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

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+// 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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comparison: ipc/chromium/src/base/message_pump_win.h

ipc/chromium/src/base/message_pump_win.h