Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / UIAutomation / UIAutomationClient / MS / Internal / Automation / QueueProcessor.cs / 1305600 / QueueProcessor.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // // Description: Class to create a queue on its own thread. // // History: // 06/17/2003 : BrendanM Ported to WCP // //--------------------------------------------------------------------------- // PRESHARP: In order to avoid generating warnings about unkown message numbers and unknown pragmas. #pragma warning disable 1634, 1691 using System.Windows.Automation; using System.Windows.Automation.Provider; using System; using System.Threading; using System.Collections; using System.Diagnostics; using MS.Internal.Automation; using MS.Win32; using System.Runtime.InteropServices; using Microsoft.Win32.SafeHandles; namespace MS.Internal.Automation { // Abstract class for worker objects queued to the QueueProcessor class internal abstract class QueueItem { internal abstract void Process(); } // Class to create a queue on its own thread. Used on the PAW client-side // to queue client callbacks. This prevents a deadlock situation when the // client calls back into PAW from w/in a callback. All events are queued // through this class. internal class QueueProcessor { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- #region Constructors // Usage is create QueueProcessor object and call StartOnThread internal QueueProcessor(int initCapacity) { _ev = new AutoResetEvent(false); _q = Queue.Synchronized(new Queue(initCapacity)); } internal QueueProcessor() : this(4) { } #endregion Constructors //------------------------------------------------------ // // Internal Methods // //----------------------------------------------------- #region Internal Methods internal void StartOnThread() { _quitting = false; // create and start a background thread for this worker window to run on // (background threads will exit if the main and foreground threads exit) ThreadStart threadStart = new ThreadStart(WaitForWork); _thread = new Thread(threadStart); _thread.IsBackground = true; _thread.Start(); } // Post a work item to the queue (from another thread) internal bool PostWorkItem(QueueItem workItem) { Debug.Assert(!_quitting, "Can't add items to queue when quitting"); _q.Enqueue(workItem); _ev.Set(); return true; } // Post a work item and wait for it to be processed // Return true if the item was processed w/in 2 sec else false internal bool PostSyncWorkItem(QueueItem workItem) { Debug.Assert(!_quitting, "Can't add items to queue when quitting"); SyncQueueItem syncItem = new SyncQueueItem(workItem); _q.Enqueue(syncItem); _ev.Set(); return syncItem._ev.WaitOne(2000, false); } // Stop queuing and clean up (from another thread) internal void PostQuit() { _quitting = true; _ev.Set(); } #endregion Internal Methods //------------------------------------------------------ // // Private Methods // //------------------------------------------------------ #region Private Methods // The loop the thread uses to wait for queue items to process private void WaitForWork() { SafeWaitHandle handle = _ev.SafeWaitHandle; UnsafeNativeMethods.MSG msg = new UnsafeNativeMethods.MSG(); while (!_quitting) { // pump any messages while (UnsafeNativeMethods.PeekMessage(ref msg, NativeMethods.HWND.NULL, 0, 0, UnsafeNativeMethods.PM_REMOVE)) { if (msg.message == UnsafeNativeMethods.WM_QUIT) { break; } // From the Windows SDK documentation: // The return value specifies the value returned by the window procedure. // Although its meaning depends on the message being dispatched, the return // value generally is ignored. #pragma warning suppress 6031, 6523 UnsafeNativeMethods.DispatchMessage(ref msg); } // do any work items in the queue DrainQueue(); int lastWin32Error = 0; int result = Misc.TryMsgWaitForMultipleObjects(handle, false, UnsafeNativeMethods.INFINITE, UnsafeNativeMethods.QS_ALLINPUT, ref lastWin32Error); if (result == UnsafeNativeMethods.WAIT_FAILED || result == UnsafeNativeMethods.WAIT_TIMEOUT) { DrainQueue(); Debug.Assert(_quitting, "MsgWaitForMultipleObjects failed while WaitForWork"); break; } } DrainQueue(); } private void DrainQueue() { // It's possible items could be enqueued between when we check for the count // and dequeue but the event is set then and we'll come back into DrainQueue. // (note: don't use a for loop here because as the counter is incremented // Count is decremented and we'll only process half the queue) while (_q.Count > 0) { // pull an item off the queue, process, then clear it QueueItem item = (QueueItem)_q.Dequeue(); if (! _quitting) { try { item.Process(); } catch (Exception e) { if (Misc.IsCriticalException(e)) throw; // Eat it. // There's no place to let this exception percolate out // to so we'll stop it here. } } } } #endregion Private Methods //----------------------------------------------------- // // Private Fields // //------------------------------------------------------ #region Private Fields Thread _thread; // the thread on which QueueItem's are processed private Queue _q; // a synchronized queue private AutoResetEvent _ev; // notifies when new queue items show up private bool _quitting; // true if need to stop queueing #endregion Private Fields } // Class is used only by QueueProcessor class itself - wraps // another QueueItem, and fires an event when it is complete. internal class SyncQueueItem : QueueItem { //----------------------------------------------------- // // Constructors // //----------------------------------------------------- #region Constructors internal SyncQueueItem(QueueItem qItem) { _ev = new AutoResetEvent(false); _qItem = qItem; } #endregion Constructors //----------------------------------------------------- // // Internal Methods // //------------------------------------------------------ #region Internal Methods internal override void Process() { _qItem.Process(); _ev.Set(); } #endregion Internal Methods //----------------------------------------------------- // // Private Fields // //------------------------------------------------------ #region Private Fields // Not many of these will be created at a time so having the // event in the class is OK and easier than having just one // that manages any [....] method call. internal AutoResetEvent _ev; private QueueItem _qItem; #endregion Private Fields } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. 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