Code:
/ Dotnetfx_Win7_3.5.1 / Dotnetfx_Win7_3.5.1 / 3.5.1 / DEVDIV / depot / DevDiv / releases / Orcas / NetFXw7 / ndp / fx / src / DataEntity / System / Data / Common / Utils / Memoizer.cs / 1 / Memoizer.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....], [....] //--------------------------------------------------------------------- using System.Collections.Generic; using System.Threading; using System.Diagnostics; namespace System.Data.Common.Utils { ////// Remembers the result of evaluating an expensive function so that subsequent /// evaluations are faster. Thread-safe. /// ///Type of the argument to the function. ///Type of the function result. internal sealed class Memoizer{ private readonly Func _function; private readonly Dictionary _resultCache; private readonly ReaderWriterLockSlim _lock; /// /// Constructs /// /// Required. Function whose values are being cached. /// Optional. Comparer used to determine if two functions arguments /// are the same. internal Memoizer(Funcfunction, IEqualityComparer argComparer) { EntityUtil.CheckArgumentNull(function, "function"); _function = function; _resultCache = new Dictionary (argComparer); _lock = new ReaderWriterLockSlim(); } /// /// Evaluates the wrapped function for the given argument. If the function has already /// been evaluated for the given argument, returns cached value. Otherwise, the value /// is computed and returned. /// /// Function argument. ///Function result. internal TResult Evaluate(TArg arg) { Result result; bool hasResult; // check to see if a result has already been computed _lock.EnterReadLock(); try { hasResult = _resultCache.TryGetValue(arg, out result); } finally { _lock.ExitReadLock(); } if (!hasResult) { // compute the new value _lock.EnterWriteLock(); try { // see if the value has been computed in the interim if (!_resultCache.TryGetValue(arg, out result)) { result = new Result(() => _function(arg)); _resultCache.Add(arg, result); } } finally { _lock.ExitWriteLock(); } } // note: you need to release the global cache lock before (potentially) acquiring // a result lock in result.GetValue() return result.GetValue(); } ////// Encapsulates a 'deferred' result. The result is constructed with a delegate (must not /// be null) and when the user requests a value the delegate is invoked and stored. /// private class Result { private TResult _value; private Func_delegate; internal Result(Func createValueDelegate) { Debug.Assert(null != createValueDelegate, "delegate must be given"); _delegate = createValueDelegate; } internal TResult GetValue() { if (null == _delegate) { // if the delegate has been cleared, it means we have already computed the value return _value; } // lock the entry while computing the value so that two threads // don't simultaneously do the work lock (this) { if (null == _delegate) { // between our initial check and our acquisition of the lock, some other // thread may have computed the value return _value; } _value = _delegate(); // ensure _delegate (and its closure) is garbage collected, and set to null // to indicate that the value has been computed _delegate = null; return _value; } } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. //---------------------------------------------------------------------- // // Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....], [....] //--------------------------------------------------------------------- using System.Collections.Generic; using System.Threading; using System.Diagnostics; namespace System.Data.Common.Utils { ////// Remembers the result of evaluating an expensive function so that subsequent /// evaluations are faster. Thread-safe. /// ///Type of the argument to the function. ///Type of the function result. internal sealed class Memoizer{ private readonly Func _function; private readonly Dictionary _resultCache; private readonly ReaderWriterLockSlim _lock; /// /// Constructs /// /// Required. Function whose values are being cached. /// Optional. Comparer used to determine if two functions arguments /// are the same. internal Memoizer(Funcfunction, IEqualityComparer argComparer) { EntityUtil.CheckArgumentNull(function, "function"); _function = function; _resultCache = new Dictionary (argComparer); _lock = new ReaderWriterLockSlim(); } /// /// Evaluates the wrapped function for the given argument. If the function has already /// been evaluated for the given argument, returns cached value. Otherwise, the value /// is computed and returned. /// /// Function argument. ///Function result. internal TResult Evaluate(TArg arg) { Result result; bool hasResult; // check to see if a result has already been computed _lock.EnterReadLock(); try { hasResult = _resultCache.TryGetValue(arg, out result); } finally { _lock.ExitReadLock(); } if (!hasResult) { // compute the new value _lock.EnterWriteLock(); try { // see if the value has been computed in the interim if (!_resultCache.TryGetValue(arg, out result)) { result = new Result(() => _function(arg)); _resultCache.Add(arg, result); } } finally { _lock.ExitWriteLock(); } } // note: you need to release the global cache lock before (potentially) acquiring // a result lock in result.GetValue() return result.GetValue(); } ////// Encapsulates a 'deferred' result. The result is constructed with a delegate (must not /// be null) and when the user requests a value the delegate is invoked and stored. /// private class Result { private TResult _value; private Func_delegate; internal Result(Func createValueDelegate) { Debug.Assert(null != createValueDelegate, "delegate must be given"); _delegate = createValueDelegate; } internal TResult GetValue() { if (null == _delegate) { // if the delegate has been cleared, it means we have already computed the value return _value; } // lock the entry while computing the value so that two threads // don't simultaneously do the work lock (this) { if (null == _delegate) { // between our initial check and our acquisition of the lock, some other // thread may have computed the value return _value; } _value = _delegate(); // ensure _delegate (and its closure) is garbage collected, and set to null // to indicate that the value has been computed _delegate = null; return _value; } } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
Link Menu
This book is available now!
