base/files/file_path_watcher_kqueue.cc - mirrors/engine - Git at Google

 // 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_kqueue.h"

 #include <fcntl.h>
 #include <sys/param.h>

 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/thread_task_runner_handle.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 {

 FilePathWatcherKQueue::FilePathWatcherKQueue() : kqueue_(-1) {}

 FilePathWatcherKQueue::~FilePathWatcherKQueue() {}

 void FilePathWatcherKQueue::ReleaseEvent(struct kevent& event) {
   CloseFileDescriptor(&event.ident);
   EventData* entry = EventDataForKevent(event);
   delete entry;
   event.udata = NULL;
 }

 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;
   }

   int last_existing_entry = 0;
   FilePath built_path;
   bool path_still_exists = true;
   for (std::vector<FilePath::StringType>::iterator i = components.begin();
       i != components.end(); ++i) {
     if (i == components.begin()) {
       built_path = FilePath(*i);
     } else {
       built_path = built_path.Append(*i);
     }
     uintptr_t fd = kNoFileDescriptor;
     if (path_still_exists) {
       fd = FileDescriptorForPath(built_path);
       if (fd == kNoFileDescriptor) {
         path_still_exists = false;
       } else {
         ++last_existing_entry;
       }
     }
     FilePath::StringType subdir = (i != (components.end() - 1)) ? *(i + 1) : "";
     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 FilePathWatcherKQueue::FileDescriptorForPath(const FilePath& path) {
   int fd = HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
   if (fd == -1)
     return kNoFileDescriptor;
   return fd;
 }

 void FilePathWatcherKQueue::CloseFileDescriptor(uintptr_t* fd) {
   if (*fd == kNoFileDescriptor) {
     return;
   }

   if (IGNORE_EINTR(close(*fd)) != 0) {
     DPLOG(ERROR) << "close";
   }
   *fd = kNoFileDescriptor;
 }

 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();
       for (; event != events_.end(); ++event) {
         if (event->ident == kevents[i].ident) {
           break;
         }
       }
       std::string path_name;
       if (event != events_.end()) {
         EventData* event_data = EventDataForKevent(*event);
         if (event_data != NULL) {
           path_name = event_data->path_.value();
         }
       }
       if (path_name.empty()) {
         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 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 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 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 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;
       }
     }
     if (valid == 0) {
       // The root of the file path is inaccessible?
       return false;
     }

     EventVector updates(valid);
     int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], valid, &updates[0],
                                     valid, NULL));
     if (!AreKeventValuesValid(&updates[0], count)) {
       return false;
     }
     update_watches = false;
     for (; valid < events_.size(); ++valid) {
       EventData* event_data = EventDataForKevent(events_[valid]);
       events_[valid].ident = FileDescriptorForPath(event_data->path_);
       if (IsKeventFileDescriptorOpen(events_[valid])) {
         update_watches = true;
         if (event_data->subdir_.empty()) {
           *target_file_affected = true;
         }
       } else {
         break;
       }
     }
   }
   return true;
 }

 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(),
                                   &timeout));

   // Error values are stored within updates, so check to make sure that no
   // errors occurred.
   if (!AreKeventValuesValid(&updates[0], count)) {
     callback_.Run(target_, true /* error */);
     Cancel();
     return;
   }

   bool update_watches = false;
   bool send_notification = false;

   // Iterate through each of the updates and react to them.
   for (int i = 0; i < count; ++i) {
     // Find our kevent record that matches the update notification.
     EventVector::iterator event = events_.begin();
     for (; event != events_.end(); ++event) {
       if (!IsKeventFileDescriptorOpen(*event) ||
           event->ident == updates[i].ident) {
         break;
       }
     }
     if (event == events_.end() || !IsKeventFileDescriptorOpen(*event)) {
       // The event may no longer exist in |events_| because another event
       // modified |events_| in such a way to make it invalid. For example if
       // the path is /foo/bar/bam and foo is deleted, NOTE_DELETE events for
       // foo, bar and bam will be sent. If foo is processed first, then
       // the file descriptors for bar and bam will already be closed and set
       // to -1 before they get a chance to be processed.
       continue;
     }

     EventData* event_data = EventDataForKevent(*event);

