github.com/searKing/golang/go@v1.2.117/sync/event.go (about)

     1  // Copyright 2021 The searKing Author. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package sync
     6  
     7  import (
     8  	"sync"
     9  	"sync/atomic"
    10  )
    11  
    12  // Event represents a one-time event that may occur in the future.
    13  // we use a fast path to avoid the more-expensive "select" below after the Event has returned once.
    14  type Event struct {
    15  	// This is on the RPC path, so we use a fast path to avoid the
    16  	// more-expensive "select" below after the resolver has returned once.
    17  	fired int32
    18  	c     chan struct{}
    19  	o     sync.Once
    20  }
    21  
    22  // Fire causes e to complete.  It is safe to call multiple times, and
    23  // concurrently.  It returns true iff this call to Fire caused the signaling
    24  // channel returned by Done to close.
    25  func (e *Event) Fire() bool {
    26  	ret := false
    27  	e.o.Do(func() {
    28  		atomic.StoreInt32(&e.fired, 1)
    29  		close(e.c)
    30  		ret = true
    31  	})
    32  	return ret
    33  }
    34  
    35  // Done returns a channel that will be closed when Fire is called.
    36  func (e *Event) Done() <-chan struct{} {
    37  	return e.c
    38  }
    39  
    40  // HasFired returns true if Fire has been called.
    41  // we use a fast path to avoid the more-expensive "select" below after the Event has returned once.
    42  func (e *Event) HasFired() bool {
    43  	return atomic.LoadInt32(&e.fired) == 1
    44  }
    45  
    46  // NewEvent returns a new, ready-to-use Event.
    47  func NewEvent() *Event {
    48  	return &Event{c: make(chan struct{})}
    49  }