tor-browser

message_pump_win.cc (20344B)

---

/* -*- 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) 2009 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.

#include "base/message_pump_win.h"

#include <math.h>

#include "base/message_loop.h"
#include "base/histogram.h"
#include "base/win_util.h"
#include "mozilla/Maybe.h"
#include "mozilla/ProfilerLabels.h"
#include "mozilla/ProfilerThreadSleep.h"
#include "WinUtils.h"

using base::Time;

namespace base {

static const wchar_t kWndClass[] = L"Chrome_MessagePumpWindow";

// Message sent to get an additional time slice for pumping (processing) another
// task (a series of such messages creates a continuous task pump).
static const int kMsgHaveWork = WM_USER + 1;

//-----------------------------------------------------------------------------
// MessagePumpWin public:

void MessagePumpWin::AddObserver(Observer* observer) {
 observers_.AddObserver(observer);
}

void MessagePumpWin::RemoveObserver(Observer* observer) {
 observers_.RemoveObserver(observer);
}

void MessagePumpWin::WillProcessMessage(const MSG& msg) {
 FOR_EACH_OBSERVER(Observer, observers_, WillProcessMessage(msg));
}

void MessagePumpWin::DidProcessMessage(const MSG& msg) {
 FOR_EACH_OBSERVER(Observer, observers_, DidProcessMessage(msg));
}

void MessagePumpWin::RunWithDispatcher(Delegate* delegate,
                                      Dispatcher* dispatcher) {
 RunState s;
 s.delegate = delegate;
 s.dispatcher = dispatcher;
 s.should_quit = false;
 s.run_depth = state_ ? state_->run_depth + 1 : 1;

 RunState* previous_state = state_;
 state_ = &s;

 DoRunLoop();

 state_ = previous_state;
}

void MessagePumpWin::Quit() {
 DCHECK(state_);
 state_->should_quit = true;
}

//-----------------------------------------------------------------------------
// MessagePumpWin protected:

int MessagePumpWin::GetCurrentDelay() const {
 if (delayed_work_time_.is_null()) return -1;

 // Be careful here.  TimeDelta has a precision of microseconds, but we want a
 // value in milliseconds.  If there are 5.5ms left, should the delay be 5 or
 // 6?  It should be 6 to avoid executing delayed work too early.
 double timeout =
     ceil((delayed_work_time_ - TimeTicks::Now()).InMillisecondsF());

 // If this value is negative, then we need to run delayed work soon.
 int delay = static_cast<int>(timeout);
 if (delay < 0) delay = 0;

 return delay;
}

//-----------------------------------------------------------------------------
// MessagePumpForUI public:

MessagePumpForUI::MessagePumpForUI() { InitMessageWnd(); }

MessagePumpForUI::~MessagePumpForUI() {
 DestroyWindow(message_hwnd_);
 UnregisterClass(kWndClass, GetModuleHandle(NULL));
}

void MessagePumpForUI::ScheduleWork() {
 if (InterlockedExchange(&have_work_, 1))
   return;  // Someone else continued the pumping.

 // Make sure the MessagePump does some work for us.
 PostMessage(message_hwnd_, kMsgHaveWork, reinterpret_cast<WPARAM>(this), 0);

 // In order to wake up any cross-process COM calls which may currently be
 // pending on the main thread, we also have to post a UI message.
 PostMessage(message_hwnd_, WM_NULL, 0, 0);
}

void MessagePumpForUI::ScheduleDelayedWork(const TimeTicks& delayed_work_time) {
 //
 // We would *like* to provide high resolution timers.  Windows timers using
 // SetTimer() have a 10ms granularity.  We have to use WM_TIMER as a wakeup
 // mechanism because the application can enter modal windows loops where it
 // is not running our MessageLoop; the only way to have our timers fire in
 // these cases is to post messages there.
 //
 // To provide sub-10ms timers, we process timers directly from our run loop.
 // For the common case, timers will be processed there as the run loop does
 // its normal work.  However, we *also* set the system timer so that WM_TIMER
 // events fire.  This mops up the case of timers not being able to work in
 // modal message loops.  It is possible for the SetTimer to pop and have no
 // pending timers, because they could have already been processed by the
 // run loop itself.
 //
 // We use a single SetTimer corresponding to the timer that will expire
 // soonest.  As new timers are created and destroyed, we update SetTimer.
 // Getting a spurrious SetTimer event firing is benign, as we'll just be
 // processing an empty timer queue.
 //
 delayed_work_time_ = delayed_work_time;

 int delay_msec = GetCurrentDelay();
 DCHECK(delay_msec >= 0);
 if (delay_msec < USER_TIMER_MINIMUM) delay_msec = USER_TIMER_MINIMUM;

