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trigger.go
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trigger.go
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//
// DISCLAIMER
//
// Copyright 2018 ArangoDB GmbH, Cologne, Germany
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Copyright holder is ArangoDB GmbH, Cologne, Germany
//
// Author Ewout Prangsma
//
package trigger
import "sync"
// Trigger is a synchronization utility used to wait (in a select statement)
// until someone triggers it.
type Trigger struct {
mu sync.Mutex
done chan struct{}
pendingTriggers int
}
// Done returns the channel to use in a select case.
// This channel is closed when someone calls Trigger.
func (t *Trigger) Done() <-chan struct{} {
t.mu.Lock()
defer t.mu.Unlock()
if t.done == nil {
t.done = make(chan struct{})
}
if t.pendingTriggers > 0 {
t.pendingTriggers = 0
d := t.done
close(t.done)
t.done = nil
return d
}
return t.done
}
// Trigger closes any Done channel.
func (t *Trigger) Trigger() {
t.mu.Lock()
defer t.mu.Unlock()
t.pendingTriggers++
if t.done != nil {
close(t.done)
t.done = nil
}
}