60 lines
1.9 KiB
C#
60 lines
1.9 KiB
C#
namespace System.Web.Mvc {
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using System;
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using System.Collections.Generic;
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using System.Diagnostics.CodeAnalysis;
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using System.Threading;
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[SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable", Justification = "Instances of this type are meant to be singletons.")]
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internal abstract class ReaderWriterCache<TKey, TValue> {
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private readonly Dictionary<TKey, TValue> _cache;
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private readonly ReaderWriterLockSlim _rwLock = new ReaderWriterLockSlim();
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protected ReaderWriterCache()
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: this(null) {
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}
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protected ReaderWriterCache(IEqualityComparer<TKey> comparer) {
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_cache = new Dictionary<TKey, TValue>(comparer);
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}
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protected Dictionary<TKey, TValue> Cache {
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get {
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return _cache;
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}
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}
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protected TValue FetchOrCreateItem(TKey key, Func<TValue> creator) {
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// first, see if the item already exists in the cache
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_rwLock.EnterReadLock();
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try {
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TValue existingEntry;
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if (_cache.TryGetValue(key, out existingEntry)) {
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return existingEntry;
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}
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}
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finally {
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_rwLock.ExitReadLock();
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}
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// insert the new item into the cache
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TValue newEntry = creator();
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_rwLock.EnterWriteLock();
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try {
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TValue existingEntry;
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if (_cache.TryGetValue(key, out existingEntry)) {
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// another thread already inserted an item, so use that one
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return existingEntry;
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}
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_cache[key] = newEntry;
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return newEntry;
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}
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finally {
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_rwLock.ExitWriteLock();
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}
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}
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}
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}
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