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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package chans
import "runtime"
// Ranger returns a Sender and a Receiver. The Receiver provides a
// Next method to retrieve values. The Sender provides a Send method
// to send values and a Close method to stop sending values. The Next
// method indicates when the Sender has been closed, and the Send
// method indicates when the Receiver has been freed.
//
// This is a convenient way to exit a goroutine sending values when
// the receiver stops reading them.
func Ranger[T any]() (*Sender[T], *Receiver[T]) {
c := make(chan T)
d := make(chan bool)
s := &Sender[T]{values: c, done: d}
r := &Receiver[T]{values: c, done: d}
runtime.SetFinalizer(r, r.finalize)
return s, r
}
// A sender is used to send values to a Receiver.
type Sender[T any] struct {
values chan<- T
done <-chan bool
}
// Send sends a value to the receiver. It returns whether any more
// values may be sent; if it returns false the value was not sent.
func (s *Sender[T]) Send(v T) bool {
select {
case s.values <- v:
return true
case <-s.done:
return false
}
}
// Close tells the receiver that no more values will arrive.
// After Close is called, the Sender may no longer be used.
func (s *Sender[T]) Close() {
close(s.values)
}
// A Receiver receives values from a Sender.
type Receiver[T any] struct {
values <-chan T
done chan<- bool
}
// Next returns the next value from the channel. The bool result
// indicates whether the value is valid, or whether the Sender has
// been closed and no more values will be received.
func (r *Receiver[T]) Next() (T, bool) {
v, ok := <-r.values
return v, ok
}
// finalize is a finalizer for the receiver.
func (r *Receiver[T]) finalize() {
close(r.done)
}
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