package smtpd

import (
	"net"
	"sync"
	"sync/atomic"
)

// onceCloseListener wraps a net.Listener, protecting it from
// multiple Close calls.
type onceCloseListener struct {
	net.Listener
	once     sync.Once
	closeErr error
}

func (oc *onceCloseListener) Close() error {
	oc.once.Do(oc.close)
	return oc.closeErr
}

func (oc *onceCloseListener) close() { oc.closeErr = oc.Listener.Close() }

type atomicBool int32

func (b *atomicBool) isSet() bool { return atomic.LoadInt32((*int32)(b)) != 0 }
func (b *atomicBool) setTrue()    { atomic.StoreInt32((*int32)(b), 1) }
func (b *atomicBool) setFalse()   { atomic.StoreInt32((*int32)(b), 0) }