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 * See CONTRIBUTORS.TXT for a full list of copyright holders.
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 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
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 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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using System;
using System.Collections.Generic;
using System.Net;
using OpenSim.Framework;
using OpenMetaverse;
using BclExtras.Collections;

using ReaderWriterLockImpl = OpenMetaverse.ReaderWriterLockSlim;

namespace OpenSim.Region.ClientStack.LindenUDP
{
    /// <summary>
    /// A thread safe mapping from endpoints to client references
    /// </summary>
    public sealed class UDPClientCollection
    {
        #region IComparers

        private sealed class IPEndPointComparer : IComparer<IPEndPoint>
        {
            public int Compare(IPEndPoint x, IPEndPoint y)
            {
                int result = x.Address.Address.CompareTo(y.Address.Address);
                if (result == 0) result = x.Port.CompareTo(y.Port);
                return result;
            }
        }

        #endregion IComparers

        /// <summary>An immutable dictionary mapping from <seealso cref="IPEndPoint"/>
        /// to <seealso cref="LLUDPClient"/> references</summary>
        private ImmutableMap<IPEndPoint, LLUDPClient> m_dict;
        /// <summary>Immutability grants thread safety for concurrent reads and
        /// read-writes, but not concurrent writes</summary>
        private object m_writeLock;

        /// <summary>Number of clients in the collection</summary>
        public int Count { get { return m_dict.Count; } }

        /// <summary>
        /// Default constructor
        /// </summary>
        public UDPClientCollection()
        {
            m_dict = new ImmutableMap<IPEndPoint, LLUDPClient>(new IPEndPointComparer());
        }

        /// <summary>
        /// Add a client reference to the collection
        /// </summary>
        /// <param name="key">Remote endpoint of the client</param>
        /// <param name="value">Reference to the client object</param>
        public void Add(IPEndPoint key, LLUDPClient value)
        {
            lock (m_writeLock)
                m_dict = m_dict.Add(key, value);
        }

        /// <summary>
        /// Remove a client from the collection
        /// </summary>
        /// <param name="key">Remote endpoint of the client</param>
        public void Remove(IPEndPoint key)
        {
            lock (m_writeLock)
                m_dict = m_dict.Delete(key);
        }

        /// <summary>
        /// Resets the client collection
        /// </summary>
        public void Clear()
        {
            lock (m_writeLock)
                m_dict = new ImmutableMap<IPEndPoint, LLUDPClient>(new IPEndPointComparer());
        }

        /// <summary>
        /// Checks if an endpoint is in the collection
        /// </summary>
        /// <param name="key">Endpoint to check for</param>
        /// <returns>True if the endpoint was found in the collection, otherwise false</returns>
        public bool ContainsKey(IPEndPoint key)
        {
            return m_dict.ContainsKey(key);
        }

        /// <summary>
        /// Attempts to fetch a value out of the collection
        /// </summary>
        /// <param name="key">Endpoint of the client to retrieve</param>
        /// <param name="value">Retrieved client, or null on lookup failure</param>
        /// <returns>True if the lookup succeeded, otherwise false</returns>
        public bool TryGetValue(IPEndPoint key, out LLUDPClient value)
        {
            return m_dict.TryGetValue(key, out value);
        }

        /// <summary>
        /// Performs a given task in parallel for each of the elements in the
        /// collection
        /// </summary>
        /// <param name="action">Action to perform on each element</param>
        public void ForEach(Action<LLUDPClient> action)
        {
            Parallel.ForEach<LLUDPClient>(m_dict.Values, action); 
        }
    }
}