opensim-development – Rev 1
?pathlinks?
/*
* 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);
}
}