mirror of https://github.com/k3s-io/k3s
307 lines
8.4 KiB
Go
307 lines
8.4 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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Package inotify implements a wrapper for the Linux inotify system.
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Example:
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watcher, err := inotify.NewWatcher()
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if err != nil {
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log.Fatal(err)
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}
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err = watcher.Watch("/tmp")
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if err != nil {
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log.Fatal(err)
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}
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for {
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select {
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case ev := <-watcher.Event:
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log.Println("event:", ev)
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case err := <-watcher.Error:
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log.Println("error:", err)
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}
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}
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*/
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package inotify // import "github.com/sigma/go-inotify"
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import (
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"errors"
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"fmt"
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"os"
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"strings"
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"sync"
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"syscall"
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"unsafe"
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)
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type Event struct {
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Mask uint32 // Mask of events
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Cookie uint32 // Unique cookie associating related events (for rename(2))
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Name string // File name (optional)
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}
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type watch struct {
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wd uint32 // Watch descriptor (as returned by the inotify_add_watch() syscall)
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flags uint32 // inotify flags of this watch (see inotify(7) for the list of valid flags)
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}
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type Watcher struct {
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mu sync.Mutex
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fd int // File descriptor (as returned by the inotify_init() syscall)
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watches map[string]*watch // Map of inotify watches (key: path)
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paths map[int]string // Map of watched paths (key: watch descriptor)
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Error chan error // Errors are sent on this channel
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Event chan *Event // Events are returned on this channel
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done chan bool // Channel for sending a "quit message" to the reader goroutine
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isClosed bool // Set to true when Close() is first called
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}
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// NewWatcher creates and returns a new inotify instance using inotify_init(2)
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func NewWatcher() (*Watcher, error) {
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fd, errno := syscall.InotifyInit()
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if fd == -1 {
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return nil, os.NewSyscallError("inotify_init", errno)
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}
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w := &Watcher{
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fd: fd,
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watches: make(map[string]*watch),
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paths: make(map[int]string),
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Event: make(chan *Event),
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Error: make(chan error),
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done: make(chan bool, 1),
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}
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go w.readEvents()
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return w, nil
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}
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// Close closes an inotify watcher instance
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// It sends a message to the reader goroutine to quit and removes all watches
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// associated with the inotify instance
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func (w *Watcher) Close() error {
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if w.isClosed {
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return nil
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}
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w.isClosed = true
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// Send "quit" message to the reader goroutine
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w.done <- true
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for path := range w.watches {
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w.RemoveWatch(path)
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}
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return nil
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}
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// AddWatch adds path to the watched file set.
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// The flags are interpreted as described in inotify_add_watch(2).
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func (w *Watcher) AddWatch(path string, flags uint32) error {
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if w.isClosed {
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return errors.New("inotify instance already closed")
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}
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watchEntry, found := w.watches[path]
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if found {
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watchEntry.flags |= flags
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flags |= syscall.IN_MASK_ADD
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}
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w.mu.Lock() // synchronize with readEvents goroutine
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wd, err := syscall.InotifyAddWatch(w.fd, path, flags)
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if err != nil {
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w.mu.Unlock()
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return &os.PathError{
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Op: "inotify_add_watch",
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Path: path,
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Err: err,
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}
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}
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if !found {
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w.watches[path] = &watch{wd: uint32(wd), flags: flags}
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w.paths[wd] = path
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}
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w.mu.Unlock()
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return nil
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}
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// Watch adds path to the watched file set, watching all events.
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func (w *Watcher) Watch(path string) error {
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return w.AddWatch(path, IN_ALL_EVENTS)
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}
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// RemoveWatch removes path from the watched file set.
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func (w *Watcher) RemoveWatch(path string) error {
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watch, ok := w.watches[path]
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if !ok {
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return errors.New(fmt.Sprintf("can't remove non-existent inotify watch for: %s", path))
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}
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success, errno := syscall.InotifyRmWatch(w.fd, watch.wd)
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if success == -1 {
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return os.NewSyscallError("inotify_rm_watch", errno)
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}
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delete(w.watches, path)
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// Locking here to protect the read from paths in readEvents.
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w.mu.Lock()
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delete(w.paths, int(watch.wd))
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w.mu.Unlock()
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return nil
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}
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// readEvents reads from the inotify file descriptor, converts the
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// received events into Event objects and sends them via the Event channel
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func (w *Watcher) readEvents() {
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var buf [syscall.SizeofInotifyEvent * 4096]byte
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for {
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n, err := syscall.Read(w.fd, buf[:])
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// See if there is a message on the "done" channel
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var done bool
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select {
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case done = <-w.done:
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default:
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}
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// If EOF or a "done" message is received
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if n == 0 || done {
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// The syscall.Close can be slow. Close
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// w.Event first.
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close(w.Event)
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err := syscall.Close(w.fd)
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if err != nil {
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w.Error <- os.NewSyscallError("close", err)
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}
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close(w.Error)
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return
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}
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if n < 0 {
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w.Error <- os.NewSyscallError("read", err)
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continue
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}
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if n < syscall.SizeofInotifyEvent {
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w.Error <- errors.New("inotify: short read in readEvents()")
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continue
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}
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var offset uint32 = 0
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// We don't know how many events we just read into the buffer
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// While the offset points to at least one whole event...
