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diff --git a/OpenSim/Framework/ICnmCache.cs b/OpenSim/Framework/ICnmCache.cs
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+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * 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.
+ *     * Neither the name of the OpenSimulator Project nor the
+ *       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
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+using System;
+using System.Collections.Generic;
+
+namespace OpenSim.Framework
+{
+    /// <summary>
+    /// Represent generic cache to store key/value pairs (elements) limited by time, size and count of elements.
+    /// </summary>
+    /// <typeparam name="TKey">
+    /// The type of keys in the cache. 
+    /// </typeparam>
+    /// <typeparam name="TValue">
+    /// The type of values in the cache. 
+    /// </typeparam>
+    /// <remarks>
+    /// <para>
+    /// Cache store limitations:
+    /// </para>
+    /// <list type="table">
+    /// <listheader>
+    /// <term>Limitation</term>
+    /// <description>Description</description>
+    /// </listheader>
+    /// <item>
+    /// <term>Time</term>
+    /// <description>
+    /// Element that is not accessed through <see cref="TryGetValue"/> or <see cref="Set"/> in last <see cref="ExpirationTime"/> are 
+    /// removed from the cache automatically. Depending on implementation of the cache some of elements may stay longer in cache. 
+    /// <see cref="IsTimeLimited"/> returns <see langword="true"/>, if cache is limited by time.
+    /// </description>
+    /// </item>
+    /// <item>
+    /// <term>Count</term>
+    /// <description>
+    /// When adding an new element to cache that already have <see cref="MaxCount"/> of elements, cache will remove less recently
+    /// used element(s) from the cache, until element fits to cache. 
+    /// <see cref="IsCountLimited"/> returns <see langword="true"/>, if cache is limiting element count.
+    /// </description>
+    /// </item>
+    /// <item>
+    /// <term>Size</term>
+    /// <description>
+    /// <description>
+    /// When adding an new element to cache that already have <see cref="MaxSize"/> of elements, cache will remove less recently
+    /// used element(s) from the cache, until element fits to cache. 
+    /// <see cref="IsSizeLimited"/> returns <see langword="true"/>, if cache is limiting total size of elements. 
+    /// Normally size is bytes used by element in the cache. But it can be any other suitable unit of measure.
+    /// </description>
+    /// </description>
+    /// </item>
+    /// </list>
+    /// </remarks>
+    public interface ICnmCache<TKey, TValue> : IEnumerable<KeyValuePair<TKey, TValue>>
+    {
+        /// <summary>
+        /// Gets current count of elements stored to <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting element count, 
+        /// <see cref="ICnmCache{TKey,TValue}"/> will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="MaxCount"/>
+        /// <seealso cref="IsCountLimited"/>
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="IsTimeLimited"/>
+        int Count { get; }
+
+        /// <summary>
+        /// Gets or sets elements expiration time.
+        /// </summary>
+        /// <value>
+        /// Elements expiration time.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// When element has been stored in <see cref="ICnmCache{TKey,TValue}"/> longer than <see cref="ExpirationTime"/> 
+        /// and it is not accessed through <see cref="TryGetValue"/> method or element's value is 
+        /// not replaced by <see cref="Set"/> method, then it is automatically removed from the 
+        /// <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </para>
+        /// <para>
+        /// It is possible that <see cref="ICnmCache{TKey,TValue}"/> implementation removes element before it's expiration time, 
+        /// because total size or count of elements stored to cache is larger than <see cref="MaxSize"/> or <see cref="MaxCount"/>.
+        /// </para>
+        /// <para>
+        /// It is also possible that element stays in cache longer than <see cref="ExpirationTime"/>.
+        /// </para>
+        /// <para>
+        /// Calling <see cref="PurgeExpired"/> try to remove all elements that are expired.
+        /// </para>
+        /// <para>
+        /// To disable time limit in cache, set <see cref="ExpirationTime"/> to <see cref="DateTime.MaxValue"/>.
