src/base/files/file_path_watcher_kqueue.cc - cobalt - 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.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.h"
 #include "base/message_loop_proxy.h"
 #include "base/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 files {

 namespace {

 // 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) {}

   // 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,
                      FilePathWatcher::Delegate* delegate) 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 of 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 int FileDescriptorForPath(const FilePath& path);

   // Closes |*fd| and sets |*fd| to -1.
   static void CloseFileDescriptor(int* fd);

   // Returns true if kevent has open file descriptor.
   static bool IsKeventFileDescriptorOpen(const struct kevent& event) {
     return event.ident != static_cast<uintptr_t>(-1);
   }

   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_;
   scoped_refptr<FilePathWatcher::Delegate> delegate_;
   FilePath target_;
   int kqueue_;

   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
 };

 void FilePathWatcherImpl::ReleaseEvent(struct kevent& event) {
   CloseFileDescriptor(reinterpret_cast<int*>(&event.ident));
   EventData* entry = EventDataForKevent(event);
   delete entry;
   event.udata = NULL;
 }

 int FilePathWatcherImpl::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);
     }
     int fd = -1;
     if (path_still_exists) {
       fd = FileDescriptorForPath(built_path);
       if (fd == -1) {
         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;
 }

 int FilePathWatcherImpl::FileDescriptorForPath(const FilePath& path) {
   return HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
 }

 void FilePathWatcherImpl::CloseFileDescriptor(int *fd) {
   if (*fd == -1) {
     return;
   }

   if (HANDLE_EINTR(close(*fd)) != 0) {
     DPLOG(ERROR) << "close";
   }
   *fd = -1;
 }

 bool FilePathWatcherImpl::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 %d", *reinterpret_cast<int*>(&kevents[i].ident));
       }
       DLOG(ERROR) << "Error: " << kevents[i].data << " for " << path_name;
       valid = false;
     }
   }
   return valid;
 }

 void FilePathWatcherImpl::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.
   int have_access = FileDescriptorForPath(next_event_data->path_);
   if (have_access == -1) {
     *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(reinterpret_cast<int*>(&local_event->ident));
     }
   } else {
     CloseFileDescriptor(&have_access);
   }
 }

 void FilePathWatcherImpl::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(reinterpret_cast<int*>(&local_event->ident));
   }
 }

 void FilePathWatcherImpl::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;
   EventData* next_event_data = EventDataForKevent(*next_event);

   // Check to see if it already has a valid file descriptor.
   if (!IsKeventFileDescriptorOpen(*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) {
   // 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 FilePathWatcherImpl::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)) {
     delegate_->OnFilePathError(target_);
     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 (!IsKeventFileDescriptorOpen(*event) || event == events_.end()) {
       // 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)) {
       delegate_->OnFilePathError(target_);
       Cancel();
     }
   }

   if (send_notification) {
     delegate_->OnFilePathChanged(target_);
   }
 }

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

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

 bool FilePathWatcherImpl::Watch(const FilePath& path,
                                 bool recursive,
                                 FilePathWatcher::Delegate* delegate) {
   DCHECK(MessageLoopForIO::current());
   DCHECK(target_.value().empty());  // Can only watch one path.
   DCHECK(delegate);
   DCHECK_EQ(kqueue_, -1);

   if (recursive) {
     // Recursive watch is not supported on this platform.
     NOTIMPLEMENTED();
     return false;
   }

   delegate_ = delegate;
   target_ = path;

   MessageLoop::current()->AddDestructionObserver(this);
   io_message_loop_ = base::MessageLoopProxy::current();

   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 FilePathWatcherImpl::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));
     return;
   }
   CancelOnMessageLoopThread();
 }

 void FilePathWatcherImpl::CancelOnMessageLoopThread() {
   DCHECK(MessageLoopForIO::current());
   if (!is_cancelled()) {
     set_cancelled();
     kqueue_watcher_.StopWatchingFileDescriptor();
     CloseFileDescriptor(&kqueue_);
     std::for_each(events_.begin(), events_.end(), ReleaseEvent);
     events_.clear();
     io_message_loop_ = NULL;
     MessageLoop::current()->RemoveDestructionObserver(this);
     delegate_ = NULL;
   }
 }

