76 lines
1.7 KiB
Go
76 lines
1.7 KiB
Go
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// Copyright (C) 2019 Storj Labs, Inc.
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// See LICENSE for copying information.
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package drpcsignal
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import (
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"sync"
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"sync/atomic"
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)
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// Signal contains an error value that can be set one and exports
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// a number of ways to inspect it.
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type Signal struct {
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set uint32
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on sync.Once
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mu sync.Mutex
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sig chan struct{}
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err error
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}
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func (s *Signal) init() { s.sig = make(chan struct{}) }
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// Signal returns a channel that will be closed when the signal is set.
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func (s *Signal) Signal() chan struct{} {
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s.on.Do(s.init)
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return s.sig
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}
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// Set stores the error in the signal. It only keeps track of the first
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// error set, and returns true if it was the first error set.
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func (s *Signal) Set(err error) (ok bool) {
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if atomic.LoadUint32(&s.set) != 0 {
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return false
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}
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return s.setSlow(err)
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}
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// setSlow is the slow path for Set, so that the fast path is inlined into
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// callers.
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func (s *Signal) setSlow(err error) (ok bool) {
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s.mu.Lock()
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if s.set == 0 {
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s.err = err
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atomic.StoreUint32(&s.set, 1)
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s.on.Do(s.init)
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close(s.sig)
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ok = true
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}
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s.mu.Unlock()
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return ok
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}
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// Get returns the error set with the signal and a boolean indicating if
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// the result is valid.
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func (s *Signal) Get() (error, bool) { //nolint
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if atomic.LoadUint32(&s.set) != 0 {
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return s.err, true
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}
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return nil, false
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}
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// IsSet returns true if the Signal is set.
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func (s *Signal) IsSet() bool {
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return atomic.LoadUint32(&s.set) != 0
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}
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// Err returns the error stored in the signal. Since one can store a nil error
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// care must be taken. A non-nil error returned from this method means that
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// the Signal has been set, but the inverse is not true.
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func (s *Signal) Err() error {
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if atomic.LoadUint32(&s.set) != 0 {
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return s.err
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}
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return nil
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}
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