ExceptQueryOperator.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Binary / ExceptQueryOperator.cs / 1305376 / ExceptQueryOperator.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 
// ExceptQueryOperator.cs 
//
// [....] 
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

using System.Collections.Generic; 
using System.Diagnostics.Contracts;
using System.Threading; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// Operator that yields the elements from the first data source that aren't in the second.
    /// This is known as the set relative complement, i.e. left - right.
    ///  
    /// 
    internal sealed class ExceptQueryOperator : 
        BinaryQueryOperator 
    {
 
        private readonly IEqualityComparer m_comparer; // An equality comparer.

        //----------------------------------------------------------------------------------------
        // Constructs a new set except operator. 
        //
 
        internal ExceptQueryOperator(ParallelQuery left, ParallelQuery right, IEqualityComparer comparer) 
            :base(left, right)
        { 
            Contract.Assert(left != null && right != null, "child data sources cannot be null");
            m_comparer = comparer;
            m_outputOrdered = LeftChild.OutputOrdered;
            SetOrdinalIndex(OrdinalIndexState.Shuffled); 
        }
 
        internal override QueryResults Open( 
            QuerySettings settings, bool preferStriping)
        { 
            // We just open our child operators, left and then right.  Do not propagate the preferStriping value, but
            // instead explicitly set it to false. Regardless of whether the parent prefers striping or range
            // partitioning, the output will be hash-partititioned.
            QueryResults leftChildResults = LeftChild.Open(settings, false); 
            QueryResults rightChildResults = RightChild.Open(settings, false);
 
            return new BinaryQueryOperatorResults(leftChildResults, rightChildResults, this, settings, false); 
        }
 
        public override void WrapPartitionedStream(
            PartitionedStream leftStream, PartitionedStream rightStream,
            IPartitionedStreamRecipient outputRecipient, bool preferStriping, QuerySettings settings)
        { 
            Contract.Assert(leftStream.PartitionCount == rightStream.PartitionCount);
 
            if (OutputOrdered) 
            {
                WrapPartitionedStreamHelper( 
                    ExchangeUtilities.HashRepartitionOrdered(
                        leftStream, null, null, m_comparer, settings.CancellationState.MergedCancellationToken),
                    rightStream, outputRecipient, settings.CancellationState.MergedCancellationToken);
            } 
            else
            { 
                WrapPartitionedStreamHelper( 
                    ExchangeUtilities.HashRepartition(
                        leftStream, null, null, m_comparer, settings.CancellationState.MergedCancellationToken), 
                    rightStream, outputRecipient, settings.CancellationState.MergedCancellationToken);
            }
        }
 
        //---------------------------------------------------------------------------------------
        // This is a helper method. WrapPartitionedStream decides what type TLeftKey is going 
        // to be, and then call this method with that key as a generic parameter. 
        //
 
        private void WrapPartitionedStreamHelper(
            PartitionedStream, TLeftKey> leftHashStream, PartitionedStream rightPartitionedStream,
            IPartitionedStreamRecipient outputRecipient, CancellationToken cancellationToken)
        { 
            int partitionCount = leftHashStream.PartitionCount;
 
            PartitionedStream, int> rightHashStream = 
                ExchangeUtilities.HashRepartition(
                    rightPartitionedStream, null, null, m_comparer, cancellationToken); 

            PartitionedStream outputStream =
                new PartitionedStream(partitionCount, leftHashStream.KeyComparer, OrdinalIndexState.Shuffled);
 
            for (int i = 0; i < partitionCount; i++)
            { 
                if (OutputOrdered) 
                {
                    outputStream[i] = new OrderedExceptQueryOperatorEnumerator( 
                        leftHashStream[i], rightHashStream[i], m_comparer, leftHashStream.KeyComparer, cancellationToken);
                }
                else
                { 
                    outputStream[i] = (QueryOperatorEnumerator)(object)
                        new ExceptQueryOperatorEnumerator(leftHashStream[i], rightHashStream[i], m_comparer, cancellationToken); 
                } 
            }
 
