path: root/Godeps/_workspace/src/github.com/rjeczalik/notify/watcher_trigger.go

// Copyright (c) 2014-2015 The Notify Authors. All rights reserved.
// Use of this source code is governed by the MIT license that can be
// found in the LICENSE file.

// +build darwin,kqueue dragonfly freebsd netbsd openbsd solaris

// watcher_trigger is used for FEN and kqueue which behave similarly:
// only files and dirs can be watched directly, but not files inside dirs.
// As a result Create events have to be generated by implementation when
// after Write event is returned for watched dir, it is rescanned and Create
// event is returned for new files and these are automatically added
// to watchlist. In case of removal of watched directory, native system returns
// events for all files, but for Rename, they also need to be generated.
// As a result native system works as something like trigger for rescan,
// but contains additional data about dir in which changes occurred. For files
// detailed data is returned.
// Usage of watcher_trigger requires:
// - trigger implementation,
// - encode func,
// - not2nat, nat2not maps.
// Required manual operations on filesystem can lead to loss of precision.

package notify

import (
    "os"
    "path/filepath"
    "strings"
    "sync"
    "syscall"
)

// trigger is to be implemented by platform implementation like FEN or kqueue.
type trigger interface {
    // Close closes watcher's main native file descriptor.
    Close() error
    // Stop waiting for new events.
    Stop() error
    // Create new instance of watched.
    NewWatched(string, os.FileInfo) (*watched, error)
    // Record internally new *watched instance.
    Record(*watched)
    // Del removes internal copy of *watched instance.
    Del(*watched)
    // Watched returns *watched instance and native events for native type.
    Watched(interface{}) (*watched, int64, error)
    // Init initializes native watcher call.
    Init() error
    // Watch starts watching provided file/dir.
    Watch(os.FileInfo, *watched, int64) error
    // Unwatch stops watching provided file/dir.
    Unwatch(*watched) error
    // Wait for new events.
    Wait() (interface{}, error)
    // IsStop checks if Wait finished because of request watcher's stop.
    IsStop(n interface{}, err error) bool
}

// encode Event to native representation. Implementation is to be provided by
// platform specific implementation.
var encode func(Event) int64

var (
    // nat2not matches native events to notify's ones. To be initialized by
    // platform dependent implementation.
    nat2not map[Event]Event
    // not2nat matches notify's events to native ones. To be initialized by
    // platform dependent implementation.
    not2nat map[Event]Event
)

// trg is a main structure implementing watcher.
type trg struct {
    sync.Mutex
    // s is a channel used to stop monitoring.
    s chan struct{}
    // c is a channel used to pass events further.
    c chan<- EventInfo
    // pthLkp is a data structure mapping file names with data about watching
    // represented by them files/directories.
    pthLkp map[string]*watched
    // t is a platform dependent implementation of trigger.
    t trigger
}

// newWatcher returns new watcher's implementation.
func newWatcher(c chan<- EventInfo) watcher {
    t := &trg{
        s:      make(chan struct{}, 1),
        pthLkp: make(map[string]*watched, 0),
        c:      c,
    }
    t.t = newTrigger(t.pthLkp)
    if err := t.t.Init(); err != nil {
        panic(err)
    }
    go t.monitor()
    return t
}

// Close implements watcher.
func (t *trg) Close() (err error) {
    t.Lock()
    if err = t.t.Stop(); err != nil {
        t.Unlock()
        return
    }
    <-t.s
    var e error
    for _, w := range t.pthLkp {
        if e = t.unwatch(w.p, w.fi); e != nil {
            dbgprintf("trg: unwatch %q failed: %q\n", w.p, e)
            err = nonil(err, e)
        }
    }
    if e = t.t.Close(); e != nil {
        dbgprintf("trg: closing native watch failed: %q\n", e)
        err = nonil(err, e)
    }
    t.Unlock()
    return
}

// send reported events one by one through chan.
func (t *trg) send(evn []event) {
    for i := range evn {
        t.c <- &evn[i]
    }
}

