message_pump_libevent refactor:

* Unify WatchSocket & WatchFileHandle.
* Better encapsulate libevent.
* Fix a bug with blocking writes in ipc_posix.cc

Review URL: http://codereview.chromium.org/13757

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@6911 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 156 insertions, 119 deletions

diff --git a/base/message_loop.cc b/base/message_loop.cc
index 898fbfa..12ad3fa 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -593,22 +593,17 @@ bool MessageLoopForIO::WaitForIOCompletion(DWORD timeout, IOHandler* filter) {
 
 #elif defined(OS_POSIX)
 
-void MessageLoopForIO::WatchSocket(int socket, short interest_mask,
-                                   struct event* e, Watcher* watcher) {
-  pump_libevent()->WatchSocket(socket, interest_mask, e, watcher);
+bool MessageLoopForIO::WatchFileDescriptor(int fd,
+                                           bool persistent,
+                                           Mode mode,
+                                           FileDescriptorWatcher *controller,
+                                           Watcher *delegate) {
+  return pump_libevent()->WatchFileDescriptor(
+      fd,
+      persistent,
+      static_cast<base::MessagePumpLibevent::Mode>(mode),
+      controller,
+      delegate);
 }
 
-void MessageLoopForIO::WatchFileHandle(int fd, short interest_mask,
-                                       struct event* e, FileWatcher* watcher) {
-  pump_libevent()->WatchFileHandle(fd, interest_mask, e, watcher);
-}
-
-
-void MessageLoopForIO::UnwatchSocket(struct event* e) {
-  pump_libevent()->UnwatchSocket(e);
-}
-
-void MessageLoopForIO::UnwatchFileHandle(struct event* e) {
-  pump_libevent()->UnwatchFileHandle(e);
-}
 #endif
diff --git a/base/message_loop.h b/base/message_loop.h
index 69db8c1..6cd0ef4 100644
--- a/base/message_loop.h
+++ b/base/message_loop.h
@@ -473,14 +473,21 @@ class MessageLoopForIO : public MessageLoop {
 
 #elif defined(OS_POSIX)
   typedef base::MessagePumpLibevent::Watcher Watcher;
-  typedef base::MessagePumpLibevent::FileWatcher FileWatcher;
-
-  // Please see MessagePumpLibevent for definitions of these methods.
-  void WatchSocket(int socket, short interest_mask,
-                   struct event* e, Watcher* watcher);
-  void WatchFileHandle(int fd, short interest_mask, event* e, FileWatcher*);
-  void UnwatchSocket(struct event* e);
-  void UnwatchFileHandle(event* e);
+  typedef base::MessagePumpLibevent::FileDescriptorWatcher
+      FileDescriptorWatcher;
+
+  enum Mode {
+    WATCH_READ = base::MessagePumpLibevent::WATCH_READ,
+    WATCH_WRITE = base::MessagePumpLibevent::WATCH_WRITE,
+    WATCH_READ_WRITE = base::MessagePumpLibevent::WATCH_READ_WRITE
+  };
+
+  // Please see MessagePumpLibevent for definition.
+  bool WatchFileDescriptor(int fd,
+                           bool persistent,
+                           Mode mode,
+                           FileDescriptorWatcher *controller,
+                           Watcher *delegate);
 #endif  // defined(OS_POSIX)
 };
 
diff --git a/base/message_pump_libevent.cc b/base/message_pump_libevent.cc
index a281980..9c13110 100644
--- a/base/message_pump_libevent.cc
+++ b/base/message_pump_libevent.cc
@@ -15,17 +15,48 @@ namespace base {
 
 // Return 0 on success
 // Too small a function to bother putting in a library?
-static int SetNonBlocking(int fd)
-{
-    int flags = fcntl(fd, F_GETFL, 0);
-    if (-1 == flags)
-      flags = 0;
-    return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+static int SetNonBlocking(int fd) {
+  int flags = fcntl(fd, F_GETFL, 0);
+  if (flags == -1)
+    flags = 0;
+  return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+}
+
+MessagePumpLibevent::FileDescriptorWatcher::FileDescriptorWatcher()
+    : is_persistent_(false),
+      event_(NULL) {
+}
+
+MessagePumpLibevent::FileDescriptorWatcher::~FileDescriptorWatcher() {
+  if (event_.get()) {
+    StopWatchingFileDescriptor();
+  }
+}
+
+void MessagePumpLibevent::FileDescriptorWatcher::Init(event *e,
+                                                      bool is_persistent) {
+  DCHECK(e);
+
+  // Cleanup any old event we might have been watching.
+  if (event_.get()) {
+    StopWatchingFileDescriptor();
+  }
+
+  is_persistent = is_persistent_;
+  event_.reset(e);
+}
+
+bool MessagePumpLibevent::FileDescriptorWatcher::StopWatchingFileDescriptor() {
+  if (event_.get() == NULL) {
+    return true;
+  }
+
+  // event_del() is a no-op of the event isn't active.
+  return (event_del(event_.get()) == 0);
 }
 
 // Called if a byte is received on the wakeup pipe.
 void MessagePumpLibevent::OnWakeup(int socket, short flags, void* context) {
-
   base::MessagePumpLibevent* that =
               static_cast<base::MessagePumpLibevent*>(context);
   DCHECK(that->wakeup_pipe_out_ == socket);
@@ -61,7 +92,7 @@ bool MessagePumpLibevent::Init() {
 
   wakeup_event_ = new event;
   event_set(wakeup_event_, wakeup_pipe_out_, EV_READ | EV_PERSIST,
-	    OnWakeup, this);
+            OnWakeup, this);
   event_base_set(event_base_, wakeup_event_);
 
   if (event_add(wakeup_event_, 0))
@@ -77,67 +108,56 @@ MessagePumpLibevent::~MessagePumpLibevent() {
   event_base_free(event_base_);
 }
 
