/
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.
// +build linux
package fsnotify
import (
"errors"
"fmt"
"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 // File descriptor (as returned by the inotify_init() syscall)
watches map[string]*watch // Map of inotify watches (key: path)
paths map[int]string // Map of watched paths (key: watch descriptor)
done chan bool // Channel for sending a "quit message" to the reader goroutine
isClosed bool // Set to true when Close() is first called
}
// NewWatcher establishes a new watcher with the underlying OS and begins waiting for events.
func NewWatcher() (*Watcher, error) {
fd, errno := syscall.InotifyInit()
if fd == -1 {
return nil, os.NewSyscallError("inotify_init", errno)
}
w := &Watcher{
fd: fd,
watches: make(map[string]*watch),
paths: make(map[int]string),
Events: make(chan Event),
Errors: make(chan error),
done: make(chan bool, 1),
}
go w.readEvents()
return w, nil
}
// Close removes all watches and closes the events channel.
func (w *Watcher) Close() error {
if w.isClosed {
return nil
}
w.isClosed = true
// Remove all watches
for name := range w.watches {
w.Remove(name)
}
// Send "quit" message to the reader goroutine
w.done <- true
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 os.NewSyscallError("inotify_add_watch", 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 the named file or directory (non-recursively).
func (w *Watcher) Remove(name string) error {
name = filepath.Clean(name)
w.mu.Lock()
defer w.mu.Unlock()
watch, ok := w.watches[name]
if !ok {
return fmt.Errorf("can't remove non-existent inotify watch for: %s", name)
}
success, errno := syscall.InotifyRmWatch(w.fd, watch.wd)
if success == -1 {
return os.NewSyscallError("inotify_rm_watch", errno)
}
delete(w.watches, name)
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
)
for {
// See if there is a message on the "done" channel
select {
case <-w.done:
syscall.Close(w.fd)
close(w.Events)
close(w.Errors)
return
default:
}
n, errno = syscall.Read(w.fd, buf[:])
// If EOF is received
if n == 0 {
syscall.Close(w.fd)
close(w.Events)
close(w.Errors)
return
}
if n < 0 {
w.Errors <- os.NewSyscallError("read", errno)
continue
}
if n < syscall.SizeofInotifyEvent {
w.Errors <- errors.New("inotify: short read in readEvents()")
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) {
w.Events <- event
}
// 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
}