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