            outputRecipient.Receive(outputStream);
        }

 
        //---------------------------------------------------------------------------------------
        // Returns an enumerable that represents the query executing sequentially. 
        // 

        internal override IEnumerable AsSequentialQuery(CancellationToken token) 
        {
            IEnumerable wrappedLeftChild = CancellableEnumerable.Wrap(LeftChild.AsSequentialQuery(token), token);
            IEnumerable wrappedRightChild = CancellableEnumerable.Wrap(RightChild.AsSequentialQuery(token), token);
            return wrappedLeftChild.Except(wrappedRightChild, m_comparer); 
        }
 
        //--------------------------------------------------------------------------------------- 
        // Whether this operator performs a premature merge.
        // 

        internal override bool LimitsParallelism
        {
            get { return false; } 
        }
 
        //---------------------------------------------------------------------------------------- 
        // This enumerator calculates the distinct set incrementally. It does this by maintaining
        // a history -- in the form of a set -- of all data already seen. It then only returns 
        // elements that have not yet been seen.
        //

        class ExceptQueryOperatorEnumerator : QueryOperatorEnumerator 
        {
            private QueryOperatorEnumerator, TLeftKey> m_leftSource; // Left data source. 
            private QueryOperatorEnumerator, int> m_rightSource; // Right data source. 
            private IEqualityComparer m_comparer; // A comparer used for equality checks/hash-coding.
            private Set m_hashLookup; // The hash lookup, used to produce the distinct set. 
            private CancellationToken m_cancellationToken;
            private Shared m_outputLoopCount;

            //--------------------------------------------------------------------------------------- 
            // Instantiates a new except query operator enumerator.
            // 
 
            internal ExceptQueryOperatorEnumerator(
                QueryOperatorEnumerator, TLeftKey> leftSource, 
                QueryOperatorEnumerator, int> rightSource,
                IEqualityComparer comparer,
                CancellationToken cancellationToken)
            { 
                Contract.Assert(leftSource != null);
                Contract.Assert(rightSource != null); 
 
                m_leftSource = leftSource;
                m_rightSource = rightSource; 
                m_comparer = comparer;
                m_cancellationToken = cancellationToken;
            }
 
            //----------------------------------------------------------------------------------------
            // Walks the two data sources, left and then right, to produce the distinct set 
            // 

            internal override bool MoveNext(ref TInputOutput currentElement, ref int currentKey) 
            {
                Contract.Assert(m_leftSource != null);
                Contract.Assert(m_rightSource != null);
 
                // Build the set out of the left data source, if we haven't already.
 
                if (m_hashLookup == null) 
                {
                    m_outputLoopCount = new Shared(0); 

                    // @
                    m_hashLookup = new Set(m_comparer);
 
                    Pair rightElement = default(Pair);
                    int rightKeyUnused = default(int); 
 
                    int i = 0;
                    while (m_rightSource.MoveNext(ref rightElement, ref rightKeyUnused)) 
                    {
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0)
                            CancellationState.ThrowIfCanceled(m_cancellationToken);
 
                        m_hashLookup.Add(rightElement.First);
                    } 
                } 

                // Now iterate over the right data source, looking for matches. 
                Pair leftElement = default(Pair);
                TLeftKey leftKeyUnused = default(TLeftKey);

                while (m_leftSource.MoveNext(ref leftElement, ref leftKeyUnused)) 
                {
                    if ((m_outputLoopCount.Value++ & CancellationState.POLL_INTERVAL) == 0) 
                        CancellationState.ThrowIfCanceled(m_cancellationToken); 

                    if (m_hashLookup.Add(leftElement.First)) 
                    {
                        // This element has never been seen. Return it.
                        currentElement = leftElement.First;
#if DEBUG 
                        currentKey = unchecked((int)0xdeadbeef);
#endif 
                        return true; 
                    }
                } 

                return false;
            }
 
            protected override void Dispose(bool disposing)
            { 
                Contract.Assert(m_leftSource != null && m_rightSource != null); 
                m_leftSource.Dispose();
                m_rightSource.Dispose(); 
            }
        }

