QuerySettings.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 / QuerySettings.cs / 1305376 / QuerySettings.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 
// QuerySettings.cs 
//
// [....] 
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

using System.Threading; 
using System.Threading.Tasks;
using System.Diagnostics.Contracts; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// This type contains query execution options specified by the user.
    /// QuerySettings are used as follows:
    /// - in the query construction phase, some settings may be uninitialized. 
    /// - at the start of the query opening phase, the WithDefaults method
    ///   is used to initialize all uninitialized settings. 
    /// - in the rest of the query opening phase, we assume that all settings 
    ///   have been initialized.
    ///  
    internal struct QuerySettings
    {
        private TaskScheduler m_taskScheduler;
        private int? m_degreeOfParallelism; 
        private CancellationState m_cancellationState;
        private ParallelExecutionMode? m_executionMode; 
        private ParallelMergeOptions? m_mergeOptions; 
        private int m_queryId;
 
        internal CancellationState CancellationState
        {
            get { return m_cancellationState; }
            set 
            {
                m_cancellationState = value; 
                Contract.Assert(m_cancellationState != null); 
            }
        } 

        // The task manager on which to execute the query.
        internal TaskScheduler TaskScheduler
        { 
            get { return m_taskScheduler; }
            set { m_taskScheduler = value; } 
        } 

        // The number of parallel tasks to utilize. 
        internal int? DegreeOfParallelism
        {
            get { return m_degreeOfParallelism; }
            set { m_degreeOfParallelism = value; } 
        }
 
        // The mode in which to execute this query. 
        internal ParallelExecutionMode? ExecutionMode
        { 
            get { return m_executionMode; }
            set { m_executionMode = value; }
        }
 
        internal ParallelMergeOptions? MergeOptions
        { 
            get { return m_mergeOptions; } 
            set { m_mergeOptions = value; }
        } 

        internal int QueryId
        {
            get 
            {
                return m_queryId; 
            } 
        }
 
        //------------------------------------------------------------------------------------
        // Constructs a new settings structure.
        //
        internal QuerySettings(TaskScheduler taskScheduler, int? degreeOfParallelism, 
            CancellationToken externalCancellationToken, ParallelExecutionMode? executionMode,
            ParallelMergeOptions? mergeOptions) 
        { 
            m_taskScheduler = taskScheduler;
            m_degreeOfParallelism = degreeOfParallelism; 
            m_cancellationState = new CancellationState(externalCancellationToken);
            m_executionMode = executionMode;
            m_mergeOptions = mergeOptions;
            m_queryId = -1; 

            Contract.Assert(m_cancellationState != null); 
        } 

        //----------------------------------------------------------------------------------- 
        // Combines two sets of options.
        //
        internal QuerySettings Merge(QuerySettings settings2)
        { 
            if (this.TaskScheduler != null && settings2.TaskScheduler != null)
            { 
                throw new InvalidOperationException(SR.GetString(SR.ParallelQuery_DuplicateTaskScheduler)); 
            }
 
            if (this.DegreeOfParallelism != null && settings2.DegreeOfParallelism != null)
            {
                throw new InvalidOperationException(SR.GetString(SR.ParallelQuery_DuplicateDOP));
            } 

            if (this.CancellationState.ExternalCancellationToken.CanBeCanceled && settings2.CancellationState.ExternalCancellationToken.CanBeCanceled) 
            { 
                throw new InvalidOperationException(SR.GetString(SR.ParallelQuery_DuplicateWithCancellation));
            } 

            if (this.ExecutionMode != null && settings2.ExecutionMode != null)
            {
                throw new InvalidOperationException(SR.GetString(SR.ParallelQuery_DuplicateExecutionMode)); 
            }
 
            if (this.MergeOptions != null && settings2.MergeOptions != null) 
            {
                throw new InvalidOperationException(SR.GetString(SR.ParallelQuery_DuplicateMergeOptions)); 
            }

