[bugfix] Fix NopDecoder

* Fixes #41

securecookie.go

@@ -102,6 +102,7 @@ var (
 	errTimestampExpired     = cookieError{typ: decodeError, msg: "expired timestamp"}
 	errDecryptionFailed     = cookieError{typ: decodeError, msg: "the value could not be decrypted"}
 	errValueNotByte         = cookieError{typ: decodeError, msg: "value not a []byte."}
+	errValueNotBytePtr      = cookieError{typ: decodeError, msg: "value not a pointer to []byte."}
 
 	// ErrMacInvalid indicates that cookie decoding failed because the HMAC
 	// could not be extracted and verified.  Direct use of this error
@@ -474,12 +475,11 @@ func (e NopEncoder) Serialize(src interface{}) ([]byte, error) {
 
 // Deserialize passes a []byte through as-is.
 func (e NopEncoder) Deserialize(src []byte, dst interface{}) error {
-	if _, ok := dst.([]byte); ok {
-		dst = src
+	if dat, ok := dst.(*[]byte); ok {
+		*dat = src
 		return nil
 	}
-
-	return errValueNotByte
+	return errValueNotBytePtr
 }
 
 // Encoding -------------------------------------------------------------------

securecookie_test.go

@@ -193,6 +193,33 @@ func TestJSONSerialization(t *testing.T) {
 	}
 }
 
+func TestNopSerialization(t *testing.T) {
+	cookieData := "fooobar123"
+	sz := NopEncoder{}
+
+	if _, err := sz.Serialize(cookieData); err != errValueNotByte {
+		t.Fatal("Expected error passing string")
+	}
+	dat, err := sz.Serialize([]byte(cookieData))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if (string(dat)) != cookieData {
+		t.Fatal("Expected serialized data to be same as source")
+	}
+
+	var dst []byte
+	if err = sz.Deserialize(dat, dst); err != errValueNotBytePtr {
+		t.Fatal("Expect error unless you pass a *[]byte")
+	}
+	if err = sz.Deserialize(dat, &dst); err != nil {
+		t.Fatal(err)
+	}
+	if (string(dst)) != cookieData {
+		t.Fatal("Expected deserialized data to be same as source")
+	}
+}
+
 func TestEncoding(t *testing.T) {
 	for _, value := range testStrings {
 		encoded := encode([]byte(value))