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// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
package internal
import "context"
// CancellationListener listens for context cancellation in a loop until the context expires or the listener is aborted.
type CancellationListener struct {
aborted bool
done chan struct{}
}
// NewCancellationListener constructs a CancellationListener.
func NewCancellationListener() *CancellationListener {
return &CancellationListener{
done: make(chan struct{}),
}
}
// Listen blocks until the provided context is cancelled or listening is aborted via the StopListening function. If this
// detects that the context has been cancelled (i.e. ctx.Err() == context.Canceled), the provided callback is called to
// abort in-progress work. Even if the context expires, this function will block until StopListening is called.
func (c *CancellationListener) Listen(ctx context.Context, abortFn func()) {
c.aborted = false
select {
case <-ctx.Done():
if ctx.Err() == context.Canceled {
c.aborted = true
abortFn()
}
<-c.done
case <-c.done:
}
}
// StopListening stops the in-progress Listen call. This blocks if there is no in-progress Listen call. This function
// will return true if the provided abort callback was called when listening for cancellation on the previous context.
func (c *CancellationListener) StopListening() bool {
c.done <- struct{}{}
return c.aborted
}
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