[NaCl SDK} Add EventListener and EventEmitter to support epoll.

native_client_sdk/src/libraries/nacl_io/event_emitter.h

+/* Copyright (c) 2013 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.

[Sam Clegg, 2013/07/17 17:34:56]

The convention for C++ headers seem to be to use single line C++
commets for the copyright header.

+ */
+#ifndef LIBRARIES_NACL_IO_EVENT_EMITTER_H_
+#define LIBRARIES_NACL_IO_EVENT_EMITTER_H_
+
+#include <map>
+#include <set>
+
+#include "nacl_io/error.h"
+
+#include "sdk_util/ref_object.h"
+#include "sdk_util/scoped_ref.h"
+#include "sdk_util/simple_lock.h"
+
+class EventEmitter;
+class EventInfo;

[Sam Clegg, 2013/07/17 17:34:56]

Remove since its is declared just below?

[binji, 2013/07/19 20:47:17]

ping

[noelallen1, 2013/07/19 21:35:43]

Done.

+class EventListener;
+
+// A ref counted object for storing the state of a single signal request.
+// Requests are unique to any FD/EventListener pair.
+struct EventInfo : public RefObject {

[binji, 2013/07/17 22:23:20]

might want to mention that this is not POD, because it derives from RefObject
(which is not POD)

[noelallen1, 2013/07/19 21:35:43]

Done.

+  volatile uint64_t data;
+  volatile uint32_t events;

[Sam Clegg, 2013/07/17 17:34:56]

Is this a bitfield of KernnelEventTypes?  Perhaps a comment to say so.

[noelallen1, 2013/07/19 21:35:43]

Done.

+  volatile uint32_t filter;

[Sam Clegg, 2013/07/17 17:34:56]

Didn't we come to the conclusion that volatile is not useful, except for people
accessing direct hardware memory (i.e. explicitly not useful in the context of
multi-threading):

http://stackoverflow.com/questions/4557979/when-to-use-volatile-with-multi-th...

[noelallen1, 2013/07/19 21:35:43]

Done.

+  // We do not use a ScopedRef to prevent circular references.
+  EventEmitter* emitter;
+  EventListener* listener;
+  uint32_t id;
+};
+
+typedef ScopedRef<EventInfo> ScopedEventInfo;
+
+typedef std::map<int, ScopedEventInfo> EventInfoMap_t;
+typedef std::set<ScopedEventInfo> EventInfoSet_t;
+
+// EventEmitter
+//
+// The EventEmitter class provides notification of events to EventListeners
+// by registering EventInfo objects and signalling the EventListener when

[binji, 2013/07/17 22:23:20]

sp: whenever their state

[binji, 2013/07/17 22:23:20]

signalled or signaled are both correct, but signaled seems to be used more here.

Same with signalling vs. signaling.

[binji, 2013/07/19 20:47:18]

ping

[noelallen1, 2013/07/19 21:35:43]

Done.

[noelallen1, 2013/07/19 21:35:43]

Done.

[noelallen1, 2013/07/19 21:35:43]

Done.

+// ever thier state is changed.
+//
+// See "Kernel Events" in event_listener.h for additional information.
+class EventEmitter : public RefObject {
+  typedef std::set<ScopedEventInfo> EventInfoSet_t;

[Sam Clegg, 2013/07/17 17:34:56]

Isn't this is duplicate of the typedef 10 lines above?  Is it needed?

[binji, 2013/07/19 20:47:18]

ping

[noelallen1, 2013/07/19 21:35:43]

Done.

[noelallen1, 2013/07/19 21:35:43]

Done.

+
+protected:
+  // Called automatically prior to delete to inform the EventListeners that
+  // this EventEmitter is abandoning an associated EventInfo.
+  virtual void Destroy();
+
+ private:
+  // Regisiter or unregister an EventInfo.  The lock of the EventListener

[binji, 2013/07/17 22:23:20]

sp: Register

[binji, 2013/07/19 20:47:18]

ping

[noelallen1, 2013/07/19 21:35:43]

Done.

[noelallen1, 2013/07/19 21:35:43]

Done.

+  // associated with this EventInfo must be held prior to calling these
+  // functions.  These functions are private to ensure they are called by the
+  // EventListener.
+  void RegisterEventInfo(const ScopedEventInfo& info);
+  void UnregisterEventInfo(const ScopedEventInfo& info);
+
+ public:
+  // Returns the current state of the emitter.

[Sam Clegg, 2013/07/17 17:34:56]

The state is a bitfield of KennelEventType?  Perhaps a typedef for this bitfield
would make the code more readable?

[noelallen1, 2013/07/19 21:35:43]

I'm going to think about that as I do the select/poll pieces.

+  virtual uint32_t GetEventStatus() = 0;
+
+  // REturns the type of the emitter (compatible with st_mode in stat)

[binji, 2013/07/17 22:23:20]

nit: Returns

[binji, 2013/07/19 20:47:18]

ping

[noelallen1, 2013/07/19 21:35:43]

Done.

[noelallen1, 2013/07/19 21:35:43]

Done.

+  virtual int GetType() = 0;
+
+ protected:
+  // Called by the thread causing the Event.
+  void RaiseEvent(uint32_t events);
+
+  // Called after registering locally, but while lock is still held.
+  virtual void ChainRegister(const ScopedEventInfo& event);

[binji, 2013/07/17 22:23:20]

I'd prefer a name that made it clear that it was called by RegisterEventInfo:

RegisterEventInfo_Chain, maybe?

[noelallen1, 2013/07/19 21:35:43]

Done.

+
+  // Called before unregistering locally, but while lock is still held.
+  virtual void ChainUnregister(const ScopedEventInfo& event);
+
+private:
+  SimpleLock emitter_lock_;
+  EventInfoSet_t events_;
+  friend class EventListener;
+};
+
+typedef ScopedRef<EventEmitter> ScopedEventEmitter;
+
+#endif  // LIBRARIES_NACL_IO_EVENT_EMITTER_H_