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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_MESSAGE_LOOP_H_
+#define BASE_MESSAGE_LOOP_H_
+
+#include <deque>
+#include <queue>
+#include <string>
+#include <vector>
+#include <map>
+
+#include "base/lock.h"
+#include "base/message_pump.h"
+#include "base/observer_list.h"
+
+#if defined(OS_WIN)
+// We need this to declare base::MessagePumpWin::Dispatcher, which we should
+// really just eliminate.
+#include "base/message_pump_win.h"
+#elif defined(OS_POSIX)
+#include "base/message_pump_libevent.h"
+#endif
+
+#include "nsAutoPtr.h"
+#include "nsThreadUtils.h"
+
+class nsIThread;
+
+namespace mozilla {
+namespace ipc {
+
+class DoWorkRunnable;
+
+} /* namespace ipc */
+} /* namespace mozilla */
+
+// A MessageLoop is used to process events for a particular thread. There is
+// at most one MessageLoop instance per thread.
+//
+// Events include at a minimum Task instances submitted to PostTask or those
+// managed by TimerManager. Depending on the type of message pump used by the
+// MessageLoop other events such as UI messages may be processed. On Windows
+// APC calls (as time permits) and signals sent to a registered set of HANDLEs
+// may also be processed.
+//
+// NOTE: Unless otherwise specified, a MessageLoop's methods may only be called
+// on the thread where the MessageLoop's Run method executes.
+//
+// NOTE: MessageLoop has task reentrancy protection. This means that if a
+// task is being processed, a second task cannot start until the first task is
+// finished. Reentrancy can happen when processing a task, and an inner
+// message pump is created. That inner pump then processes native messages
+// which could implicitly start an inner task. Inner message pumps are created
+// with dialogs (DialogBox), common dialogs (GetOpenFileName), OLE functions
+// (DoDragDrop), printer functions (StartDoc) and *many* others.
+//
+// Sample workaround when inner task processing is needed:
+// bool old_state = MessageLoop::current()->NestableTasksAllowed();
+// MessageLoop::current()->SetNestableTasksAllowed(true);
+// HRESULT hr = DoDragDrop(...); // Implicitly runs a modal message loop here.
+// MessageLoop::current()->SetNestableTasksAllowed(old_state);
+// // Process hr (the result returned by DoDragDrop().
+//
+// Please be SURE your task is reentrant (nestable) and all global variables
+// are stable and accessible before calling SetNestableTasksAllowed(true).
+//
+class MessageLoop : public base::MessagePump::Delegate {
+
+ friend class mozilla::ipc::DoWorkRunnable;
+
+public:
+ // A DestructionObserver is notified when the current MessageLoop is being
+ // destroyed. These obsevers are notified prior to MessageLoop::current()
+ // being changed to return NULL. This gives interested parties the chance to
+ // do final cleanup that depends on the MessageLoop.
+ //
+ // NOTE: Any tasks posted to the MessageLoop during this notification will
+ // not be run. Instead, they will be deleted.
+ //
+ class DestructionObserver {
+ public:
+ virtual ~DestructionObserver() {}
+ virtual void WillDestroyCurrentMessageLoop() = 0;
+ };
+
+ // Add a DestructionObserver, which will start receiving notifications
+ // immediately.
+ void AddDestructionObserver(DestructionObserver* destruction_observer);
+
+ // Remove a DestructionObserver. It is safe to call this method while a
+ // DestructionObserver is receiving a notification callback.
+ void RemoveDestructionObserver(DestructionObserver* destruction_observer);
+
+ // The "PostTask" family of methods call the task's Run method asynchronously
+ // from within a message loop at some point in the future.
+ //
+ // With the PostTask variant, tasks are invoked in FIFO order, inter-mixed
+ // with normal UI or IO event processing. With the PostDelayedTask variant,
+ // tasks are called after at least approximately 'delay_ms' have elapsed.
+ //
+ // The NonNestable variants work similarly except that they promise never to
+ // dispatch the task from a nested invocation of MessageLoop::Run. Instead,
+ // such tasks get deferred until the top-most MessageLoop::Run is executing.
+ //
+ // The MessageLoop takes ownership of the Task, and deletes it after it has
+ // been Run().
+ //
+ // NOTE: These methods may be called on any thread. The Task will be invoked
+ // on the thread that executes MessageLoop::Run().
