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54 lines
1.0 KiB
54 lines
1.0 KiB
package sync
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import "sync"
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// OnceErr wraps the behavior of recording an error
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// once and signal on a channel when this has occurred.
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// Signaling is done by closing of the channel.
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//
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// Type is safe for concurrent usage.
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type OnceErr struct {
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mu sync.RWMutex
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err error
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ch chan struct{}
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}
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// NewOnceErr return a new OnceErr
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func NewOnceErr() *OnceErr {
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return &OnceErr{
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ch: make(chan struct{}, 1),
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}
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}
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// Err acquires a read-lock and returns an
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// error if one has been set.
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func (e *OnceErr) Err() error {
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e.mu.RLock()
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err := e.err
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e.mu.RUnlock()
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return err
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}
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// SetError acquires a write-lock and will set
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// the underlying error value if one has not been set.
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func (e *OnceErr) SetError(err error) {
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if err == nil {
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return
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}
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e.mu.Lock()
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if e.err == nil {
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e.err = err
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close(e.ch)
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}
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e.mu.Unlock()
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}
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// ErrorSet returns a channel that will be used to signal
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// that an error has been set. This channel will be closed
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// when the error value has been set for OnceErr.
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func (e *OnceErr) ErrorSet() <-chan struct{} {
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return e.ch
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}
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