OrderPreservingMergeHelper.cs source code in C# .NET

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Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / Merging / OrderPreservingMergeHelper.cs / 1305376 / OrderPreservingMergeHelper.cs
                        

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

using System.Collections.Generic; 
using System.Threading.Tasks;
using System.Diagnostics.Contracts; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// The order preserving merge helper guarantees the output stream is in a specific order. This is done
    /// by comparing keys from a set of already-sorted input partitions, and coalescing output data using
    /// incremental key comparisons. 
    /// 
    ///  
    ///  
    internal class OrderPreservingMergeHelper : IMergeHelper
    { 
        private QueryTaskGroupState m_taskGroupState; // State shared among tasks.
        private PartitionedStream m_partitions; // Source partitions.
        private Shared m_results; // The array where results are stored.
        private TaskScheduler m_taskScheduler; // The task manager to execute the query. 

        //------------------------------------------------------------------------------------ 
        // Instantiates a new merge helper. 
        //
        // Arguments: 
        //     partitions   - the source partitions from which to consume data.
        //     ignoreOutput - whether we're enumerating "for effect" or for output.
        //
 
        internal OrderPreservingMergeHelper(PartitionedStream partitions, TaskScheduler taskScheduler,
            CancellationState cancellationState, int queryId) 
        { 
            Contract.Assert(partitions != null);
 
            TraceHelpers.TraceInfo("KeyOrderPreservingMergeHelper::.ctor(..): creating an order preserving merge helper");

            m_taskGroupState = new QueryTaskGroupState(cancellationState, queryId);
            m_partitions = partitions; 
            m_results = new Shared(null);
            m_taskScheduler = taskScheduler; 
        } 

        //----------------------------------------------------------------------------------- 
        // Schedules execution of the merge itself.
        //
        // Arguments:
        //    ordinalIndexState - the state of the ordinal index of the merged partitions 
        //
 
        void IMergeHelper.Execute() 
        {
            OrderPreservingSpoolingTask.Spool(m_taskGroupState, m_partitions, m_results, m_taskScheduler); 
        }

        //-----------------------------------------------------------------------------------
        // Gets the enumerator from which to enumerate output results. 
        //
 
        IEnumerator IMergeHelper.GetEnumerator() 
        {
            Contract.Assert(m_results.Value != null); 
            return ((IEnumerable)m_results.Value).GetEnumerator();
        }

 
        //-----------------------------------------------------------------------------------
        // Returns the results as an array. 
        // 

        public TInputOutput[] GetResultsAsArray() 
        {
            return m_results.Value;
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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