The Tor Browser: ipc/chromium/src/base/message_pump

ipc/chromium/src/base/message_pump_win.h@6474c204b198 (annotated)

ipc/chromium/src/base/message_pump_win.h

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // 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_PUMP_WIN_H_
 #define BASE_MESSAGE_PUMP_WIN_H_
 #include <windows.h>
 #include <list>
 #include "base/lock.h"
 #include "base/message_pump.h"
 #include "base/observer_list.h"
 #include "base/scoped_handle.h"
 #include "base/time.h"
 namespace base {
 // MessagePumpWin serves as the base for specialized versions of the MessagePump
 // for Windows. It provides basic functionality like handling of observers and
 // controlling the lifetime of the message pump.
 class MessagePumpWin : public MessagePump {
  public:
   // An Observer is an object that receives global notifications from the
   // MessageLoop.
   //
   // NOTE: An Observer implementation should be extremely fast!
   //
   class Observer {
    public:
     virtual ~Observer() {}
     // This method is called before processing a message.
     // The message may be undefined in which case msg.message is 0
     virtual void WillProcessMessage(const MSG& msg) = 0;
     // This method is called when control returns from processing a UI message.
     // The message may be undefined in which case msg.message is 0
     virtual void DidProcessMessage(const MSG& msg) = 0;
   };
   // Dispatcher is used during a nested invocation of Run to dispatch events.
   // If Run is invoked with a non-NULL Dispatcher, MessageLoop does not
   // dispatch events (or invoke TranslateMessage), rather every message is
   // passed to Dispatcher's Dispatch method for dispatch. It is up to the
   // Dispatcher to dispatch, or not, the event.
   //
   // The nested loop is exited by either posting a quit, or returning false
   // from Dispatch.
   class Dispatcher {
    public:
     virtual ~Dispatcher() {}
     // Dispatches the event. If true is returned processing continues as
     // normal. If false is returned, the nested loop exits immediately.
     virtual bool Dispatch(const MSG& msg) = 0;
   };
   MessagePumpWin() : have_work_(0), state_(NULL) {}
   virtual ~MessagePumpWin() {}
   // Add an Observer, which will start receiving notifications immediately.
   void AddObserver(Observer* observer);
   // Remove an Observer.  It is safe to call this method while an Observer is
   // receiving a notification callback.
   void RemoveObserver(Observer* observer);
   // Give a chance to code processing additional messages to notify the
   // message loop observers that another message has been processed.
   void WillProcessMessage(const MSG& msg);
   void DidProcessMessage(const MSG& msg);
   // Like MessagePump::Run, but MSG objects are routed through dispatcher.
   void RunWithDispatcher(Delegate* delegate, Dispatcher* dispatcher);
   // MessagePump methods:
   virtual void Run(Delegate* delegate) { RunWithDispatcher(delegate, NULL); }
   virtual void Quit();
  protected:
   struct RunState {
     Delegate* delegate;
     Dispatcher* dispatcher;
     // Used to flag that the current Run() invocation should return ASAP.
     bool should_quit;
     // Used to count how many Run() invocations are on the stack.
     int run_depth;
   };
   virtual void DoRunLoop() = 0;
   int GetCurrentDelay() const;
   ObserverList<Observer> observers_;
   // The time at which delayed work should run.
   TimeTicks delayed_work_time_;
   // A boolean value used to indicate if there is a kMsgDoWork message pending
   // in the Windows Message queue.  There is at most one such message, and it
   // can drive execution of tasks when a native message pump is running.
   LONG have_work_;
   // State for the current invocation of Run.
   RunState* state_;
 };
 //-----------------------------------------------------------------------------
 // MessagePumpForUI extends MessagePumpWin with methods that are particular to a
 // MessageLoop instantiated with TYPE_UI.
 //
 // MessagePumpForUI implements a "traditional" Windows message pump. It contains
 // a nearly infinite loop that peeks out messages, and then dispatches them.
 // Intermixed with those peeks are callouts to DoWork for pending tasks, and
 // DoDelayedWork for pending timers. When there are no events to be serviced,
 // this pump goes into a wait state. In most cases, this message pump handles
 // all processing.
 //
 // However, when a task, or windows event, invokes on the stack a native dialog
 // box or such, that window typically provides a bare bones (native?) message
 // pump.  That bare-bones message pump generally supports little more than a
