| // Copyright 2010 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // +build linux |
| |
| package fsnotify |
| |
| import ( |
| "errors" |
| "fmt" |
| "io" |
| "os" |
| "path/filepath" |
| "strings" |
| "sync" |
| "syscall" |
| "unsafe" |
| ) |
| |
| // Watcher watches a set of files, delivering events to a channel. |
| type Watcher struct { |
| Events chan Event |
| Errors chan error |
| mu sync.Mutex // Map access |
| fd int |
| poller *fdPoller |
| watches map[string]*watch // Map of inotify watches (key: path) |
| paths map[int]string // Map of watched paths (key: watch descriptor) |
| done chan struct{} // Channel for sending a "quit message" to the reader goroutine |
| doneResp chan struct{} // Channel to respond to Close |
| } |
| |
| // NewWatcher establishes a new watcher with the underlying OS and begins waiting for events. |
| func NewWatcher() (*Watcher, error) { |
| // Create inotify fd |
| fd, errno := syscall.InotifyInit() |
| if fd == -1 { |
| return nil, errno |
| } |
| // Create epoll |
| poller, err := newFdPoller(fd) |
| if err != nil { |
| syscall.Close(fd) |
| return nil, err |
| } |
| w := &Watcher{ |
| fd: fd, |
| poller: poller, |
| watches: make(map[string]*watch), |
| paths: make(map[int]string), |
| Events: make(chan Event), |
| Errors: make(chan error), |
| done: make(chan struct{}), |
| doneResp: make(chan struct{}), |
| } |
| |
| go w.readEvents() |
| return w, nil |
| } |
| |
| func (w *Watcher) isClosed() bool { |
| select { |
| case <-w.done: |
| return true |
| default: |
| return false |
| } |
| } |
| |
| // Close removes all watches and closes the events channel. |
| func (w *Watcher) Close() error { |
| if w.isClosed() { |
| return nil |
| } |
| |
| // Send 'close' signal to goroutine, and set the Watcher to closed. |
| close(w.done) |
| |
| // Wake up goroutine |
| w.poller.wake() |
| |
| // Wait for goroutine to close |
| <-w.doneResp |
| |
| return nil |
| } |
| |
| // Add starts watching the named file or directory (non-recursively). |
| func (w *Watcher) Add(name string) error { |
| name = filepath.Clean(name) |
| if w.isClosed() { |
| return errors.New("inotify instance already closed") |
| } |
| |
| const agnosticEvents = syscall.IN_MOVED_TO | syscall.IN_MOVED_FROM | |
| syscall.IN_CREATE | syscall.IN_ATTRIB | syscall.IN_MODIFY | |
| syscall.IN_MOVE_SELF | syscall.IN_DELETE | syscall.IN_DELETE_SELF |
| |
| var flags uint32 = agnosticEvents |
| |
| w.mu.Lock() |
| watchEntry, found := w.watches[name] |
| w.mu.Unlock() |
| if found { |
| watchEntry.flags |= flags |
| flags |= syscall.IN_MASK_ADD |
| } |
| wd, errno := syscall.InotifyAddWatch(w.fd, name, flags) |
| if wd == -1 { |
| return errno |
| } |
| |
| w.mu.Lock() |
| w.watches[name] = &watch{wd: uint32(wd), flags: flags} |
| w.paths[wd] = name |
| w.mu.Unlock() |
| |
| return nil |
| } |
| |
| // Remove stops watching the named file or directory (non-recursively). |
| func (w *Watcher) Remove(name string) error { |
| name = filepath.Clean(name) |
| |
| // Fetch the watch. |
| w.mu.Lock() |
| defer w.mu.Unlock() |
| watch, ok := w.watches[name] |
| |
| // Remove it from inotify. |
| if !ok { |
| return fmt.Errorf("can't remove non-existent inotify watch for: %s", name) |
| } |
| // inotify_rm_watch will return EINVAL if the file has been deleted; |
| // the inotify will already have been removed. |
| // That means we can safely delete it from our watches, whatever inotify_rm_watch does. |
| delete(w.watches, name) |
| success, errno := syscall.InotifyRmWatch(w.fd, watch.wd) |
| if success == -1 { |
| // TODO: Perhaps it's not helpful to return an error here in every case. |
| // the only two possible errors are: |
| // EBADF, which happens when w.fd is not a valid file descriptor of any kind. |
| // EINVAL, which is when fd is not an inotify descriptor or wd is not a valid watch descriptor. |
| // Watch descriptors are invalidated when they are removed explicitly or implicitly; |
| // explicitly by inotify_rm_watch, implicitly when the file they are watching is deleted. |
| return errno |
| } |
| return nil |
| } |
| |
| type watch struct { |
| wd uint32 // Watch descriptor (as returned by the inotify_add_watch() syscall) |
| flags uint32 // inotify flags of this watch (see inotify(7) for the list of valid flags) |
| } |
| |
| // readEvents reads from the inotify file descriptor, converts the |
| // received events into Event objects and sends them via the Events channel |
| func (w *Watcher) readEvents() { |
| var ( |
