message_pump_libevent refactor:

base/message_pump_libevent.h

 // 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/scoped_ptr.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:
-  // Used with WatchSocket to asynchronously monitor the I/O readiness of a
-  // socket.
+
+  // Object returned by WatchFileDescriptor to manage further watching.
+  class FileDescriptorWatcher {
+    public:
+     FileDescriptorWatcher();
+     ~FileDescriptorWatcher();  // Implicitly calls StopWatching.

[Mark Mentovai, 2008/12/15 21:43:40]

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.
+     scoped_ptr<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 a ready socket is detected.
-    virtual void OnSocketReady(short eventmask) = 0;
-  };
-
-  // Used with WatchFileHandle to monitor I/O readiness for a File Handle.
-  class FileWatcher {
-   public:
-    virtual ~FileWatcher() {}
-    // Called from MessageLoop::Run when a non-blocking read/write can be made.
-    virtual void OnFileReadReady(int fd) = 0;
-    virtual void OnFileWriteReady(int fd) = 0;
+    // 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();
   virtual ~MessagePumpLibevent();
 
-  // Have the current thread's message loop watch for a ready socket.
-  // Caller must provide a struct event for this socket for libevent's use.
-  // The event and interest_mask fields are defined in libevent.
+  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): hide libevent better; abstraction still too leaky
-  // TODO(dkegel): better error handing
   // TODO(dkegel): switch to edge-triggered readiness notification
-  void WatchSocket(int socket, short interest_mask, event* e, Watcher*);
-
-  // TODO(playmobil): Merge this with WatchSocket().
-  void WatchFileHandle(int fd, short interest_mask, event* e, FileWatcher*);
-
-  // Stop watching a socket.
-  // Event was previously initialized by WatchSocket.
-  void UnwatchSocket(event* e);
-
-  // Stop watching a File Handle.
-  // Event was previously initialized by WatchFileHandle.
-  void UnwatchFileHandle(event* e);
+  bool WatchFileDescriptor(int fd,
+                           bool persistent,
+                           Mode mode,
+                           FileDescriptorWatcher *controller,
+                           Watcher *delegate);
 
   // MessagePump methods:
   virtual void Run(Delegate* delegate);
   virtual void Quit();
   virtual void ScheduleWork();
   virtual void ScheduleDelayedWork(const Time& delayed_work_time);
 
  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.
   Time 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 socket is ready
-  static void OnReadinessNotification(int socket, short flags, void* context);
-
-  // Called by libevent to tell us a registered fd is ready.
-  static void OnFileReadReadinessNotification(int fd, short flags,
-                                              void* context);
-  static void OnFileWriteReadinessNotification(int fd, short flags,
-                                               void* context);
+  // 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);
   // ... 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_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePumpLibevent);
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_PUMP_LIBEVENT_H_