vendor/google.golang.org/grpc/internal/grpcsync/event.go

   1 /*
   2  *
   3  * Copyright 2018 gRPC authors.
   4  *
   5  * Licensed under the Apache License, Version 2.0 (the "License");
   6  * you may not use this file except in compliance with the License.
   7  * You may obtain a copy of the License at
   8  *
   9  *     http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software
  12  * distributed under the License is distributed on an "AS IS" BASIS,
  13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14  * See the License for the specific language governing permissions and
  15  * limitations under the License.
  16  *
  17  */
  18
  19 // Package grpcsync implements additional synchronization primitives built upon
  20 // the sync package.
  21 package grpcsync
  22
  23 import (
  24         "sync"
  25         "sync/atomic"
  26 )
  27
  28 // Event represents a one-time event that may occur in the future.
  29 type Event struct {
  30         fired int32
  31         c     chan struct{}
  32         o     sync.Once
  33 }
  34
  35 // Fire causes e to complete.  It is safe to call multiple times, and
  36 // concurrently.  It returns true iff this call to Fire caused the signaling
  37 // channel returned by Done to close.
  38 func (e *Event) Fire() bool {
  39         ret := false
  40         e.o.Do(func() {
  41                 atomic.StoreInt32(&e.fired, 1)
  42                 close(e.c)
  43                 ret = true
  44         })
  45         return ret
  46 }
  47
  48 // Done returns a channel that will be closed when Fire is called.
  49 func (e *Event) Done() <-chan struct{} {
  50         return e.c
  51 }
  52
  53 // HasFired returns true if Fire has been called.
  54 func (e *Event) HasFired() bool {
  55         return atomic.LoadInt32(&e.fired) == 1
  56 }
  57
  58 // NewEvent returns a new, ready-to-use Event.
  59 func NewEvent() *Event {
  60         return &Event{c: make(chan struct{})}
  61 }