pkg/utf: fixed layout, added todos, updated docs and homepage pubspec links

pkg/utf/lib/list_range.dart

-// 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;
-  }
-}
-