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      1 /*
      2  * Copyright (C) 2011 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  *
     14  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     15  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     17  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     18  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     19  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     20  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     21  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 #ifndef WebThread_h
     26 #define WebThread_h
     27 
     28 #include "WebCommon.h"
     29 
     30 namespace blink {
     31 
     32 // Provides an interface to an embedder-defined thread implementation.
     33 //
     34 // Deleting the thread blocks until all pending, non-delayed tasks have been
     35 // run.
     36 class BLINK_PLATFORM_EXPORT WebThread {
     37 public:
     38     class Task {
     39     public:
     40         virtual ~Task() { }
     41         virtual void run() = 0;
     42     };
     43 
     44     class BLINK_PLATFORM_EXPORT TaskObserver {
     45     public:
     46         virtual ~TaskObserver() { }
     47         virtual void willProcessTask() = 0;
     48         virtual void didProcessTask() = 0;
     49     };
     50 
     51     // postTask() and postDelayedTask() take ownership of the passed Task
     52     // object. It is safe to invoke postTask() and postDelayedTask() from any
     53     // thread.
     54     virtual void postTask(Task*) = 0;
     55     virtual void postDelayedTask(Task*, long long delayMs) = 0;
     56 
     57     virtual bool isCurrentThread() const = 0;
     58 
     59     virtual void addTaskObserver(TaskObserver*) { }
     60     virtual void removeTaskObserver(TaskObserver*) { }
     61 
     62     // enterRunLoop() processes tasks posted to this WebThread. This call does not return until some task calls exitRunLoop().
     63     // WebThread does not support nesting, meaning that once the run loop is entered for a given WebThread it is not valid to
     64     // call enterRunLoop() again.
     65     virtual void enterRunLoop() = 0;
     66 
     67     // exitRunLoop() runs tasks until there are no tasks available to run, then returns control to the caller of enterRunLoop().
     68     // Must be called when the WebThread is running.
     69     virtual void exitRunLoop() = 0;
     70 
     71     virtual ~WebThread() { }
     72 };
     73 
     74 } // namespace blink
     75 
     76 #endif
     77