Use FSEvents for recursive file watch on Mac

base/files/file_path_watcher_kqueue.cc

 // 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/files/file_path_watcher.h"
+#include "base/files/file_path_watcher_kqueue.h"
 
 #include <fcntl.h>
-#include <sys/event.h>
 #include <sys/param.h>
 
-#include <vector>
-
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/logging.h"
-#include "base/message_loop/message_loop.h"
-#include "base/message_loop/message_loop_proxy.h"
 #include "base/strings/stringprintf.h"
 
 // On some platforms these are not defined.
 #if !defined(EV_RECEIPT)
 #define EV_RECEIPT 0
 #endif
 #if !defined(O_EVTONLY)
 #define O_EVTONLY O_RDONLY
 #endif
 
 namespace base {
 
-namespace {
+FilePathWatcherKQueue::FilePathWatcherKQueue() : kqueue_(-1) {}
 
-// Mac-specific file watcher implementation based on kqueue.
-// Originally it was based on FSEvents so that the semantics were equivalent
-// on Linux, OSX and Windows where it was able to detect:
-// - file creation/deletion/modification in a watched directory
-// - file creation/deletion/modification for a watched file
-// - modifications to the paths to a watched object that would affect the
-//   object such as renaming/attibute changes etc.
-// The FSEvents version did all of the above except handling attribute changes
-// to path components. Unfortunately FSEvents appears to have an issue where the
-// current implementation (Mac OS X 10.6.7) sometimes drops events and doesn't
-// send notifications. See
-// http://code.google.com/p/chromium/issues/detail?id=54822#c31 for source that
-// will reproduce the problem. FSEvents also required having a CFRunLoop
-// backing the thread that it was running on, that caused added complexity
-// in the interfaces.
-// The kqueue implementation will handle all of the items in the list above
-// except for detecting modifications to files in a watched directory. It will
-// detect the creation and deletion of files, just not the modification of
-// files. It does however detect the attribute changes that the FSEvents impl
-// would miss.
-class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
-                            public MessageLoopForIO::Watcher,
-                            public MessageLoop::DestructionObserver {
- public:
-  FilePathWatcherImpl() : kqueue_(-1) {}
+FilePathWatcherKQueue::~FilePathWatcherKQueue() {}
 