// singlewatch starts to watch given p file/directory.
func (t *trg) singlewatch(p string, e Event, direct mode, fi os.FileInfo) (err error) {
    w, ok := t.pthLkp[p]
    if !ok {
        if w, err = t.t.NewWatched(p, fi); err != nil {
            return
        }
    }
    switch direct {
    case dir:
        w.eDir |= e
    case ndir:
        w.eNonDir |= e
    case both:
        w.eDir |= e
        w.eNonDir |= e
    }
    var ee int64
    // Native Write event is added to wait for Create events (Write event on
    // directory triggers it's rescan).
    if e&Create != 0 && fi.IsDir() {
        ee = int64(not2nat[Write])
    }
    if err = t.t.Watch(fi, w, encode(w.eDir|w.eNonDir)|ee); err != nil {
        return
    }
    if !ok {
        t.t.Record(w)
        return nil
    }
    return errAlreadyWatched
}

// decode converts event received from native to notify.Event
// representation taking into account requested events (w).
func decode(o int64, w Event) (e Event) {
    for f, n := range nat2not {
        if o&int64(f) != 0 {
            if w&f != 0 {
                e |= f
            }
            if w&n != 0 {
                e |= n
            }
        }
    }

    return
}

func (t *trg) watch(p string, e Event, fi os.FileInfo) error {
    if err := t.singlewatch(p, e, dir, fi); err != nil {
        if err != errAlreadyWatched {
            return nil
        }
    }
    if fi.IsDir() {
        err := t.walk(p, func(fi os.FileInfo) (err error) {
            if err = t.singlewatch(filepath.Join(p, fi.Name()), e, ndir,
                fi); err != nil {
                if err != errAlreadyWatched {
                    return
                }
            }
            return nil
        })
        if err != nil {
            return err
        }
    }
    return nil
}

// walk runs f func on each file/dir from p directory.
func (t *trg) walk(p string, fn func(os.FileInfo) error) error {
    fp, err := os.Open(p)
    if err != nil {
        return err
    }
    ls, err := fp.Readdir(0)
    fp.Close()
    if err != nil {
        return err
    }
    for i := range ls {
        if err := fn(ls[i]); err != nil {
            return err
        }
    }
    return nil
}

func (t *trg) unwatch(p string, fi os.FileInfo) error {
    if fi.IsDir() {
        err := t.walk(p, func(fi os.FileInfo) error {
            err := t.singleunwatch(filepath.Join(p, fi.Name()), ndir)
            if err != errNotWatched {
                return err
            }
            return nil
        })
        if err != nil {
            return err
        }
    }
    return t.singleunwatch(p, dir)
}

// Watch implements Watcher interface.
func (t *trg) Watch(p string, e Event) error {
    fi, err := os.Stat(p)
    if err != nil {
        return err
    }
    t.Lock()
    err = t.watch(p, e, fi)
    t.Unlock()
    return err
}

// Unwatch implements Watcher interface.
func (t *trg) Unwatch(p string) error {
    fi, err := os.Stat(p)
    if err != nil {
        return err
    }
    t.Lock()
    err = t.unwatch(p, fi)
    t.Unlock()
    return err
}

// Rewatch implements Watcher interface.
//
// TODO(rjeczalik): This is a naive hack. Rewrite might help.
func (t *trg) Rewatch(p string, _, e Event) error {
    fi, err := os.Stat(p)
    if err != nil {
        return err
    }
    t.Lock()
    if err = t.unwatch(p, fi); err == nil {
        // TODO(rjeczalik): If watch fails then we leave trigger in inconsistent
        // state. Handle? Panic? Native version of rewatch?
        err = t.watch(p, e, fi)
    }
    t.Unlock()
    return nil
}

func (*trg) file(w *watched, n interface{}, e Event) (evn []event) {
    evn = append(evn, event{w.p, e, w.fi.IsDir(), n})
    return
}

