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Side by Side Diff: base/message_pump_libevent.h

Issue 17078005: Move message_pump to base/message_loop. (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Created 7 years, 6 months ago
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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef BASE_MESSAGE_PUMP_LIBEVENT_H_
6 #define BASE_MESSAGE_PUMP_LIBEVENT_H_
7
8 #include "base/basictypes.h"
9 #include "base/compiler_specific.h"
10 #include "base/memory/weak_ptr.h"
11 #include "base/message_pump.h"
12 #include "base/observer_list.h"
13 #include "base/threading/thread_checker.h"
14 #include "base/time.h"
15
16 // Declare structs we need from libevent.h rather than including it
17 struct event_base;
18 struct event;
19
20 namespace base {
21
22 // Class to monitor sockets and issue callbacks when sockets are ready for I/O
23 // TODO(dkegel): add support for background file IO somehow
24 class BASE_EXPORT MessagePumpLibevent : public MessagePump {
25 public:
26 class IOObserver {
27 public:
28 IOObserver() {}
29
30 // An IOObserver is an object that receives IO notifications from the
31 // MessagePump.
32 //
33 // NOTE: An IOObserver implementation should be extremely fast!
34 virtual void WillProcessIOEvent() = 0;
35 virtual void DidProcessIOEvent() = 0;
36
37 protected:
38 virtual ~IOObserver() {}
39 };
40
41 // Used with WatchFileDescriptor to asynchronously monitor the I/O readiness
42 // of a file descriptor.
43 class Watcher {
44 public:
45 // Called from MessageLoop::Run when an FD can be read from/written to
46 // without blocking
47 virtual void OnFileCanReadWithoutBlocking(int fd) = 0;
48 virtual void OnFileCanWriteWithoutBlocking(int fd) = 0;
49
50 protected:
51 virtual ~Watcher() {}
52 };
53
54 // Object returned by WatchFileDescriptor to manage further watching.
55 class FileDescriptorWatcher {
56 public:
57 FileDescriptorWatcher();
58 ~FileDescriptorWatcher(); // Implicitly calls StopWatchingFileDescriptor.
59
60 // NOTE: These methods aren't called StartWatching()/StopWatching() to
61 // avoid confusion with the win32 ObjectWatcher class.
62
63 // Stop watching the FD, always safe to call. No-op if there's nothing
64 // to do.
65 bool StopWatchingFileDescriptor();
66
67 private:
68 friend class MessagePumpLibevent;
69 friend class MessagePumpLibeventTest;
70
71 // Called by MessagePumpLibevent, ownership of |e| is transferred to this
72 // object.
73 void Init(event* e);
74
75 // Used by MessagePumpLibevent to take ownership of event_.
76 event* ReleaseEvent();
77
78 void set_pump(MessagePumpLibevent* pump) { pump_ = pump; }
79 MessagePumpLibevent* pump() const { return pump_; }
80
81 void set_watcher(Watcher* watcher) { watcher_ = watcher; }
82
83 void OnFileCanReadWithoutBlocking(int fd, MessagePumpLibevent* pump);
84 void OnFileCanWriteWithoutBlocking(int fd, MessagePumpLibevent* pump);
85
86 event* event_;
87 MessagePumpLibevent* pump_;
88 Watcher* watcher_;
89 base::WeakPtrFactory<FileDescriptorWatcher> weak_factory_;
90
91 DISALLOW_COPY_AND_ASSIGN(FileDescriptorWatcher);
92 };
93
94 enum Mode {
95 WATCH_READ = 1 << 0,
96 WATCH_WRITE = 1 << 1,
97 WATCH_READ_WRITE = WATCH_READ | WATCH_WRITE
98 };
99
100 MessagePumpLibevent();
101
102 // Have the current thread's message loop watch for a a situation in which
103 // reading/writing to the FD can be performed without blocking.
104 // Callers must provide a preallocated FileDescriptorWatcher object which
105 // can later be used to manage the lifetime of this event.
106 // If a FileDescriptorWatcher is passed in which is already attached to
107 // an event, then the effect is cumulative i.e. after the call |controller|
108 // will watch both the previous event and the new one.
109 // If an error occurs while calling this method in a cumulative fashion, the
110 // event previously attached to |controller| is aborted.
111 // Returns true on success.
112 // Must be called on the same thread the message_pump is running on.
113 // TODO(dkegel): switch to edge-triggered readiness notification
114 bool WatchFileDescriptor(int fd,
115 bool persistent,
116 int mode,
117 FileDescriptorWatcher *controller,
118 Watcher *delegate);
119
120 void AddIOObserver(IOObserver* obs);
121 void RemoveIOObserver(IOObserver* obs);
122
123 // MessagePump methods:
124 virtual void Run(Delegate* delegate) OVERRIDE;
125 virtual void Quit() OVERRIDE;
126 virtual void ScheduleWork() OVERRIDE;
127 virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) OVERRIDE;
128
129 protected:
130 virtual ~MessagePumpLibevent();
131
132 private:
133 friend class MessagePumpLibeventTest;
134
135 void WillProcessIOEvent();
136 void DidProcessIOEvent();
137
138 // Risky part of constructor. Returns true on success.
139 bool Init();
140
141 // Called by libevent to tell us a registered FD can be read/written to.
142 static void OnLibeventNotification(int fd, short flags,
143 void* context);
144
145 // Unix pipe used to implement ScheduleWork()
146 // ... callback; called by libevent inside Run() when pipe is ready to read
147 static void OnWakeup(int socket, short flags, void* context);
148
149 // This flag is set to false when Run should return.
150 bool keep_running_;
151
152 // This flag is set when inside Run.
153 bool in_run_;
154
155 // This flag is set if libevent has processed I/O events.
156 bool processed_io_events_;
157
158 // The time at which we should call DoDelayedWork.
159 TimeTicks delayed_work_time_;
160
161 // Libevent dispatcher. Watches all sockets registered with it, and sends
162 // readiness callbacks when a socket is ready for I/O.
163 event_base* event_base_;
164
165 // ... write end; ScheduleWork() writes a single byte to it
166 int wakeup_pipe_in_;
167 // ... read end; OnWakeup reads it and then breaks Run() out of its sleep
168 int wakeup_pipe_out_;
169 // ... libevent wrapper for read end
170 event* wakeup_event_;
171
172 ObserverList<IOObserver> io_observers_;
173 ThreadChecker watch_file_descriptor_caller_checker_;
174 DISALLOW_COPY_AND_ASSIGN(MessagePumpLibevent);
175 };
176
177 } // namespace base
178
179 #endif // BASE_MESSAGE_PUMP_LIBEVENT_H_
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