gecko-dev/xpcom/threads/nsThread.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla code.
 *
 * The Initial Developer of the Original Code is Google Inc.
 * Portions created by the Initial Developer are Copyright (C) 2006
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *  Darin Fisher <darin@meer.net>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#ifndef nsThread_h__
#define nsThread_h__

#include "mozilla/Mutex.h"
#include "nsIThreadInternal.h"
#include "nsISupportsPriority.h"
#include "nsEventQueue.h"
#include "nsThreadUtils.h"
#include "nsString.h"
#include "nsTObserverArray.h"

// A native thread
class nsThread : public nsIThreadInternal, public nsISupportsPriority
{
public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIEVENTTARGET
  NS_DECL_NSITHREAD
  NS_DECL_NSITHREADINTERNAL
  NS_DECL_NSISUPPORTSPRIORITY

  enum MainThreadFlag {
    MAIN_THREAD,
    NOT_MAIN_THREAD
  };

  nsThread(MainThreadFlag aMainThread, PRUint32 aStackSize);

  // Initialize this as a wrapper for a new PRThread.
  nsresult Init();

  // Initialize this as a wrapper for the current PRThread.
  nsresult InitCurrentThread();

  // The PRThread corresponding to this thread.
  PRThread *GetPRThread() { return mThread; }

  // If this flag is true, then the nsThread was created using
  // nsIThreadManager::NewThread.
  bool ShutdownRequired() { return mShutdownRequired; }

  // Clear the observer list.
  void ClearObservers() { mEventObservers.Clear(); }

private:
  friend class nsThreadShutdownEvent;

  ~nsThread();

  bool ShuttingDown() { return mShutdownContext != nsnull; }

  static void ThreadFunc(void *arg);

  // Helper
  already_AddRefed<nsIThreadObserver> GetObserver() {
    nsIThreadObserver *obs;
    nsThread::GetObserver(&obs);
    return already_AddRefed<nsIThreadObserver>(obs);
  }

  // Wrappers for event queue methods:
  bool GetEvent(bool mayWait, nsIRunnable **event) {
    return mEvents->GetEvent(mayWait, event);
  }
  nsresult PutEvent(nsIRunnable *event);

  // Wrapper for nsEventQueue that supports chaining.
  class nsChainedEventQueue {
  public:
    nsChainedEventQueue(nsIThreadEventFilter *filter = nsnull)
      : mNext(nsnull), mFilter(filter) {
    }

    bool GetEvent(bool mayWait, nsIRunnable **event) {
      return mQueue.GetEvent(mayWait, event);
    }

    bool PutEvent(nsIRunnable *event);
    
    bool HasPendingEvent() {
      return mQueue.HasPendingEvent();
    }

    class nsChainedEventQueue *mNext;
  private:
    nsCOMPtr<nsIThreadEventFilter> mFilter;
    nsEventQueue mQueue;
  };

  // This lock protects access to mObserver, mEvents and mEventsAreDoomed.
  // All of those fields are only modified on the thread itself (never from
  // another thread).  This means that we can avoid holding the lock while
  // using mObserver and mEvents on the thread itself.  When calling PutEvent
  // on mEvents, we have to hold the lock to synchronize with PopEventQueue.
  mozilla::Mutex mLock;

  nsCOMPtr<nsIThreadObserver> mObserver;

  // Only accessed on the target thread.
  nsAutoTObserverArray<nsCOMPtr<nsIThreadObserver>, 2> mEventObservers;

  nsChainedEventQueue *mEvents;   // never null
  nsChainedEventQueue  mEventsRoot;

  PRInt32   mPriority;
  PRThread *mThread;
  PRUint32  mRunningEvent;  // counter
  PRUint32  mStackSize;

  struct nsThreadShutdownContext *mShutdownContext;

  bool mShutdownRequired;
  bool mShutdownPending;
  // Set to true when events posted to this thread will never run.
  bool mEventsAreDoomed;
  MainThreadFlag mIsMainThread;
};

//-----------------------------------------------------------------------------

class nsThreadSyncDispatch : public nsRunnable {
public:
  nsThreadSyncDispatch(nsIThread *origin, nsIRunnable *task)
    : mOrigin(origin), mSyncTask(task), mResult(NS_ERROR_NOT_INITIALIZED) {
  }

  bool IsPending() {
    return mSyncTask != nsnull;
  }

  nsresult Result() {
    return mResult;
  }

private:
  NS_DECL_NSIRUNNABLE

  nsCOMPtr<nsIThread> mOrigin;
  nsCOMPtr<nsIRunnable> mSyncTask;
  nsresult mResult;
};

namespace mozilla {

/**
 * This function causes the main thread to fire a memory pressure event at its
 * next available opportunity.
 *
 * You may call this function from any thread.
 */
void ScheduleMemoryPressureEvent();

} // namespace mozilla

#endif  // nsThread_h__