| // Copyright (c) 2013, 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. |
| |
| import 'dart:collection'; |
| |
| /// Iterable that iterates over lists of values from other iterables. |
| /// |
| /// When [iterator] is read, an [Iterator] is created for each [Iterable] in |
| /// the [Iterable] passed to the constructor. |
| /// |
| /// As long as all these iterators have a next value, those next values are |
| /// combined into a single list, which becomes the next value of this |
| /// [Iterable]'s [Iterator]. As soon as any of the iterators run out, |
| /// the zipped iterator also stops. |
| class IterableZip<T> extends IterableBase<List<T>> { |
| final Iterable<Iterable<T>> _iterables; |
| |
| IterableZip(Iterable<Iterable<T>> iterables) : _iterables = iterables; |
| |
| /// Returns an iterator that combines values of the iterables' iterators |
| /// as long as they all have values. |
| @override |
| Iterator<List<T>> get iterator { |
| var iterators = _iterables.map((x) => x.iterator).toList(growable: false); |
| // TODO(lrn): Return an empty iterator directly if iterators is empty? |
| return _IteratorZip<T>(iterators); |
| } |
| } |
| |
| class _IteratorZip<T> implements Iterator<List<T>> { |
| final List<Iterator<T>> _iterators; |
| List<T> _current; |
| |
| _IteratorZip(List<Iterator<T>> iterators) : _iterators = iterators; |
| |
| @override |
| bool moveNext() { |
| if (_iterators.isEmpty) return false; |
| for (var i = 0; i < _iterators.length; i++) { |
| if (!_iterators[i].moveNext()) { |
| _current = null; |
| return false; |
| } |
| } |
| _current = List(_iterators.length); |
| for (var i = 0; i < _iterators.length; i++) { |
| _current[i] = _iterators[i].current; |
| } |
| return true; |
| } |
| |
| @override |
| List<T> get current => _current; |
| } |