82 lines
1.2 KiB
Go
82 lines
1.2 KiB
Go
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package main
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import (
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"errors"
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"fmt"
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"sync/atomic"
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"time"
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)
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type Context struct {
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done chan struct{}
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closed int32
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}
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func WithTimeout(parent Context, duration time.Duration) (*Context, func()) {
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if atomic.LoadInt32(&parent.closed) == 1 {
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return nil, nil // don't use nil
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}
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ctx := &Context{
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done: make(chan struct{}),
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}
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cancel := func() {
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if atomic.CompareAndSwapInt32(&ctx.closed, 0, 1) {
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close(ctx.done)
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}
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}
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go func() {
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timer := time.NewTimer(duration)
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defer timer.Stop()
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select {
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case <-parent.Done():
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case <-timer.C:
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}
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cancel()
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}()
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return ctx, cancel
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}
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func (c *Context) Done() <-chan struct{} {
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return c.done
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}
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func (c *Context) Err() error {
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select {
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case <-c.done:
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return errors.New("context deadline exceeded")
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default:
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return nil
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}
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}
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func (c *Context) Deadline() (time.Time, bool) {
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// not implemented
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return time.Time{}, false
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}
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func (c *Context) Value(any) any {
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// not implemented
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return nil
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}
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func main() {
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ctx, cancel := WithTimeout(Context{}, time.Second)
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defer cancel()
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timer := time.NewTimer(5 * time.Second)
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defer timer.Stop()
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select {
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case <-timer.C:
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fmt.Println("finished")
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case <-ctx.Done():
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fmt.Println("canceled")
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}
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}
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