--- /dev/null
+// 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"
+ "unsafe"
+
+ "golang.org/x/sys/unix"
+)
+
+// 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 := unix.InotifyInit1(unix.IN_CLOEXEC)
+ if fd == -1 {
+ return nil, errno
+ }
+ // Create epoll
+ poller, err := newFdPoller(fd)
+ if err != nil {
+ unix.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 = unix.IN_MOVED_TO | unix.IN_MOVED_FROM |
+ unix.IN_CREATE | unix.IN_ATTRIB | unix.IN_MODIFY |
+ unix.IN_MOVE_SELF | unix.IN_DELETE | unix.IN_DELETE_SELF
+
+ var flags uint32 = agnosticEvents
+
+ w.mu.Lock()
+ defer w.mu.Unlock()
+ watchEntry := w.watches[name]
+ if watchEntry != nil {
+ flags |= watchEntry.flags | unix.IN_MASK_ADD
+ }
+ wd, errno := unix.InotifyAddWatch(w.fd, name, flags)
+ if wd == -1 {
+ return errno
+ }
+
+ if watchEntry == nil {
+ w.watches[name] = &watch{wd: uint32(wd), flags: flags}
+ w.paths[wd] = name
+ } else {
+ watchEntry.wd = uint32(wd)
+ watchEntry.flags = flags
+ }
+
+ 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)
+ }
+
+ // We successfully removed the watch if InotifyRmWatch doesn't return an
+ // error, we need to clean up our internal state to ensure it matches
+ // inotify's kernel state.
+ delete(w.paths, int(watch.wd))
+ delete(w.watches, name)
+
+ // inotify_rm_watch will return EINVAL if the file has been deleted;
+ // the inotify will already have been removed.
+ // watches and pathes are deleted in ignoreLinux() implicitly and asynchronously
+ // by calling inotify_rm_watch() below. e.g. readEvents() goroutine receives IN_IGNORE
+ // so that EINVAL means that the wd is being rm_watch()ed or its file removed
+ // by another thread and we have not received IN_IGNORE event.
+ success, errno := unix.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 [unix.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 unix.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 = unix.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 == unix.EINTR {
+ continue
+ }
+
+ // unix.Read might have been woken up by Close. If so, we're done.
+ if w.isClosed() {
+ return
+ }
+
+ if n < unix.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 occurred 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-unix.SizeofInotifyEvent) {
+ // Point "raw" to the event in the buffer
+ raw := (*unix.InotifyEvent)(unsafe.Pointer(&buf[offset]))
+
+ mask := uint32(raw.Mask)
+ nameLen := uint32(raw.Len)
+
+ if mask&unix.IN_Q_OVERFLOW != 0 {
+ select {
+ case w.Errors <- ErrEventOverflow:
+ case <-w.done:
+ return
+ }
+ }
+
+ // 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, ok := w.paths[int(raw.Wd)]
+ // IN_DELETE_SELF occurs when the file/directory being watched is removed.
+ // This is a sign to clean up the maps, otherwise we are no longer in sync
+ // with the inotify kernel state which has already deleted the watch
+ // automatically.
+ if ok && mask&unix.IN_DELETE_SELF == unix.IN_DELETE_SELF {
+ delete(w.paths, int(raw.Wd))
+ delete(w.watches, name)
+ }
+ w.mu.Unlock()
+
+ if nameLen > 0 {
+ // Point "bytes" at the first byte of the filename
+ bytes := (*[unix.PathMax]byte)(unsafe.Pointer(&buf[offset+unix.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 += unix.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&unix.IN_IGNORED == unix.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&unix.IN_CREATE == unix.IN_CREATE || mask&unix.IN_MOVED_TO == unix.IN_MOVED_TO {
+ e.Op |= Create
+ }
+ if mask&unix.IN_DELETE_SELF == unix.IN_DELETE_SELF || mask&unix.IN_DELETE == unix.IN_DELETE {
+ e.Op |= Remove
+ }
+ if mask&unix.IN_MODIFY == unix.IN_MODIFY {
+ e.Op |= Write
+ }
+ if mask&unix.IN_MOVE_SELF == unix.IN_MOVE_SELF || mask&unix.IN_MOVED_FROM == unix.IN_MOVED_FROM {
+ e.Op |= Rename
+ }
+ if mask&unix.IN_ATTRIB == unix.IN_ATTRIB {
+ e.Op |= Chmod
+ }
+ return e
+}
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