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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_MESSAGE_LOOP_MESSAGE_PUMP_LIBEVENT_H_
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#define BASE_MESSAGE_LOOP_MESSAGE_PUMP_LIBEVENT_H_
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#include "base/basictypes.h"
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#include "base/compiler_specific.h"
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#include "base/memory/weak_ptr.h"
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#include "base/message_loop/message_pump.h"
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#include "base/observer_list.h"
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#include "base/threading/thread_checker.h"
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#include "base/time/time.h"
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// Declare structs we need from libevent.h rather than including it
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// Class to monitor sockets and issue callbacks when sockets are ready for I/O
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// TODO(dkegel): add support for background file IO somehow
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class BASE_EXPORT MessagePumpLibevent : public MessagePump {
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// An IOObserver is an object that receives IO notifications from the
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// NOTE: An IOObserver implementation should be extremely fast!
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virtual void WillProcessIOEvent() = 0;
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virtual void DidProcessIOEvent() = 0;
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virtual ~IOObserver() {}
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// Used with WatchFileDescriptor to asynchronously monitor the I/O readiness
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// of a file descriptor.
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// Called from MessageLoop::Run when an FD can be read from/written to
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virtual void OnFileCanReadWithoutBlocking(int fd) = 0;
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virtual void OnFileCanWriteWithoutBlocking(int fd) = 0;
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// Object returned by WatchFileDescriptor to manage further watching.
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class FileDescriptorWatcher {
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FileDescriptorWatcher();
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~FileDescriptorWatcher(); // Implicitly calls StopWatchingFileDescriptor.
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// NOTE: These methods aren't called StartWatching()/StopWatching() to
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// avoid confusion with the win32 ObjectWatcher class.
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// Stop watching the FD, always safe to call. No-op if there's nothing
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bool StopWatchingFileDescriptor();
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friend class MessagePumpLibevent;
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friend class MessagePumpLibeventTest;
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// Called by MessagePumpLibevent, ownership of |e| is transferred to this
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// Used by MessagePumpLibevent to take ownership of event_.
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event* ReleaseEvent();
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void set_pump(MessagePumpLibevent* pump) { pump_ = pump; }
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MessagePumpLibevent* pump() const { return pump_; }
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void set_watcher(Watcher* watcher) { watcher_ = watcher; }
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void OnFileCanReadWithoutBlocking(int fd, MessagePumpLibevent* pump);
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void OnFileCanWriteWithoutBlocking(int fd, MessagePumpLibevent* pump);
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MessagePumpLibevent* pump_;
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WeakPtrFactory<FileDescriptorWatcher> weak_factory_;
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DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher);
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WATCH_READ_WRITE = WATCH_READ | WATCH_WRITE
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MessagePumpLibevent();
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virtual ~MessagePumpLibevent();
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// Have the current thread's message loop watch for a a situation in which
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// reading/writing to the FD can be performed without blocking.
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// Callers must provide a preallocated FileDescriptorWatcher object which
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// can later be used to manage the lifetime of this event.
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// If a FileDescriptorWatcher is passed in which is already attached to
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// an event, then the effect is cumulative i.e. after the call |controller|
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// will watch both the previous event and the new one.
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// If an error occurs while calling this method in a cumulative fashion, the
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// event previously attached to |controller| is aborted.
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// Returns true on success.
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// Must be called on the same thread the message_pump is running on.
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// TODO(dkegel): switch to edge-triggered readiness notification
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bool WatchFileDescriptor(int fd,
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FileDescriptorWatcher *controller,
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void AddIOObserver(IOObserver* obs);
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void RemoveIOObserver(IOObserver* obs);
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// MessagePump methods:
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virtual void Run(Delegate* delegate) OVERRIDE;
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virtual void Quit() OVERRIDE;
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virtual void ScheduleWork() OVERRIDE;
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virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
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friend class MessagePumpLibeventTest;
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void WillProcessIOEvent();
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void DidProcessIOEvent();
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// Risky part of constructor. Returns true on success.
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// Called by libevent to tell us a registered FD can be read/written to.
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static void OnLibeventNotification(int fd, short flags,
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// Unix pipe used to implement ScheduleWork()
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// ... callback; called by libevent inside Run() when pipe is ready to read
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static void OnWakeup(int socket, short flags, void* context);
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// This flag is set to false when Run should return.
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// This flag is set when inside Run.
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// This flag is set if libevent has processed I/O events.
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bool processed_io_events_;
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// The time at which we should call DoDelayedWork.
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TimeTicks delayed_work_time_;
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// Libevent dispatcher. Watches all sockets registered with it, and sends
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// readiness callbacks when a socket is ready for I/O.
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event_base* event_base_;
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// ... write end; ScheduleWork() writes a single byte to it
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// ... read end; OnWakeup reads it and then breaks Run() out of its sleep
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int wakeup_pipe_out_;
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// ... libevent wrapper for read end
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event* wakeup_event_;
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ObserverList<IOObserver> io_observers_;
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ThreadChecker watch_file_descriptor_caller_checker_;
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DISALLOW_COPY_AND_ASSIGN(MessagePumpLibevent);
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#endif // BASE_MESSAGE_LOOP_MESSAGE_PUMP_LIBEVENT_H_