SimpleMapCache.cs

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/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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;
using System.Collections.Generic;

namespace Lucene.Net.Util.Cache
{
    
    /// <summary> Simple cache implementation that uses a HashMap to store (key, value) pairs.
    /// This cache is not synchronized, use <see cref="Cache{TKey, TValue}.SynchronizedCache(Cache{TKey, TValue})" />
    /// if needed.
    /// </summary>
    public class SimpleMapCache<TKey, TValue> : Cache<TKey, TValue>
    {
        internal System.Collections.Generic.Dictionary<TKey, TValue> map;

        public SimpleMapCache()
            : this(new System.Collections.Generic.Dictionary<TKey, TValue>())
        {
        }

        public SimpleMapCache(System.Collections.Generic.Dictionary<TKey, TValue> map)
        {
            this.map = map;
        }
        
        public override TValue Get(System.Object key)
        {
            return map[(TKey)key];
        }
        
        public override void  Put(TKey key, TValue value_Renamed)
        {
            map[key] = value_Renamed;
        }
        
        public override bool ContainsKey(System.Object key)
        {
            return map.ContainsKey((TKey)key);
        }

        protected override void Dispose(bool disposing)
        {
            // do nothing
        }

        /// <summary> Returns a Set containing all keys in this cache.</summary>
        public virtual System.Collections.Generic.HashSet<TKey> KeySet()
        {
            return new HashSet<TKey>(map.Keys);
        }
        
        internal override Cache<TKey, TValue> GetSynchronizedCache()
        {
            return new SynchronizedSimpleMapCache(this);
        }
        
        // Why does does this use both inheritance and composition?
        private class SynchronizedSimpleMapCache : SimpleMapCache<TKey, TValue>
        {
            private System.Object mutex;
            private SimpleMapCache<TKey, TValue> cache;

            private bool isDisposed;

            internal SynchronizedSimpleMapCache(SimpleMapCache<TKey, TValue> cache)
            {
                this.cache = cache;
                this.mutex = this;
            }
            
            public override void  Put(TKey key, TValue value_Renamed)
            {
                lock (mutex)
                {
                    cache.Put(key, value_Renamed);
                }
            }
            
            public override TValue Get(System.Object key)
            {
                lock (mutex)
                {
                    return cache.Get(key);
                }
            }
            
            public override bool ContainsKey(System.Object key)
            {
                lock (mutex)
                {
                    return cache.ContainsKey(key);
                }
            }
            
            protected override void Dispose(bool disposing)
            {
                lock (mutex)
                {
                    if (isDisposed) return;

                    if (disposing)
                    {
                        cache.Dispose(disposing);
                    }

                    isDisposed = true;
                    base.Dispose(disposing);
                }
            }
            
            public override HashSet<TKey> KeySet()
            {
                lock (mutex)
                {
                    return cache.KeySet();
                }
            }
            
            internal override Cache<TKey, TValue> GetSynchronizedCache()
            {
                return this;
            }
        }
    }
}