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="IsTimeLimited"/>
+        /// <seealso cref="IsCountLimited"/>
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="PurgeExpired"/>
+        /// <seealso cref="Count"/>
+        /// <seealso cref="MaxCount"/>
+        /// <seealso cref="MaxSize"/>
+        /// <seealso cref="Size"/>
+        TimeSpan ExpirationTime { get; set; }
+
+        /// <summary>
+        /// Gets a value indicating whether or not access to the <see cref="ICnmCache{TKey,TValue}"/> is synchronized (thread safe).
+        /// </summary>
+        /// <value>
+        /// <see langword="true"/> if access to the <see cref="ICnmCache{TKey,TValue}"/> is synchronized (thread safe); 
+        /// otherwise, <see langword="false"/>. 
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// To get synchronized (thread safe) access to <see cref="ICnmCache{TKey,TValue}"/> object, use 
+        /// <see cref="CnmSynchronizedCache{TKey,TValue}.Synchronized"/> in <see cref="CnmSynchronizedCache{TKey,TValue}"/> class
+        /// to retrieve synchronized wrapper for <see cref="ICnmCache{TKey,TValue}"/> object.
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="SyncRoot"/>
+        /// <seealso cref="CnmSynchronizedCache{TKey,TValue}"/>
+        bool IsSynchronized { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether <see cref="ICnmCache{TKey,TValue}"/> is limiting count of elements.
+        /// </summary>
+        /// <value>
+        /// <see langword="true"/> if the <see cref="ICnmCache{TKey,TValue}"/> count of elements is limited; 
+        /// otherwise, <see langword="false"/>. 
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting element count, 
+        /// <see cref="ICnmCache{TKey,TValue}"/> will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="Count"/>
+        /// <seealso cref="MaxCount"/> 
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="IsTimeLimited"/>
+        bool IsCountLimited { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether <see cref="ICnmCache{TKey,TValue}"/> is limiting size of elements.
+        /// </summary>
+        /// <value>
+        /// <see langword="true"/> if the <see cref="ICnmCache{TKey,TValue}"/> total size of elements is limited; 
+        /// otherwise, <see langword="false"/>. 
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting total size of elements, 
+        /// <see cref="ICnmCache{TKey,TValue}"/> will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="MaxElementSize"/>
+        /// <seealso cref="Size"/>
+        /// <seealso cref="MaxSize"/>
+        /// <seealso cref="IsCountLimited"/>
+        /// <seealso cref="IsTimeLimited"/>
+        bool IsSizeLimited { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether elements stored to <see cref="ICnmCache{TKey,TValue}"/> have limited inactivity time.
+        /// </summary>
+        /// <value>
+        /// <see langword="true"/> if the <see cref="ICnmCache{TKey,TValue}"/> has a fixed total size of elements; 
+        /// otherwise, <see langword="false"/>. 
+        /// </value>
+        /// <remarks>
+        /// If <see cref="ICnmCache{TKey,TValue}"/> have limited inactivity time and element is not accessed through <see cref="Set"/>
+        /// or <see cref="TryGetValue"/> methods in <see cref="ExpirationTime"/> , then element is automatically removed from 
+        /// the cache. Depending on implementation of the <see cref="ICnmCache{TKey,TValue}"/>, some of the elements may 
+        /// stay longer in cache.
