Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Unary / ContainsSearchOperator.cs / 1305376 / ContainsSearchOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // ContainsSearchOperator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; using System.Diagnostics.Contracts; using System.Threading; namespace System.Linq.Parallel { ////// Contains is quite similar to the any/all operator above. Each partition searches a /// subset of elements for a match, and the first one to find a match signals to the rest /// of the partititons to stop searching. /// ///internal sealed class ContainsSearchOperator : UnaryQueryOperator { private readonly TInput m_searchValue; // The value for which we are searching. private readonly IEqualityComparer m_comparer; // The comparer to use for equality tests. //---------------------------------------------------------------------------------------- // Constructs a new instance of the contains search operator. // // Arguments: // child - the child tree to enumerate. // searchValue - value we are searching for. // comparer - a comparison routine used to test equality. // internal ContainsSearchOperator(IEnumerable child, TInput searchValue, IEqualityComparer comparer) :base(child) { Contract.Assert(child != null, "child data source cannot be null"); m_searchValue = searchValue; if (comparer == null) { m_comparer = EqualityComparer .Default; } else { m_comparer = comparer; } } //--------------------------------------------------------------------------------------- // Executes the entire query tree, and aggregates the individual partition results to // form an overall answer to the search operation. // internal bool Aggregate() { // Because the final reduction is typically much cheaper than the intermediate // reductions over the individual partitions, and because each parallel partition // could do a lot of work to produce a single output element, we prefer to turn off // pipelining, and process the final reductions serially. using (IEnumerator enumerator = GetEnumerator(ParallelMergeOptions.FullyBuffered, true)) { // Any value of true means the element was found. We needn't consult all partitions while (enumerator.MoveNext()) { if (enumerator.Current) { return true; } } } return false; } //--------------------------------------------------------------------------------------- // 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; PartitionedStream outputStream = new PartitionedStream (partitionCount, Util.GetDefaultComparer (), OrdinalIndexState.Correct); // Create a shared cancelation variable Shared resultFoundFlag = new Shared (false); for (int i = 0; i < partitionCount; i++) { outputStream[i] = new ContainsSearchOperatorEnumerator (inputStream[i], m_searchValue, m_comparer, i, resultFoundFlag, settings.CancellationState.MergedCancellationToken); } recipient.Receive(outputStream); } //--------------------------------------------------------------------------------------- // Returns an enumerable that represents the query executing sequentially. // internal override IEnumerable AsSequentialQuery(CancellationToken token) { Contract.Assert(false, "This method should never be called as it is an ending operator with LimitsParallelism=false."); throw new NotSupportedException(); } //---------------------------------------------------------------------------------------- // Whether this operator performs a premature merge. // internal override bool LimitsParallelism { get { return false; } } //--------------------------------------------------------------------------------------- // This enumerator performs the search over its input data source. It also cancels peer // enumerators when an answer was found, and polls this cancelation flag to stop when // requested. // class ContainsSearchOperatorEnumerator : QueryOperatorEnumerator { private readonly QueryOperatorEnumerator m_source; // The source data. private readonly TInput m_searchValue; // The value for which we are searching. private readonly IEqualityComparer m_comparer; // The comparer to use for equality tests. private readonly int m_partitionIndex; // This partition's unique index. private readonly Shared m_resultFoundFlag; // Whether to cancel the operation. private CancellationToken m_cancellationToken; //---------------------------------------------------------------------------------------- // Instantiates a new any/all search operator. // internal ContainsSearchOperatorEnumerator(QueryOperatorEnumerator source, TInput searchValue, IEqualityComparer comparer, int partitionIndex, Shared resultFoundFlag, CancellationToken cancellationToken) { Contract.Assert(source != null); Contract.Assert(comparer != null); Contract.Assert(resultFoundFlag != null); m_source = source; m_searchValue = searchValue; m_comparer = comparer; m_partitionIndex = partitionIndex; m_resultFoundFlag = resultFoundFlag; m_cancellationToken = cancellationToken; } //---------------------------------------------------------------------------------------- // This enumerates the entire input source to perform the search. If another peer // partition finds an answer before us, we will voluntarily return (propagating the // peer's result). // internal override bool MoveNext(ref bool currentElement, ref int currentKey) { Contract.Assert(m_comparer != null); // Avoid enumerating if we've already found an answer. if (m_resultFoundFlag.Value) return false; // We just scroll through the enumerator and accumulate the result. TInput element = default(TInput); TKey keyUnused = default(TKey); if (m_source.MoveNext(ref element, ref keyUnused)) { currentElement = false; currentKey = m_partitionIndex; // Continue walking the data so long as we haven't found an item that satisfies // the condition we are searching for. int i = 0; do { if ((i++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); if (m_resultFoundFlag.Value) { // If cancelation occurred, it's because a successful answer was found. return false; } if (m_comparer.Equals(element, m_searchValue)) { // We have found an item that satisfies the search. Cancel other // workers that are concurrently searching, and return. m_resultFoundFlag.Value = true; currentElement = true; break; } } while (m_source.MoveNext(ref element, ref keyUnused)); 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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