+
+ void PostTask(already_AddRefed<mozilla::Runnable> task);
+
+ void PostDelayedTask(already_AddRefed<mozilla::Runnable> task, int delay_ms);
+
+ // PostIdleTask is not thread safe and should be called on this thread
+ void PostIdleTask(already_AddRefed<mozilla::Runnable> task);
+
+ // Run the message loop.
+ void Run();
+
+ // Signals the Run method to return after it is done processing all pending
+ // messages. This method may only be called on the same thread that called
+ // Run, and Run must still be on the call stack.
+ //
+ // Use QuitTask if you need to Quit another thread's MessageLoop, but note
+ // that doing so is fairly dangerous if the target thread makes nested calls
+ // to MessageLoop::Run. The problem being that you won't know which nested
+ // run loop you are quiting, so be careful!
+ //
+ void Quit();
+
+ // Invokes Quit on the current MessageLoop when run. Useful to schedule an
+ // arbitrary MessageLoop to Quit.
+ class QuitTask : public mozilla::Runnable {
+ public:
+ NS_IMETHOD Run() override {
+ MessageLoop::current()->Quit();
+ return NS_OK;
+ }
+ };
+
+ // A MessageLoop has a particular type, which indicates the set of
+ // asynchronous events it may process in addition to tasks and timers.
+ //
+ // TYPE_DEFAULT
+ // This type of ML only supports tasks and timers.
+ //
+ // TYPE_UI
+ // This type of ML also supports native UI events (e.g., Windows messages).
+ // See also MessageLoopForUI.
+ //
+ // TYPE_IO
+ // This type of ML also supports asynchronous IO. See also
+ // MessageLoopForIO.
+ //
+ // TYPE_MOZILLA_CHILD
+ // This type of ML is used in Mozilla child processes which initialize
+ // XPCOM and use the gecko event loop.
+ //
+ // TYPE_MOZILLA_PARENT
+ // This type of ML is used in Mozilla parent processes which initialize
+ // XPCOM and use the gecko event loop.
+ //
+ // TYPE_MOZILLA_NONMAINTHREAD
+ // This type of ML is used in Mozilla parent processes which initialize
+ // XPCOM and use the nsThread event loop.
+ //
+ // TYPE_MOZILLA_NONMAINUITHREAD
+ // This type of ML is used in Mozilla processes which initialize XPCOM
+ // and use TYPE_UI loop logic.
+ //
+ enum Type {
+ TYPE_DEFAULT,
+ TYPE_UI,
+ TYPE_IO,
+ TYPE_MOZILLA_CHILD,
+ TYPE_MOZILLA_PARENT,
+ TYPE_MOZILLA_NONMAINTHREAD,
+ TYPE_MOZILLA_NONMAINUITHREAD
+ };
+
+ // Normally, it is not necessary to instantiate a MessageLoop. Instead, it
+ // is typical to make use of the current thread's MessageLoop instance.
+ explicit MessageLoop(Type type = TYPE_DEFAULT, nsIThread* aThread = nullptr);
+ ~MessageLoop();
+
+ // Returns the type passed to the constructor.
+ Type type() const { return type_; }
+
+ // Unique, non-repeating ID for this message loop.
+ int32_t id() const { return id_; }
+
+ // Optional call to connect the thread name with this loop.
+ void set_thread_name(const std::string& aThreadName) {
+ DCHECK(thread_name_.empty()) << "Should not rename this thread!";
+ thread_name_ = aThreadName;
+ }
+ const std::string& thread_name() const { return thread_name_; }
+
+ // Returns the MessageLoop object for the current thread, or null if none.
+ static MessageLoop* current();
+
+ // Enables or disables the recursive task processing. This happens in the case
+ // of recursive message loops. Some unwanted message loop may occurs when
+ // using common controls or printer functions. By default, recursive task
+ // processing is disabled.
+ //
+ // The specific case where tasks get queued is:
+ // - The thread is running a message loop.
+ // - It receives a task #1 and execute it.
+ // - The task #1 implicitly start a message loop, like a MessageBox in the
+ // unit test. This can also be StartDoc or GetSaveFileName.
+ // - The thread receives a task #2 before or while in this second message
+ // loop.
+ // - With NestableTasksAllowed set to true, the task #2 will run right away.
+ // Otherwise, it will get executed right after task #1 completes at "thread
+ // message loop level".
