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// SPDX-FileCopyrightText: © 2024 Grégoire Duchêne <gduchene@awhk.org>
// SPDX-License-Identifier: ISC
package core
import (
"errors"
"sync/atomic"
)
var ErrPromiseFulfilled = errors.New("promise fulfilled already")
type Promise[T any] struct {
value chan T
error chan error
closed int32
_ NoCopy
}
func NewPromise[T any]() *Promise[T] {
return &Promise[T]{value: make(chan T, 1), error: make(chan error, 1), closed: 0}
}
func (p *Promise[T]) Err() <-chan error { return p.error }
func (p *Promise[T]) FailWith(err error) error {
if !atomic.CompareAndSwapInt32(&p.closed, 0, 1) {
return ErrPromiseFulfilled
}
p.error <- err
close(p.error)
return nil
}
func (p *Promise[T]) SucceedWith(value T) error {
if !atomic.CompareAndSwapInt32(&p.closed, 0, 1) {
return ErrPromiseFulfilled
}
p.value <- value
close(p.value)
return nil
}
func (p *Promise[T]) Value() <-chan T { return p.value }
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