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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Unary / IndexedWhereQueryOperator.cs / 1305376 / IndexedWhereQueryOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // IndexedWhereQueryOperator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; using System.Diagnostics.Contracts; using System.Threading; namespace System.Linq.Parallel { ////// A variant of the Where operator that supplies element index while performing the /// filtering operation. This requires cooperation with partitioning and merging to /// guarantee ordering is preserved. /// /// @ internal sealed class IndexedWhereQueryOperator : UnaryQueryOperator { // Predicate function. Used to filter out non-matching elements during execution. private Func m_predicate; private bool m_prematureMerge = false; // Whether to prematurely merge the input of this operator. //---------------------------------------------------------------------------------------- // Initializes a new where operator. // // Arguments: // child - the child operator or data source from which to pull data // predicate - a delegate representing the predicate function // // Assumptions: // predicate must be non null. // internal IndexedWhereQueryOperator(IEnumerable child, Func predicate) :base(child) { Contract.Assert(child != null, "child data source cannot be null"); Contract.Assert(predicate != null, "need a filter function"); m_predicate = predicate; // In an indexed Select, elements must be returned in the order in which // indices were assigned. m_outputOrdered = true; InitOrdinalIndexState(); } private void InitOrdinalIndexState() { if (ExchangeUtilities.IsWorseThan(Child.OrdinalIndexState, OrdinalIndexState.Correct)) { m_prematureMerge = true; } SetOrdinalIndexState(OrdinalIndexState.Increasing); } //--------------------------------------------------------------------------------------- // Just opens the current operator, including opening the child and wrapping it with // partitions as needed. // internal override QueryResults Open( QuerySettings settings, bool preferStriping) { QueryResults childQueryResults = Child.Open(settings, preferStriping); return new UnaryQueryOperatorResults(childQueryResults, this, settings, preferStriping); } internal override void WrapPartitionedStream ( PartitionedStream inputStream, IPartitionedStreamRecipient recipient, bool preferStriping, QuerySettings settings) { int partitionCount = inputStream.PartitionCount; // If the index is not correct, we need to reindex. PartitionedStream inputStreamInt; if (m_prematureMerge) { ListQueryResults listResults = ExecuteAndCollectResults(inputStream, partitionCount, Child.OutputOrdered, preferStriping, settings); inputStreamInt = listResults.GetPartitionedStream(); } else { Contract.Assert(typeof(TKey) == typeof(int)); inputStreamInt = (PartitionedStream )(object)inputStream; } // Since the index is correct, the type of the index must be int PartitionedStream outputStream = new PartitionedStream (partitionCount, Util.GetDefaultComparer (), OrdinalIndexState); for (int i = 0; i < partitionCount; i++) { outputStream[i] = new IndexedWhereQueryOperatorEnumerator(inputStreamInt[i], m_predicate, settings.CancellationState.MergedCancellationToken); } recipient.Receive(outputStream); } //--------------------------------------------------------------------------------------- // Returns an enumerable that represents the query executing sequentially. // internal override IEnumerable AsSequentialQuery(CancellationToken token) { IEnumerable wrappedChild = CancellableEnumerable.Wrap(Child.AsSequentialQuery(token), token); return wrappedChild.Where(m_predicate); } //--------------------------------------------------------------------------------------- // Whether this operator performs a premature merge. // internal override bool LimitsParallelism { get { return m_prematureMerge; } } //------------------------------------------------------------------------------------ // An enumerator that implements the filtering logic. // private class IndexedWhereQueryOperatorEnumerator : QueryOperatorEnumerator { private readonly QueryOperatorEnumerator m_source; // The data source to enumerate. private readonly Func m_predicate; // The predicate used for filtering. private CancellationToken m_cancellationToken; private Shared m_outputLoopCount; //----------------------------------------------------------------------------------- // Instantiates a new enumerator. // internal IndexedWhereQueryOperatorEnumerator(QueryOperatorEnumerator source, Func predicate, CancellationToken cancellationToken) { Contract.Assert(source != null); Contract.Assert(predicate != null); m_source = source; m_predicate = predicate; m_cancellationToken = cancellationToken; } //------------------------------------------------------------------------------------ // Moves to the next matching element in the underlying data stream. // internal override bool MoveNext(ref TInputOutput currentElement, ref int currentKey) { Contract.Assert(m_predicate != null, "expected a compiled operator"); // Iterate through the input until we reach the end of the sequence or find // an element matching the predicate. if (m_outputLoopCount == null) m_outputLoopCount = new Shared (0); while (m_source.MoveNext(ref currentElement, ref currentKey)) { if ((m_outputLoopCount.Value++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); if (m_predicate(currentElement, currentKey)) { return true; } } return false; } protected override void Dispose(bool disposing) { Contract.Assert(m_source != null); m_source.Dispose(); } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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