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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / Utils / ExceptionAggregator.cs / 1305376 / ExceptionAggregator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // ExceptionAggregator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System; using System.Collections.Generic; using System.Threading; namespace System.Linq.Parallel { internal static class ExceptionAggregator { ////// WrapEnumerable.ExceptionAggregator wraps the enumerable with another enumerator that will /// catch exceptions, and wrap each with an AggregateException. /// /// If PLINQ decides to execute a query sequentially, we will reuse LINQ-to-objects /// implementations for the different operators. However, we still need to throw /// AggregateException in the cases when parallel execution would have thrown an /// AggregateException. Thus, we introduce a wrapper enumerator that catches exceptions /// and wraps them with an AggregateException. /// internal static IEnumerableWrapEnumerable (IEnumerable source, CancellationState cancellationState) { using (IEnumerator enumerator = source.GetEnumerator()) { while (true) { TElement elem = default(TElement); try { if (!enumerator.MoveNext()) { yield break; } elem = enumerator.Current; } catch (ThreadAbortException) { // Do not wrap ThreadAbortExceptions throw; } catch (Exception ex) { ThrowOCEorAggregateException(ex, cancellationState); } yield return elem; } } } /// /// A variant of WrapEnumerable that accepts a QueryOperatorEnumerator{,} instead of an IEnumerable{}. /// The code duplication is necessary to avoid extra virtual method calls that would otherwise be needed to /// convert the QueryOperatorEnumerator{,} to an IEnumerator{}. /// internal static IEnumerableWrapQueryEnumerator (QueryOperatorEnumerator source, CancellationState cancellationState) { TElement elem = default(TElement); TIgnoreKey ignoreKey = default(TIgnoreKey); try { while (true) { try { if (!source.MoveNext(ref elem, ref ignoreKey)) { yield break; } } catch (ThreadAbortException) { // Do not wrap ThreadAbortExceptions throw; } catch (Exception ex) { ThrowOCEorAggregateException(ex, cancellationState); } yield return elem; } } finally { source.Dispose(); } } /// /// Accepts an exception, wraps it as if it was crossing the parallel->sequential boundary, and throws the /// wrapped exception. In sequential fallback cases, we use this method to throw exceptions that are consistent /// with exceptions thrown by PLINQ when the query is executed by worker tasks. /// /// The exception will be wrapped into an AggregateException, except for the case when the query is being /// legitimately cancelled, in which case we will propagate the CancellationException with the appropriate /// token. /// internal static void ThrowOCEorAggregateException(Exception ex, CancellationState cancellationState) { if (ThrowAnOCE(ex, cancellationState)) { CancellationState.ThrowWithStandardMessageIfCanceled( cancellationState.ExternalCancellationToken); } else { throw new AggregateException(ex); } } ////// Wraps a function with a try/catch that morphs all exceptions into AggregateException. /// ///The input argument type. ///The return value type. /// A function to use internally. /// The cancellation state to use. ///A new function containing exception wrapping logic. internal static FuncWrapFunc (Func f, CancellationState cancellationState) { return t => { U retval = default(U); try { retval = f(t); } catch (ThreadAbortException) { // Do not wrap ThreadAbortExceptions throw; } catch (Exception ex) { ThrowOCEorAggregateException(ex, cancellationState); } return retval; }; } // return: true ==> throw an OCE(externalCT) // false ==> thrown an AggregateException(ex). private static bool ThrowAnOCE(Exception ex, CancellationState cancellationState) { // if the query has been canceled and the exception represents this, we want to throw OCE // but otherwise we want to throw an AggregateException to mimic normal Plinq operation // See QueryTaskGroupState.WaitAll for the main plinq exception handling logic. // check for co-operative cancellation. OperationCanceledException cancelEx = ex as OperationCanceledException; if (cancelEx != null && cancelEx.CancellationToken == cancellationState.ExternalCancellationToken && cancellationState.ExternalCancellationToken.IsCancellationRequested) { return true; // let the OCE(extCT) be rethrown. } // check for external cancellation which triggered the mergedToken. if (cancelEx != null && cancelEx.CancellationToken == cancellationState.MergedCancellationToken && cancellationState.MergedCancellationToken.IsCancellationRequested && cancellationState.ExternalCancellationToken.IsCancellationRequested) { return true; // convert internal cancellation back to OCE(extCT). } return false; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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