-  // MessageLoopForIO::Watcher overrides.
-  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
-  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
-
-  // MessageLoop::DestructionObserver overrides.
-  virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
-
-  // FilePathWatcher::PlatformDelegate overrides.
-  virtual bool Watch(const FilePath& path,
-                     bool recursive,
-                     const FilePathWatcher::Callback& callback) OVERRIDE;
-  virtual void Cancel() OVERRIDE;
-
- protected:
-  virtual ~FilePathWatcherImpl() {}
-
- private:
-  class EventData {
-   public:
-    EventData(const FilePath& path, const FilePath::StringType& subdir)
-        : path_(path), subdir_(subdir) { }
-    FilePath path_;  // Full path to this item.
-    FilePath::StringType subdir_;  // Path to any sub item.
-  };
-  typedef std::vector<struct kevent> EventVector;
-
-  // Can only be called on |io_message_loop_|'s thread.
-  virtual void CancelOnMessageLoopThread() OVERRIDE;
-
-  // Returns true if the kevent values are error free.
-  bool AreKeventValuesValid(struct kevent* kevents, int count);
-
-  // Respond to a change of attributes of the path component represented by
-  // |event|. Sets |target_file_affected| to true if |target_| is affected.
-  // Sets |update_watches| to true if |events_| need to be updated.
-  void HandleAttributesChange(const EventVector::iterator& event,
-                              bool* target_file_affected,
-                              bool* update_watches);
-
-  // Respond to a move or deletion of the path component represented by
-  // |event|. Sets |target_file_affected| to true if |target_| is affected.
-  // Sets |update_watches| to true if |events_| need to be updated.
-  void HandleDeleteOrMoveChange(const EventVector::iterator& event,
-                                bool* target_file_affected,
-                                bool* update_watches);
-
-  // Respond to a creation of an item in the path component represented by
-  // |event|. Sets |target_file_affected| to true if |target_| is affected.
-  // Sets |update_watches| to true if |events_| need to be updated.
-  void HandleCreateItemChange(const EventVector::iterator& event,
-                              bool* target_file_affected,
-                              bool* update_watches);
-
-  // Update |events_| with the current status of the system.
-  // Sets |target_file_affected| to true if |target_| is affected.
-  // Returns false if an error occurs.
-  bool UpdateWatches(bool* target_file_affected);
-
-  // Fills |events| with one kevent per component in |path|.
-  // Returns the number of valid events created where a valid event is
-  // defined as one that has a ident (file descriptor) field != -1.
-  static int EventsForPath(FilePath path, EventVector *events);
-
-  // Release a kevent generated by EventsForPath.
-  static void ReleaseEvent(struct kevent& event);
-
-  // Returns a file descriptor that will not block the system from deleting
-  // the file it references.
-  static uintptr_t FileDescriptorForPath(const FilePath& path);
-
-  static const uintptr_t kNoFileDescriptor = static_cast<uintptr_t>(-1);
-
-  // Closes |*fd| and sets |*fd| to -1.
-  static void CloseFileDescriptor(uintptr_t* fd);
-
-  // Returns true if kevent has open file descriptor.
-  static bool IsKeventFileDescriptorOpen(const struct kevent& event) {
-    return event.ident != kNoFileDescriptor;
-  }
-
-  static EventData* EventDataForKevent(const struct kevent& event) {
-    return reinterpret_cast<EventData*>(event.udata);
-  }
-
-  EventVector events_;
-  scoped_refptr<base::MessageLoopProxy> io_message_loop_;
-  MessageLoopForIO::FileDescriptorWatcher kqueue_watcher_;
-  FilePathWatcher::Callback callback_;
-  FilePath target_;
-  int kqueue_;
-
-  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
-};
-
-void FilePathWatcherImpl::ReleaseEvent(struct kevent& event) {
+void FilePathWatcherKQueue::ReleaseEvent(struct kevent& event) {
   CloseFileDescriptor(&event.ident);
   EventData* entry = EventDataForKevent(event);
   delete entry;
   event.udata = NULL;
 }
 
-int FilePathWatcherImpl::EventsForPath(FilePath path, EventVector* events) {
+int FilePathWatcherKQueue::EventsForPath(FilePath path, EventVector* events) {
   DCHECK(MessageLoopForIO::current());
   // Make sure that we are working with a clean slate.
   DCHECK(events->empty());
 
   std::vector<FilePath::StringType> components;
   path.GetComponents(&components);
 
   if (components.size() < 1) {
     return -1;
   }
@@ skipping 21 matching lines @@
     EventData* data = new EventData(built_path, subdir);
     struct kevent event;
     EV_SET(&event, fd, EVFILT_VNODE, (EV_ADD | EV_CLEAR | EV_RECEIPT),
            (NOTE_DELETE | NOTE_WRITE | NOTE_ATTRIB |
             NOTE_RENAME | NOTE_REVOKE | NOTE_EXTEND), 0, data);
     events->push_back(event);
   }
   return last_existing_entry;
 }
 
-uintptr_t FilePathWatcherImpl::FileDescriptorForPath(const FilePath& path) {
+uintptr_t FilePathWatcherKQueue::FileDescriptorForPath(const FilePath& path) {
   int fd = HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
   if (fd == -1)
     return kNoFileDescriptor;
   return fd;
 }
 
-void FilePathWatcherImpl::CloseFileDescriptor(uintptr_t* fd) {
+void FilePathWatcherKQueue::CloseFileDescriptor(uintptr_t* fd) {
   if (*fd == kNoFileDescriptor) {
     return;
   }
 
   if (IGNORE_EINTR(close(*fd)) != 0) {
     DPLOG(ERROR) << "close";
   }
   *fd = kNoFileDescriptor;
 }
 
