modernuo/Projects/Server/Collections/ArrayEnumerator.cs

/*************************************************************************
 * ModernUO                                                              *
 * Copyright (C) 2019-2021 - ModernUO Development Team                   *
 * Email: hi@modernuo.com                                                *
 * File: ArrayEnumerator.cs                                              *
 *                                                                       *
 * This program is free software: you can redistribute it and/or modify  *
 * it under the terms of the GNU General Public License as published by  *
 * the Free Software Foundation, either version 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 *************************************************************************/

using System;
using System.Collections;
using System.Collections.Generic;

namespace Server.Collections
{
    /// <summary>
    /// Non-thread safe, non-guarded enumerator for classes that have internal arrays.
    /// Recommended to copy this and use it as a nested struct.
    /// Recommend adding version checking to properly guard against modification during enumeration.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public struct ArrayEnumerator<T> : IEnumerator<T>
    {
        private readonly T[] _array;
        private int _index;
        private T? _current;

        public ArrayEnumerator(T[] array)
        {
            _array = array;
            _index = 0;
            _current = default;
        }

        public void Dispose()
        {
        }

        public bool MoveNext()
        {
            T[] localList = _array;

            if ((uint)_index < (uint)localList.Length)
            {
                _current = _array[_index++];
                return true;
            }

            return false;
        }

        public T? Current => _current!;

        object IEnumerator.Current
        {
            get
            {
                if (_index == 0 || _index == _array.Length + 1)
                {
                    throw new InvalidOperationException(nameof(_index));
                }

                return _current;
            }
        }

        void IEnumerator.Reset()
        {
            _index = 0;
            _current = default;
        }
    }
}