TUN-528: Move cloudflared into a separate repo

h2mux/booleanfuse.go

@@ -0,0 +1,50 @@
+package h2mux
+
+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
+}