-bool FilePathWatcherImpl::AreKeventValuesValid(struct kevent* kevents,
+bool FilePathWatcherKQueue::AreKeventValuesValid(struct kevent* kevents,
                                                int count) {
   if (count < 0) {
     DPLOG(ERROR) << "kevent";
     return false;
   }
   bool valid = true;
   for (int i = 0; i < count; ++i) {
     if (kevents[i].flags & EV_ERROR && kevents[i].data) {
       // Find the kevent in |events_| that matches the kevent with the error.
       EventVector::iterator event = events_.begin();
@@ skipping 13 matching lines @@
         path_name = base::StringPrintf(
             "fd %ld", reinterpret_cast<long>(&kevents[i].ident));
       }
       DLOG(ERROR) << "Error: " << kevents[i].data << " for " << path_name;
       valid = false;
     }
   }
   return valid;
 }
 
-void FilePathWatcherImpl::HandleAttributesChange(
+void FilePathWatcherKQueue::HandleAttributesChange(
     const EventVector::iterator& event,
     bool* target_file_affected,
     bool* update_watches) {
   EventVector::iterator next_event = event + 1;
   EventData* next_event_data = EventDataForKevent(*next_event);
   // Check to see if the next item in path is still accessible.
   uintptr_t have_access = FileDescriptorForPath(next_event_data->path_);
   if (have_access == kNoFileDescriptor) {
     *target_file_affected = true;
     *update_watches = true;
     EventVector::iterator local_event(event);
     for (; local_event != events_.end(); ++local_event) {
       // Close all nodes from the event down. This has the side effect of
       // potentially rendering other events in |updates| invalid.
       // There is no need to remove the events from |kqueue_| because this
       // happens as a side effect of closing the file descriptor.
       CloseFileDescriptor(&local_event->ident);
     }
   } else {
     CloseFileDescriptor(&have_access);
   }
 }
 
-void FilePathWatcherImpl::HandleDeleteOrMoveChange(
+void FilePathWatcherKQueue::HandleDeleteOrMoveChange(
     const EventVector::iterator& event,
     bool* target_file_affected,
     bool* update_watches) {
   *target_file_affected = true;
   *update_watches = true;
   EventVector::iterator local_event(event);
   for (; local_event != events_.end(); ++local_event) {
     // Close all nodes from the event down. This has the side effect of
     // potentially rendering other events in |updates| invalid.
     // There is no need to remove the events from |kqueue_| because this
     // happens as a side effect of closing the file descriptor.
     CloseFileDescriptor(&local_event->ident);
   }
 }
 
-void FilePathWatcherImpl::HandleCreateItemChange(
+void FilePathWatcherKQueue::HandleCreateItemChange(
     const EventVector::iterator& event,
     bool* target_file_affected,
     bool* update_watches) {
   // Get the next item in the path.
   EventVector::iterator next_event = event + 1;
   // Check to see if it already has a valid file descriptor.
   if (!IsKeventFileDescriptorOpen(*next_event)) {
     EventData* next_event_data = EventDataForKevent(*next_event);
     // If not, attempt to open a file descriptor for it.
     next_event->ident = FileDescriptorForPath(next_event_data->path_);
     if (IsKeventFileDescriptorOpen(*next_event)) {
       *update_watches = true;
       if (next_event_data->subdir_.empty()) {
         *target_file_affected = true;
       }
     }
   }
 }
 
-bool FilePathWatcherImpl::UpdateWatches(bool* target_file_affected) {
+bool FilePathWatcherKQueue::UpdateWatches(bool* target_file_affected) {
   // Iterate over events adding kevents for items that exist to the kqueue.
   // Then check to see if new components in the path have been created.
   // Repeat until no new components in the path are detected.
   // This is to get around races in directory creation in a watched path.
   bool update_watches = true;
   while (update_watches) {
     size_t valid;
     for (valid = 0; valid < events_.size(); ++valid) {
       if (!IsKeventFileDescriptorOpen(events_[valid])) {
         break;
@@ skipping 20 matching lines @@
           *target_file_affected = true;
         }
       } else {
         break;
       }
     }
   }
   return true;
 }
 