        class OrderedExceptQueryOperatorEnumerator : QueryOperatorEnumerator 
        {
            private QueryOperatorEnumerator, TLeftKey> m_leftSource; // Left data source. 
            private QueryOperatorEnumerator, int> m_rightSource; // Right data source. 
            private IEqualityComparer m_comparer; // A comparer used for equality checks/hash-coding.
            private IComparer m_leftKeyComparer; // A comparer for order keys. 
            private IEnumerator, Pair>> m_outputEnumerator; // The enumerator output elements + order keys.
            private CancellationToken m_cancellationToken;

            //---------------------------------------------------------------------------------------- 
            // Instantiates a new except query operator enumerator.
            // 
 
            internal OrderedExceptQueryOperatorEnumerator(
                QueryOperatorEnumerator, TLeftKey> leftSource, 
                QueryOperatorEnumerator, int> rightSource,
                IEqualityComparer comparer, IComparer leftKeyComparer,
                CancellationToken cancellationToken)
            { 
                Contract.Assert(leftSource != null);
                Contract.Assert(rightSource != null); 
 
                m_leftSource = leftSource;
                m_rightSource = rightSource; 
                m_comparer = comparer;
                m_leftKeyComparer = leftKeyComparer;
                m_cancellationToken = cancellationToken;
            } 

            //--------------------------------------------------------------------------------------- 
            // Walks the two data sources, left and then right, to produce the distinct set 
            //
 
            internal override bool MoveNext(ref TInputOutput currentElement, ref TLeftKey currentKey)
            {
                Contract.Assert(m_leftSource != null);
                Contract.Assert(m_rightSource != null); 

                // Build the set out of the left data source, if we haven't already. 
                if (m_outputEnumerator == null) 
                {
                    // @ 
                    Set rightLookup = new Set(m_comparer);

                    Pair rightElement = default(Pair);
                    int rightKeyUnused = default(int); 
                    int i=0;
                    while (m_rightSource.MoveNext(ref rightElement, ref rightKeyUnused)) 
                    { 
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0)
                            CancellationState.ThrowIfCanceled(m_cancellationToken); 

                        rightLookup.Add(rightElement.First);
                    }
 
                    var leftLookup =
                        new Dictionary, Pair>( 
                            new WrapperEqualityComparer(m_comparer)); 

                    Pair leftElement = default(Pair); 
                    TLeftKey leftKey = default(TLeftKey);
                    while (m_leftSource.MoveNext(ref leftElement, ref leftKey))
                    {
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0) 
                            CancellationState.ThrowIfCanceled(m_cancellationToken);
 
                        if (rightLookup.Contains(leftElement.First)) 
                        {
                            continue; 
                        }

                        Pair oldEntry;
                        Wrapper wrappedLeftElement = new Wrapper(leftElement.First); 
                        if (!leftLookup.TryGetValue(wrappedLeftElement, out oldEntry) || m_leftKeyComparer.Compare(leftKey, oldEntry.Second) < 0)
                        { 
                            // For each "elem" value, we store the smallest key, and the element value that had that key. 
                            // Note that even though two element values are "equal" according to the EqualityComparer,
                            // we still cannot choose arbitrarily which of the two to yield. 
                            leftLookup[wrappedLeftElement] = new Pair(leftElement.First, leftKey);
                        }
                    }
 
                    m_outputEnumerator = leftLookup.GetEnumerator();
                } 
 
                if (m_outputEnumerator.MoveNext())
                { 
                    Pair currentPair = m_outputEnumerator.Current.Value;
                    currentElement = currentPair.First;
                    currentKey = currentPair.Second;
                    return true; 
                }
 
                return false; 
            }
 
            protected override void Dispose(bool disposing)
            {
                Contract.Assert(m_leftSource != null && m_rightSource != null);
                m_leftSource.Dispose(); 
                m_rightSource.Dispose();
            } 
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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ExceptQueryOperator.cs source code in C# .NET

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