CountAggregationOperator.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Inlined / CountAggregationOperator.cs / 1305376 / CountAggregationOperator.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 
// CountAggregationOperator.cs 
//
// [....] 
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

using System.Collections.Generic; 
using System.Diagnostics.Contracts;
using System.Threading; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// An inlined count aggregation and its enumerator.
    /// 
    ///  
    internal sealed class CountAggregationOperator : InlinedAggregationOperator
    { 
 
        //----------------------------------------------------------------------------------------
        // Constructs a new instance of the operator. 
        //

        internal CountAggregationOperator(IEnumerable child) : base(child)
        { 
        }
 
        //--------------------------------------------------------------------------------------- 
        // Executes the entire query tree, and aggregates the intermediate results into the
        // final result based on the binary operators and final reduction. 
        //
        // Return Value:
        //     The single result of aggregation.
        // 

        protected override int InternalAggregate(ref Exception singularExceptionToThrow) 
        { 
            // Because the final reduction is typically much cheaper than the intermediate
            // reductions over the individual partitions, and because each parallel partition 
            // will 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))
            { 
                // We just reduce the elements in each output partition.
                int count = 0; 
                while (enumerator.MoveNext()) 
                {
                    checked 
                    {
                        count += enumerator.Current;
                    }
                } 

                return count; 
            } 
        }
 
        //---------------------------------------------------------------------------------------
        // Creates an enumerator that is used internally for the final aggregation step.
        //
 
        protected override QueryOperatorEnumerator CreateEnumerator(
            int index, int count, QueryOperatorEnumerator source, object sharedData, 
            CancellationToken cancellationToken) 
        {
            return new CountAggregationOperatorEnumerator(source, index, cancellationToken); 
        }

        //---------------------------------------------------------------------------------------
        // This enumerator type encapsulates the intermediary aggregation over the underlying 
        // (possibly partitioned) data source.
        // 
 
        private class CountAggregationOperatorEnumerator : InlinedAggregationOperatorEnumerator
        { 
            private readonly QueryOperatorEnumerator m_source; // The source data.

            //----------------------------------------------------------------------------------------
            // Instantiates a new aggregation operator. 
            //
 
            internal CountAggregationOperatorEnumerator(QueryOperatorEnumerator source, int partitionIndex, 
                CancellationToken cancellationToken) :
                base(partitionIndex, cancellationToken) 
            {
                Contract.Assert(source != null);
                m_source = source;
            } 

            //--------------------------------------------------------------------------------------- 
            // Counts the elements in the underlying data source, walking the entire thing the first 
            // time MoveNext is called on this object.
            // 

            protected override bool MoveNextCore(ref int currentElement)
            {
                TSource elementUnused = default(TSource); 
                TKey keyUnused = default(TKey);
 
                QueryOperatorEnumerator source = m_source; 
                if (source.MoveNext(ref elementUnused, ref keyUnused))
                { 
                    // We just scroll through the enumerator and keep a running count.
                    int count = 0;
                    int i = 0;
                    do 
                    {
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0) 
                            CancellationState.ThrowIfCanceled(m_cancellationToken); 
                        checked
                        { 
                            count++;
                        }
                    }
                    while (source.MoveNext(ref elementUnused, ref keyUnused)); 

                    currentElement = count; 
                    return true; 
                }
 
                return false;
            }

            //---------------------------------------------------------------------------------------- 
            // Dispose of resources associated with the underlying enumerator.
            // 
 
            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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