src/DotPulsar/Internal/IdLookup.cs

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections.Generic;

namespace DotPulsar.Internal
{
    public sealed class IdLookup<T> where T : class
    {
        private T?[] _items;

        public IdLookup() => _items = new T[1];

        public bool IsEmpty()
        {
            for (var i = 0; i < _items.Length; ++i)
            {
                if (_items[i] != null)
                    return false;
            }

            return true;
        }

        public ulong Add(T item)
        {
            for (var i = 0; i < _items.Length; ++i)
            {
                if (_items[i] != null)
                    continue;

                _items[i] = item;
                return (ulong)i;
            }

            var newArray = new T[_items.Length + 1];
            _items.CopyTo(newArray, 0);
            var id = newArray.Length - 1;
            newArray[id] = item;
            _items = newArray;
            return (ulong)id;
        }

        public T? Remove(ulong id)
        {
            var item = _items[(int)id];
            _items[(int)id] = null;
            return item;
        }

        public T[] RemoveAll()
        {
            var items = new List<T>();
            for (var i = 0; i < _items.Length; ++i)
            {
                var item = _items[i];
                if (item != null)
                {
                    items.Add(item);
                    _items[i] = null;
                }
            }
            return items.ToArray();
        }

        public T? this[ulong id]
        {
            get => _items[(int)id];
        }
    }
}