     // If the subdir is empty, this is the last item on the path and is the
     // target file.
     bool target_file_affected = event_data->subdir_.empty();
     if ((updates[i].fflags & NOTE_ATTRIB) && !target_file_affected) {
       HandleAttributesChange(event, &target_file_affected, &update_watches);
     }
     if (updates[i].fflags & (NOTE_DELETE | NOTE_REVOKE | NOTE_RENAME)) {
       HandleDeleteOrMoveChange(event, &target_file_affected, &update_watches);
     }
     if ((updates[i].fflags & NOTE_WRITE) && !target_file_affected) {
       HandleCreateItemChange(event, &target_file_affected, &update_watches);
     }
     send_notification |= target_file_affected;
   }

   if (update_watches) {
     if (!UpdateWatches(&send_notification)) {
       callback_.Run(target_, true /* error */);
       Cancel();
     }
   }

   if (send_notification) {
     callback_.Run(target_, false);
   }
 }

 void FilePathWatcherKQueue::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }

 void FilePathWatcherKQueue::WillDestroyCurrentMessageLoop() {
   CancelOnMessageLoopThread();
 }

 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 using kqueue.
     NOTIMPLEMENTED();
     return false;
   }

   callback_ = callback;
   target_ = path;

   MessageLoop::current()->AddDestructionObserver(this);
   io_task_runner_ = ThreadTaskRunnerHandle::Get();

   kqueue_ = kqueue();
   if (kqueue_ == -1) {
     DPLOG(ERROR) << "kqueue";
     return false;
   }

   int last_entry = EventsForPath(target_, &events_);
   DCHECK_NE(last_entry, 0);

   EventVector responses(last_entry);

   int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], last_entry,
                                   &responses[0], last_entry, NULL));
   if (!AreKeventValuesValid(&responses[0], count)) {
     // Calling Cancel() here to close any file descriptors that were opened.
     // This would happen in the destructor anyways, but FilePathWatchers tend to
     // 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 FilePathWatcherKQueue::Cancel() {
   SingleThreadTaskRunner* task_runner = io_task_runner_.get();
   if (!task_runner) {
     set_cancelled();
     return;
   }
   if (!task_runner->BelongsToCurrentThread()) {
     task_runner->PostTask(FROM_HERE,
                           base::Bind(&FilePathWatcherKQueue::Cancel, this));
     return;
   }
   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_task_runner_ = NULL;
     MessageLoop::current()->RemoveDestructionObserver(this);
     callback_.Reset();
   }
 }

 }  // namespace base
	// 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_kqueue.h"

	#include <fcntl.h>
	#include <sys/param.h>

	#include "base/bind.h"
	#include "base/files/file_util.h"
	#include "base/logging.h"
	#include "base/strings/stringprintf.h"
	#include "base/thread_task_runner_handle.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 {

	FilePathWatcherKQueue::FilePathWatcherKQueue() : kqueue_(-1) {}

	FilePathWatcherKQueue::~FilePathWatcherKQueue() {}

	void FilePathWatcherKQueue::ReleaseEvent(struct kevent& event) {
	CloseFileDescriptor(&event.ident);
	EventData* entry = EventDataForKevent(event);
	delete entry;
	event.udata = NULL;
	}

	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;
	}

	int last_existing_entry = 0;
	FilePath built_path;
	bool path_still_exists = true;
	for (std::vector<FilePath::StringType>::iterator i = components.begin();
	i != components.end(); ++i) {
	if (i == components.begin()) {
	built_path = FilePath(*i);
	} else {
	built_path = built_path.Append(*i);
	}
	uintptr_t fd = kNoFileDescriptor;
	if (path_still_exists) {
	fd = FileDescriptorForPath(built_path);
	if (fd == kNoFileDescriptor) {
	path_still_exists = false;
	} else {
	++last_existing_entry;
	}
	}
	FilePath::StringType subdir = (i != (components.end() - 1)) ? *(i + 1) : "";
	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 FilePathWatcherKQueue::FileDescriptorForPath(const FilePath& path) {
	int fd = HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
	if (fd == -1)
	return kNoFileDescriptor;
	return fd;
	}

	void FilePathWatcherKQueue::CloseFileDescriptor(uintptr_t* fd) {
	if (*fd == kNoFileDescriptor) {
	return;
	}

	if (IGNORE_EINTR(close(*fd)) != 0) {
	DPLOG(ERROR) << "close";
	}
	*fd = kNoFileDescriptor;
	}

	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();
	for (; event != events_.end(); ++event) {
	if (event->ident == kevents[i].ident) {
	break;
	}
	}
	std::string path_name;
	if (event != events_.end()) {
	EventData* event_data = EventDataForKevent(*event);
	if (event_data != NULL) {
	path_name = event_data->path_.value();
	}
	}
	if (path_name.empty()) {
	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 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 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 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 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;
	}
	}
	if (valid == 0) {
	// The root of the file path is inaccessible?
	return false;
	}

