smartcontract: add CallFlag.Has() helper

pkg/smartcontract/call_flags.go

@@ -13,3 +13,8 @@ const (
 	ReadOnly = AllowStates | AllowCall | AllowNotify
 	All      = ReadOnly | AllowModifyStates
 )
+
+// Has returns true iff all bits set in cf are also set in f.
+func (f CallFlag) Has(cf CallFlag) bool {
+	return f&cf == cf
+}

pkg/smartcontract/call_flags_test.go

@@ -0,0 +1,14 @@
+package smartcontract
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCallFlag_Has(t *testing.T) {
+	require.True(t, AllowCall.Has(AllowCall))
+	require.True(t, (AllowCall | AllowNotify).Has(AllowCall))
+	require.False(t, (AllowCall).Has(AllowCall|AllowNotify))
+	require.True(t, All.Has(ReadOnly))
+}