xpcom/threads/nsIEventTarget.idl

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   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 #include "nsISupports.idl"
   8 #include "nsIRunnable.idl"
   9 %{C++
  10 #include "nsCOMPtr.h"
  11 #include "mozilla/AlreadyAddRefed.h"
  12 #include "mozilla/Atomics.h"
  13 %}
  14
  15 native alreadyAddRefed_nsIRunnable(already_AddRefed<nsIRunnable>);
  16
  17 [builtinclass, scriptable, uuid(a03b8b63-af8b-4164-b0e5-c41e8b2b7cfa)]
  18 interface nsIEventTarget : nsISupports
  19 {
  20   /* until we can get rid of all uses, keep the non-alreadyAddRefed<> version */
  21 %{C++
  22     nsresult Dispatch(nsIRunnable* aEvent, uint32_t aFlags) {
  23       return Dispatch(nsCOMPtr<nsIRunnable>(aEvent).forget(), aFlags);
  24     }
  25 %}
  26
  27   /**
  28    * This flag specifies the default mode of event dispatch, whereby the event
  29    * is simply queued for later processing.  When this flag is specified,
  30    * dispatch returns immediately after the event is queued.
  31    */
  32   const unsigned long DISPATCH_NORMAL = 0;
  33
  34   /**
  35    * This flag specifies the synchronous mode of event dispatch, in which the
  36    * dispatch method does not return until the event has been processed.
  37    *
  38    * NOTE: passing this flag to dispatch may have the side-effect of causing
  39    * other events on the current thread to be processed while waiting for the
  40    * given event to be processed.
  41    */
  42   const unsigned long DISPATCH_SYNC = 1;
  43
  44   /**
  45    * This flag specifies that the dispatch is occurring from a running event
  46    * that was dispatched to the same event target, and that event is about to
  47    * finish.
  48    *
  49    * A thread pool can use this as an optimization hint to not spin up
  50    * another thread, since the current thread is about to become idle.
  51    *
  52    * These events are always async.
  53    */
  54   const unsigned long DISPATCH_AT_END = 2;
  55
  56   /**
  57    * This flag specifies that the dispatched event may block the thread on
  58    * which it executes, usually by doing some sort of I/O.  This information
  59    * may be used by the event target to execute the job on a thread
  60    * specifically dedicated to doing I/O, leaving other threads available for
  61    * CPU-intensive work.
  62    */
  63   const unsigned long DISPATCH_EVENT_MAY_BLOCK = 4;
  64
  65   /**
  66    * IsOnCurrentThread() should return true if events dispatched to this target
  67    * can possibly run on the current thread, and false otherwise. In the case
  68    * of an nsIEventTarget for a thread pool, it should return true on all
  69    * threads in the pool. In the case of a non-thread nsIEventTarget such as
  70    * ThrottledEventQueue, it should return true on the thread where events are
  71    * expected to be processed, even if no events from the queue are actually
  72    * being processed right now.
  73    *
  74    * When called on an nsISerialEventTarget, IsOnCurrentThread can be used to
  75    * ensure that no other thread has "ownership" of the event target. As such,
  76    * it's useful for asserting that an object is only used on a particular
  77    * thread. IsOnCurrentThread can't guarantee that the current event has been
  78    * dispatched through a particular event target.
  79    *
  80    * The infallible version of IsOnCurrentThread() is optimized to avoid a
  81    * virtual call for non-thread event targets. Thread targets should set
  82    * mThread to their virtual PRThread. Non-thread targets should leave
  83    * mThread null and implement IsOnCurrentThreadInfallible() to
  84    * return the correct answer.
  85    *
  86    * The fallible version of IsOnCurrentThread may return errors, such as during
  87    * shutdown. If it does not return an error, it should return the same result
  88    * as the infallible version. The infallible method should return the correct
  89    * result regardless of whether the fallible method returns an error.
  90    */
  91   %{C++
  92 public:
  93   // Infallible. Defined in nsThreadUtils.cpp. Delegates to
  94   // IsOnCurrentThreadInfallible when mThread is null.