 // Create a WM_TIMER event that will wake us up to check for any pending
 // timers (in case we are running within a nested, external sub-pump).
 SetTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this), delay_msec, NULL);
}

void MessagePumpForUI::PumpOutPendingPaintMessages() {
 // If we are being called outside of the context of Run, then don't try to do
 // any work.
 if (!state_) return;

 // Create a mini-message-pump to force immediate processing of only Windows
 // WM_PAINT messages.  Don't provide an infinite loop, but do enough peeking
 // to get the job done.  Actual common max is 4 peeks, but we'll be a little
 // safe here.
 const int kMaxPeekCount = 20;
 int peek_count;
 for (peek_count = 0; peek_count < kMaxPeekCount; ++peek_count) {
   MSG msg;
   if (!PeekMessage(&msg, NULL, 0, 0, PM_REMOVE | PM_QS_PAINT)) break;
   ProcessMessageHelper(msg);
   if (state_->should_quit) break;
 }
}

//-----------------------------------------------------------------------------
// MessagePumpForUI private:

// static
LRESULT CALLBACK MessagePumpForUI::WndProcThunk(HWND hwnd, UINT message,
                                               WPARAM wparam, LPARAM lparam) {
 switch (message) {
   case kMsgHaveWork:
     reinterpret_cast<MessagePumpForUI*>(wparam)->HandleWorkMessage();
     break;
   case WM_TIMER:
     reinterpret_cast<MessagePumpForUI*>(wparam)->HandleTimerMessage();
     break;
 }
 return DefWindowProc(hwnd, message, wparam, lparam);
}

void MessagePumpForUI::DoRunLoop() {
 // IF this was just a simple PeekMessage() loop (servicing all possible work
 // queues), then Windows would try to achieve the following order according
 // to MSDN documentation about PeekMessage with no filter):
 //    * Sent messages
 //    * Posted messages
 //    * Sent messages (again)
 //    * WM_PAINT messages
 //    * WM_TIMER messages
 //
 // Summary: none of the above classes is starved, and sent messages has twice
 // the chance of being processed (i.e., reduced service time).

 for (;;) {
   // If we do any work, we may create more messages etc., and more work may
   // possibly be waiting in another task group.  When we (for example)
   // ProcessNextWindowsMessage(), there is a good chance there are still more
   // messages waiting.  On the other hand, when any of these methods return
   // having done no work, then it is pretty unlikely that calling them again
   // quickly will find any work to do.  Finally, if they all say they had no
   // work, then it is a good time to consider sleeping (waiting) for more
   // work.

   bool more_work_is_plausible = ProcessNextWindowsMessage();
   if (state_->should_quit) break;

   more_work_is_plausible |= state_->delegate->DoWork();
   if (state_->should_quit) break;

   more_work_is_plausible |=
       state_->delegate->DoDelayedWork(&delayed_work_time_);
   // If we did not process any delayed work, then we can assume that our
   // existing WM_TIMER if any will fire when delayed work should run.  We
   // don't want to disturb that timer if it is already in flight.  However,
   // if we did do all remaining delayed work, then lets kill the WM_TIMER.
   if (more_work_is_plausible && delayed_work_time_.is_null())
     KillTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this));
   if (state_->should_quit) break;

   if (more_work_is_plausible) continue;

   more_work_is_plausible = state_->delegate->DoIdleWork();
   if (state_->should_quit) break;

   if (more_work_is_plausible) continue;

   WaitForWork();  // Wait (sleep) until we have work to do again.
 }
}

void MessagePumpForUI::InitMessageWnd() {
 HINSTANCE hinst = GetModuleHandle(NULL);

