forked from cerc-io/plugeth
305 lines
9.6 KiB
Go
305 lines
9.6 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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// +build linux
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package fsnotify
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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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const (
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// Options for inotify_init() are not exported
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// sys_IN_CLOEXEC uint32 = syscall.IN_CLOEXEC
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// sys_IN_NONBLOCK uint32 = syscall.IN_NONBLOCK
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// Options for AddWatch
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sys_IN_DONT_FOLLOW uint32 = syscall.IN_DONT_FOLLOW
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sys_IN_ONESHOT uint32 = syscall.IN_ONESHOT
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sys_IN_ONLYDIR uint32 = syscall.IN_ONLYDIR
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// The "sys_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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// sys_IN_MASK_ADD uint32 = syscall.IN_MASK_ADD
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// Events
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sys_IN_ACCESS uint32 = syscall.IN_ACCESS
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sys_IN_ALL_EVENTS uint32 = syscall.IN_ALL_EVENTS
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sys_IN_ATTRIB uint32 = syscall.IN_ATTRIB
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sys_IN_CLOSE uint32 = syscall.IN_CLOSE
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sys_IN_CLOSE_NOWRITE uint32 = syscall.IN_CLOSE_NOWRITE
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sys_IN_CLOSE_WRITE uint32 = syscall.IN_CLOSE_WRITE
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sys_IN_CREATE uint32 = syscall.IN_CREATE
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sys_IN_DELETE uint32 = syscall.IN_DELETE
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sys_IN_DELETE_SELF uint32 = syscall.IN_DELETE_SELF
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sys_IN_MODIFY uint32 = syscall.IN_MODIFY
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sys_IN_MOVE uint32 = syscall.IN_MOVE
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sys_IN_MOVED_FROM uint32 = syscall.IN_MOVED_FROM
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sys_IN_MOVED_TO uint32 = syscall.IN_MOVED_TO
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sys_IN_MOVE_SELF uint32 = syscall.IN_MOVE_SELF
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sys_IN_OPEN uint32 = syscall.IN_OPEN
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sys_AGNOSTIC_EVENTS = sys_IN_MOVED_TO | sys_IN_MOVED_FROM | sys_IN_CREATE | sys_IN_ATTRIB | sys_IN_MODIFY | sys_IN_MOVE_SELF | sys_IN_DELETE | sys_IN_DELETE_SELF
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// Special events
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sys_IN_ISDIR uint32 = syscall.IN_ISDIR
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sys_IN_IGNORED uint32 = syscall.IN_IGNORED
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sys_IN_Q_OVERFLOW uint32 = syscall.IN_Q_OVERFLOW
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sys_IN_UNMOUNT uint32 = syscall.IN_UNMOUNT
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)
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type FileEvent 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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// IsCreate reports whether the FileEvent was triggered by a creation
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func (e *FileEvent) IsCreate() bool {
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return (e.mask&sys_IN_CREATE) == sys_IN_CREATE || (e.mask&sys_IN_MOVED_TO) == sys_IN_MOVED_TO
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}
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// IsDelete reports whether the FileEvent was triggered by a delete
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func (e *FileEvent) IsDelete() bool {
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return (e.mask&sys_IN_DELETE_SELF) == sys_IN_DELETE_SELF || (e.mask&sys_IN_DELETE) == sys_IN_DELETE
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}
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// IsModify reports whether the FileEvent was triggered by a file modification or attribute change
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func (e *FileEvent) IsModify() bool {
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return ((e.mask&sys_IN_MODIFY) == sys_IN_MODIFY || (e.mask&sys_IN_ATTRIB) == sys_IN_ATTRIB)
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}
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// IsRename reports whether the FileEvent was triggered by a change name
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func (e *FileEvent) IsRename() bool {
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return ((e.mask&sys_IN_MOVE_SELF) == sys_IN_MOVE_SELF || (e.mask&sys_IN_MOVED_FROM) == sys_IN_MOVED_FROM)
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}
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// IsAttrib reports whether the FileEvent was triggered by a change in the file metadata.
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func (e *FileEvent) IsAttrib() bool {
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return (e.mask & sys_IN_ATTRIB) == sys_IN_ATTRIB
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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 // Map access
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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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fsnFlags map[string]uint32 // Map of watched files to flags used for filter
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fsnmut sync.Mutex // Protects access to fsnFlags.
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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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internalEvent chan *FileEvent // Events are queued on this channel
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Event chan *FileEvent // 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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fsnFlags: make(map[string]uint32),
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paths: make(map[int]string),
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internalEvent: make(chan *FileEvent),
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Event: make(chan *FileEvent),
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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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go w.purgeEvents()
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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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// Remove all watches
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for path := range w.watches {
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w.RemoveWatch(path)
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}
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// Send "quit" message to the reader goroutine
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w.done <- true
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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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w.mu.Lock()
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watchEntry, found := w.watches[path]
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w.mu.Unlock()
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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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wd, errno := syscall.InotifyAddWatch(w.fd, path, flags)
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if wd == -1 {
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return errno
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}
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w.mu.Lock()
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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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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, sys_AGNOSTIC_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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w.mu.Lock()
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defer w.mu.Unlock()
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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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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 (
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buf [syscall.SizeofInotifyEvent * 4096]byte // Buffer for a maximum of 4096 raw events
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n int // Number of bytes read with read()
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errno error // Syscall errno
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)
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for {
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// See if there is a message on the "done" channel
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select {
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case <-w.done:
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syscall.Close(w.fd)
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close(w.internalEvent)
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close(w.Error)
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return
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default:
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}
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n, errno = syscall.Read(w.fd, buf[:])
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// If EOF is received
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if n == 0 {
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syscall.Close(w.fd)
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close(w.internalEvent)
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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", errno)
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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(FileEvent)
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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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event.Name = w.paths[int(raw.Wd)]
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w.mu.Unlock()
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watchedName := event.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 events that are not ignored on the events channel
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if !event.ignoreLinux() {
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// Setup FSNotify flags (inherit from directory watch)
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w.fsnmut.Lock()
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if _, fsnFound := w.fsnFlags[event.Name]; !fsnFound {
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if fsnFlags, watchFound := w.fsnFlags[watchedName]; watchFound {
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w.fsnFlags[event.Name] = fsnFlags
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} else {
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w.fsnFlags[event.Name] = FSN_ALL
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}
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}
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w.fsnmut.Unlock()
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w.internalEvent <- 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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// Certain types of events can be "ignored" and not sent over the Event
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// channel. Such as events marked ignore by the kernel, or MODIFY events
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// against files that do not exist.
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func (e *FileEvent) ignoreLinux() bool {
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// Ignore anything the inotify API says to ignore
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if e.mask&sys_IN_IGNORED == sys_IN_IGNORED {
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return true
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}
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// If the event is not a DELETE or RENAME, the file must exist.
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// Otherwise the event is ignored.
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// *Note*: this was put in place because it was seen that a MODIFY
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// event was sent after the DELETE. This ignores that MODIFY and
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// assumes a DELETE will come or has come if the file doesn't exist.
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if !(e.IsDelete() || e.IsRename()) {
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_, statErr := os.Lstat(e.Name)
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return os.IsNotExist(statErr)
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}
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return false
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}
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