gfx/layers/ipc/SynchronousTask.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef MOZILLA_GFX_SYNCHRONOUSTASK_H
   8 #define MOZILLA_GFX_SYNCHRONOUSTASK_H
   9
  10 #include "mozilla/ReentrantMonitor.h"  // for ReentrantMonitor, etc
  11
  12 namespace mozilla {
  13 namespace layers {
  14
  15 // Helper that creates a monitor and a "done" flag, then enters the monitor.
  16 class MOZ_STACK_CLASS SynchronousTask {
  17   friend class AutoCompleteTask;
  18
  19  public:
  20   explicit SynchronousTask(const char* name) : mMonitor(name), mDone(false) {}
  21
  22   nsresult Wait(PRIntervalTime aInterval = PR_INTERVAL_NO_TIMEOUT) {
  23     ReentrantMonitorAutoEnter lock(mMonitor);
  24
  25     // For indefinite timeouts, wait in a while loop to handle spurious
  26     // wakeups.
  27     while (aInterval == PR_INTERVAL_NO_TIMEOUT && !mDone) {
  28       mMonitor.Wait();
  29     }
  30
  31     // For finite timeouts, we only check once for completion, and otherwise
  32     // rely on the ReentrantMonitor to manage the interval. If the monitor
  33     // returns too early, we'll never know, but we can check if the mDone
  34     // flag was set to true, indicating that the task finished successfully.
  35     if (!mDone) {
  36       // We ignore the return value from ReentrantMonitor::Wait, because it's
  37       // always NS_OK, even in the case of timeout.
  38       mMonitor.Wait(aInterval);
  39
  40       if (!mDone) {
  41         return NS_ERROR_ABORT;
  42       }
  43     }
  44
  45     return NS_OK;
  46   }
  47
  48  private:
  49   void Complete() {
  50     ReentrantMonitorAutoEnter lock(mMonitor);
  51     mDone = true;
  52     mMonitor.NotifyAll();
  53   }
  54
  55  private:
  56   ReentrantMonitor mMonitor MOZ_UNANNOTATED;
  57   bool mDone;
  58 };
  59
  60 class MOZ_STACK_CLASS AutoCompleteTask final {
  61  public:
  62   explicit AutoCompleteTask(SynchronousTask* aTask) : mTask(aTask) {}
  63   ~AutoCompleteTask() { mTask->Complete(); }
  64
  65  private:
  66   SynchronousTask* mTask;
  67 };
  68
  69 }  // namespace layers
  70 }  // namespace mozilla
  71
  72 #endif