Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / Merging / SynchronousChannelMergeEnumerator.cs / 1305376 / SynchronousChannelMergeEnumerator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // SynchronousChannelMergeEnumerator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Diagnostics.Contracts; namespace System.Linq.Parallel { ////// This enumerator merges multiple input channels into a single output stream. The merging process just /// goes from left-to-right, enumerating each channel in succession in its entirety. /// Assumptions: /// Before enumerating this object, all producers for all channels must have finished enqueueing new /// elements. /// ///internal sealed class SynchronousChannelMergeEnumerator : MergeEnumerator { private SynchronousChannel [] m_channels; // The channel array we will enumerate, from left-to-right. private int m_channelIndex; // The current channel index. This moves through the array as we enumerate. private T m_currentElement; // The last element remembered during enumeration. //------------------------------------------------------------------------------------ // Instantiates a new enumerator for a set of channels. // internal SynchronousChannelMergeEnumerator( QueryTaskGroupState taskGroupState, SynchronousChannel [] channels) : base(taskGroupState) { Contract.Assert(channels != null); #if DEBUG foreach (SynchronousChannel c in channels) Contract.Assert(c != null); #endif m_channels = channels; m_channelIndex = -1; } //----------------------------------------------------------------------------------- // Retrieves the current element. // // Notes: // This throws if we haven't begun enumerating or have gone past the end of the // data source. // public override T Current { get { // If we're at the beginning or the end of the array, it's invalid to be // retrieving the current element. We throw. if (m_channelIndex == -1 || m_channelIndex == m_channels.Length) { throw new InvalidOperationException(SR.GetString(SR.PLINQ_CommonEnumerator_Current_NotStarted)); } return m_currentElement; } } //----------------------------------------------------------------------------------- // Positions the enumerator over the next element. This includes merging as we // enumerate, by just incrementing indexes, etc. // // Return Value: // True if there's a current element, false if we've reached the end. // public override bool MoveNext() { Contract.Assert(m_channels != null); // If we're at the start, initialize the index. if (m_channelIndex == -1) { m_channelIndex = 0; } // If the index has reached the end, we bail. while (m_channelIndex != m_channels.Length) { SynchronousChannel current = m_channels[m_channelIndex]; Contract.Assert(current != null); if (current.Count == 0) { // We're done with this channel, move on to the next one. We don't // have to check that it's "done" since this is a synchronous consumer. m_channelIndex++; } else { // Remember the "current" element and return. m_currentElement = current.Dequeue(); return true; } } TraceHelpers.TraceInfo("[timing]: {0}: Completed the merge", DateTime.Now.Ticks); // If we got this far, it means we've exhausted our channels. Contract.Assert(m_channelIndex == m_channels.Length); return false; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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