 WNDCLASSEX wc = {0};
 wc.cbSize = sizeof(wc);
 wc.lpfnWndProc = WndProcThunk;
 wc.hInstance = hinst;
 wc.lpszClassName = kWndClass;
 RegisterClassEx(&wc);

 message_hwnd_ =
     CreateWindow(kWndClass, 0, 0, 0, 0, 0, 0, HWND_MESSAGE, 0, hinst, 0);
 DCHECK(message_hwnd_);
}

void MessagePumpForUI::WaitForWork() {
 AUTO_PROFILER_LABEL("MessagePumpForUI::WaitForWork", IDLE);

 // Wait until a message is available, up to the time needed by the timer
 // manager to fire the next set of timers.
 int delay = GetCurrentDelay();
 if (delay < 0)  // Negative value means no timers waiting.
   delay = INFINITE;

 mozilla::widget::WinUtils::WaitForMessage(delay);
}

void MessagePumpForUI::HandleWorkMessage() {
 // If we are being called outside of the context of Run, then don't try to do
 // any work.  This could correspond to a MessageBox call or something of that
 // sort.
 if (!state_) {
   // Since we handled a kMsgHaveWork message, we must still update this flag.
   InterlockedExchange(&have_work_, 0);
   return;
 }

 // Let whatever would have run had we not been putting messages in the queue
 // run now.  This is an attempt to make our dummy message not starve other
 // messages that may be in the Windows message queue.
 ProcessPumpReplacementMessage();

 // Now give the delegate a chance to do some work.  He'll let us know if he
 // needs to do more work.
 if (state_->delegate->DoWork()) ScheduleWork();
}

void MessagePumpForUI::HandleTimerMessage() {
 KillTimer(message_hwnd_, reinterpret_cast<UINT_PTR>(this));

 // If we are being called outside of the context of Run, then don't do
 // anything.  This could correspond to a MessageBox call or something of
 // that sort.
 if (!state_) return;

 state_->delegate->DoDelayedWork(&delayed_work_time_);
 if (!delayed_work_time_.is_null()) {
   // A bit gratuitous to set delayed_work_time_ again, but oh well.
   ScheduleDelayedWork(delayed_work_time_);
 }
}

bool MessagePumpForUI::ProcessNextWindowsMessage() {
 // If there are sent messages in the queue then PeekMessage internally
 // dispatches the message and returns false. We return true in this
 // case to ensure that the message loop peeks again instead of calling
 // MsgWaitForMultipleObjectsEx again.
 bool sent_messages_in_queue = false;
 DWORD queue_status = ::GetQueueStatus(QS_SENDMESSAGE);
 if (HIWORD(queue_status) & QS_SENDMESSAGE) sent_messages_in_queue = true;

 MSG msg;
 if (::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
   return ProcessMessageHelper(msg);

 return sent_messages_in_queue;
}

bool MessagePumpForUI::ProcessMessageHelper(const MSG& msg) {
 if (WM_QUIT == msg.message) {
   // WM_QUIT is the standard way to exit a ::GetMessage() loop. Our
   // MessageLoop has its own quit mechanism, so WM_QUIT is unexpected and
   // should be ignored.
   return true;
 }

 // While running our main message pump, we discard kMsgHaveWork messages.
 if (msg.message == kMsgHaveWork && msg.hwnd == message_hwnd_)
   return ProcessPumpReplacementMessage();

 WillProcessMessage(msg);

 if (state_->dispatcher) {
   if (!state_->dispatcher->Dispatch(msg)) state_->should_quit = true;
 } else {
   ::TranslateMessage(&msg);
   ::DispatchMessage(&msg);
 }

 DidProcessMessage(msg);
 return true;
}

bool MessagePumpForUI::ProcessPumpReplacementMessage() {
 // When we encounter a kMsgHaveWork message, this method is called to peek
 // and process a replacement message, such as a WM_PAINT or WM_TIMER.  The
 // goal is to make the kMsgHaveWork as non-intrusive as possible, even though
 // a continuous stream of such messages are posted.  This method carefully
 // peeks a message while there is no chance for a kMsgHaveWork to be pending,
 // then resets the have_work_ flag (allowing a replacement kMsgHaveWork to
 // possibly be posted), and finally dispatches that peeked replacement.  Note
 // that the re-post of kMsgHaveWork may be asynchronous to this thread!!