+        /// </remarks>
+        /// <seealso cref="ExpirationTime"/>
+        /// <seealso cref="PurgeExpired"/>
+        /// <seealso cref="IsCountLimited"/>
+        /// <seealso cref="IsSizeLimited"/>
+        bool IsTimeLimited { get; }
+        
+        /// <summary>
+        /// Gets or sets maximal allowed count of elements that can be stored to <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>
+        /// <see cref="int.MaxValue"/>, if <see cref="ICnmCache{TKey,TValue}"/> is not limited by count of elements; 
+        /// otherwise maximal allowed count of elements.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting element count, 
+        /// <see cref="ICnmCache{TKey,TValue}"/> will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        int MaxCount { get; set; }
+
+        /// <summary>
+        /// <para>Gets maximal allowed element size.</para>
+        /// </summary>
+        /// <value>
+        /// Maximal allowed element size.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// If element's size is larger than <see cref="MaxElementSize"/>, then element is 
+        /// not added to the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="Set"/>
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="Size"/>
+        /// <seealso cref="MaxSize"/>
+        long MaxElementSize { get; }
+
+        /// <summary>
+        /// Gets or sets maximal allowed total size for elements stored to <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>
+        /// Maximal allowed total size for elements stored to <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// Normally size is total bytes used by elements in the cache. But it can be any other suitable unit of measure.
+        /// </para>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting total size of elements, 
+        /// <see cref="ICnmCache{TKey,TValue}"/> will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        /// <exception cref="ArgumentOutOfRangeException">value is less than 0.</exception>
+        /// <seealso cref="MaxElementSize"/>
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="Size"/>
+        long MaxSize { get; set; }
+
+        /// <summary>
+        /// Gets total size of elements stored to <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>
+        /// Total size of elements stored to <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// Normally bytes, but can be any suitable unit of measure.
+        /// </para>
+        /// <para>
+        /// Element's size is given when element is added or replaced by <see cref="Set"/> method. 
+        /// </para>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting total size of elements, 
+        /// <see cref="ICnmCache{TKey,TValue}"/> will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="MaxElementSize"/>
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="MaxSize"/>
+        /// <seealso cref="IsCountLimited"/>
+        /// <seealso cref="ExpirationTime"/>
+        long Size { get; }
+
+        /// <summary>
+        /// Gets an object that can be used to synchronize access to the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <value>
+        /// An object that can be used to synchronize access to the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </value>
+        /// <remarks>
+        /// <para>
+        /// To get synchronized (thread safe) access to <see cref="ICnmCache{TKey,TValue}"/>, use <see cref="CnmSynchronizedCache{TKey,TValue}"/> 
+        /// method <see cref="CnmSynchronizedCache{TKey,TValue}.Synchronized"/> to retrieve synchronized wrapper interface to 
+        /// <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="IsSynchronized"/>
+        /// <seealso cref="CnmSynchronizedCache{TKey,TValue}"/>
+        object SyncRoot { get; }
+
+        /// <summary>
+        /// Removes all elements from the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <seealso cref="Set"/>
+        /// <seealso cref="Remove"/>
+        /// <seealso cref="RemoveRange"/>
+        /// <seealso cref="TryGetValue"/>
+        /// <seealso cref="PurgeExpired"/>
+        void Clear();
+
+        /// <summary>
+        /// Purge expired elements from the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// Element becomes expired when last access time to it has been longer time than <see cref="ExpirationTime"/>.
+        /// </para>
+        /// <para>
+        /// Depending on <see cref="ICnmCache{TKey,TValue}"/> implementation, some of expired elements
+        /// may stay longer than <see cref="ExpirationTime"/> in the cache.
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="IsTimeLimited"/>
+        /// <seealso cref="ExpirationTime"/>
+        /// <seealso cref="Set"/>
+        /// <seealso cref="Remove"/>
+        /// <seealso cref="RemoveRange"/>
+        /// <seealso cref="TryGetValue"/>
+        /// <seealso cref="Clear"/>
+        void PurgeExpired();
+
+        /// <summary>
+        /// Removes element associated with <paramref name="key"/> from the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <param name="key">
+        /// The key that is associated with element to remove from the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        /// <paramref name="key"/> is <see langword="null"/>.
+        /// </exception>
+        /// <seealso cref="Set"/>
+        /// <seealso cref="RemoveRange"/>
+        /// <seealso cref="TryGetValue"/>
+        /// <seealso cref="Clear"/>
+        /// <seealso cref="PurgeExpired"/>
+        void Remove(TKey key);
+
+        /// <summary>
+        /// Removes elements that are associated with one of <paramref name="keys"/> from the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <param name="keys">
+        /// The keys that are associated with elements to remove from the <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        /// <paramref name="keys"/> is <see langword="null"/>.
