/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsIEventTarget.idl"
#include "nsIThread.idl"

[uuid(ef194cab-3f86-4b61-b132-e5e96a79e5d1)]
interface nsIThreadPoolListener : nsISupports
{
  /**
   * Called when a new thread is created by the thread pool. The notification
   * happens on the newly-created thread.
   */
  void onThreadCreated();

  /**
   * Called when a thread is about to be destroyed by the thread pool. The
   * notification happens on the thread that is about to be destroyed.
   */
  void onThreadShuttingDown();
};

/**
 * An interface to a thread pool.  A thread pool creates a limited number of
 * anonymous (unnamed) worker threads.  An event dispatched to the thread pool
 * will be run on the next available worker thread.
 */
[uuid(76ce99c9-8e43-489a-9789-f27cc4424965)]
interface nsIThreadPool : nsIEventTarget
{
  /**
   * Set the entire pool's QoS priority. If the priority has not changed, do nothing.
   * Existing threads will update their QoS priority the next time they become
   * active, and newly created threads will set this QoS priority upon creation.
   */
   [noscript] void setQoSForThreads(in nsIThread_QoSPriority aPriority);

  /**
   * Shutdown the thread pool.  This method may not be executed from any thread
   * in the thread pool.  Instead, it is meant to be executed from another
   * thread (usually the thread that created this thread pool).  When this
   * function returns, the thread pool and all of its threads will be shutdown,
   * and it will no longer be possible to dispatch tasks to the thread pool.
   *
   * As a side effect, events on the current thread will be processed.
   */
  void shutdown();

  /**
   * Shutdown the thread pool, but only wait for aTimeoutMs. After the timeout
   * expires, any threads that have not shutdown yet are leaked and will not
   * block shutdown.
   *
   * This method should only be used at during shutdown to cleanup threads that
   * made blocking calls to code outside our control, and can't be safely
   * terminated. We choose to leak them intentionally to avoid a shutdown hang.
   */
  [noscript] void shutdownWithTimeout(in long aTimeoutMs);

  /**
   * Get/set the maximum number of threads allowed at one time in this pool.
   */
  attribute unsigned long threadLimit;

  /**
   * Get/set the maximum number of idle threads kept alive.
   */
  attribute unsigned long idleThreadLimit;

  /**
   * Get/set the amount of time in milliseconds before an idle thread is
   * destroyed.
   */
  attribute unsigned long idleThreadTimeout;

  /**
   * If set to true the idle timeout will be calculated as idleThreadTimeout
   * divideded by the number of idle threads at the moment.  This may help
   * save memory allocations but still keep reasonable amount of idle threads.
   * Default is false, use |idleThreadTimeout| for all threads.
   */
  attribute boolean idleThreadTimeoutRegressive;

  /**
   * Get/set the number of bytes reserved for the stack of all threads in
   * the pool. By default this is nsIThreadManager::DEFAULT_STACK_SIZE.
   */
  attribute unsigned long threadStackSize;

  /**
   * An optional listener that will be notified when a thread is created or
   * destroyed in the course of the thread pool's operation.
   *
   * A listener will only receive notifications about threads created after the
   * listener is set so it is recommended that the consumer set the listener
   * before dispatching the first event. A listener that receives an
   * onThreadCreated() notification is guaranteed to always receive the
   * corresponding onThreadShuttingDown() notification.
   *
   * The thread pool takes ownership of the listener and releases it when the
   * shutdown() method is called. Threads created after the listener is set will
   * also take ownership of the listener so that the listener will be kept alive
   * long enough to receive the guaranteed onThreadShuttingDown() notification.
   */
  attribute nsIThreadPoolListener listener;

  /**
   * Set the label for threads in the pool. All threads will be named
   * "<aName> #<n>", where <n> is a serial number.
   */
  void setName(in ACString aName);
};