+ void SetNestableTasksAllowed(bool allowed);
+ void ScheduleWork();
+ bool NestableTasksAllowed() const;
+
+ // Enables or disables the restoration during an exception of the unhandled
+ // exception filter that was active when Run() was called. This can happen
+ // if some third party code call SetUnhandledExceptionFilter() and never
+ // restores the previous filter.
+ void set_exception_restoration(bool restore) {
+ exception_restoration_ = restore;
+ }
+
+#if defined(OS_WIN)
+ void set_os_modal_loop(bool os_modal_loop) {
+ os_modal_loop_ = os_modal_loop;
+ }
+
+ bool & os_modal_loop() {
+ return os_modal_loop_;
+ }
+#endif // OS_WIN
+
+ // Set the timeouts for background hang monitoring.
+ // A value of 0 indicates there is no timeout.
+ void set_hang_timeouts(uint32_t transient_timeout_ms,
+ uint32_t permanent_timeout_ms) {
+ transient_hang_timeout_ = transient_timeout_ms;
+ permanent_hang_timeout_ = permanent_timeout_ms;
+ }
+ uint32_t transient_hang_timeout() const {
+ return transient_hang_timeout_;
+ }
+ uint32_t permanent_hang_timeout() const {
+ return permanent_hang_timeout_;
+ }
+
+ //----------------------------------------------------------------------------
+ protected:
+ struct RunState {
+ // Used to count how many Run() invocations are on the stack.
+ int run_depth;
+
+ // Used to record that Quit() was called, or that we should quit the pump
+ // once it becomes idle.
+ bool quit_received;
+
+#if defined(OS_WIN)
+ base::MessagePumpWin::Dispatcher* dispatcher;
+#endif
+ };
+
+ class AutoRunState : RunState {
+ public:
+ explicit AutoRunState(MessageLoop* loop);
+ ~AutoRunState();
+ private:
+ MessageLoop* loop_;
+ RunState* previous_state_;
+ };
+
+ // This structure is copied around by value.
+ struct PendingTask {
+ RefPtr<mozilla::Runnable> task; // The task to run.
+ base::TimeTicks delayed_run_time; // The time when the task should be run.
+ int sequence_num; // Secondary sort key for run time.
+ bool nestable; // OK to dispatch from a nested loop.
+
+ PendingTask(already_AddRefed<mozilla::Runnable> aTask, bool aNestable)
+ : task(aTask), sequence_num(0), nestable(aNestable) {
+ }
+
+ PendingTask(PendingTask&& aOther)
+ : task(aOther.task.forget()),
+ delayed_run_time(aOther.delayed_run_time),
+ sequence_num(aOther.sequence_num),
+ nestable(aOther.nestable) {
+ }
+
+ // std::priority_queue<T>::top is dumb, so we have to have this.
+ PendingTask(const PendingTask& aOther)
+ : task(aOther.task),
+ delayed_run_time(aOther.delayed_run_time),
+ sequence_num(aOther.sequence_num),
+ nestable(aOther.nestable) {
+ }
+ PendingTask& operator=(const PendingTask& aOther)
+ {
+ task = aOther.task;
+ delayed_run_time = aOther.delayed_run_time;
+ sequence_num = aOther.sequence_num;
+ nestable = aOther.nestable;
+ return *this;
+ }
+
+ // Used to support sorting.
+ bool operator<(const PendingTask& other) const;
+ };
+
+ typedef std::queue<PendingTask> TaskQueue;
+ typedef std::priority_queue<PendingTask> DelayedTaskQueue;
+
+#if defined(OS_WIN)
+ base::MessagePumpWin* pump_win() {
+ return static_cast<base::MessagePumpWin*>(pump_.get());
+ }
+#elif defined(OS_POSIX)
+ base::MessagePumpLibevent* pump_libevent() {
+ return static_cast<base::MessagePumpLibevent*>(pump_.get());
+ }
+#endif
+
+ // A function to encapsulate all the exception handling capability in the
+ // stacks around the running of a main message loop. It will run the message
+ // loop in a SEH try block or not depending on the set_SEH_restoration()
+ // flag.
+ void RunHandler();
+
+ // A surrounding stack frame around the running of the message loop that
+ // supports all saving and restoring of state, as is needed for any/all (ugly)
+ // recursive calls.
+ void RunInternal();
+
+ // Called to process any delayed non-nestable tasks.
