[#174] subnet: Add `UserAllowed` method

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

subnet/subnet_contract.go

@@ -442,6 +442,32 @@ func RemoveUser(subnetID []byte, groupID []byte, userID []byte) {
 	deleteKeyFromList(ctx, userID, stKey)
 }
 
+const groupIDSize = 4
+
+// UserAllowed returns bool that indicates if node is included in the
+// specified subnet or not.
+func UserAllowed(subnetID []byte, user []byte) bool {
+	ctx := storage.GetContext()
+
+	stKey := append([]byte{ownerPrefix}, subnetID...)
+	if storage.Get(ctx, stKey) == nil {
+		panic("userAllowed: " + ErrSubNotExist)
+	}
+
+	stKey[0] = userPrefix
+	prefixLen := len(stKey) + groupIDSize
+
+	iter := storage.Find(ctx, stKey, storage.KeysOnly)
+	for iterator.Next(iter) {
+		key := iterator.Value(iter).([]byte)
+		if common.BytesEqual(user, key[prefixLen:]) {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Version returns version of the contract.
 func Version() int {
 	return common.Version

tests/subnet_test.go

@@ -285,6 +285,25 @@ func TestSubnet_RemoveUser(t *testing.T) {
 	cAdm.InvokeFail(t, method+errSeparator+subnet.ErrUserNotExist, method, id, groupId, user)
 }
 
+func TestSubnet_UserAllowed(t *testing.T) {
+	e := newSubnetInvoker(t)
+
+	id, owner := createSubnet(t, e)
+
+	groupId := randomBytes(4)
+
+	user := randomBytes(27)
+
+	const method = "userAllowed"
+
+	cOwn := e.WithSigners(owner)
+	cOwn.InvokeFail(t, method+errSeparator+subnet.ErrSubNotExist, method, []byte{0, 0, 0, 0}, user)
+
+	cOwn.Invoke(t, stackitem.NewBool(false), method, id, user)
+	cOwn.Invoke(t, stackitem.Null{}, "addUser", id, groupId, user)
+	cOwn.Invoke(t, stackitem.NewBool(true), method, id, user)
+}
+
 func createSubnet(t *testing.T, e *neotest.ContractInvoker) (id []byte, owner neotest.Signer) {
 	var (
 		ok  bool