 // peek of the Windows message queue, followed by a dispatch of the peeked
 // message.  MessageLoop extends that bare-bones message pump to also service
 // Tasks, at the cost of some complexity.
 //
 // The basic structure of the extension (refered to as a sub-pump) is that a
 // special message, kMsgHaveWork, is repeatedly injected into the Windows
 // Message queue.  Each time the kMsgHaveWork message is peeked, checks are
 // made for an extended set of events, including the availability of Tasks to
 // run.
 //
 // After running a task, the special message kMsgHaveWork is again posted to
 // the Windows Message queue, ensuring a future time slice for processing a
 // future event.  To prevent flooding the Windows Message queue, care is taken
 // to be sure that at most one kMsgHaveWork message is EVER pending in the
 // Window's Message queue.
 //
 // There are a few additional complexities in this system where, when there are
 // no Tasks to run, this otherwise infinite stream of messages which drives the
 // sub-pump is halted.  The pump is automatically re-started when Tasks are
 // queued.
 //
 // A second complexity is that the presence of this stream of posted tasks may
 // prevent a bare-bones message pump from ever peeking a WM_PAINT or WM_TIMER.
 // Such paint and timer events always give priority to a posted message, such as
 // kMsgHaveWork messages.  As a result, care is taken to do some peeking in
 // between the posting of each kMsgHaveWork message (i.e., after kMsgHaveWork
 // is peeked, and before a replacement kMsgHaveWork is posted).
 //
 // NOTE: Although it may seem odd that messages are used to start and stop this
 // flow (as opposed to signaling objects, etc.), it should be understood that
 // the native message pump will *only* respond to messages.  As a result, it is
 // an excellent choice.  It is also helpful that the starter messages that are
 // placed in the queue when new task arrive also awakens DoRunLoop.
 //
 class MessagePumpForUI : public MessagePumpWin {
  public:
   MessagePumpForUI();
   virtual ~MessagePumpForUI();
   // MessagePump methods:
   virtual void ScheduleWork();
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time);
   // Applications can call this to encourage us to process all pending WM_PAINT
   // messages.  This method will process all paint messages the Windows Message
   // queue can provide, up to some fixed number (to avoid any infinite loops).
   void PumpOutPendingPaintMessages();
  private:
   static LRESULT CALLBACK WndProcThunk(
       HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
   virtual void DoRunLoop();
   void InitMessageWnd();
   void WaitForWork();
   void HandleWorkMessage();
   void HandleTimerMessage();
   bool ProcessNextWindowsMessage();
   bool ProcessMessageHelper(const MSG& msg);
   bool ProcessPumpReplacementMessage();
   // A hidden message-only window.
   HWND message_hwnd_;
 };
 //-----------------------------------------------------------------------------
 // MessagePumpForIO extends MessagePumpWin with methods that are particular to a
 // MessageLoop instantiated with TYPE_IO. This version of MessagePump does not
 // deal with Windows mesagges, and instead has a Run loop based on Completion
 // Ports so it is better suited for IO operations.
 //
 class MessagePumpForIO : public MessagePumpWin {
  public:
   struct IOContext;
   // Clients interested in receiving OS notifications when asynchronous IO
   // operations complete should implement this interface and register themselves
   // with the message pump.
   //
   // Typical use #1:
   //   // Use only when there are no user's buffers involved on the actual IO,
   //   // so that all the cleanup can be done by the message pump.
   //   class MyFile : public IOHandler {
   //     MyFile() {
   //       ...
   //       context_ = new IOContext;
   //       context_->handler = this;
   //       message_pump->RegisterIOHandler(file_, this);
   //     }
   //     ~MyFile() {
   //       if (pending_) {
   //         // By setting the handler to NULL, we're asking for this context
   //         // to be deleted when received, without calling back to us.
   //         context_->handler = NULL;
   //       } else {
   //         delete context_;
   //      }
   //     }
   //     virtual void OnIOCompleted(IOContext* context, DWORD bytes_transfered,
   //                                DWORD error) {
   //         pending_ = false;
   //     }
   //     void DoSomeIo() {
   //       ...
   //       // The only buffer required for this operation is the overlapped
   //       // structure.
   //       ConnectNamedPipe(file_, &context_->overlapped);
   //       pending_ = true;
   //     }
