gecko-dev/xpcom/threads/nsIThread.idl

/* -*- 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 "nsIIdlePeriod.idl"

%{C++
#include "mozilla/AlreadyAddRefed.h"
%}

[ptr] native PRThread(PRThread);

native alreadyAddRefed_nsIIdlePeriod(already_AddRefed<nsIIdlePeriod>);

/**
 * This interface provides a high-level abstraction for an operating system
 * thread.
 *
 * Threads have a built-in event queue, and a thread is an event target that
 * can receive nsIRunnable objects (events) to be processed on the thread.
 *
 * See nsIThreadManager for the API used to create and locate threads.
 */
[scriptable, uuid(5801d193-29d1-4964-a6b7-70eb697ddf2b)]
interface nsIThread : nsIEventTarget
{
  /**
   * @returns
   *   The NSPR thread object corresponding to this nsIThread.
   */
  [noscript] readonly attribute PRThread PRThread;

  /**
   * @returns
   *  Whether or not this thread may call into JS. Used in the profiler
   *  to avoid some unnecessary locking.
   */
  [noscript] attribute boolean CanInvokeJS;


  /**
   * Shutdown the thread.  This method prevents further dispatch of events to
   * the thread, and it causes any pending events to run to completion before
   * the thread joins (see PR_JoinThread) with the current thread.  During this
   * method call, events for the current thread may be processed.
   *
   * This method MAY NOT be executed from the thread itself.  Instead, it is
   * meant to be executed from another thread (usually the thread that created
   * this thread or the main application thread).  When this function returns,
   * the thread will be shutdown, and it will no longer be possible to dispatch
   * events to the thread.
   *
   * @throws NS_ERROR_UNEXPECTED
   *   Indicates that this method was erroneously called when this thread was
   *   the current thread, that this thread was not created with a call to
   *   nsIThreadManager::NewThread, or if this method was called more than once
   *   on the thread object.
   */
  void shutdown();

  /**
   * This method may be called to determine if there are any events ready to be
   * processed.  It may only be called when this thread is the current thread.
   *
   * Because events may be added to this thread by another thread, a "false"
   * result does not mean that this thread has no pending events.  It only
   * means that there were no pending events when this method was called.
   *
   * @returns
   *   A boolean value that if "true" indicates that this thread has one or
   *   more pending events.
   *
   * @throws NS_ERROR_UNEXPECTED
   *   Indicates that this method was erroneously called when this thread was
   *   not the current thread.
   */
  boolean hasPendingEvents();

  /**
   * Process the next event.  If there are no pending events, then this method
   * may wait -- depending on the value of the mayWait parameter -- until an
   * event is dispatched to this thread.  This method is re-entrant but may
   * only be called if this thread is the current thread.
   *
   * @param mayWait
   *   A boolean parameter that if "true" indicates that the method may block
   *   the calling thread to wait for a pending event.
   *
   * @returns
   *   A boolean value that if "true" indicates that an event was processed.
   *
   * @throws NS_ERROR_UNEXPECTED
   *   Indicates that this method was erroneously called when this thread was
   *   not the current thread.
   */
  boolean processNextEvent(in boolean mayWait);

  /**
   * Shutdown the thread asynchronously.  This method immediately prevents
   * further dispatch of events to the thread, and it causes any pending events
   * to run to completion before this thread joins with the current thread.
   *
   * UNLIKE shutdown() this does not process events on the current thread.
   * Instead it merely ensures that the current thread continues running until
   * this thread has shut down.
   *
   * This method MAY NOT be executed from the thread itself.  Instead, it is
   * meant to be executed from another thread (usually the thread that created
   * this thread or the main application thread).  When this function returns,
   * the thread will continue running until it exhausts its event queue.
   *
   * @throws NS_ERROR_UNEXPECTED
   *   Indicates that this method was erroneously called when this thread was
   *   the current thread, that this thread was not created with a call to
   *   nsIThreadManager::NewThread, or if this method was called more than once
   *   on the thread object.
   */
  void asyncShutdown();

  /**
   * Register an instance of nsIIdlePeriod which works as a facade of
   * the abstract notion of a "current idle period". The
   * nsIIdlePeriod should always represent the "current" idle period
   * with regard to expected work for the thread. The thread is free
   * to use this when there are no higher prioritized tasks to process
   * to determine if it is reasonable to schedule tasks that could run
   * when the thread is idle. The responsibility of the registered
   * nsIIdlePeriod is to answer with an estimated deadline at which
   * the thread should expect that it could receive new higher
   * priority tasks.
   */
  [noscript] void registerIdlePeriod(in alreadyAddRefed_nsIIdlePeriod aIdlePeriod);

  /**
   * Dispatch an event to the thread's idle queue.  This function may be called
   * from any thread, and it may be called re-entrantly.
   *
   * @param event
   *   The alreadyAddRefed<> event to dispatch.
   *   NOTE that the event will be leaked if it fails to dispatch.
   *
   * @throws NS_ERROR_INVALID_ARG
   *   Indicates that event is null.
   * @throws NS_ERROR_UNEXPECTED
   *   Indicates that the thread is shutting down and has finished processing
   * events, so this event would never run and has not been dispatched.
   */
  [noscript, binaryname(IdleDispatch)] void idleDispatchFromC(in alreadyAddRefed_nsIRunnable event);

  /**
   * Dispatch an event to the thread's idle queue.  This function may be called
   * from any thread, and it may be called re-entrantly.
   *
   * @param event
   *   The (raw) event to dispatch.
   *
   * @throws NS_ERROR_INVALID_ARG
   *   Indicates that event is null.
   * @throws NS_ERROR_UNEXPECTED
   *   Indicates that the thread is shutting down and has finished processing
   * events, so this event would never run and has not been dispatched.
   */
  [binaryname(IdleDispatchFromScript)] void idleDispatch(in nsIRunnable event);
};