 MSG msg;
 bool have_message = false;
 if (MessageLoop::current()->os_modal_loop()) {
   // We only peek out WM_PAINT and WM_TIMER here for reasons mentioned above.
   have_message = ::PeekMessage(&msg, NULL, WM_PAINT, WM_PAINT, PM_REMOVE) ||
                  ::PeekMessage(&msg, NULL, WM_TIMER, WM_TIMER, PM_REMOVE);
 } else {
   have_message = (0 != ::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE));

   if (have_message && msg.message == WM_NULL)
     have_message = (0 != ::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE));
 }

 DCHECK(!have_message || kMsgHaveWork != msg.message ||
        msg.hwnd != message_hwnd_);

 // Since we discarded a kMsgHaveWork message, we must update the flag.
 int old_have_work = InterlockedExchange(&have_work_, 0);
 DCHECK(old_have_work);

 // We don't need a special time slice if we didn't have_message to process.
 if (!have_message) return false;

 if (WM_QUIT == msg.message) {
   // If we're in a nested ::GetMessage() loop then we must let that loop see
   // the WM_QUIT in order for it to exit. If we're in DoRunLoop then the re-
   // posted WM_QUIT will be either ignored, or handled, by
   // ProcessMessageHelper() called directly from ProcessNextWindowsMessage().
   ::PostQuitMessage(static_cast<int>(msg.wParam));
   // Note: we *must not* ScheduleWork() here as WM_QUIT is a low-priority
   // message on Windows (it is only returned by ::PeekMessage() when idle) :
   // https://blogs.msdn.microsoft.com/oldnewthing/20051104-33/?p=33453. As
   // such posting a kMsgHaveWork message via ScheduleWork() would cause an
   // infinite loop (kMsgHaveWork message handled first means we end up here
   // again and repost WM_QUIT+ScheduleWork() again, etc.). Not leaving a
   // kMsgHaveWork message behind however is also problematic as unwinding
   // multiple layers of nested ::GetMessage() loops can result in starving
   // application tasks. TODO(https://crbug.com/890016) : Fix this.

   // The return value is mostly irrelevant but return true like we would after
   // processing a QuitClosure() task.
   return true;
 }

 // Guarantee we'll get another time slice in the case where we go into native
 // windows code. This ScheduleWork() may hurt performance a tiny bit when
 // tasks appear very infrequently, but when the event queue is busy, the
 // kMsgHaveWork events get (percentage wise) rarer and rarer.
 ScheduleWork();
 return ProcessMessageHelper(msg);
}

//-----------------------------------------------------------------------------
// MessagePumpForIO public:

MessagePumpForIO::MessagePumpForIO() {
 port_.Set(CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 1));
 DCHECK(port_.IsValid());
}

void MessagePumpForIO::ScheduleWork() {
 if (InterlockedExchange(&have_work_, 1))
   return;  // Someone else continued the pumping.

 // Make sure the MessagePump does some work for us.
 BOOL ret =
     PostQueuedCompletionStatus(port_, 0, reinterpret_cast<ULONG_PTR>(this),
                                reinterpret_cast<OVERLAPPED*>(this));
 DCHECK(ret);
}

void MessagePumpForIO::ScheduleDelayedWork(const TimeTicks& delayed_work_time) {
 // We know that we can't be blocked right now since this method can only be
 // called on the same thread as Run, so we only need to update our record of
 // how long to sleep when we do sleep.
 delayed_work_time_ = delayed_work_time;
}

void MessagePumpForIO::RegisterIOHandler(HANDLE file_handle,
                                        IOHandler* handler) {
 ULONG_PTR key = reinterpret_cast<ULONG_PTR>(handler);
 HANDLE port = CreateIoCompletionPort(file_handle, port_, key, 1);
 DCHECK(port == port_.Get());
}

