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package cond
import (
"sync"
)
// NewStatefulCond returns a stateful version of sync.Cond . This cond will
// never block on `Wait()` if `Signal()` has been called after the `Wait()` last
// returned. This is useful for avoiding to take a lock on `cond.Locker` for
// signalling.
func NewStatefulCond(l sync.Locker) *StatefulCond {
sc := &StatefulCond{main: l}
sc.c = sync.NewCond(&sc.mu)
return sc
}
type StatefulCond struct {
main sync.Locker
mu sync.Mutex
c *sync.Cond
signalled bool
}
func (s *StatefulCond) Wait() {
s.main.Unlock()
s.mu.Lock()
if !s.signalled {
s.c.Wait()
}
s.signalled = false
s.mu.Unlock()
s.main.Lock()
}
func (s *StatefulCond) Signal() {
s.mu.Lock()
s.signalled = true
s.c.Signal()
s.mu.Unlock()
}
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