using System;
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using Microsoft.Extensions.Caching.Memory;
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using System.Threading;
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namespace IStation
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{
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internal sealed partial class SharedMemoryCache
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{
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/// <summary>
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/// Attempts to get cache value of type T, otherwise sets a cache item by key, function and optional eviction
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="key">A unique identifier for the cache entry to insert</param>
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/// <param name="valueFunction">A function to execute to get the value for the cache entry</param>
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/// <param name="policy">(Optional) An object that contains eviction details for the cache entry</param>
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/// <returns>An object of type T, or default T</returns>
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public T GetSet<T>(string key, Func<T> valueFunction, int? seconds)
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{
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bool found;
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T value = this.Get<T>(key, out found);
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Exception ex_func = null;
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if (!found)
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{
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this._cacheKeysBeingHandled.TryAdd(key, new CacheKeyBeingHandled());
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lock (this._cacheKeysBeingHandled[key].GetSetOperation.Lock)
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{
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// re-check to see if another thread beat us to setting this value
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value = this.Get<T>(key, out found);
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if (!found)
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{
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// set, so function can be cancelled if a direct set of the same type occurs
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this._cacheKeysBeingHandled[key].GetSetOperation.Type = typeof(T);
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// put the function into it's own thread (so it can be cancelled)
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this._cacheKeysBeingHandled[key].GetSetOperation.Thread = new Thread(() =>
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{
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var aborted = false;
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var success = false;
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try
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{
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value = valueFunction();
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success = true;
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}
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catch (ThreadAbortException)
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{
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aborted = true;
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}
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#region 用于处理valueFunction引发异常
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catch (Exception ex)
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{
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aborted = true;
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ex_func = ex;
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}
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#endregion
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finally
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{
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if (aborted)
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{
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value = (T)this._cacheKeysBeingHandled[key].GetSetOperation.Value; // cast should always be valid as this method is the only thing that sets it
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}
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else if (success)
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{
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if (value == null)
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{
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if (!this._isWiping)
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{
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((IMemoryCacheDirect)this).Remove(key);
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}
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}
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else
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{
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((IMemoryCacheDirect)this).Set(key, value, seconds);
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}
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}
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}
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});
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this._cacheKeysBeingHandled[key].GetSetOperation.Thread.Start();
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this._cacheKeysBeingHandled[key].GetSetOperation.Thread.Join();
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}
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}
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this._cacheKeysBeingHandled.TryRemove(key, out CacheKeyBeingHandled cacheKeyBeingHandled);
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}
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if (ex_func != null)
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throw ex_func;
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return value;
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}
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/// <summary>
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/// Attempts to get cache value of type T, otherwise sets a cache item by key, value and optional eviction
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/// </summary>
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/// <typeparam name="T"></typeparam>
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/// <param name="key">A unique identifier for the cache entry to insert</param>
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/// <param name="value">The data for the cache entry</param>
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/// <param name="policy">(Optional) An object that contains eviction details for the cache item</param>
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/// <returns>An object of type T, or default T</returns>
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public T GetSet<T>(string key, T value, int? seconds)
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{
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bool found;
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var cachedValue = this.Get<T>(key, out found);
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if (!found)
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{
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Set(key, value, seconds);
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return value;
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}
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return cachedValue;
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}
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}
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}
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