pkg/shelf

pkg/shelf/lib/src/string_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 shelf.string_scanner;
+
+/// A class that scans through a string using [Pattern]s.
+class StringScanner {
+  /// The string being scanned through.
+  final String string;
+
+  /// The current position of the scanner in the string, in characters.
+  int get position => _position;
+  set position(int position) {
+    if (position < 0 || position > string.length) {
+      throw new ArgumentError("Invalid position $position");
+    }
+
+    _position = position;
+  }
+  int _position = 0;
+
+  /// 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;
+
+  /// The portion of the string that hasn't yet been scanned.
+  String get rest => string.substring(position);
+
+  /// Whether the scanner has completely consumed [string].
+  bool get isDone => position == string.length;
+
+  /// Creates a new [StringScanner] that starts scanning from [position].
+  ///
+  /// [position] defaults to 0, the beginning of the string.
+  StringScanner(this.string, {int position}) {
+    if (position != null) this.position = position;
+  }
+
+  /// If [pattern] matches at the current position 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) _position = _lastMatch.end;
+    return success;
+  }
+
+  /// If [pattern] matches at the current position of the string, scans forward
+  /// until the end of the match.
+  ///
+  /// If [pattern] did not match, throws a [FormatException] with [message].
+  void expect(Pattern pattern, String message) {
+    if (scan(pattern)) return;
+    throw new FormatException(message);
+  }
+
+  /// Returns whether or not [pattern] matches at the current position of the
+  /// string.
+  ///
+  /// This doesn't move the scan pointer forward.
+  bool matches(Pattern pattern) {
+    _lastMatch = pattern.matchAsPrefix(string, position);
+    return _lastMatch != null;
+  }
+}