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for offset <= uint32(n-syscall.SizeofInotifyEvent) {
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// Point "raw" to the event in the buffer
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raw := (*syscall.InotifyEvent)(unsafe.Pointer(&buf[offset]))
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event := new(Event)
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event.Mask = uint32(raw.Mask)
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event.Cookie = uint32(raw.Cookie)
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nameLen := uint32(raw.Len)
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// If the event happened to the watched directory or the watched file, the kernel
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// doesn't append the filename to the event, but we would like to always fill the
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// the "Name" field with a valid filename. We retrieve the path of the watch from
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// the "paths" map.
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w.mu.Lock()
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name, ok := w.paths[int(raw.Wd)]
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w.mu.Unlock()
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if ok {
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event.Name = name
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if nameLen > 0 {
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// Point "bytes" at the first byte of the filename
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bytes := (*[syscall.PathMax]byte)(unsafe.Pointer(&buf[offset+syscall.SizeofInotifyEvent]))
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// The filename is padded with NUL bytes. TrimRight() gets rid of those.
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event.Name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000")
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}
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// Send the event on the events channel
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w.Event <- event
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}
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// Move to the next event in the buffer
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offset += syscall.SizeofInotifyEvent + nameLen
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}
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}
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}
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// String formats the event e in the form
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// "filename: 0xEventMask = IN_ACCESS|IN_ATTRIB_|..."
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func (e *Event) String() string {
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var events string = ""
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m := e.Mask
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for _, b := range eventBits {
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if m&b.Value == b.Value {
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m &^= b.Value
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events += "|" + b.Name
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}
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}
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if m != 0 {
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events += fmt.Sprintf("|%#x", m)
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}
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if len(events) > 0 {
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events = " == " + events[1:]
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}
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return fmt.Sprintf("%q: %#x%s", e.Name, e.Mask, events)
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}
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const (
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// Options for inotify_init() are not exported
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// IN_CLOEXEC uint32 = syscall.IN_CLOEXEC
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// IN_NONBLOCK uint32 = syscall.IN_NONBLOCK
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// Options for AddWatch
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IN_DONT_FOLLOW uint32 = syscall.IN_DONT_FOLLOW
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IN_ONESHOT uint32 = syscall.IN_ONESHOT
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IN_ONLYDIR uint32 = syscall.IN_ONLYDIR
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// The "IN_MASK_ADD" option is not exported, as AddWatch
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// adds it automatically, if there is already a watch for the given path
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// IN_MASK_ADD uint32 = syscall.IN_MASK_ADD
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// Events
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IN_ACCESS uint32 = syscall.IN_ACCESS
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IN_ALL_EVENTS uint32 = syscall.IN_ALL_EVENTS
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IN_ATTRIB uint32 = syscall.IN_ATTRIB
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IN_CLOSE uint32 = syscall.IN_CLOSE
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IN_CLOSE_NOWRITE uint32 = syscall.IN_CLOSE_NOWRITE
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IN_CLOSE_WRITE uint32 = syscall.IN_CLOSE_WRITE
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IN_CREATE uint32 = syscall.IN_CREATE
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IN_DELETE uint32 = syscall.IN_DELETE
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IN_DELETE_SELF uint32 = syscall.IN_DELETE_SELF
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IN_MODIFY uint32 = syscall.IN_MODIFY
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IN_MOVE uint32 = syscall.IN_MOVE
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IN_MOVED_FROM uint32 = syscall.IN_MOVED_FROM
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IN_MOVED_TO uint32 = syscall.IN_MOVED_TO
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IN_MOVE_SELF uint32 = syscall.IN_MOVE_SELF
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IN_OPEN uint32 = syscall.IN_OPEN
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// Special events
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IN_ISDIR uint32 = syscall.IN_ISDIR
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IN_IGNORED uint32 = syscall.IN_IGNORED
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IN_Q_OVERFLOW uint32 = syscall.IN_Q_OVERFLOW
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IN_UNMOUNT uint32 = syscall.IN_UNMOUNT
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)
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var eventBits = []struct {
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Value uint32
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Name string
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}{
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{IN_ACCESS, "IN_ACCESS"},
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{IN_ATTRIB, "IN_ATTRIB"},
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{IN_CLOSE, "IN_CLOSE"},
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{IN_CLOSE_NOWRITE, "IN_CLOSE_NOWRITE"},
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{IN_CLOSE_WRITE, "IN_CLOSE_WRITE"},
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{IN_CREATE, "IN_CREATE"},
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{IN_DELETE, "IN_DELETE"},
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{IN_DELETE_SELF, "IN_DELETE_SELF"},
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{IN_MODIFY, "IN_MODIFY"},
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{IN_MOVE, "IN_MOVE"},
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{IN_MOVED_FROM, "IN_MOVED_FROM"},
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{IN_MOVED_TO, "IN_MOVED_TO"},
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{IN_MOVE_SELF, "IN_MOVE_SELF"},
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{IN_OPEN, "IN_OPEN"},
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{IN_ISDIR, "IN_ISDIR"},
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{IN_IGNORED, "IN_IGNORED"},
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{IN_Q_OVERFLOW, "IN_Q_OVERFLOW"},
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{IN_UNMOUNT, "IN_UNMOUNT"},
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}
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