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