/* -*- 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 ***** */

#include "nsTaskQueue.h"
#include "nsAutoLock.h"
#include "nsCOMPtr.h"

nsTaskQueue::nsTaskQueue()
  : mMonitor(nsAutoMonitor::NewMonitor("xpcom.taskqueue"))
  , mHead(nsnull)
  , mTail(nsnull)
  , mOffsetHead(0)
  , mOffsetTail(0)
{
}

nsTaskQueue::~nsTaskQueue()
{
  nsAutoMonitor::DestroyMonitor(mMonitor);
}

PRBool
nsTaskQueue::GetPendingTask(PRBool wait, nsIRunnable **result)
{
  nsAutoMonitor mon(mMonitor);

  while (IsEmpty()) {
    if (!wait) {
      if (result)
        *result = nsnull;
      return PR_FALSE;
    }
    mon.Wait();
  }

  if (result)
    *result = mHead->mTasks[mOffsetHead++];

  // Check if mHead points to empty Page
  if (mOffsetHead == TASKS_PER_PAGE) {
    Page *dead = mHead;
    mHead = mHead->mNext;
    FreePage(dead);
    mOffsetHead = 0;
  }

  return PR_TRUE;
}

PRBool
nsTaskQueue::PutTask(nsIRunnable *runnable)
{
  // Avoid calling AddRef+Release while holding our monitor.
  nsCOMPtr<nsIRunnable> task(runnable);
  PRBool rv = PR_TRUE;
  {
    nsAutoMonitor mon(mMonitor);

    if (!mHead) {
      mHead = NewPage();
      if (!mHead) {
        rv = PR_FALSE;
      } else {
        mTail = mHead;
        mOffsetHead = 0;
        mOffsetTail = 0;
      }
    } else if (mOffsetTail == TASKS_PER_PAGE) {
      Page *page = NewPage();
      if (!page) {
        rv = PR_FALSE;
      } else {
        mTail->mNext = page;
        mTail = page;
        mOffsetTail = 0;
      }
    }
    if (rv) {
      task.swap(mTail->mTasks[mOffsetTail]);
      ++mOffsetTail;
      mon.NotifyAll();
    }
  }
  return rv;
}