apewer-dotnet/Apewer.Source/Externals/MySql.Data-6.10.9/MySqlClient/Common/Cache.cs

#if MYSQL_6_10

// Copyright ?2004, 2016 Oracle and/or its affiliates. All rights reserved.
//
// MySQL Connector/NET is licensed under the terms of the GPLv2
// <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most 
// MySQL Connectors. There are special exceptions to the terms and 
// conditions of the GPLv2 as it is applied to this software, see the 
// FLOSS License Exception
// <http://www.mysql.com/about/legal/licensing/foss-exception.html>.
//
// 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; version 2 of the License.
//
// This program is distributed in the hope that it will be useful, but 
// WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
// for more details.
//
// You should have received a copy of the GNU General Public License along 
// with this program; if not, write to the Free Software Foundation, Inc., 
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System.Collections.Generic;

namespace Externals.MySql.Data.Common
{
    internal class Cache<TKeyType, TValueType>
    {
        private readonly int _capacity;
        private readonly Queue<TKeyType> _keyQ;
        private readonly Dictionary<TKeyType, TValueType> _contents;

        public Cache(int initialCapacity, int capacity)
        {
            _capacity = capacity;
            _contents = new Dictionary<TKeyType, TValueType>(initialCapacity);

            if (capacity > 0)
                _keyQ = new Queue<TKeyType>(initialCapacity);
        }

        public TValueType this[TKeyType key]
        {
            get
            {
                TValueType val;
                if (_contents.TryGetValue(key, out val))
                    return val;
                else
                    return default(TValueType);
            }
            set { InternalAdd(key, value); }
        }

        public void Add(TKeyType key, TValueType value)
        {
            InternalAdd(key, value);
        }

        private void InternalAdd(TKeyType key, TValueType value)
        {
            if (!_contents.ContainsKey(key))
            {

                if (_capacity > 0)
                {
                    _keyQ.Enqueue(key);

                    if (_keyQ.Count > _capacity)
                        _contents.Remove(_keyQ.Dequeue());
                }
            }

            _contents[key] = value;
        }
    }
}

#endif