355 lines
8.7 KiB
Go
355 lines
8.7 KiB
Go
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// Copyright (c) 2014-2015 The Notify Authors. All rights reserved.
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// Use of this source code is governed by the MIT license that can be
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// found in the LICENSE file.
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package notify
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import "sync"
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// watchAdd TODO(rjeczalik)
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func watchAdd(nd node, c chan<- EventInfo, e Event) eventDiff {
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diff := nd.Watch.Add(c, e)
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if wp := nd.Child[""].Watch; len(wp) != 0 {
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e = wp.Total()
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diff[0] |= e
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diff[1] |= e
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if diff[0] == diff[1] {
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return none
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}
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}
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return diff
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}
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// watchAddInactive TODO(rjeczalik)
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func watchAddInactive(nd node, c chan<- EventInfo, e Event) eventDiff {
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wp := nd.Child[""].Watch
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if wp == nil {
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wp = make(watchpoint)
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nd.Child[""] = node{Watch: wp}
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}
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diff := wp.Add(c, e)
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e = nd.Watch.Total()
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diff[0] |= e
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diff[1] |= e
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if diff[0] == diff[1] {
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return none
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}
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return diff
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}
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// watchCopy TODO(rjeczalik)
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func watchCopy(src, dst node) {
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for c, e := range src.Watch {
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if c == nil {
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continue
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}
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watchAddInactive(dst, c, e)
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}
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if wpsrc := src.Child[""].Watch; len(wpsrc) != 0 {
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wpdst := dst.Child[""].Watch
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for c, e := range wpsrc {
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if c == nil {
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continue
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}
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wpdst.Add(c, e)
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}
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}
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}
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// watchDel TODO(rjeczalik)
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func watchDel(nd node, c chan<- EventInfo, e Event) eventDiff {
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diff := nd.Watch.Del(c, e)
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if wp := nd.Child[""].Watch; len(wp) != 0 {
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diffInactive := wp.Del(c, e)
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e = wp.Total()
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// TODO(rjeczalik): add e if e != all?
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diff[0] |= diffInactive[0] | e
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diff[1] |= diffInactive[1] | e
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if diff[0] == diff[1] {
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return none
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}
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}
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return diff
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}
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// watchTotal TODO(rjeczalik)
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func watchTotal(nd node) Event {
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e := nd.Watch.Total()
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if wp := nd.Child[""].Watch; len(wp) != 0 {
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e |= wp.Total()
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}
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return e
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}
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// watchIsRecursive TODO(rjeczalik)
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func watchIsRecursive(nd node) bool {
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ok := nd.Watch.IsRecursive()
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// TODO(rjeczalik): add a test for len(wp) != 0 change the condition.
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if wp := nd.Child[""].Watch; len(wp) != 0 {
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// If a watchpoint holds inactive watchpoints, it means it's a parent
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// one, which is recursive by nature even though it may be not recursive
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// itself.
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ok = true
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}
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return ok
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}
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// recursiveTree TODO(rjeczalik)
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type recursiveTree struct {
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rw sync.RWMutex // protects root
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root root
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// TODO(rjeczalik): merge watcher + recursiveWatcher after #5 and #6
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w interface {
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watcher
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recursiveWatcher
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}
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c chan EventInfo
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}
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// newRecursiveTree TODO(rjeczalik)
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func newRecursiveTree(w recursiveWatcher, c chan EventInfo) *recursiveTree {
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t := &recursiveTree{
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root: root{nd: newnode("")},
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w: struct {
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watcher
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recursiveWatcher
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}{w.(watcher), w},
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c: c,
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}
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go t.dispatch()
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return t
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}
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// dispatch TODO(rjeczalik)
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func (t *recursiveTree) dispatch() {
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for ei := range t.c {
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dbgprintf("dispatching %v on %q", ei.Event(), ei.Path())
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go func(ei EventInfo) {
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nd, ok := node{}, false
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dir, base := split(ei.Path())
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fn := func(it node, isbase bool) error {
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if isbase {
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nd = it
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} else {
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it.Watch.Dispatch(ei, recursive)
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}
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return nil
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}
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t.rw.RLock()
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defer t.rw.RUnlock()
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// Notify recursive watchpoints found on the path.
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if err := t.root.WalkPath(dir, fn); err != nil {
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dbgprint("dispatch did not reach leaf:", err)
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return
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}
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// Notify parent watchpoint.
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nd.Watch.Dispatch(ei, 0)
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// If leaf watchpoint exists, notify it.
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if nd, ok = nd.Child[base]; ok {
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nd.Watch.Dispatch(ei, 0)
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}
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}(ei)
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}
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}
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// Watch TODO(rjeczalik)
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func (t *recursiveTree) Watch(path string, c chan<- EventInfo, events ...Event) error {
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if c == nil {
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panic("notify: Watch using nil channel")
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}
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// Expanding with empty event set is a nop.
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if len(events) == 0 {
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return nil
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}
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path, isrec, err := cleanpath(path)
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if err != nil {
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return err
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}
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eventset := joinevents(events)
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if isrec {
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eventset |= recursive
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}
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t.rw.Lock()
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defer t.rw.Unlock()
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// case 1: cur is a child
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//
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// Look for parent watch which already covers the given path.
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parent := node{}
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self := false
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err = t.root.WalkPath(path, func(nd node, isbase bool) error {
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if watchTotal(nd) != 0 {
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parent = nd
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self = isbase
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return errSkip
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}
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return nil
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})
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cur := t.root.Add(path) // add after the walk, so it's less to traverse
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if err == nil && parent.Watch != nil {
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// Parent watch found. Register inactive watchpoint, so we have enough
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// information to shrink the eventset on eventual Stop.
