void scan() {
+  }
+
+  final List<ScannedRegion> comments = [];
+}
+
+/// Computes a list of source regions that are Dart string literals. Will split
+/// string literal regions that include $expr or ${expr} regions into two string
+/// literals (one before and one after). Handles string literals that span
+/// multiple lines.
+class StringLiteralScanner {
+  Scanner _scanner;
+  CommentScanner(String source, {int tokenPos: 0, int line: 0, int column: 0}) {
+    _scanner =
+        new Scanner(source, tokenPos: tokenPos, line: line, column: column);
+  }
+
+  void scan() {
+  }
+
+  final List<ScannedRegion> stringLiterals = [];
+}