Implement the Unmarshaler and Marshaler interfaces.

This allows an AtomicBool to be Unmarshalled from the JSON
representation of a normal boolean and respectively marshall
it into the JSON representation of normal booleans.

This makes it easier to use AtomicBool in structs. For they can
now be read from JSON files and serialized back into them.

bool.go

@@ -2,7 +2,12 @@
 // better performance.
 package abool
 
-import "sync/atomic"
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"sync/atomic"
+)
 
 // New creates an AtomicBool with default set to false.
 func New() *AtomicBool {
@@ -69,3 +74,24 @@ func (ab *AtomicBool) SetToIf(old, new bool) (set bool) {
 	}
 	return atomic.CompareAndSwapInt32((*int32)(ab), o, n)
 }
+
+// Marshal an AtomicBool into JSON like a normal bool
+func (ab *AtomicBool) MarshalJSON() ([]byte, error) {
+	return json.Marshal(ab.IsSet())
+}
+
+// Unmarshall normal bool's into AtomicBool
+func (ab *AtomicBool) UnmarshalJSON(b []byte) error {
+	var v interface{}
+	if err := json.Unmarshal(b, &v); err != nil {
+		return err
+	}
+
+	switch value := v.(type) {
+	case bool:
+		ab.SetTo(value)
+		return nil
+	default:
+		return errors.New(fmt.Sprintf("%s is an invalid JSON representation for an AtomicBool\n", b))
+	}
+}

bool_test.go

@@ -1,6 +1,7 @@
 package abool
 
 import (
+	"encoding/json"
 	"math"
 	"sync"
 	"sync/atomic"
@@ -181,6 +182,52 @@ func TestRace(t *testing.T) {
 	wg.Wait()
 }
 
+func TestFalseUnmarshall(t *testing.T) {
+	// Marshall a normal bool into JSON byte slice
+	b, err := json.Marshal(false)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Create an AtomicBool
+	v := New()
+
+	// Try to unmarshall the JSON byte slice of a
+	// a normal bool into an AtomicBool
+	err = v.UnmarshalJSON(b)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Check if our AtomicBool is set to false
+	if v.IsSet() == true {
+		t.Errorf("Expected AtomicBool to represent false but IsSet() returns true")
+	}
+}
+
+func TestTrueUnmarshall(t *testing.T) {
+	// Marshall a normal bool into JSON byte slice
+	b, err := json.Marshal(true)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Create an AtomicBool
+	v := New()
+
+	// Try to unmarshall the JSON byte slice of a
+	// a normal bool into an AtomicBool
+	err = v.UnmarshalJSON(b)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Check if our AtomicBool is set to false
+	if v.IsSet() == false {
+		t.Errorf("Expected AtomicBool to represent true but IsSet() returns false. %+v", v)
+	}
+}
+
 func ExampleAtomicBool() {
 	cond := New() // default to false
 	any := true