func (t *trg) dir(w *watched, n interface{}, e, ge Event) (evn []event) {
    // If it's dir and delete we have to send it and continue, because
    // other processing relies on opening (in this case not existing) dir.
    // Events for contents of this dir are reported by native impl.
    // However events for rename must be generated for all monitored files
    // inside of moved directory, because native impl does not report it independently
    // for each file descriptor being moved in result of move action on
    // parent dirLiczba dostępnych dni urlopowych: 0ectory.
    if (ge & (not2nat[Rename] | not2nat[Remove])) != 0 {
        // Write is reported also for Remove on directory. Because of that
        // we have to filter it out explicitly.
        evn = append(evn, event{w.p, e & ^Write & ^not2nat[Write], true, n})
        if ge&not2nat[Rename] != 0 {
            for p := range t.pthLkp {
                if strings.HasPrefix(p, w.p+string(os.PathSeparator)) {
                    if err := t.singleunwatch(p, both); err != nil && err != errNotWatched &&
                        !os.IsNotExist(err) {
                        dbgprintf("trg: failed stop watching moved file (%q): %q\n",
                            p, err)
                    }
                    if (w.eDir|w.eNonDir)&(not2nat[Rename]|Rename) != 0 {
                        evn = append(evn, event{
                            p, (w.eDir | w.eNonDir) & e &^ Write &^ not2nat[Write],
                            w.fi.IsDir(), nil,
                        })
                    }
                }
            }
        }
        t.t.Del(w)
        return
    }
    if (ge & not2nat[Write]) != 0 {
        switch err := t.walk(w.p, func(fi os.FileInfo) error {
            p := filepath.Join(w.p, fi.Name())
            switch err := t.singlewatch(p, w.eDir, ndir, fi); {
            case os.IsNotExist(err) && ((w.eDir & Remove) != 0):
                evn = append(evn, event{p, Remove, fi.IsDir(), n})
            case err == errAlreadyWatched:
            case err != nil:
                dbgprintf("trg: watching %q failed: %q", p, err)
            case (w.eDir & Create) != 0:
                evn = append(evn, event{p, Create, fi.IsDir(), n})
            default:
            }
            return nil
        }); {
        case os.IsNotExist(err):
            return
        case err != nil:
            dbgprintf("trg: dir processing failed: %q", err)
        default:
        }
    }
    return
}

type mode uint

const (
    dir mode = iota
    ndir
    both
)

// unwatch stops watching p file/directory.
func (t *trg) singleunwatch(p string, direct mode) error {
    w, ok := t.pthLkp[p]
    if !ok {
        return errNotWatched
    }
    switch direct {
    case dir:
        w.eDir = 0
    case ndir:
        w.eNonDir = 0
    case both:
        w.eDir, w.eNonDir = 0, 0
    }
    if err := t.t.Unwatch(w); err != nil {
        return err
    }
    if w.eNonDir|w.eDir != 0 {
        mod := dir
        if w.eNonDir == 0 {
            mod = ndir
        }
        if err := t.singlewatch(p, w.eNonDir|w.eDir, mod,
            w.fi); err != nil && err != errAlreadyWatched {
            return err
        }
    } else {
        t.t.Del(w)
    }
    return nil
}

func (t *trg) monitor() {
    var (
        n   interface{}
        err error
    )
    for {
        switch n, err = t.t.Wait(); {
        case err == syscall.EINTR:
        case t.t.IsStop(n, err):
            t.s <- struct{}{}
            return
        case err != nil:
            dbgprintf("trg: failed to read events: %q\n", err)
        default:
            t.send(t.process(n))
        }
    }
}

// process event returned by port_get call.
func (t *trg) process(n interface{}) (evn []event) {
    t.Lock()
    w, ge, err := t.t.Watched(n)
    if err != nil {
        t.Unlock()
        dbgprintf("trg: %v event lookup failed: %q", Event(ge), err)
        return
    }

    e := decode(ge, w.eDir|w.eNonDir)
    if ge&int64(not2nat[Remove]|not2nat[Rename]) == 0 {
        switch fi, err := os.Stat(w.p); {
        case err != nil:
        default:
            if err = t.t.Watch(fi, w, (encode(w.eDir | w.eNonDir))); err != nil {
                dbgprintf("trg: %q is no longer watched: %q", w.p, err)
                t.t.Del(w)
            }
        }
    }
    if e == Event(0) {
        t.Unlock()
        return
    }

    if w.fi.IsDir() {
        evn = append(evn, t.dir(w, n, e, Event(ge))...)
    } else {
        evn = append(evn, t.file(w, n, e)...)
    }
    if Event(ge)&(not2nat[Remove]|not2nat[Rename]) != 0 {
        t.t.Del(w)
    }
    t.Unlock()
    return
}