	EventVector updates(valid);
	int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], valid, &updates[0],
	valid, NULL));
	if (!AreKeventValuesValid(&updates[0], count)) {
	return false;
	}
	update_watches = false;
	for (; valid < events_.size(); ++valid) {
	EventData* event_data = EventDataForKevent(events_[valid]);
	events_[valid].ident = FileDescriptorForPath(event_data->path_);
	if (IsKeventFileDescriptorOpen(events_[valid])) {
	update_watches = true;
	if (event_data->subdir_.empty()) {
	*target_file_affected = true;
	}
	} else {
	break;
	}
	}
	}
	return true;
	}

	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(),
	&timeout));

	// Error values are stored within updates, so check to make sure that no
	// errors occurred.
	if (!AreKeventValuesValid(&updates[0], count)) {
	callback_.Run(target_, true /* error */);
	Cancel();
	return;
	}

	bool update_watches = false;
	bool send_notification = false;

	// Iterate through each of the updates and react to them.
	for (int i = 0; i < count; ++i) {
	// Find our kevent record that matches the update notification.
	EventVector::iterator event = events_.begin();
	for (; event != events_.end(); ++event) {
	if (!IsKeventFileDescriptorOpen(*event) \|\|
	event->ident == updates[i].ident) {
	break;
	}
	}
	if (event == events_.end() \|\| !IsKeventFileDescriptorOpen(*event)) {
	// The event may no longer exist in \|events_\| because another event
	// modified \|events_\| in such a way to make it invalid. For example if
	// the path is /foo/bar/bam and foo is deleted, NOTE_DELETE events for
	// foo, bar and bam will be sent. If foo is processed first, then
	// the file descriptors for bar and bam will already be closed and set
	// to -1 before they get a chance to be processed.
	continue;
	}

	EventData* event_data = EventDataForKevent(*event);

	// If the subdir is empty, this is the last item on the path and is the
	// target file.
	bool target_file_affected = event_data->subdir_.empty();
	if ((updates[i].fflags & NOTE_ATTRIB) && !target_file_affected) {
	HandleAttributesChange(event, &target_file_affected, &update_watches);
	}
	if (updates[i].fflags & (NOTE_DELETE \| NOTE_REVOKE \| NOTE_RENAME)) {
	HandleDeleteOrMoveChange(event, &target_file_affected, &update_watches);
	}
	if ((updates[i].fflags & NOTE_WRITE) && !target_file_affected) {
	HandleCreateItemChange(event, &target_file_affected, &update_watches);
	}
	send_notification \|= target_file_affected;
	}

	if (update_watches) {
	if (!UpdateWatches(&send_notification)) {
	callback_.Run(target_, true /* error */);
	Cancel();
	}
	}

	if (send_notification) {
	callback_.Run(target_, false);
	}
	}

	void FilePathWatcherKQueue::OnFileCanWriteWithoutBlocking(int fd) {
	NOTREACHED();
	}

	void FilePathWatcherKQueue::WillDestroyCurrentMessageLoop() {
	CancelOnMessageLoopThread();
	}

	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 using kqueue.
	NOTIMPLEMENTED();
	return false;
	}

	callback_ = callback;
	target_ = path;

	MessageLoop::current()->AddDestructionObserver(this);
	io_task_runner_ = ThreadTaskRunnerHandle::Get();

	kqueue_ = kqueue();
	if (kqueue_ == -1) {
	DPLOG(ERROR) << "kqueue";
	return false;
	}

	int last_entry = EventsForPath(target_, &events_);
	DCHECK_NE(last_entry, 0);

	EventVector responses(last_entry);

	int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], last_entry,
	&responses[0], last_entry, NULL));
	if (!AreKeventValuesValid(&responses[0], count)) {
	// Calling Cancel() here to close any file descriptors that were opened.
	// This would happen in the destructor anyways, but FilePathWatchers tend to
	// 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 FilePathWatcherKQueue::Cancel() {
	SingleThreadTaskRunner* task_runner = io_task_runner_.get();
	if (!task_runner) {
	set_cancelled();
	return;
	}
	if (!task_runner->BelongsToCurrentThread()) {
	task_runner->PostTask(FROM_HERE,
	base::Bind(&FilePathWatcherKQueue::Cancel, this));
	return;
	}
	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_task_runner_ = NULL;
	MessageLoop::current()->RemoveDestructionObserver(this);
	callback_.Reset();
	}
	}

	} // namespace base