            TaskScheduler tm = (this.TaskScheduler == null) ? settings2.TaskScheduler : this.TaskScheduler;
            int? dop = this.DegreeOfParallelism.HasValue ? this.DegreeOfParallelism : settings2.DegreeOfParallelism; 
            CancellationToken externalCancellationToken = (this.CancellationState.ExternalCancellationToken.CanBeCanceled) ? this.CancellationState.ExternalCancellationToken : settings2.CancellationState.ExternalCancellationToken;
            ParallelExecutionMode? executionMode = this.ExecutionMode.HasValue ? this.ExecutionMode : settings2.ExecutionMode; 
            ParallelMergeOptions? mergeOptions = this.MergeOptions.HasValue ? this.MergeOptions : settings2.MergeOptions; 

            return new QuerySettings(tm, dop, externalCancellationToken, executionMode, mergeOptions); 
        }

        internal QuerySettings WithPerExecutionSettings()
        { 
            return WithPerExecutionSettings(new CancellationTokenSource(), new Shared(false));
        } 
 
        internal QuerySettings WithPerExecutionSettings(CancellationTokenSource topLevelCancellationTokenSource, Shared topLevelDisposedFlag)
        { 
            //Initialize a new QuerySettings structure and copy in the current settings.
            //Note: this has the very important effect of newing a fresh CancellationSettings,
            //      and _not_ copying in the current internalCancellationSource or topLevelDisposedFlag which should not be
            //      propogated to internal query executions. (This affects SelectMany execution and specifically fixes bug:535510) 
            //      The fresh toplevel parameters are used instead.
            QuerySettings settings = new QuerySettings(TaskScheduler, DegreeOfParallelism, CancellationState.ExternalCancellationToken, ExecutionMode, MergeOptions); 
 
            Contract.Assert(topLevelCancellationTokenSource != null, "There should always be a top-level cancellation signal specified.");
            settings.CancellationState.InternalCancellationTokenSource = topLevelCancellationTokenSource; 

            //Merge internal and external tokens to form the combined token
             settings.CancellationState.MergedCancellationTokenSource =
                    CancellationTokenSource.CreateLinkedTokenSource(settings.CancellationState.InternalCancellationTokenSource.Token, settings.CancellationState.ExternalCancellationToken); 

            // and copy in the topLevelDisposedFlag 
            settings.CancellationState.TopLevelDisposedFlag = topLevelDisposedFlag; 

            Contract.Assert(settings.CancellationState.InternalCancellationTokenSource != null); 
            Contract.Assert(settings.CancellationState.MergedCancellationToken.CanBeCanceled);
            Contract.Assert(settings.CancellationState.TopLevelDisposedFlag != null);

            // Finally, assign a query Id to the settings 
#if !PFX_LEGACY_3_5
            settings.m_queryId = PlinqEtwProvider.NextQueryId(); 
#endif 

            return settings; 
        }

        //-----------------------------------------------------------------------------------
        // Copies the settings, replacing unspecified settings with defaults. 
        //
        internal QuerySettings WithDefaults() 
        { 
            QuerySettings settings = this;
            if (settings.TaskScheduler == null) 
            {
                settings.TaskScheduler = TaskScheduler.Default;
            }
 
            if (settings.DegreeOfParallelism == null)
            { 
                settings.DegreeOfParallelism = Scheduling.GetDefaultDegreeOfParallelism(); 
            }
 
            if (settings.ExecutionMode == null)
            {
                settings.ExecutionMode = ParallelExecutionMode.Default;
            } 

            if (settings.MergeOptions == null) 
            { 
                settings.MergeOptions = ParallelMergeOptions.Default;
            } 

            if (settings.MergeOptions == ParallelMergeOptions.Default)
            {
                settings.MergeOptions = ParallelMergeOptions.AutoBuffered; 
            }
 
            Contract.Assert(settings.TaskScheduler != null); 
            Contract.Assert(settings.DegreeOfParallelism.HasValue);
            Contract.Assert(settings.DegreeOfParallelism.Value >= 1 && settings.DegreeOfParallelism <= Scheduling.MAX_SUPPORTED_DOP); 
            Contract.Assert(settings.ExecutionMode != null);
            Contract.Assert(settings.MergeOptions != null);

            Contract.Assert(settings.MergeOptions != ParallelMergeOptions.Default); 

            return settings; 
        } 

        // Returns the default settings 
        internal static QuerySettings Empty {
            get { return new QuerySettings(null, null, new CancellationToken(), null, null); }
        }
 
        // Cleanup internal state once the entire query is complete.
        // (this should not be performed after a 'premature-query' completes as the state should live 
        // uninterrupted for the duration of the full query.) 
        public void CleanStateAtQueryEnd()
        { 
            m_cancellationState.MergedCancellationTokenSource.Dispose();
        }
    }
} 

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