-void FilePathWatcherImpl::OnFileCanReadWithoutBlocking(int fd) {
+void FilePathWatcherKQueue::OnFileCanReadWithoutBlocking(int fd) {
   DCHECK(MessageLoopForIO::current());
   DCHECK_EQ(fd, kqueue_);
   DCHECK(events_.size());
 
   // Request the file system update notifications that have occurred and return
   // them in |updates|. |count| will contain the number of updates that have
   // occurred.
   EventVector updates(events_.size());
   struct timespec timeout = {0, 0};
   int count = HANDLE_EINTR(kevent(kqueue_, NULL, 0, &updates[0], updates.size(),
@@ skipping 52 matching lines @@
       callback_.Run(target_, true /* error */);
       Cancel();
     }
   }
 
   if (send_notification) {
     callback_.Run(target_, false);
   }
 }
 
-void FilePathWatcherImpl::OnFileCanWriteWithoutBlocking(int fd) {
+void FilePathWatcherKQueue::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }
 
-void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
+void FilePathWatcherKQueue::WillDestroyCurrentMessageLoop() {
   CancelOnMessageLoopThread();
 }
 
-bool FilePathWatcherImpl::Watch(const FilePath& path,
-                                bool recursive,
-                                const FilePathWatcher::Callback& callback) {
+bool FilePathWatcherKQueue::Watch(const FilePath& path,
+                                  bool recursive,
+                                  const FilePathWatcher::Callback& callback) {
   DCHECK(MessageLoopForIO::current());
   DCHECK(target_.value().empty());  // Can only watch one path.
   DCHECK(!callback.is_null());
   DCHECK_EQ(kqueue_, -1);
 
   if (recursive) {
-    // Recursive watch is not supported on this platform.
+    // Recursive watch is not supported using kqueue.
     NOTIMPLEMENTED();
     return false;
   }
 
   callback_ = callback;
   target_ = path;
 
   MessageLoop::current()->AddDestructionObserver(this);
   io_message_loop_ = base::MessageLoopProxy::current();
 
@@ skipping 16 matching lines @@
     // be long lived, and if an error has occurred, there is no reason to waste
     // the file descriptors.
     Cancel();
     return false;
   }
 
   return MessageLoopForIO::current()->WatchFileDescriptor(
       kqueue_, true, MessageLoopForIO::WATCH_READ, &kqueue_watcher_, this);
 }
 
-void FilePathWatcherImpl::Cancel() {
+void FilePathWatcherKQueue::Cancel() {
   base::MessageLoopProxy* proxy = io_message_loop_.get();
   if (!proxy) {
     set_cancelled();
     return;
   }
   if (!proxy->BelongsToCurrentThread()) {
     proxy->PostTask(FROM_HERE,
-                    base::Bind(&FilePathWatcherImpl::Cancel, this));
+                    base::Bind(&FilePathWatcherKQueue::Cancel, this));
     return;
   }
   CancelOnMessageLoopThread();
 }
 
-void FilePathWatcherImpl::CancelOnMessageLoopThread() {
+void FilePathWatcherKQueue::CancelOnMessageLoopThread() {
   DCHECK(MessageLoopForIO::current());
   if (!is_cancelled()) {
     set_cancelled();
     kqueue_watcher_.StopWatchingFileDescriptor();
     if (IGNORE_EINTR(close(kqueue_)) != 0) {
       DPLOG(ERROR) << "close kqueue";
     }
     kqueue_ = -1;
     std::for_each(events_.begin(), events_.end(), ReleaseEvent);
     events_.clear();
     io_message_loop_ = NULL;
     MessageLoop::current()->RemoveDestructionObserver(this);
     callback_.Reset();
   }
 }
 
-}  // namespace
-
-FilePathWatcher::FilePathWatcher() {
-  impl_ = new FilePathWatcherImpl();
-}
-
 }  // namespace base