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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_PUMP_LIBEVENT_H_
#define BASE_MESSAGE_PUMP_LIBEVENT_H_
#include "base/message_pump.h"
#include "base/time.h"
// Declare structs we need from libevent.h rather than including it
struct event_base;
struct event;
namespace base {
// Class to monitor sockets and issue callbacks when sockets are ready for I/O
// TODO(dkegel): add support for background file IO somehow
class MessagePumpLibevent : public MessagePump {
public:
// Object returned by WatchFileDescriptor to manage further watching.
class FileDescriptorWatcher {
public:
FileDescriptorWatcher();
~FileDescriptorWatcher(); // Implicitly calls StopWatchingFileDescriptor.
// NOTE: These methods aren't called StartWatching()/StopWatching() to
// avoid confusion with the win32 ObjectWatcher class.
// Stop watching the FD, always safe to call. No-op if there's nothing
// to do.
bool StopWatchingFileDescriptor();
private:
// Called by MessagePumpLibevent, ownership of |e| is transferred to this
// object.
void Init(event* e, bool is_persistent);
// Used by MessagePumpLibevent to take ownership of event_.
event* ReleaseEvent();
friend class MessagePumpLibevent;
private:
bool is_persistent_; // false if this event is one-shot.
event* event_;
DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher);
};
// Used with WatchFileDescptor to asynchronously monitor the I/O readiness of
// a File Descriptor.
class Watcher {
public:
virtual ~Watcher() {}
// Called from MessageLoop::Run when an FD can be read from/written to
// without blocking
virtual void OnFileCanReadWithoutBlocking(int fd) = 0;
virtual void OnFileCanWriteWithoutBlocking(int fd) = 0;
};
MessagePumpLibevent();
enum Mode {
WATCH_READ = 1 << 0,
WATCH_WRITE = 1 << 1,
WATCH_READ_WRITE = WATCH_READ | WATCH_WRITE
};
// Have the current thread's message loop watch for a a situation in which
// reading/writing to the FD can be performed without Blocking.
// Callers must provide a preallocated FileDescriptorWatcher object which
// can later be used to manage the Lifetime of this event.
// If a FileDescriptorWatcher is passed in which is already attached to
// an event, then the effect is cumulative i.e. after the call |controller|
// will watch both the previous event and the new one.
// If an error occurs while calling this method in a cumulative fashion, the
// event previously attached to |controller| is aborted.
// Returns true on success.
// TODO(dkegel): switch to edge-triggered readiness notification
bool WatchFileDescriptor(int fd, bool persistent, Mode mode,
FileDescriptorWatcher* controller,
Watcher* delegate);
// This is analagous to FileDescriptorWatcher above, which really is
// just a wrapper around libevent's |struct event|. This class acts
// as a sort of "scoped event watcher" in that it guarantees that
// when this class is out of scope, the signal-event it wraps is
// removed from libevent's guts.
//
// XXX/cjones: this isn't my favorite API, but preserving it in
// order to match code above
class SignalEvent {
friend class MessagePumpLibevent;
public:
SignalEvent();
~SignalEvent(); // implicitly calls StopCatching()
// Have libevent forget this event.
bool StopCatching();
private:
void Init(event* e);
event* ReleaseEvent();
event* event_;
DISALLOW_COPY_AND_ASSIGN(SignalEvent);
};
class SignalWatcher {
public:
virtual ~SignalWatcher() {}
// Called from MessageLoop::Run when |sig| has been delivered to
// this process
virtual void OnSignal(int sig) = 0;
};
// Have the current thread's message loop catch the signal |sig|.
// Multiple watchers can catch the same signal; they're all notified
// upon its delivery. Callers must provide a preallocated
// SignalEvent object which can be used to manage the lifetime of
// this event. Returns true on success.
bool CatchSignal(int sig, SignalEvent* sigevent, SignalWatcher* delegate);
// MessagePump methods:
virtual void Run(Delegate* delegate) override;
virtual void Quit() override;
virtual void ScheduleWork() override;
virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) override;
protected:
virtual ~MessagePumpLibevent();
private:
// Risky part of constructor. Returns true on success.
bool Init();
// This flag is set to false when Run should return.
bool keep_running_;
// This flag is set when inside Run.
bool in_run_;
// The time at which we should call DoDelayedWork.
TimeTicks delayed_work_time_;
// Libevent dispatcher. Watches all sockets registered with it, and sends
// readiness callbacks when a socket is ready for I/O.
event_base* event_base_;
// Called by libevent to tell us a registered FD can be read/written to.
static void OnLibeventNotification(int fd, short flags, void* context);
// Called by libevent upon receiving a signal
static void OnLibeventSignalNotification(int sig, short flags, void* context);
// Unix pipe used to implement ScheduleWork()
// ... callback; called by libevent inside Run() when pipe is ready to read
static void OnWakeup(int socket, short flags, void* context);
// ... write end; ScheduleWork() writes a single byte to it
int wakeup_pipe_in_;
// ... read end; OnWakeup reads it and then breaks Run() out of its sleep
int wakeup_pipe_out_;
// ... libevent wrapper for read end
event* wakeup_event_;
// Set to false when calling event_base_loop and to true when either of the
// OnWakeup, OnLibeventNotification or OnLibeventSignalNotification callbacks
// is called.
// Used to ensure our calls to profiler_thread_sleep and profiler_thread_wake
// are paired correctly.
static bool awake_;
DISALLOW_COPY_AND_ASSIGN(MessagePumpLibevent);
};
} // namespace base
#endif // BASE_MESSAGE_PUMP_LIBEVENT_H_