Index: packages/collection/lib/src/combined_wrappers/combined_list.dart |
diff --git a/packages/collection/lib/src/combined_wrappers/combined_list.dart b/packages/collection/lib/src/combined_wrappers/combined_list.dart |
new file mode 100644 |
index 0000000000000000000000000000000000000000..d2e03499bf7e99fe0fccedc0367d42ffbeb350ee |
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+++ b/packages/collection/lib/src/combined_wrappers/combined_list.dart |
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+// Copyright (c) 2017, 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'; |
+ |
+/// A view of several lists combined into a single list. |
+/// |
+/// All methods and accessors treat the [CombinedListView] list as if it were a |
+/// single concatenated list, but the underlying implementation is based on |
+/// lazily accessing individual list instances. This means that if the |
+/// underlying lists change, the [CombinedListView] will reflect those changes. |
+/// |
+/// The index operator (`[]`) and [length] property of a [CombinedListView] are |
+/// both `O(lists)` rather than `O(1)`. A [CombinedListView] is unmodifiable. |
+class CombinedListView<T> extends ListBase<T> |
+ implements UnmodifiableListView<T> { |
+ static void _throw() { |
+ throw new UnsupportedError('Cannot modify an unmodifiable List'); |
+ } |
+ |
+ /// The lists that this combines. |
+ final List<List<T>> _lists; |
+ |
+ /// Creates a combined view of [lists]. |
+ CombinedListView(this._lists); |
+ |
+ set length(int length) { |
+ _throw(); |
+ } |
+ |
+ int get length => _lists.fold(0, (length, list) => length + list.length); |
+ |
+ T operator [](int index) { |
+ var initialIndex = index; |
+ for (var i = 0; i < _lists.length; i++) { |
+ var list = _lists[i]; |
+ if (index < list.length) { |
+ return list[index]; |
+ } |
+ index -= list.length; |
+ } |
+ throw new RangeError.index(initialIndex, this, 'index', null, length); |
+ } |
+ |
+ void operator []=(int index, T value) { |
+ _throw(); |
+ } |
+ |
+ void clear() { |
+ _throw(); |
+ } |
+ |
+ bool remove(Object element) { |
+ _throw(); |
+ return null; |
+ } |
+ |
+ void removeWhere(bool filter(T element)) { |
+ _throw(); |
+ } |
+ |
+ void retainWhere(bool filter(T element)) { |
+ _throw(); |
+ } |
+} |