initial import

core/syncx/onceguard.go

@@ -0,0 +1,15 @@
+package syncx
+
+import "sync/atomic"
+
+type OnceGuard struct {
+	done uint32
+}
+
+func (og *OnceGuard) Taken() bool {
+	return atomic.LoadUint32(&og.done) == 1
+}
+
+func (og *OnceGuard) Take() bool {
+	return atomic.CompareAndSwapUint32(&og.done, 0, 1)
+}