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Diffstat (limited to 'src/inotify/inotify_linux.go')
| -rw-r--r-- | src/inotify/inotify_linux.go | 300 |
1 files changed, 300 insertions, 0 deletions
diff --git a/src/inotify/inotify_linux.go b/src/inotify/inotify_linux.go new file mode 100644 index 0000000..41ac558 --- /dev/null +++ b/src/inotify/inotify_linux.go @@ -0,0 +1,300 @@ +// 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. + +/* +Package inotify implements a wrapper for the Linux inotify system. + +Example: + watcher, err := inotify.NewWatcher() + if err != nil { + log.Fatal(err) + } + err = watcher.Watch("/tmp") + if err != nil { + log.Fatal(err) + } + for { + select { + case ev := <-watcher.Event: + log.Println("event:", ev) + case err := <-watcher.Error: + log.Println("error:", err) + } + } + +*/ +package inotify + +import ( + "errors" + "fmt" + "os" + "strings" + "sync" + "syscall" + "unsafe" +) + +type Event struct { + Mask uint32 // Mask of events + Cookie uint32 // Unique cookie associating related events (for rename(2)) + Name string // File name (optional) +} + +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) +} + +type Watcher struct { + mu sync.Mutex + 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) + Error chan error // Errors are sent on this channel + Event chan *Event // Events are returned on this channel + done chan bool // Channel for sending a "quit message" to the reader goroutine + isClosed bool // Set to true when Close() is first called +} + +// NewWatcher creates and returns a new inotify instance using inotify_init(2) +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), + Event: make(chan *Event), + Error: make(chan error), + done: make(chan bool, 1), + } + + go w.readEvents() + return w, nil +} + +// Close closes an inotify watcher instance +// It sends a message to the reader goroutine to quit and removes all watches +// associated with the inotify instance +func (w *Watcher) Close() error { + if w.isClosed { + return nil + } + w.isClosed = true + + // Send "quit" message to the reader goroutine + w.done <- true + for path := range w.watches { + w.RemoveWatch(path) + } + + return nil +} + +// AddWatch adds path to the watched file set. +// The flags are interpreted as described in inotify_add_watch(2). +func (w *Watcher) AddWatch(path string, flags uint32) error { + if w.isClosed { + return errors.New("inotify instance already closed") + } + + watchEntry, found := w.watches[path] + if found { + watchEntry.flags |= flags + flags |= syscall.IN_MASK_ADD + } + + w.mu.Lock() // synchronize with readEvents goroutine + + wd, err := syscall.InotifyAddWatch(w.fd, path, flags) + if err != nil { + w.mu.Unlock() + return &os.PathError{ + Op: "inotify_add_watch", + Path: path, + Err: err, + } + } + + if !found { + w.watches[path] = &watch{wd: uint32(wd), flags: flags} + w.paths[wd] = path + } + w.mu.Unlock() + return nil +} + +// Watch adds path to the watched file set, watching all events. +func (w *Watcher) Watch(path string) error { + return w.AddWatch(path, IN_ALL_EVENTS) +} + +// RemoveWatch removes path from the watched file set. +func (w *Watcher) RemoveWatch(path string) error { + watch, ok := w.watches[path] + if !ok { + return errors.New(fmt.Sprintf("can't remove non-existent inotify watch for: %s", path)) + } + success, errno := syscall.InotifyRmWatch(w.fd, watch.wd) + if success == -1 { + return os.NewSyscallError("inotify_rm_watch", errno) + } + delete(w.watches, path) + return nil +} + +// readEvents reads from the inotify file descriptor, converts the +// received events into Event objects and sends them via the Event channel +func (w *Watcher) readEvents() { + var