-void MessagePumpLibevent::WatchSocket(int socket, short interest_mask,
-                                      event* e, Watcher* watcher) {
+bool MessagePumpLibevent::WatchFileDescriptor(int fd,
+                                              bool persistent,
+                                              Mode mode,
+                                              FileDescriptorWatcher *controller,
+                                              Watcher *delegate) {
+  DCHECK(fd > 0);
+  DCHECK(controller);
+  DCHECK(delegate);
+  DCHECK(mode == WATCH_READ || mode == WATCH_WRITE || mode == WATCH_READ_WRITE);
 
-  // Set current interest mask and message pump for this event
-  event_set(e, socket, interest_mask, OnReadinessNotification, watcher);
+  int event_mask = persistent ? EV_PERSIST : 0;
+  if (mode == WATCH_READ || mode == WATCH_READ_WRITE) {
+    event_mask |= EV_READ;
+  }
+  if (mode == WATCH_WRITE || mode == WATCH_READ_WRITE) {
+    event_mask |= EV_WRITE;
+  }
+
+  // Ownership is transferred to the controller.
+  scoped_ptr<event> evt(new event);
+  // Set current interest mask and message pump for this event.
+  event_set(evt.get(), fd, event_mask | EV_READ, OnLibeventNotification,
+            delegate);
 
   // Tell libevent which message pump this socket will belong to when we add it.
-  event_base_set(event_base_, e);
+  if (event_base_set(event_base_, evt.get()) != 0) {
+    return false;
+  }
 
   // Add this socket to the list of monitored sockets.
-  if (event_add(e, NULL))
-    NOTREACHED();
-}
-
-void MessagePumpLibevent::WatchFileHandle(int fd, short interest_mask,
-                                          event* e, FileWatcher* watcher) {
-  // Set current interest mask and message pump for this event
-  if ((interest_mask & EV_READ) != 0) {
-    event_set(e, fd, interest_mask, OnFileReadReadinessNotification, watcher);
-  } else {
-    event_set(e, fd, interest_mask, OnFileWriteReadinessNotification, watcher);
+  if (event_add(evt.get(), NULL) != 0) {
+    return false;
   }
 
-  // Tell libevent which message pump this fd will belong to when we add it.
-  event_base_set(event_base_, e);
-
-  // Add this fd to the list of monitored sockets.
-  if (event_add(e, NULL))
-    NOTREACHED();
-}
-
-void MessagePumpLibevent::UnwatchSocket(event* e) {
-  // Remove this socket from the list of monitored sockets.
-  if (event_del(e))
-    NOTREACHED();
+  // Transfer ownership of e to controller.
+  controller->Init(evt.release(), persistent);
+  return true;
 }
 
-void MessagePumpLibevent::UnwatchFileHandle(event* e) {
-  // Remove this fd from the list of monitored fds.
-  if (event_del(e))
-    NOTREACHED();
-}
 
-void MessagePumpLibevent::OnReadinessNotification(int socket, short flags,
-                                                  void* context) {
-  // The given socket is ready for I/O.
-  // Tell the owner what kind of I/O the socket is ready for.
+void MessagePumpLibevent::OnLibeventNotification(int fd, short flags,
+                                                 void* context) {
   Watcher* watcher = static_cast<Watcher*>(context);
-  watcher->OnSocketReady(flags);
-}
 
-void MessagePumpLibevent::OnFileReadReadinessNotification(int fd, short flags,
-                                                          void* context) {
-  FileWatcher* watcher = static_cast<FileWatcher*>(context);
-  watcher->OnFileReadReady(fd);
-}
-
-void MessagePumpLibevent::OnFileWriteReadinessNotification(int fd, short flags,
-                                                           void* context) {
-  FileWatcher* watcher = static_cast<FileWatcher*>(context);
-  watcher->OnFileWriteReady(fd);
+  if (flags & EV_WRITE) {
+    watcher->OnFileCanWriteWithoutBlocking(fd);
+  }
+  if (flags & EV_READ) {
+    watcher->OnFileCanReadWithoutBlocking(fd);
+  }
 }
 
 // Reentrant!
diff --git a/base/message_pump_libevent.h b/base/message_pump_libevent.h
index b54bc36..36475c1 100644
--- a/base/message_pump_libevent.h
+++ b/base/message_pump_libevent.h
@@ -6,6 +6,7 @@
 #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
@@ -18,46 +19,65 @@ namespace base {
 // 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.
-  class Watcher {
-   public:
-    virtual ~Watcher() {}
-    // Called from MessageLoop::Run when a ready socket is detected.
-    virtual void OnSocketReady(short eventmask) = 0;
+
+  // Object returned by WatchFileDescriptor to manage further watching.
+  class FileDescriptorWatcher {
+    public:
+     FileDescriptorWatcher();
+     ~FileDescriptorWatcher();  // Implicitly calls StopWatching.
+
+     // 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.
+     // If this FileWatcher is already watching an event, the previous event is
+     // terminated and cleaned up here.
+     void Init(event* e, bool is_persistent);
+     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 WatchFileHandle to monitor I/O readiness for a File Handle.
-  class FileWatcher {
+  // Used with WatchFileDescptor to asynchronously monitor the I/O readiness of
+  // a File Descriptor.
+  class Watcher {
    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;
+    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();
   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,
+    WATCH_WRITE,
+    WATCH_READ_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.
   // 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);
@@ -83,14 +103,9 @@ class MessagePumpLibevent : public MessagePump {
   // 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