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// return t.resetwatchpoint(parent, parent, c, eventset|inactive)
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var diff eventDiff
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if self {
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diff = watchAdd(cur, c, eventset)
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} else {
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diff = watchAddInactive(parent, c, eventset)
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}
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switch {
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case diff == none:
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// the parent watchpoint already covers requested subtree with its
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// eventset
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case diff[0] == 0:
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// TODO(rjeczalik): cleanup this panic after implementation is stable
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panic("dangling watchpoint: " + parent.Name)
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default:
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if isrec || watchIsRecursive(parent) {
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err = t.w.RecursiveRewatch(parent.Name, parent.Name, diff[0], diff[1])
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} else {
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err = t.w.Rewatch(parent.Name, diff[0], diff[1])
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}
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if err != nil {
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watchDel(parent, c, diff.Event())
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return err
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}
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watchAdd(cur, c, eventset)
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// TODO(rjeczalik): account top-most path for c
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return nil
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}
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if !self {
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watchAdd(cur, c, eventset)
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}
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return nil
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}
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// case 2: cur is new parent
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//
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// Look for children nodes, unwatch n-1 of them and rewatch the last one.
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var children []node
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fn := func(nd node) error {
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if len(nd.Watch) == 0 {
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return nil
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}
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children = append(children, nd)
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return errSkip
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}
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switch must(cur.Walk(fn)); len(children) {
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case 0:
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// no child watches, cur holds a new watch
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case 1:
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watchAdd(cur, c, eventset) // TODO(rjeczalik): update cache c subtree root?
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watchCopy(children[0], cur)
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err = t.w.RecursiveRewatch(children[0].Name, cur.Name, watchTotal(children[0]),
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watchTotal(cur))
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if err != nil {
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// Clean inactive watchpoint. The c chan did not exist before.
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cur.Child[""] = node{}
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delete(cur.Watch, c)
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return err
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}
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return nil
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default:
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watchAdd(cur, c, eventset)
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// Copy children inactive watchpoints to the new parent.
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for _, nd := range children {
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watchCopy(nd, cur)
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}
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// Watch parent subtree.
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if err = t.w.RecursiveWatch(cur.Name, watchTotal(cur)); err != nil {
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// Clean inactive watchpoint. The c chan did not exist before.
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cur.Child[""] = node{}
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delete(cur.Watch, c)
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return err
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}
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// Unwatch children subtrees.
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var e error
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for _, nd := range children {
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if watchIsRecursive(nd) {
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e = t.w.RecursiveUnwatch(nd.Name)
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} else {
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e = t.w.Unwatch(nd.Name)
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}
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if e != nil {
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err = nonil(err, e)
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// TODO(rjeczalik): child is still watched, warn all its watchpoints
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// about possible duplicate events via Error event
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}
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}
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return err
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}
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// case 3: cur is new, alone node
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switch diff := watchAdd(cur, c, eventset); {
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case diff == none:
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// TODO(rjeczalik): cleanup this panic after implementation is stable
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panic("watch requested but no parent watchpoint found: " + cur.Name)
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case diff[0] == 0:
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if isrec {
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err = t.w.RecursiveWatch(cur.Name, diff[1])
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} else {
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err = t.w.Watch(cur.Name, diff[1])
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}
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if err != nil {
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watchDel(cur, c, diff.Event())
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return err
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}
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default:
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// TODO(rjeczalik): cleanup this panic after implementation is stable
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panic("watch requested but no parent watchpoint found: " + cur.Name)
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}
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return nil
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}
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// Stop TODO(rjeczalik)
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//
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// TODO(rjeczalik): Split parent watchpoint - transfer watches to children
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// if parent is no longer needed. This carries a risk that underlying
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// watcher calls could fail - reconsider if it's worth the effort.
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func (t *recursiveTree) Stop(c chan<- EventInfo) {
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var err error
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fn := func(nd node) (e error) {
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diff := watchDel(nd, c, all)
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switch {
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case diff == none && watchTotal(nd) == 0:
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// TODO(rjeczalik): There's no watchpoints deeper in the tree,
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// probably we should remove the nodes as well.
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return nil
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case diff == none:
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// Removing c from nd does not require shrinking its eventset.
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case diff[1] == 0:
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if watchIsRecursive(nd) {
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e = t.w.RecursiveUnwatch(nd.Name)
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} else {
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e = t.w.Unwatch(nd.Name)
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}
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default:
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if watchIsRecursive(nd) {
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e = t.w.RecursiveRewatch(nd.Name, nd.Name, diff[0], diff[1])
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} else {
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e = t.w.Rewatch(nd.Name, diff[0], diff[1])
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}
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}
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fn := func(nd node) error {
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watchDel(nd, c, all)
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return nil
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}
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err = nonil(err, e, nd.Walk(fn))
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// TODO(rjeczalik): if e != nil store dummy chan in nd.Watch just to
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// retry un/rewatching next time and/or let the user handle the failure
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// vie Error event?
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return errSkip
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}
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t.rw.Lock()
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e := t.root.Walk("", fn) // TODO(rjeczalik): use max root per c
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t.rw.Unlock()
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if e != nil {
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err = nonil(err, e)
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}
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dbgprintf("Stop(%p) error: %v\n", c, err)
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}
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// Close TODO(rjeczalik)
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func (t *recursiveTree) Close() error {
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err := t.w.Close()
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close(t.c)
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return err
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}
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