Merge pull request #3 from barryz/add_flip_method

Add Toggle method to invert the value

README.md

@@ -18,6 +18,7 @@ cond.IsSet()               // Returns true
 cond.UnSet()               // Set to false
 cond.SetTo(true)           // Set to whatever you want
 cond.SetToIf(false, true)  // Set to true if it is false, returns false(not set)
+cond.Toggle() *AtomicBool  // Negates boolean atomically and returns a new AtomicBool object which holds previous boolean value.
 
 
 // embedding
@@ -26,24 +27,32 @@ type Foo struct {
 }
 ```
 
-## Benchmark:
+## Benchmark
 
-- Go 1.6.2
+- Go 1.11.5
-- OS X 10.11.4
+- OS X 10.14.5
 
 ```shell
 # Read
-BenchmarkMutexRead-4       	100000000	        21.0 ns/op
+BenchmarkMutexRead-4            100000000               14.7 ns/op
-BenchmarkAtomicValueRead-4 	200000000	         6.30 ns/op
+BenchmarkAtomicValueRead-4      2000000000               0.45 ns/op
-BenchmarkAtomicBoolRead-4  	300000000	         4.21 ns/op  # <--- This package
+BenchmarkAtomicBoolRead-4       2000000000               0.35 ns/op  # <--- This package
 
 # Write
-BenchmarkMutexWrite-4      	100000000	        21.6 ns/op
+BenchmarkMutexWrite-4           100000000               14.5 ns/op
-BenchmarkAtomicValueWrite-4	 30000000	        43.4 ns/op
+BenchmarkAtomicValueWrite-4     100000000               10.5 ns/op
-BenchmarkAtomicBoolWrite-4 	200000000	         9.87 ns/op  # <--- This package
+BenchmarkAtomicBoolWrite-4      300000000                5.21 ns/op  # <--- This package
 
 # CAS
-BenchmarkMutexCAS-4        	 30000000	        44.9 ns/op
+BenchmarkMutexCAS-4             50000000                31.3 ns/op
-BenchmarkAtomicBoolCAS-4   	100000000	        11.7 ns/op   # <--- This package
+BenchmarkAtomicBoolCAS-4        200000000                7.18 ns/op  # <--- This package
+
+# Toggle
+BenchmarkMutexToggle-4          50000000                32.6 ns/op
+BenchmarkAtomicBoolToggle-4     300000000                5.21 ns/op  # <--- This package
 ```
 
+## Thanks to these Contributors
+
+- [@barryz](https://github.com/barryz)
+    - Added the `Toggle` method

bool.go

@@ -37,10 +37,10 @@ func (ab *AtomicBool) UnSet() {
 
 // IsSet returns whether the Boolean is true
 func (ab *AtomicBool) IsSet() bool {
-	return atomic.LoadInt32((*int32)(ab)) == 1
+	return atomic.LoadInt32((*int32)(ab))&1 == 1
 }
 
-// SetTo sets the boolean with given Boolean
+// SetTo sets the boolean with given Boolean.
 func (ab *AtomicBool) SetTo(yes bool) {
 	if yes {
 		atomic.StoreInt32((*int32)(ab), 1)
@@ -49,6 +49,11 @@ func (ab *AtomicBool) SetTo(yes bool) {
 	}
 }
 
+// Toggle inverts the boolean then returns the value before inverting.
+func (ab *AtomicBool) Toggle() bool {
+	return atomic.AddInt32((*int32)(ab), 1)&1 == 0
+}
+
 // SetToIf sets the Boolean to new only if the Boolean matches the old
 // Returns whether the set was done
 func (ab *AtomicBool) SetToIf(old, new bool) (set bool) {

bool_test.go

@@ -1,12 +1,15 @@
 package abool
 
 import (
+	"math"
 	"sync"
 	"sync/atomic"
 	"testing"
 )
 
 func TestBool(t *testing.T) {
+	t.Parallel()
+
 	v := NewBool(true)
 	if !v.IsSet() {
 		t.Fatal("NewValue(true) failed")
@@ -49,12 +52,80 @@ func TestBool(t *testing.T) {
 	if set := v.SetToIf(false, true); !set || !v.IsSet() {
 		t.Fatal("AtomicBool.SetTo(false, true) failed")
 	}
+
+	v = New()
+	if v.IsSet() {
+		t.Fatal("Empty value of AtomicBool should be false")
+	}
+
+	_ = 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 TestToogleAfterOverflow(t *testing.T) {
+	t.Parallel()
+
+	var value int32 = math.MaxInt32
+	v := (*AtomicBool)(&value)
+
+	valueBeforeToggle := *(*int32)(v)
+
+	// test first toggle after overflow
+	v.Toggle()
+	expected := math.MaxInt32%2 == 0
+	if v.IsSet() != expected {
+		t.Fatalf("AtomicBool.Toogle() doesn't work after overflow, expected: %v, got %v", expected, v.IsSet())
+	}
+
+	// make sure overflow happened
+	var valueAfterToggle int32 = *(*int32)(v)
+	if valueAfterToggle >= valueBeforeToggle {
+		t.Fatalf("Overflow does not happen as expected, before %d, after: %d", valueBeforeToggle, valueAfterToggle)
+	}
+
+	// test second toggle after overflow
+	v.Toggle()
+	expected = !expected
+	if v.IsSet() != expected {
+		t.Fatalf("AtomicBool.Toogle() doesn't work after the second call after overflow, expected: %v, got %v", expected, v.IsSet())
+	}
 }
 
 func TestRace(t *testing.T) {
+	t.Parallel()
+
 	repeat := 10000
 	var wg sync.WaitGroup
-	wg.Add(repeat * 3)
+	wg.Add(repeat * 4)
 	v := New()
 
 	// Writer
@@ -80,6 +151,15 @@ func TestRace(t *testing.T) {
 			wg.Done()
 		}
 	}()
+
+	// Reader And Writer
+	go func() {
+		for i := 0; i < repeat; i++ {
+			v.Toggle()
+			wg.Done()
+		}
+	}()
+
 	wg.Wait()
 }
 
@@ -89,6 +169,7 @@ func ExampleAtomicBool() {
 	cond.IsSet()     // returns true
 	cond.UnSet()     // set to false
 	cond.SetTo(true) // set to whatever you want
+	cond.Toggle()    // toggles the boolean value
 }
 
 // Benchmark Read
@@ -174,3 +255,25 @@ func BenchmarkAtomicBoolCAS(b *testing.B) {
 		v.SetToIf(false, true)
 	}
 }
+
+// Benchmark toggle boolean value
+
+func BenchmarkMutexToggle(b *testing.B) {
+	var m sync.RWMutex
+	var v bool
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		m.Lock()
+		v = !v
+		m.Unlock()
+	}
+	b.StopTimer()
+}
+
+func BenchmarkAtomicBoolToggle(b *testing.B) {
+	v := New()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		v.Toggle()
+	}
+}