   //     bool pending_;
   //     IOContext* context_;
   //     HANDLE file_;
   //   };
   //
   // Typical use #2:
   //   class MyFile : public IOHandler {
   //     MyFile() {
   //       ...
   //       message_pump->RegisterIOHandler(file_, this);
   //     }
   //     // Plus some code to make sure that this destructor is not called
   //     // while there are pending IO operations.
   //     ~MyFile() {
   //     }
   //     virtual void OnIOCompleted(IOContext* context, DWORD bytes_transfered,
   //                                DWORD error) {
   //       ...
   //       delete context;
   //     }
   //     void DoSomeIo() {
   //       ...
   //       IOContext* context = new IOContext;
   //       // This is not used for anything. It just prevents the context from
   //       // being considered "abandoned".
   //       context->handler = this;
   //       ReadFile(file_, buffer, num_bytes, &read, &context->overlapped);
   //     }
   //     HANDLE file_;
   //   };
   //
   // Typical use #3:
   // Same as the previous example, except that in order to deal with the
   // requirement stated for the destructor, the class calls WaitForIOCompletion
   // from the destructor to block until all IO finishes.
   //     ~MyFile() {
   //       while(pending_)
   //         message_pump->WaitForIOCompletion(INFINITE, this);
   //     }
   //
   class IOHandler {
    public:
     virtual ~IOHandler() {}
     // This will be called once the pending IO operation associated with
     // |context| completes. |error| is the Win32 error code of the IO operation
     // (ERROR_SUCCESS if there was no error). |bytes_transfered| will be zero
     // on error.
     virtual void OnIOCompleted(IOContext* context, DWORD bytes_transfered,
                                DWORD error) = 0;
   };
   // The extended context that should be used as the base structure on every
   // overlapped IO operation. |handler| must be set to the registered IOHandler
   // for the given file when the operation is started, and it can be set to NULL
   // before the operation completes to indicate that the handler should not be
   // called anymore, and instead, the IOContext should be deleted when the OS
   // notifies the completion of this operation. Please remember that any buffers
   // involved with an IO operation should be around until the callback is
   // received, so this technique can only be used for IO that do not involve
   // additional buffers (other than the overlapped structure itself).
   struct IOContext {
     OVERLAPPED overlapped;
     IOHandler* handler;
   };
   MessagePumpForIO();
   virtual ~MessagePumpForIO() {}
   // MessagePump methods:
   virtual void ScheduleWork();
   virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time);
   // Register the handler to be used when asynchronous IO for the given file
   // completes. The registration persists as long as |file_handle| is valid, so
   // |handler| must be valid as long as there is pending IO for the given file.
   void RegisterIOHandler(HANDLE file_handle, IOHandler* handler);
   // Waits for the next IO completion that should be processed by |filter|, for
   // up to |timeout| milliseconds. Return true if any IO operation completed,
   // regardless of the involved handler, and false if the timeout expired. If
   // the completion port received any message and the involved IO handler
   // matches |filter|, the callback is called before returning from this code;
   // if the handler is not the one that we are looking for, the callback will
   // be postponed for another time, so reentrancy problems can be avoided.
   // External use of this method should be reserved for the rare case when the
   // caller is willing to allow pausing regular task dispatching on this thread.
   bool WaitForIOCompletion(DWORD timeout, IOHandler* filter);
  private:
   struct IOItem {
     IOHandler* handler;
     IOContext* context;
     DWORD bytes_transfered;
     DWORD error;
   };
   virtual void DoRunLoop();
   void WaitForWork();
   bool MatchCompletedIOItem(IOHandler* filter, IOItem* item);
   bool GetIOItem(DWORD timeout, IOItem* item);
   bool ProcessInternalIOItem(const IOItem& item);
   // The completion port associated with this thread.
   ScopedHandle port_;
   // This list will be empty almost always. It stores IO completions that have
   // not been delivered yet because somebody was doing cleanup.
   std::list<IOItem> completed_io_;
 };
 }  // namespace base
 #endif  // BASE_MESSAGE_PUMP_WIN_H_

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ipc/chromium/src/base/message_pump_win.h@6474c204b198 (annotated)

ipc/chromium/src/base/message_pump_win.h