 }  // namespace

 FilePathWatcher::FilePathWatcher() {
   impl_ = new FilePathWatcherImpl();
 }

 }  // namespace files
 }  // 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.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.h"
	#include "base/message_loop_proxy.h"
	#include "base/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 files {

	namespace {

	// 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) {}

	// 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,
	FilePathWatcher::Delegate* delegate) 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 of 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 int FileDescriptorForPath(const FilePath& path);

	// Closes \|fd\| and sets \|fd\| to -1.
	static void CloseFileDescriptor(int* fd);

	// Returns true if kevent has open file descriptor.
	static bool IsKeventFileDescriptorOpen(const struct kevent& event) {
	return event.ident != static_cast<uintptr_t>(-1);
	}

	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_;
	scoped_refptr<FilePathWatcher::Delegate> delegate_;
	FilePath target_;
	int kqueue_;

	DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
	};

	void FilePathWatcherImpl::ReleaseEvent(struct kevent& event) {
	CloseFileDescriptor(reinterpret_cast<int*>(&event.ident));
	EventData* entry = EventDataForKevent(event);
	delete entry;
	event.udata = NULL;
	}

	int FilePathWatcherImpl::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);
	}
	int fd = -1;
	if (path_still_exists) {
	fd = FileDescriptorForPath(built_path);
	if (fd == -1) {
	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;
	}

	int FilePathWatcherImpl::FileDescriptorForPath(const FilePath& path) {
	return HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
	}

	void FilePathWatcherImpl::CloseFileDescriptor(int *fd) {
	if (*fd == -1) {
	return;
	}

	if (HANDLE_EINTR(close(*fd)) != 0) {
	DPLOG(ERROR) << "close";
	}
	*fd = -1;
	}

	bool FilePathWatcherImpl::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 %d", reinterpret_cast<int>(&kevents[i].ident));
	}
	DLOG(ERROR) << "Error: " << kevents[i].data << " for " << path_name;
	valid = false;
	}
	}
	return valid;
	}

	void FilePathWatcherImpl::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.
	int have_access = FileDescriptorForPath(next_event_data->path_);
	if (have_access == -1) {
	*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(reinterpret_cast<int*>(&local_event->ident));
	}
	} else {
	CloseFileDescriptor(&have_access);
	}
	}

	void FilePathWatcherImpl::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(reinterpret_cast<int*>(&local_event->ident));
	}
	}

	void FilePathWatcherImpl::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;
	EventData* next_event_data = EventDataForKevent(*next_event);

	// Check to see if it already has a valid file descriptor.
	if (!IsKeventFileDescriptorOpen(*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) {
	// 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 FilePathWatcherImpl::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)) {
	delegate_->OnFilePathError(target_);
	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 (!IsKeventFileDescriptorOpen(*event) \|\| event == events_.end()) {
	// 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)) {
	delegate_->OnFilePathError(target_);
	Cancel();
	}
	}

	if (send_notification) {
	delegate_->OnFilePathChanged(target_);
	}
	}

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

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

	bool FilePathWatcherImpl::Watch(const FilePath& path,
	bool recursive,
	FilePathWatcher::Delegate* delegate) {
	DCHECK(MessageLoopForIO::current());
	DCHECK(target_.value().empty()); // Can only watch one path.
	DCHECK(delegate);
	DCHECK_EQ(kqueue_, -1);

	if (recursive) {
	// Recursive watch is not supported on this platform.
	NOTIMPLEMENTED();
	return false;
	}

	delegate_ = delegate;
	target_ = path;

	MessageLoop::current()->AddDestructionObserver(this);
	io_message_loop_ = base::MessageLoopProxy::current();

	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 FilePathWatcherImpl::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));
	return;
	}
	CancelOnMessageLoopThread();
	}

	void FilePathWatcherImpl::CancelOnMessageLoopThread() {
	DCHECK(MessageLoopForIO::current());
	if (!is_cancelled()) {
	set_cancelled();
	kqueue_watcher_.StopWatchingFileDescriptor();
	CloseFileDescriptor(&kqueue_);
	std::for_each(events_.begin(), events_.end(), ReleaseEvent);
	events_.clear();
	io_message_loop_ = NULL;
	MessageLoop::current()->RemoveDestructionObserver(this);
	delegate_ = NULL;
	}
	}

	} // namespace

	FilePathWatcher::FilePathWatcher() {
	impl_ = new FilePathWatcherImpl();
	}

	} // namespace files
	} // namespace base