blob: f4b58f59e434744cda2998e1973e3fa753d827b2 [file] [log] [blame]
// Copyright (c) 2012 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/compiler_specific.h"
#include "base/location.h"
#include "base/macros.h"
#include "base/message_loop/message_pump.h"
#include "base/threading/thread_checker.h"
#include "base/time/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 BASE_EXPORT MessagePumpLibevent : public MessagePump {
// Used with WatchFileDescriptor to asynchronously monitor the I/O readiness
// of a file descriptor.
class 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;
virtual ~Watcher() = default;
// Object returned by WatchFileDescriptor to manage further watching.
class FileDescriptorWatcher {
explicit FileDescriptorWatcher(const Location& from_here);
~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();
const Location& created_from_location() { return created_from_location_; }
friend class MessagePumpLibevent;
friend class MessagePumpLibeventTest;
// Called by MessagePumpLibevent, ownership of |e| is transferred to this
// object.
void Init(event* e);
// Used by MessagePumpLibevent to take ownership of event_.
event* ReleaseEvent();
void set_pump(MessagePumpLibevent* pump) { pump_ = pump; }
MessagePumpLibevent* pump() const { return pump_; }
void set_watcher(Watcher* watcher) { watcher_ = watcher; }
void OnFileCanReadWithoutBlocking(int fd, MessagePumpLibevent* pump);
void OnFileCanWriteWithoutBlocking(int fd, MessagePumpLibevent* pump);
event* event_;
MessagePumpLibevent* pump_;
Watcher* watcher_;
// If this pointer is non-NULL, the pointee is set to true in the
// destructor.
bool* was_destroyed_;
const Location created_from_location_;
enum Mode {
WATCH_READ = 1 << 0,
WATCH_WRITE = 1 << 1,
~MessagePumpLibevent() override;
// 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.
// Must be called on the same thread the message_pump is running on.
// TODO(dkegel): switch to edge-triggered readiness notification
bool WatchFileDescriptor(int fd,
bool persistent,
int mode,
FileDescriptorWatcher* controller,
Watcher* delegate);
// MessagePump methods:
void Run(Delegate* delegate) override;
void Quit() override;
void ScheduleWork() override;
void ScheduleDelayedWork(const TimeTicks& delayed_work_time) override;
friend class MessagePumpLibeventTest;
// Risky part of constructor. Returns true on success.
bool Init();
// Called by libevent to tell us a registered FD can be read/written to.
static void OnLibeventNotification(int fd, 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);
// This flag is set to false when Run should return.
bool keep_running_;
// This flag is set when inside Run.
bool in_run_;
// This flag is set if libevent has processed I/O events.
bool processed_io_events_;
// 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_;
// ... 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_;
ThreadChecker watch_file_descriptor_caller_checker_;
} // namespace base