+ bool ProcessNextDelayedNonNestableTask();
+
+ //----------------------------------------------------------------------------
+ // Run a work_queue_ task or new_task, and delete it (if it was processed by
+ // PostTask). If there are queued tasks, the oldest one is executed and
+ // new_task is queued. new_task is optional and can be NULL. In this NULL
+ // case, the method will run one pending task (if any exist). Returns true if
+ // it executes a task. Queued tasks accumulate only when there is a
+ // non-nestable task currently processing, in which case the new_task is
+ // appended to the list work_queue_. Such re-entrancy generally happens when
+ // an unrequested message pump (typical of a native dialog) is executing in
+ // the context of a task.
+ bool QueueOrRunTask(already_AddRefed<mozilla::Runnable> new_task);
+
+ // Runs the specified task and deletes it.
+ void RunTask(already_AddRefed<mozilla::Runnable> task);
+
+ // Calls RunTask or queues the pending_task on the deferred task list if it
+ // cannot be run right now. Returns true if the task was run.
+ bool DeferOrRunPendingTask(PendingTask&& pending_task);
+
+ // Adds the pending task to delayed_work_queue_.
+ void AddToDelayedWorkQueue(const PendingTask& pending_task);
+
+ // Load tasks from the incoming_queue_ into work_queue_ if the latter is
+ // empty. The former requires a lock to access, while the latter is directly
+ // accessible on this thread.
+ void ReloadWorkQueue();
+
+ // Delete tasks that haven't run yet without running them. Used in the
+ // destructor to make sure all the task's destructors get called. Returns
+ // true if some work was done.
+ bool DeletePendingTasks();
+
+ // Post a task to our incomming queue.
+ void PostTask_Helper(already_AddRefed<mozilla::Runnable> task, int delay_ms);
+
+ // base::MessagePump::Delegate methods:
+ virtual bool DoWork() override;
+ virtual bool DoDelayedWork(base::TimeTicks* next_delayed_work_time) override;
+ virtual bool DoIdleWork() override;
+
+ Type type_;
+ int32_t id_;
+
+ // A list of tasks that need to be processed by this instance. Note that
+ // this queue is only accessed (push/pop) by our current thread.
+ TaskQueue work_queue_;
+
+ // Contains delayed tasks, sorted by their 'delayed_run_time' property.
+ DelayedTaskQueue delayed_work_queue_;
+
+ // A queue of non-nestable tasks that we had to defer because when it came
+ // time to execute them we were in a nested message loop. They will execute
+ // once we're out of nested message loops.
+ TaskQueue deferred_non_nestable_work_queue_;
+
+ RefPtr<base::MessagePump> pump_;
+
+ base::ObserverList<DestructionObserver> destruction_observers_;
+
+ // A recursion block that prevents accidentally running additonal tasks when
+ // insider a (accidentally induced?) nested message pump.
+ bool nestable_tasks_allowed_;
+
+ bool exception_restoration_;
+
+ std::string thread_name_;
+
+ // A null terminated list which creates an incoming_queue of tasks that are
+ // aquired under a mutex for processing on this instance's thread. These tasks
+ // have not yet been sorted out into items for our work_queue_ vs items that
+ // will be handled by the TimerManager.
+ TaskQueue incoming_queue_;
+ // Protect access to incoming_queue_.
+ Lock incoming_queue_lock_;
+
+ RunState* state_;
+ int run_depth_base_;
+
+#if defined(OS_WIN)
+ // Should be set to true before calling Windows APIs like TrackPopupMenu, etc
+ // which enter a modal message loop.
+ bool os_modal_loop_;
+#endif
+
+ // Timeout values for hang monitoring
+ uint32_t transient_hang_timeout_;
+ uint32_t permanent_hang_timeout_;
+
+ // The next sequence number to use for delayed tasks.
+ int next_sequence_num_;
+
+ DISALLOW_COPY_AND_ASSIGN(MessageLoop);
+};
+
+//-----------------------------------------------------------------------------
+// MessageLoopForUI extends MessageLoop with methods that are particular to a
+// MessageLoop instantiated with TYPE_UI.
+//
+// This class is typically used like so:
+// MessageLoopForUI::current()->...call some method...
+//
+class MessageLoopForUI : public MessageLoop {
+ public:
+ explicit MessageLoopForUI(Type aType=TYPE_UI) : MessageLoop(aType) {
+ }
+
+ // Returns the MessageLoopForUI of the current thread.