Buy at Amazon US or
Buy at Amazon UK
- ExpressionBuilder.cs
- SchemaSetCompiler.cs
- DataGridRelationshipRow.cs
- ProtectedProviderSettings.cs
- ContentTypeSettingClientMessageFormatter.cs
- WebServiceErrorEvent.cs
- SolidColorBrush.cs
- SimplePropertyEntry.cs
- TextParagraphProperties.cs
- ReferencedType.cs
- XsltContext.cs
- EdmFunctionAttribute.cs
- Themes.cs
- Rijndael.cs
- ConnectionConsumerAttribute.cs
- ObjectKeyFrameCollection.cs
- Baml2006Reader.cs
- BrowserDefinition.cs
- ComplexTypeEmitter.cs
- WebConfigurationHostFileChange.cs
- RewritingValidator.cs
- DBConnection.cs
- DataGridViewHitTestInfo.cs
- SByteConverter.cs
- ViewEvent.cs
- InspectionWorker.cs
- cookiecollection.cs
- LayoutEngine.cs
- XmlSchemaSet.cs
- CLSCompliantAttribute.cs
- KeyGestureConverter.cs
- XmlQualifiedName.cs
- ThreadPool.cs
- HandlerFactoryWrapper.cs
- AvtEvent.cs
- XsltContext.cs
- ComponentDispatcher.cs
- WindowsStatic.cs
- XamlTypeMapper.cs
- UIPermission.cs
- XPathAncestorIterator.cs
- _RequestCacheProtocol.cs
- RouteUrlExpressionBuilder.cs
- SettingsContext.cs
- TabControlCancelEvent.cs
- AssemblyAssociatedContentFileAttribute.cs
- FrameworkTemplate.cs
- ZipIOLocalFileDataDescriptor.cs
- WindowsUserNameSecurityTokenAuthenticator.cs
- OpenTypeLayout.cs
- SharedUtils.cs
- ExtendedPropertyDescriptor.cs
- SelectionRangeConverter.cs
- FontWeights.cs
- DriveInfo.cs
- DecimalAnimation.cs
- Internal.cs
- TransactionScope.cs
- InteropAutomationProvider.cs
- VirtualPath.cs
- WrappedDispatcherException.cs
- CombinedGeometry.cs
- QilBinary.cs
- Logging.cs
- GlobalizationSection.cs
- StringUtil.cs
- SecurityRequiresReviewAttribute.cs
- DatePickerTextBox.cs
- OleDbMetaDataFactory.cs
- DataGridViewSelectedRowCollection.cs
- WindowsEditBox.cs
- XmlSequenceWriter.cs
- ValueType.cs
- ComponentResourceManager.cs
- DataRow.cs
- DoWhileDesigner.xaml.cs
- DbCommandTree.cs
- ActivityLocationReferenceEnvironment.cs
- EUCJPEncoding.cs
- StaticContext.cs
- Comparer.cs
- smtppermission.cs
- RemotingServices.cs
- SafeFileMappingHandle.cs
- RowCache.cs
- ExceptionUtil.cs
- basevalidator.cs
- ConfigXmlCDataSection.cs
- EntityDataSourceWrapperCollection.cs
- CustomWebEventKey.cs
- RelatedCurrencyManager.cs
- storepermissionattribute.cs
- _ShellExpression.cs
- SimpleRecyclingCache.cs
- NativeMethods.cs
- SettingsSavedEventArgs.cs
- SendKeys.cs
- TransformCollection.cs
- XslCompiledTransform.cs
- ListControlConvertEventArgs.cs