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inotify.go
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inotify.go
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// 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.
//go:build linux
// +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 {
// Store fd here as os.File.Read() will no longer return on close after
// calling Fd(). See: https://github.com/golang/go/issues/26439
fd int
Events chan Event
Errors chan error
mu sync.Mutex // Map access
inotifyFile *os.File
watches map[string]*watch // Map of inotify watches (key: path)
paths map[int]watchPath // 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
}
type watchPath struct {
path string
recurse bool
}
// NewWatcher establishes a new watcher with the underlying OS and begins waiting for events.
func NewWatcher() (*Watcher, error) {
// Create inotify fd
// Need to set the FD to nonblocking mode in order for SetDeadline methods to work
// Otherwise, blocking i/o operations won't terminate on close
fd, errno := unix.InotifyInit1(unix.IN_CLOEXEC | unix.IN_NONBLOCK)
if fd == -1 {
return nil, errno
}
w := &Watcher{
fd: fd,
inotifyFile: os.NewFile(uintptr(fd), ""),
watches: make(map[string]*watch),
paths: make(map[int]watchPath),
Events: make(chan Event),
Errors: make(chan error),
done: make(chan struct{}),
doneResp: make(chan struct{}),
}
go w.readEvents()
return w, nil
}
// Returns true if the event was sent, or false if watcher is closed.
func (w *Watcher) sendEvent(e Event) bool {
select {
case w.Events <- e:
return true
case <-w.done:
}
return false
}
// Returns true if the error was sent, or false if watcher is closed.
func (w *Watcher) sendError(err error) bool {
select {
case w.Errors <- err:
return true
case <-w.done:
}
return false
}
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 {
w.mu.Lock()
if w.isClosed() {
w.mu.Unlock()
return nil
}
// Send 'close' signal to goroutine, and set the Watcher to closed.
close(w.done)
w.mu.Unlock()
// Causes any blocking reads to return with an error, provided the file still supports deadline operations
err := w.inotifyFile.Close()
if err != nil {
return err
}
// Wait for goroutine to close
<-w.doneResp
return nil
}
// Add starts watching a file or directory.
//
// If the path is a directory then changes to that directory are watched
// non-recursively. If the path ends with "/..." changes in the entire directory
// tree are watched. ErrNotDirectory is returned when using "/..." on a file.
//
// Symlinks are not followed.
func (w *Watcher) Add(path string) error {
path = filepath.Clean(path)
if w.isClosed() {
return errors.New("inotify instance already closed")
}
path, recurse := recursivePath(path)
if recurse {
dirs, err := findDirs(path)
if err != nil {
return err
}
for _, d := range dirs {
err := w.add(d, true)
if err != nil {
return err
}
}
return nil
}
return w.add(path, false)
}
func (w *Watcher) add(path string, recurse bool) error {
var flags uint32 = 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
w.mu.Lock()
defer w.mu.Unlock()
watchEntry := w.watches[path]
if watchEntry != nil {
flags |= watchEntry.flags | unix.IN_MASK_ADD
}
wd, errno := unix.InotifyAddWatch(w.fd, path, flags)
if wd == -1 {
return errno
}
if watchEntry == nil {
w.watches[path] = &watch{wd: uint32(wd), flags: flags}
w.paths[wd] = watchPath{path: path, recurse: recurse}
} else {
watchEntry.wd = uint32(wd)
watchEntry.flags = flags
}
return nil
}
// Remove stops watching a file or directory.
//
// If a path was added recursively with "..." then it will stop watching the
// entire directory tree. You can optionally add "..."; in this case
// Remove("path") and Remove("path/...") behave identical.
//
// In other cases adding "..." will any watches in that tree (if any).
// ErrNotDirectory is returned when using "..." on a file.
func (w *Watcher) Remove(path string) error {
path = filepath.Clean(path)
// Fetch the watch.
w.mu.Lock()
defer w.mu.Unlock()
watch, ok := w.watches[path]
// Remove it from inotify.
if !ok {
return fmt.Errorf("%w: %s", ErrNonExistentWatch, path)
}
// 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, path)
// 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
}
// WatchList returns the directories and files that are being monitered.
func (w *Watcher) WatchList() []string {
w.mu.Lock()
defer w.mu.Unlock()
entries := make([]string, 0, len(w.watches))
for pathname := range w.watches {
entries = append(entries, pathname)
}
return entries
}
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
errno error // Syscall errno
)
defer close(w.doneResp)
defer close(w.Errors)
defer close(w.Events)
for {
// See if we have been closed.
if w.isClosed() {
return
}
n, err := w.inotifyFile.Read(buf[:])
switch {
case errors.Unwrap(err) == os.ErrClosed:
return
case err != nil:
if !w.sendError(err) {
return
}
continue
}
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()")
}
if !w.sendError(err) {
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) {
var (
// 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 {
if !w.sendError(ErrEventOverflow) {
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()
watchPath, ok := w.paths[int(raw.Wd)]
name := watchPath.path
// 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]))[:nameLen:nameLen]
// The filename is padded with NULL bytes. TrimRight() gets rid of those.
name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000")
}
event := w.newEvent(name, mask)
// Send the events that are not ignored on the events channel
if mask&unix.IN_IGNORED == 0 {
if !w.sendEvent(event) {
return
}
}
// Move to the next event in the buffer
offset += unix.SizeofInotifyEvent + nameLen
}
}
}
// Check if path was added as a recursive watch ("dir/...").
//
// Returns the watch for the path, or nil.
func (w *Watcher) isRecursive(path string) *watch {
ww, ok := w.watches[path]
if !ok {
// path could be a file, so also check the Dir.
path = filepath.Dir(path)
ww, ok = w.watches[path]
if !ok {
return nil
}
}
if !w.paths[int(ww.wd)].recurse {
return nil
}
return ww
}
// newEvent returns an platform-independent Event based on an inotify mask.
func (w *Watcher) 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
// Add new directories on recursive watches.
if mask&unix.IN_ISDIR == unix.IN_ISDIR {
ww := w.isRecursive(name)
if ww != nil {
//err := w.add(name, true)
err := w.Add(filepath.Join(name, "..."))
if err != nil {
// TODO: not sure if this has a nice error message.
// Also, this path could have been removed by now;
// should probably filter ENOENT or something.
w.sendError(err)
}
}
}
}
if mask&unix.IN_DELETE_SELF == unix.IN_DELETE_SELF || mask&unix.IN_DELETE == unix.IN_DELETE {
// TODO: remove recursive watches.
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_ISDIR == unix.IN_ISDIR {
// TODO: should probably remove some things as well.
// ww := w.isRecursive(name)
// if ww != nil {
// err := w.Add(filepath.Join(name, "..."))
// if err != nil {
// // TODO: not sure if this has a nice error message.
// // Also, this path could have been removed by now;
// // should probably filter ENOENT or something.
// w.sendError(err)
// }
// }
}
}
if mask&unix.IN_ATTRIB == unix.IN_ATTRIB {
e.Op |= Chmod
}
return e
}