Index: packages/collection/lib/src/iterable_zip.dart |
diff --git a/packages/collection/lib/src/iterable_zip.dart b/packages/collection/lib/src/iterable_zip.dart |
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index 0000000000000000000000000000000000000000..b9834370673fdb614c51e9f972b202415b5a376b |
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+++ b/packages/collection/lib/src/iterable_zip.dart |
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+// 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) : this._iterables = iterables; |
+ |
+ /// Returns an iterator that combines values of the iterables' iterators |
+ /// as long as they all have values. |
+ 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 new _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; |
+ |
+ bool moveNext() { |
+ if (_iterators.isEmpty) return false; |
+ for (int i = 0; i < _iterators.length; i++) { |
+ if (!_iterators[i].moveNext()) { |
+ _current = null; |
+ return false; |
+ } |
+ } |
+ _current = new List(_iterators.length); |
+ for (int i = 0; i < _iterators.length; i++) { |
+ _current[i] = _iterators[i].current; |
+ } |
+ return true; |
+ } |
+ |
+ List<T> get current => _current; |
+} |