sdk/tools/dom/nnbd_src/_ListIterators.dart

// Copyright (c) 2011, 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 html;

// Iterator for arrays with fixed size.
class FixedSizeListIterator<T> implements Iterator<T> {
  final List<T> _array;
  final int _length; // Cache array length for faster access.
  int _position;
  T? _current;

  FixedSizeListIterator(List<T> array)
      : _array = array,
        _position = -1,
        _length = array.length;

  bool moveNext() {
    int nextPosition = _position + 1;
    if (nextPosition < _length) {
      _current = _array[nextPosition];
      _position = nextPosition;
      return true;
    }
    _current = null;
    _position = _length;
    return false;
  }

  T get current => _current as T;
}

// Iterator for arrays with variable size.
class _VariableSizeListIterator<T> implements Iterator<T> {
  final List<T> _array;
  int _position;
  T? _current;

  _VariableSizeListIterator(List<T> array)
      : _array = array,
        _position = -1;

  bool moveNext() {
    int nextPosition = _position + 1;
    if (nextPosition < _array.length) {
      _current = _array[nextPosition];
      _position = nextPosition;
      return true;
    }
    _current = null;
    _position = _array.length;
    return false;
  }

  T get current => _current as T;
}