Index: pkg/utf/lib/list_range.dart |
diff --git a/pkg/utf/lib/list_range.dart b/pkg/utf/lib/list_range.dart |
new file mode 100644 |
index 0000000000000000000000000000000000000000..06adb76c6416e7064d047d2a7af18cf77b785124 |
--- /dev/null |
+++ b/pkg/utf/lib/list_range.dart |
@@ -0,0 +1,78 @@ |
+// 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 utf; |
+ |
+/** |
+ * _ListRange in an internal type used to create a lightweight Interable on a |
+ * range within a source list. DO NOT MODIFY the underlying list while |
+ * iterating over it. The results of doing so are undefined. |
+ */ |
+// TODO(floitsch): Consider removing the extend and switch to implements since |
+// that's cheaper to allocate. |
+class _ListRange extends IterableBase { |
+ final List _source; |
+ final int _offset; |
+ final int _length; |
+ |
+ _ListRange(source, [offset = 0, length]) : |
+ this._source = source, |
+ this._offset = offset, |
+ this._length = (length == null ? source.length - offset : length) { |
+ if (_offset < 0 || _offset > _source.length) { |
+ throw new RangeError.value(_offset); |
+ } |
+ if (_length != null && (_length < 0)) { |
+ throw new RangeError.value(_length); |
+ } |
+ if (_length + _offset > _source.length) { |
+ throw new RangeError.value(_length + _offset); |
+ } |
+ } |
+ |
+ _ListRangeIterator get iterator => |
+ new _ListRangeIteratorImpl(_source, _offset, _offset + _length); |
+ |
+ int get length => _length; |
+} |
+ |
+/** |
+ * The _ListRangeIterator provides more capabilities than a standard iterator, |
+ * including the ability to get the current position, count remaining items, |
+ * and move forward/backward within the iterator. |
+ */ |
+abstract class _ListRangeIterator implements Iterator<int> { |
+ bool moveNext(); |
+ int get current; |
+ int get position; |
+ void backup([by]); |
+ int get remaining; |
+ void skip([count]); |
+} |
+ |
+class _ListRangeIteratorImpl implements _ListRangeIterator { |
+ final List<int> _source; |
+ int _offset; |
+ final int _end; |
+ |
+ _ListRangeIteratorImpl(this._source, int offset, this._end) |
+ : _offset = offset - 1; |
+ |
+ int get current => _source[_offset]; |
+ |
+ bool moveNext() => ++_offset < _end; |
+ |
+ int get position => _offset; |
+ |
+ void backup([int by = 1]) { |
+ _offset -= by; |
+ } |
+ |
+ int get remaining => _end - _offset - 1; |
+ |
+ void skip([int count = 1]) { |
+ _offset += count; |
+ } |
+} |
+ |