Merge pull request #6 from schicho/hide-datastructure

Reintroduce Toggle

bool.go

@@ -24,21 +24,23 @@ func NewBool(ok bool) *AtomicBool {
 // AtomicBool is an atomic Boolean.
 // Its methods are all atomic, thus safe to be called by multiple goroutines simultaneously.
 // Note: When embedding into a struct one should always use *AtomicBool to avoid copy.
-type AtomicBool int32
+type AtomicBool struct {
+	boolean int32
+}
 
 // Set sets the Boolean to true.
 func (ab *AtomicBool) Set() {
-	atomic.StoreInt32((*int32)(ab), 1)
+	atomic.StoreInt32(&ab.boolean, 1)
 }
 
 // UnSet sets the Boolean to false.
 func (ab *AtomicBool) UnSet() {
-	atomic.StoreInt32((*int32)(ab), 0)
+	atomic.StoreInt32(&ab.boolean, 0)
 }
 
 // IsSet returns whether the Boolean is true.
 func (ab *AtomicBool) IsSet() bool {
-	return atomic.LoadInt32((*int32)(ab)) == 1
+	return atomic.LoadInt32(&ab.boolean)&1 == 1
 }
 
 // IsNotSet returns whether the Boolean is false.
@@ -49,9 +51,21 @@ func (ab *AtomicBool) IsNotSet() bool {
 // SetTo sets the boolean with given Boolean.
 func (ab *AtomicBool) SetTo(yes bool) {
 	if yes {
-		atomic.StoreInt32((*int32)(ab), 1)
+		atomic.StoreInt32(&ab.boolean, 1)
 	} else {
-		atomic.StoreInt32((*int32)(ab), 0)
+		atomic.StoreInt32(&ab.boolean, 0)
+	}
+}
+
+// Toggle inverts the Boolean then returns the value before inverting.
+// Based on: https://github.com/uber-go/atomic/blob/3504dfaa1fa414923b1c8693f45d2f6931daf229/bool_ext.go#L40
+func (ab *AtomicBool) Toggle() bool {
+	var old bool
+	for {
+		old = ab.IsSet()
+		if ab.SetToIf(old, !old) {
+			return old
+		}
 	}
 }
 
@@ -65,7 +79,7 @@ func (ab *AtomicBool) SetToIf(old, new bool) (set bool) {
 	if new {
 		n = 1
 	}
-	return atomic.CompareAndSwapInt32((*int32)(ab), o, n)
+	return atomic.CompareAndSwapInt32(&ab.boolean, o, n)
 }
 
 // MarshalJSON behaves the same as if the AtomicBool is a builtin.bool.

bool_test.go

@@ -72,6 +72,43 @@ func TestSetTo(t *testing.T) {
 	}
 }
 
+func TestToggle(t *testing.T) {
+	t.Parallel()
+	v := New()
+
+	_ = v.Toggle()
+	if !v.IsSet() {
+		t.Fatal("AtomicBool.Toggle() to true failed")
+	}
+
+	prev := v.Toggle()
+	if v.IsSet() == prev {
+		t.Fatal("AtomicBool.Toggle() to false failed")
+	}
+}
+
+func TestToogleMultipleTimes(t *testing.T) {
+	t.Parallel()
+
+	v := New()
+	pre := !v.IsSet()
+	for i := 0; i < 100; i++ {
+		v.SetTo(false)
+		for j := 0; j < i; j++ {
+			pre = v.Toggle()
+		}
+
+		expected := i%2 != 0
+		if v.IsSet() != expected {
+			t.Fatalf("AtomicBool.Toogle() doesn't work after %d calls, expected: %v, got %v", i, expected, v.IsSet())
+		}
+
+		if pre == v.IsSet() {
+			t.Fatalf("AtomicBool.Toogle() returned wrong value at the %dth calls, expected: %v, got %v", i, !v.IsSet(), pre)
+		}
+	}
+}
+
 func TestRace(t *testing.T) {
 	repeat := 10000
 	var wg sync.WaitGroup
@@ -104,6 +141,22 @@ func TestRace(t *testing.T) {
 	wg.Wait()
 }
 
+func TestSetToIfAfterMultipleToggles(t *testing.T) {
+	v := New() // false
+
+	v.Toggle() // true
+	v.Toggle() // false
+	v.Toggle() // true
+
+	// As v is true, it should now be flipped to false
+	v.SetToIf(true, false)
+	expected := false
+
+	if v.IsSet() != expected {
+		t.Fatalf("Toggling the value atleast 3 times, until it's true, `SetToIf(true, false)` should flip v to false, expected: %v, got %v", expected, v.IsSet())
+	}
+}
+
 func TestJSONCompatibleWithBuiltinBool(t *testing.T) {
 	for _, value := range []bool{true, false} {
 		// Test bool -> bytes -> AtomicBool
@@ -181,6 +234,14 @@ func ExampleAtomicBool() {
 	cond.SetToIf(new, old) // Sets to `new` only if the Boolean matches the `old`, returns whether succeeded
 }
 
+func BenchmarkAtomicBoolToggle(b *testing.B) {
+	v := New()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = v.Toggle()
+	}
+}
+
 // Benchmark Read
 
 func BenchmarkMutexRead(b *testing.B) {