| // Copyright (c) 2012, 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 dart.collection; |
| |
| /** |
| * The [HasNextIterator] class wraps an [Iterator] and provides methods to |
| * iterate over an object using `hasNext` and `next`. |
| * |
| * An [HasNextIterator] does not implement the [Iterator] interface. |
| */ |
| class HasNextIterator<E> { |
| static const int _HAS_NEXT_AND_NEXT_IN_CURRENT = 0; |
| static const int _NO_NEXT = 1; |
| static const int _NOT_MOVED_YET = 2; |
| |
| Iterator _iterator; |
| int _state = _NOT_MOVED_YET; |
| |
| HasNextIterator(this._iterator); |
| |
| bool get hasNext { |
| if (_state == _NOT_MOVED_YET) _move(); |
| return _state == _HAS_NEXT_AND_NEXT_IN_CURRENT; |
| } |
| |
| E next() { |
| // Call to hasNext is necessary to make sure we are positioned at the first |
| // element when we start iterating. |
| if (!hasNext) throw new StateError("No more elements"); |
| assert(_state == _HAS_NEXT_AND_NEXT_IN_CURRENT); |
| E result = _iterator.current; |
| _move(); |
| return result; |
| } |
| |
| void _move() { |
| if (_iterator.moveNext()) { |
| _state = _HAS_NEXT_AND_NEXT_IN_CURRENT; |
| } else { |
| _state = _NO_NEXT; |
| } |
| } |
| } |