Patch for bug 74983 (among others) to be applied to M11 696 branch.

content/common/file_path_watcher/file_path_watcher_mac.cc

+// Copyright (c) 2011 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 "content/common/file_path_watcher/file_path_watcher.h"
+
+#include <fcntl.h>
+#include <sys/event.h>
+#include <sys/param.h>
+
+#include <vector>
+
+#include "base/file_util.h"
+#include "base/message_loop.h"
+#include "base/message_loop_proxy.h"
+#include "base/stringprintf.h"
+
+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) {}
+  virtual ~FilePathWatcherImpl() {}
+
+  // 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,
+                     FilePathWatcher::Delegate* delegate) OVERRIDE;
+  virtual void Cancel() OVERRIDE;
+
+ 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) {
+    PLOG(ERROR) << "close";
+  }
+  *fd = -1;
+}
+
+bool FilePathWatcherImpl::AreKeventValuesValid(struct kevent* kevents,
+                                               int count) {
+  if (count < 0) {
+    PLOG(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));
+      }
+      LOG(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());
+  CHECK_EQ(fd, kqueue_);
+  CHECK(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,
+                                FilePathWatcher::Delegate* delegate) {
+  DCHECK(MessageLoopForIO::current());
+  DCHECK(target_.value().empty());  // Can only watch one path.
+  DCHECK(delegate);
+  DCHECK_EQ(kqueue_, -1);
+
+  delegate_ = delegate;
+  target_ = path;
+
+  MessageLoop::current()->AddDestructionObserver(this);
+  io_message_loop_ = base::MessageLoopProxy::CreateForCurrentThread();
+
+  kqueue_ = kqueue();
+  if (kqueue_ == -1) {
+    PLOG(ERROR) << "kqueue";
+    return false;
+  }
+
+  int last_entry = EventsForPath(target_, &events_);
+  CHECK_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,
+                    NewRunnableMethod(this, &FilePathWatcherImpl::Cancel));
+    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_.release();
+    MessageLoop::current()->RemoveDestructionObserver(this);
+    delegate_ = NULL;
+  }
+}
+
+}  // namespace
+
+FilePathWatcher::FilePathWatcher() {
+  impl_ = new FilePathWatcherImpl();
+}