+ static MessageLoopForUI* current() {
+ MessageLoop* loop = MessageLoop::current();
+ if (!loop)
+ return NULL;
+ Type type = loop->type();
+ DCHECK(type == MessageLoop::TYPE_UI ||
+ type == MessageLoop::TYPE_MOZILLA_PARENT ||
+ type == MessageLoop::TYPE_MOZILLA_CHILD);
+ return static_cast<MessageLoopForUI*>(loop);
+ }
+
+#if defined(OS_WIN)
+ typedef base::MessagePumpWin::Dispatcher Dispatcher;
+ typedef base::MessagePumpWin::Observer Observer;
+
+ // Please see MessagePumpWin for definitions of these methods.
+ void Run(Dispatcher* dispatcher);
+ void AddObserver(Observer* observer);
+ void RemoveObserver(Observer* observer);
+ void WillProcessMessage(const MSG& message);
+ void DidProcessMessage(const MSG& message);
+ void PumpOutPendingPaintMessages();
+
+ protected:
+ // TODO(rvargas): Make this platform independent.
+ base::MessagePumpForUI* pump_ui() {
+ return static_cast<base::MessagePumpForUI*>(pump_.get());
+ }
+#endif // defined(OS_WIN)
+};
+
+// Do not add any member variables to MessageLoopForUI! This is important b/c
+// MessageLoopForUI is often allocated via MessageLoop(TYPE_UI). Any extra
+// data that you need should be stored on the MessageLoop's pump_ instance.
+COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForUI),
+ MessageLoopForUI_should_not_have_extra_member_variables);
+
+//-----------------------------------------------------------------------------
+// MessageLoopForIO extends MessageLoop with methods that are particular to a
+// MessageLoop instantiated with TYPE_IO.
+//
+// This class is typically used like so:
+// MessageLoopForIO::current()->...call some method...
+//
+class MessageLoopForIO : public MessageLoop {
+ public:
+ MessageLoopForIO() : MessageLoop(TYPE_IO) {
+ }
+
+ // Returns the MessageLoopForIO of the current thread.
+ static MessageLoopForIO* current() {
+ MessageLoop* loop = MessageLoop::current();
+ DCHECK_EQ(MessageLoop::TYPE_IO, loop->type());
+ return static_cast<MessageLoopForIO*>(loop);
+ }
+
+#if defined(OS_WIN)
+ typedef base::MessagePumpForIO::IOHandler IOHandler;
+ typedef base::MessagePumpForIO::IOContext IOContext;
+
+ // Please see MessagePumpWin for definitions of these methods.
+ void RegisterIOHandler(HANDLE file_handle, IOHandler* handler);
+ bool WaitForIOCompletion(DWORD timeout, IOHandler* filter);
+
+ protected:
+ // TODO(rvargas): Make this platform independent.
+ base::MessagePumpForIO* pump_io() {
+ return static_cast<base::MessagePumpForIO*>(pump_.get());
+ }
+
+#elif defined(OS_POSIX)
+ typedef base::MessagePumpLibevent::Watcher Watcher;
+ typedef base::MessagePumpLibevent::FileDescriptorWatcher
+ FileDescriptorWatcher;
+ typedef base::LineWatcher LineWatcher;
+
+ enum Mode {
+ WATCH_READ = base::MessagePumpLibevent::WATCH_READ,
+ WATCH_WRITE = base::MessagePumpLibevent::WATCH_WRITE,
+ WATCH_READ_WRITE = base::MessagePumpLibevent::WATCH_READ_WRITE
+ };
+
+ // Please see MessagePumpLibevent for definition.
+ bool WatchFileDescriptor(int fd,
+ bool persistent,
+ Mode mode,
+ FileDescriptorWatcher *controller,
+ Watcher *delegate);
+
+ typedef base::MessagePumpLibevent::SignalEvent SignalEvent;
+ typedef base::MessagePumpLibevent::SignalWatcher SignalWatcher;
+ bool CatchSignal(int sig,
+ SignalEvent* sigevent,
+ SignalWatcher* delegate);
+
+#endif // defined(OS_POSIX)
+};
+
+// Do not add any member variables to MessageLoopForIO! This is important b/c
+// MessageLoopForIO is often allocated via MessageLoop(TYPE_IO). Any extra
+// data that you need should be stored on the MessageLoop's pump_ instance.
+COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
+ MessageLoopForIO_should_not_have_extra_member_variables);
+
+#endif // BASE_MESSAGE_LOOP_H_