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package errors
import (
"sync/atomic"
"unsafe"
)
// OnceError is an error structure that supports safe multi
// threaded usage and setting only once (until reset).
type OnceError struct{ err unsafe.Pointer }
// NewOnce returns a new OnceError instance.
func NewOnce() OnceError {
return OnceError{
err: nil,
}
}
// Store will safely set the OnceError to value, no-op if nil.
func (e *OnceError) Store(err error) {
// Nothing to do
if err == nil {
return
}
// Only set if not already
atomic.CompareAndSwapPointer(
&e.err,
nil,
unsafe.Pointer(&err),
)
}
// Load will load the currently stored error.
func (e *OnceError) Load() error {
return *(*error)(atomic.LoadPointer(&e.err))
}
// IsSet returns whether OnceError has been set.
func (e *OnceError) IsSet() bool {
return (atomic.LoadPointer(&e.err) != nil)
}
// Reset will reset the OnceError value.
func (e *OnceError) Reset() {
atomic.StorePointer(&e.err, nil)
}
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