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package nowish
import (
"errors"
"sync/atomic"
"time"
)
// ErrTimeoutStarted is returned if a Timeout interface is attempted to be reused while still in operation
var ErrTimeoutStarted = errors.New("nowish: timeout already started")
// timeoutState provides a thread-safe timeout state mechanism
type timeoutState uint32
// start attempts to start the state, must be already reset, returns success
func (t *timeoutState) start() bool {
return atomic.CompareAndSwapUint32((*uint32)(t), 0, 1)
}
// stop attempts to stop the state, must already be started, returns success
func (t *timeoutState) stop() bool {
return atomic.CompareAndSwapUint32((*uint32)(t), 1, 2)
}
// reset is fairly self explanatory
func (t *timeoutState) reset() {
atomic.StoreUint32((*uint32)(t), 0)
}
// Timeout provides a reusable structure for enforcing timeouts with a cancel
type Timeout interface {
// Start starts the timer with supplied timeout. If timeout is reached before
// cancel then supplied timeout hook will be called. Error may be called if
// Timeout is already running when this function is called
Start(time.Duration, func()) error
// Cancel cancels the currently running timer. If a cancel is achieved, then
// this function will return after the timeout goroutine is finished
Cancel()
}
// NewTimeout returns a new Timeout instance
func NewTimeout() Timeout {
t := &timeout{
tk: time.NewTicker(time.Minute),
ch: make(chan struct{}),
}
t.tk.Stop() // don't keep it running
return t
}
// timeout is the Timeout implementation that we force
// initialization on via NewTimeout by unexporting it
type timeout struct {
noCopy noCopy //nolint noCopy because a copy will mess with atomics
tk *time.Ticker // tk is the underlying timeout-timer
ch chan struct{} // ch is the cancel propagation channel
st timeoutState // st stores the current timeout state (and protects concurrent use)
}
func (t *timeout) Start(d time.Duration, hook func()) error {
// Attempt to acquire start
if !t.st.start() {
return ErrTimeoutStarted
}
// Start the ticker
t.tk.Reset(d)
go func() {
cancelled := false
select {
// Timeout reached
case <-t.tk.C:
if !t.st.stop() {
// cancel was called in the nick of time
<-t.ch
cancelled = true
}
// Cancel called
case <-t.ch:
cancelled = true
}
// Stop ticker
t.tk.Stop()
// If timed out call hook
if !cancelled {
hook()
}
// Finally, reset state
t.st.reset()
}()
return nil
}
func (t *timeout) Cancel() {
// Attempt to acquire stop
if !t.st.stop() {
return
}
// Send a cancel signal
t.ch <- struct{}{}
}
|