  95   bool IsOnCurrentThread();
  96
  97 protected:
  98   mozilla::Atomic<PRThread*> mThread;
  99
 100   nsIEventTarget() : mThread(nullptr) {}
 101   %}
 102   // Note that this method is protected.  We define it through IDL, rather than
 103   // in a %{C++ block, to ensure that the correct method indices are recorded
 104   // for XPConnect purposes.
 105   [noscript,notxpcom] boolean isOnCurrentThreadInfallible();
 106   %{C++
 107 public:
 108   %}
 109
 110   // Fallible version of IsOnCurrentThread.
 111   boolean isOnCurrentThread();
 112
 113   /**
 114    * Dispatch an event to this event target.  This function may be called from
 115    * any thread, and it may be called re-entrantly.
 116    *
 117    * @param event
 118    *   The alreadyAddRefed<> event to dispatch.
 119    *   NOTE that the event will be leaked if it fails to dispatch.
 120    * @param flags
 121    *   The flags modifying event dispatch.  The flags are described in detail
 122    *   below.
 123    *
 124    * @throws NS_ERROR_INVALID_ARG
 125    *   Indicates that event is null.
 126    * @throws NS_ERROR_UNEXPECTED
 127    *   Indicates that the thread is shutting down and has finished processing
 128    * events, so this event would never run and has not been dispatched.
 129    */
 130   [noscript, binaryname(Dispatch)] void dispatchFromC(in alreadyAddRefed_nsIRunnable event,
 131                                                       [default(DISPATCH_NORMAL)] in unsigned long flags);
 132   /**
 133    * Version of Dispatch to expose to JS, which doesn't require an alreadyAddRefed<>
 134    * (it will be converted to that internally)
 135    *
 136    * @param event
 137    *   The (raw) event to dispatch.
 138    * @param flags
 139    *   The flags modifying event dispatch.  The flags are described in detail
 140    *   below.
 141    *
 142    * @throws NS_ERROR_INVALID_ARG
 143    *   Indicates that event is null.
 144    * @throws NS_ERROR_UNEXPECTED
 145    *   Indicates that the thread is shutting down and has finished processing
 146    * events, so this event would never run and has not been dispatched.
 147    */
 148   [binaryname(DispatchFromScript)] void dispatch(in nsIRunnable event, in unsigned long flags);
 149   /**
 150    * Dispatch an event to this event target, but do not run it before delay
 151    * milliseconds have passed.  This function may be called from any thread.
 152    *
 153    * @param event
 154    *   The alreadyAddrefed<> event to dispatch.
 155    * @param delay
 156    *   The delay (in ms) before running the event.  If event does not rise to
 157    *   the top of the event queue before the delay has passed, it will be set
 158    *   aside to execute once the delay has passed.  Otherwise, it will be
 159    *   executed immediately.
 160    *
 161    * @throws NS_ERROR_INVALID_ARG
 162    *   Indicates that event is null.
 163    * @throws NS_ERROR_UNEXPECTED
 164    *   Indicates that the thread is shutting down and has finished processing
 165    * events, so this event would never run and has not been dispatched, or
 166    * that delay is zero.
 167    */
 168   [noscript] void delayedDispatch(in alreadyAddRefed_nsIRunnable event, in unsigned long delay);
 169 };
 170
 171 %{C++
 172 // convenient aliases:
 173 #define NS_DISPATCH_NORMAL nsIEventTarget::DISPATCH_NORMAL
 174 #define NS_DISPATCH_SYNC   nsIEventTarget::DISPATCH_SYNC
 175 #define NS_DISPATCH_AT_END nsIEventTarget::DISPATCH_AT_END
 176 #define NS_DISPATCH_EVENT_MAY_BLOCK nsIEventTarget::DISPATCH_EVENT_MAY_BLOCK
 177
 178 // Convenient NS_DECL variant that includes some C++-only methods.
 179 #define NS_DECL_NSIEVENTTARGET_FULL                                   \
 180     NS_DECL_NSIEVENTTARGET                                            \
 181     /* Avoid hiding these methods */                                  \
 182     using nsIEventTarget::Dispatch;                                   \
 183     using nsIEventTarget::IsOnCurrentThread;
 184 %}