buf [syscall.SizeofInotifyEvent * 4096]byte + + for { + n, err := syscall.Read(w.fd, buf[:]) + // See if there is a message on the "done" channel + var done bool + select { + case done = <-w.done: + default: + } + + // If EOF or a "done" message is received + if n == 0 || done { + // The syscall.Close can be slow. Close + // w.Event first. + close(w.Event) + err := syscall.Close(w.fd) + if err != nil { + w.Error <- os.NewSyscallError("close", err) + } + close(w.Error) + return + } + if n < 0 { + w.Error <- os.NewSyscallError("read", err) + continue + } + if n < syscall.SizeofInotifyEvent { + w.Error <- errors.New("inotify: short read in readEvents()") + continue + } + + var offset uint32 = 0 + // 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])) + event := new(Event) + event.Mask = uint32(raw.Mask) + event.Cookie = uint32(raw.Cookie) + 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() + event.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 NUL bytes. TrimRight() gets rid of those. + event.Name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000") + } + // Send the event on the events channel + w.Event <- event + + // Move to the next event in the buffer + offset += syscall.SizeofInotifyEvent + nameLen + } + } +} + +// String formats the event e in the form +// "filename: 0xEventMask = IN_ACCESS|IN_ATTRIB_|..." +func (e *Event) String() string { + var events string = "" + + m := e.Mask + for _, b := range eventBits { + if m&b.Value == b.Value { + m &^= b.Value + events += "|" + b.Name + } + } + + if m != 0 { + events += fmt.Sprintf("|%#x", m) + } + if len(events) > 0 { + events = " == " + events[1:] + } + + return fmt.Sprintf("%q: %#x%s", e.Name, e.Mask, events) +} + +const ( + // Options for inotify_init() are not exported + // IN_CLOEXEC uint32 = syscall.IN_CLOEXEC + // IN_NONBLOCK uint32 = syscall.IN_NONBLOCK + + // Options for AddWatch + IN_DONT_FOLLOW uint32 = syscall.IN_DONT_FOLLOW + IN_ONESHOT uint32 = syscall.IN_ONESHOT + IN_ONLYDIR uint32 = syscall.IN_ONLYDIR + + // The "IN_MASK_ADD" option is not exported, as AddWatch + // adds it automatically, if there is already a watch for the given path + // IN_MASK_ADD uint32 = syscall.IN_MASK_ADD + + // Events + IN_ACCESS uint32 = syscall.IN_ACCESS + IN_ALL_EVENTS uint32 = syscall.IN_ALL_EVENTS + IN_ATTRIB uint32 = syscall.IN_ATTRIB + IN_CLOSE uint32 = syscall.IN_CLOSE + IN_CLOSE_NOWRITE uint32 = syscall.IN_CLOSE_NOWRITE + IN_CLOSE_WRITE uint32 = syscall.IN_CLOSE_WRITE + IN_CREATE uint32 = syscall.IN_CREATE + IN_DELETE uint32 = syscall.IN_DELETE + IN_DELETE_SELF uint32 = syscall.IN_DELETE_SELF + IN_MODIFY uint32 = syscall.IN_MODIFY + IN_MOVE uint32 = syscall.IN_MOVE + IN_MOVED_FROM uint32 = syscall.IN_MOVED_FROM + IN_MOVED_TO uint32 = syscall.IN_MOVED_TO + IN_MOVE_SELF uint32 = syscall.IN_MOVE_SELF + IN_OPEN uint32 = syscall.IN_OPEN + + // Special events + IN_ISDIR uint32 = syscall.IN_ISDIR + IN_IGNORED uint32 = syscall.IN_IGNORED + IN_Q_OVERFLOW uint32 = syscall.IN_Q_OVERFLOW + IN_UNMOUNT uint32 = syscall.IN_UNMOUNT +) + +var eventBits = []struct { + Value uint32 + Name string +}{ + {IN_ACCESS, "IN_ACCESS"}, + {IN_ATTRIB, "IN_ATTRIB"}, + {IN_CLOSE, "IN_CLOSE"}, + {IN_CLOSE_NOWRITE, "IN_CLOSE_NOWRITE"}, + {IN_CLOSE_WRITE, "IN_CLOSE_WRITE"}, + {IN_CREATE, "IN_CREATE"}, + {IN_DELETE, "IN_DELETE"}, + {IN_DELETE_SELF, "IN_DELETE_SELF"}, + {IN_MODIFY, "IN_MODIFY"}, + {IN_MOVE, "IN_MOVE"}, + {IN_MOVED_FROM, "IN_MOVED_FROM"}, + {IN_MOVED_TO, "IN_MOVED_TO"}, + {IN_MOVE_SELF, "IN_MOVE_SELF"}, + {IN_OPEN, "IN_OPEN"}, + {IN_ISDIR, "IN_ISDIR"}, + {IN_IGNORED, "IN_IGNORED"}, + {IN_Q_OVERFLOW, "IN_Q_OVERFLOW"}, + {IN_UNMOUNT, "IN_UNMOUNT"}, +} |