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// 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.
package notify
// EventDiff describes a change to an event set - EventDiff[0] is an old state,
// while EventDiff[1] is a new state. If event set has not changed (old == new),
// functions typically return the None value.
type eventDiff [2]Event
func (diff eventDiff) Event() Event {
return diff[1] &^ diff[0]
}
// Watchpoint
//
// The nil key holds total event set - logical sum for all registered events.
// It speeds up computing EventDiff for Add method.
//
// The rec key holds an event set for a watchpoints created by RecursiveWatch
// for a Watcher implementation which is not natively recursive.
type watchpoint map[chan<- EventInfo]Event
// None is an empty event diff, think null object.
var none eventDiff
// rec is just a placeholder
var rec = func() (ch chan<- EventInfo) {
ch = make(chan<- EventInfo)
close(ch)
return
}()
func (wp watchpoint) dryAdd(ch chan<- EventInfo, e Event) eventDiff {
if e &^= internal; wp[ch]&e == e {
return none
}
total := wp[ch] &^ internal
return eventDiff{total, total | e}
}
// Add assumes neither c nor e are nil or zero values.
func (wp watchpoint) Add(c chan<- EventInfo, e Event) (diff eventDiff) {
wp[c] |= e
diff[0] = wp[nil]
diff[1] = diff[0] | e
wp[nil] = diff[1] &^ omit
// Strip diff from internal events.
diff[0] &^= internal
diff[1] &^= internal
if diff[0] == diff[1] {
return none
}
return
}
func (wp watchpoint) Del(c chan<- EventInfo, e Event) (diff eventDiff) {
wp[c] &^= e
if wp[c] == 0 {
delete(wp, c)
}
diff[0] = wp[nil]
delete(wp, nil)
if len(wp) != 0 {
// Recalculate total event set.
for _, e := range wp {
diff[1] |= e
}
wp[nil] = diff[1] &^ omit
}
// Strip diff from internal events.
diff[0] &^= internal
diff[1] &^= internal
if diff[0] == diff[1] {
return none
}
return
}
func (wp watchpoint) Dispatch(ei EventInfo, extra Event) {
e := eventmask(ei, extra)
if !matches(wp[nil], e) {
return
}
for ch, eset := range wp {
if ch != nil && matches(eset, e) {
select {
case ch <- ei:
default: // Drop event if receiver is too slow
dbgprintf("dropped %s on %q: receiver too slow", ei.Event(), ei.Path())
}
}
}
}
func (wp watchpoint) Total() Event {
return wp[nil] &^ internal
}
func (wp watchpoint) IsRecursive() bool {
return wp[nil]&recursive != 0
}
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