package supervisor import "sync" // booleanFuse is a data structure that can be set once to a particular value using Fuse(value). // Subsequent calls to Fuse() will have no effect. type booleanFuse struct { value int32 mu sync.Mutex cond *sync.Cond } func newBooleanFuse() *booleanFuse { f := &booleanFuse{} f.cond = sync.NewCond(&f.mu) return f } // Value gets the value func (f *booleanFuse) Value() bool { // 0: unset // 1: set true // 2: set false f.mu.Lock() defer f.mu.Unlock() return f.value == 1 } func (f *booleanFuse) Fuse(result bool) { f.mu.Lock() defer f.mu.Unlock() newValue := int32(2) if result { newValue = 1 } if f.value == 0 { f.value = newValue f.cond.Broadcast() } } // Await blocks until Fuse has been called at least once. func (f *booleanFuse) Await() bool { f.mu.Lock() defer f.mu.Unlock() for f.value == 0 { f.cond.Wait() } return f.value == 1 }