| buf [syscall.SizeofInotifyEvent * 4096]byte // Buffer for a maximum of 4096 raw events |
| n int // Number of bytes read with read() |
| errno error // Syscall errno |
| ok bool // For poller.wait |
| ) |
| |
| defer close(w.doneResp) |
| defer close(w.Errors) |
| defer close(w.Events) |
| defer syscall.Close(w.fd) |
| defer w.poller.close() |
| |
| for { |
| // See if we have been closed. |
| if w.isClosed() { |
| return |
| } |
| |
| ok, errno = w.poller.wait() |
| if errno != nil { |
| select { |
| case w.Errors <- errno: |
| case <-w.done: |
| return |
| } |
| continue |
| } |
| |
| if !ok { |
| continue |
| } |
| |
| n, errno = syscall.Read(w.fd, buf[:]) |
| // If a signal interrupted execution, see if we've been asked to close, and try again. |
| // http://man7.org/linux/man-pages/man7/signal.7.html : |
| // "Before Linux 3.8, reads from an inotify(7) file descriptor were not restartable" |
| if errno == syscall.EINTR { |
| continue |
| } |
| |
| // syscall.Read might have been woken up by Close. If so, we're done. |
| if w.isClosed() { |
| return |
| } |
| |
| if n < syscall.SizeofInotifyEvent { |
| var err error |
| if n == 0 { |
| // If EOF is received. This should really never happen. |
| err = io.EOF |
| } else if n < 0 { |
| // If an error occured while reading. |
| err = errno |
| } else { |
| // Read was too short. |
| err = errors.New("notify: short read in readEvents()") |
| } |
| select { |
| case w.Errors <- err: |
| case <-w.done: |
| return |
| } |
| continue |
| } |
| |
| var offset uint32 |
| // We don't know how many events we just read into the buffer |
| // While the offset points to at least one whole event... |
| for offset <= uint32(n-syscall.SizeofInotifyEvent) { |
| // Point "raw" to the event in the buffer |
| raw := (*syscall.InotifyEvent)(unsafe.Pointer(&buf[offset])) |
| |
| mask := uint32(raw.Mask) |
| nameLen := uint32(raw.Len) |
| // If the event happened to the watched directory or the watched file, the kernel |
| // doesn't append the filename to the event, but we would like to always fill the |
| // the "Name" field with a valid filename. We retrieve the path of the watch from |
| // the "paths" map. |
| w.mu.Lock() |
| name := w.paths[int(raw.Wd)] |
| w.mu.Unlock() |
| if nameLen > 0 { |
| // Point "bytes" at the first byte of the filename |
| bytes := (*[syscall.PathMax]byte)(unsafe.Pointer(&buf[offset+syscall.SizeofInotifyEvent])) |
| // The filename is padded with NULL bytes. TrimRight() gets rid of those. |
| name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000") |
| } |
| |
| event := newEvent(name, mask) |
| |
| // Send the events that are not ignored on the events channel |
| if !event.ignoreLinux(mask) { |
| select { |
| case w.Events <- event: |
| case <-w.done: |
| return |
| } |
| } |
| |
| // Move to the next event in the buffer |
| offset += syscall.SizeofInotifyEvent + nameLen |
| } |
| } |
| } |
| |
| // Certain types of events can be "ignored" and not sent over the Events |
| // channel. Such as events marked ignore by the kernel, or MODIFY events |
| // against files that do not exist. |
| func (e *Event) ignoreLinux(mask uint32) bool { |
| // Ignore anything the inotify API says to ignore |
| if mask&syscall.IN_IGNORED == syscall.IN_IGNORED { |
| return true |
| } |
| |
| // If the event is not a DELETE or RENAME, the file must exist. |
| // Otherwise the event is ignored. |
| // *Note*: this was put in place because it was seen that a MODIFY |
| // event was sent after the DELETE. This ignores that MODIFY and |
| // assumes a DELETE will come or has come if the file doesn't exist. |
| if !(e.Op&Remove == Remove || e.Op&Rename == Rename) { |
| _, statErr := os.Lstat(e.Name) |
| return os.IsNotExist(statErr) |
| } |
| return false |
| } |
| |
| // newEvent returns an platform-independent Event based on an inotify mask. |
| func newEvent(name string, mask uint32) Event { |
| e := Event{Name: name} |
| if mask&syscall.IN_CREATE == syscall.IN_CREATE || mask&syscall.IN_MOVED_TO == syscall.IN_MOVED_TO { |
| e.Op |= Create |
| } |
| if mask&syscall.IN_DELETE_SELF == syscall.IN_DELETE_SELF || mask&syscall.IN_DELETE == syscall.IN_DELETE { |
| e.Op |= Remove |
| } |
| if mask&syscall.IN_MODIFY == syscall.IN_MODIFY { |
| e.Op |= Write |
| } |
| if mask&syscall.IN_MOVE_SELF == syscall.IN_MOVE_SELF || mask&syscall.IN_MOVED_FROM == syscall.IN_MOVED_FROM { |
| e.Op |= Rename |
| } |
| if mask&syscall.IN_ATTRIB == syscall.IN_ATTRIB { |
| e.Op |= Chmod |
| } |
| return e |
| } |