//-----------------------------------------------------------------------------
// MessagePumpForIO private:

void MessagePumpForIO::DoRunLoop() {
 for (;;) {
   // If we do any work, we may create more messages etc., and more work may
   // possibly be waiting in another task group.  When we (for example)
   // WaitForIOCompletion(), there is a good chance there are still more
   // messages waiting.  On the other hand, when any of these methods return
   // having done no work, then it is pretty unlikely that calling them
   // again quickly will find any work to do.  Finally, if they all say they
   // had no work, then it is a good time to consider sleeping (waiting) for
   // more work.

   bool more_work_is_plausible = state_->delegate->DoWork();
   if (state_->should_quit) break;

   more_work_is_plausible |= WaitForIOCompletion(0, NULL);
   if (state_->should_quit) break;

   more_work_is_plausible |=
       state_->delegate->DoDelayedWork(&delayed_work_time_);
   if (state_->should_quit) break;

   if (more_work_is_plausible) continue;

   more_work_is_plausible = state_->delegate->DoIdleWork();
   if (state_->should_quit) break;

   if (more_work_is_plausible) continue;

   WaitForWork();  // Wait (sleep) until we have work to do again.
 }
}

// Wait until IO completes, up to the time needed by the timer manager to fire
// the next set of timers.
void MessagePumpForIO::WaitForWork() {
 // We do not support nested IO message loops. This is to avoid messy
 // recursion problems.
 DCHECK(state_->run_depth == 1) << "Cannot nest an IO message loop!";

 int timeout = GetCurrentDelay();
 if (timeout < 0)  // Negative value means no timers waiting.
   timeout = INFINITE;

 WaitForIOCompletion(timeout, NULL);
}

bool MessagePumpForIO::WaitForIOCompletion(DWORD timeout, IOHandler* filter) {
 IOItem item;
 if (completed_io_.empty() || !MatchCompletedIOItem(filter, &item)) {
   // We have to ask the system for another IO completion.
   if (!GetIOItem(timeout, &item)) return false;

   if (ProcessInternalIOItem(item)) return true;
 }

 if (item.context->handler) {
   if (filter && item.handler != filter) {
     // Save this item for later
     completed_io_.push_back(item);
   } else {
     DCHECK(item.context->handler == item.handler);
     item.handler->OnIOCompleted(item.context, item.bytes_transfered,
                                 item.error);
   }
 } else {
   // The handler must be gone by now, just cleanup the mess.
   delete item.context;
 }
 return true;
}

// Asks the OS for another IO completion result.
bool MessagePumpForIO::GetIOItem(DWORD timeout, IOItem* item) {
 memset(item, 0, sizeof(*item));
 ULONG_PTR key = 0;
 OVERLAPPED* overlapped = NULL;
 BOOL success;
 {
   AUTO_PROFILER_LABEL("MessagePumpForIO::GetIOItem::Wait", IDLE);
#ifdef MOZ_GECKO_PROFILER
   mozilla::Maybe<mozilla::AutoProfilerThreadSleep> profilerThreadSleep;
   if (timeout != 0) {
     profilerThreadSleep.emplace();
   }
#endif
   success = GetQueuedCompletionStatus(port_.Get(), &item->bytes_transfered,
                                       &key, &overlapped, timeout);
 }
 if (!success) {
   if (!overlapped) return false;  // Nothing in the queue.
   item->error = GetLastError();
   item->bytes_transfered = 0;
 }

 item->handler = reinterpret_cast<IOHandler*>(key);
 item->context = reinterpret_cast<IOContext*>(overlapped);
 return true;
}

bool MessagePumpForIO::ProcessInternalIOItem(const IOItem& item) {
 if (this == reinterpret_cast<MessagePumpForIO*>(item.context) &&
     this == reinterpret_cast<MessagePumpForIO*>(item.handler)) {
   // This is our internal completion.
   DCHECK(!item.bytes_transfered);
   InterlockedExchange(&have_work_, 0);
   return true;
 }
 return false;
}

// Returns a completion item that was previously received.
bool MessagePumpForIO::MatchCompletedIOItem(IOHandler* filter, IOItem* item) {
 DCHECK(!completed_io_.empty());
 for (std::list<IOItem>::iterator it = completed_io_.begin();
      it != completed_io_.end(); ++it) {
   if (!filter || it->handler == filter) {
     *item = *it;
     completed_io_.erase(it);
     return true;
   }
 }
 return false;
}

}  // namespace base