+        /// </exception>
+        /// <seealso cref="Set"/>
+        /// <seealso cref="Remove"/>
+        /// <seealso cref="TryGetValue"/>
+        /// <seealso cref="Clear"/>
+        /// <seealso cref="PurgeExpired"/>
+        void RemoveRange(IEnumerable<TKey> keys);
+
+        /// <summary>
+        /// Add or replace an element with the provided <paramref name="key"/>, <paramref name="value"/> and <paramref name="size"/> to 
+        /// <see cref="ICnmCache{TKey,TValue}"/>.
+        /// </summary>
+        /// <param name="key">
+        /// The object used as the key of the element. Can't be <see langword="null"/> reference.
+        /// </param>
+        /// <param name="value">
+        /// The object used as the value of the element to add or replace. <see langword="null"/> is allowed.
+        /// </param>
+        /// <param name="size">
+        /// The element's size. Normally bytes, but can be any suitable unit of measure.
+        /// </param>
+        /// <returns>
+        /// <see langword="true"/> if element has been added successfully to the <see cref="ICnmCache{TKey,TValue}"/>; 
+        /// otherwise <see langword="false"/>.
+        /// </returns>
+        /// <exception cref="ArgumentNullException">
+        /// <paramref name="key"/>is <see langword="null"/>.
+        /// </exception>
+        /// <exception cref="ArgumentOutOfRangeException">
+        /// The element's <paramref name="size"/> is less than 0.
+        /// </exception>
+        /// <remarks>
+        /// <para>
+        /// If element's <paramref name="size"/> is larger than <see cref="MaxElementSize"/>, then element is 
+        /// not added to the <see cref="ICnmCache{TKey,TValue}"/>, however - possible older element is 
+        /// removed from the <see cref="ICnmCache{TKey,TValue}"/>. 
+        /// </para>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting total size of elements, 
+        /// <see cref="ICnmCache{TKey,TValue}"/>will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// <para>
+        /// When adding an new element to <see cref="ICnmCache{TKey,TValue}"/> that is limiting element count, 
+        /// <see cref="ICnmCache{TKey,TValue}"/>will remove less recently used elements until it can fit an new element. 
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="IsSizeLimited"/>
+        /// <seealso cref="IsCountLimited"/>
+        /// <seealso cref="Remove"/>
+        /// <seealso cref="RemoveRange"/>
+        /// <seealso cref="TryGetValue"/>
+        /// <seealso cref="Clear"/>
+        /// <seealso cref="PurgeExpired"/>
+        bool Set(TKey key, TValue value, long size);
+
+        /// <summary>
+        /// Gets the <paramref name="value"/> associated with the specified <paramref name="key"/>.
+        /// </summary>
+        /// <returns>
+        /// <see langword="true"/>if the <see cref="ICnmCache{TKey,TValue}"/> contains an element with 
+        /// the specified key; otherwise, <see langword="false"/>.
+        /// </returns>
+        /// <param name="key">
+        /// The key whose <paramref name="value"/> to get.
+        /// </param>
+        /// <param name="value">
+        /// When this method returns, the value associated with the specified <paramref name="key"/>, 
+        /// if the <paramref name="key"/> is found; otherwise, the 
+        /// default value for the type of the <paramref name="value"/> parameter. This parameter is passed uninitialized.
+        /// </param>
+        /// <exception cref="ArgumentNullException">
+        /// <paramref name="key"/>is <see langword="null"/>.
+        /// </exception>
+        /// <seealso cref="Set"/>
+        /// <seealso cref="Remove"/>
+        /// <seealso cref="RemoveRange"/>
+        /// <seealso cref="Clear"/>
+        /// <seealso cref="PurgeExpired"/>
+        bool TryGetValue(TKey key, out TValue value);
+    }
+}