[ONOS-6316]create gRPC northbound Host Service and add unit tests

Change-Id: I385f52576000affd2523579c6a6f4c6d57e69938
diff --git a/incubator/protobuf/models/src/main/java/org/onosproject/incubator/protobuf/models/net/HostLocationProtoTranslator.java b/incubator/protobuf/models/src/main/java/org/onosproject/incubator/protobuf/models/net/HostLocationProtoTranslator.java
new file mode 100644
index 0000000..098a276
--- /dev/null
+++ b/incubator/protobuf/models/src/main/java/org/onosproject/incubator/protobuf/models/net/HostLocationProtoTranslator.java
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.incubator.protobuf.models.net;
+
+import org.onosproject.grpc.net.models.ConnectPointProtoOuterClass.ConnectPointProto;
+import org.onosproject.grpc.net.models.HostLocationProtoOuterClass.HostLocationProto;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.HostLocation;
+import org.onosproject.net.PortNumber;
+
+/**
+ * gRPC HostLocationProto message to equivalent ONOS Host location conversion related utilities.
+ */
+public final class HostLocationProtoTranslator {
+
+    /**
+     * Translates gRPC HostLocation to {@link HostLocation}.
+     *
+     * @param hostLocation gRPC message
+     * @return {@link HostLocation}
+     */
+    public static HostLocation translate(HostLocationProto hostLocation) {
+
+        if (hostLocation.equals(HostLocationProto.getDefaultInstance())) {
+            return null;
+        }
+
+        return new HostLocation(DeviceId.deviceId(hostLocation.getConnectPoint().getDeviceId()),
+                                PortNumber.portNumber(hostLocation.getConnectPoint().getPortNumber()), 0L);
+    }
+
+    /**
+     * Translates {@link HostLocation} to gRPC HostLocation message.
+     *
+     * @param hostLocation {@link HostLocation}
+     * @return gRPC HostLocation message
+     */
+    public static HostLocationProto translate(HostLocation hostLocation) {
+
+        if (hostLocation != null) {
+            return HostLocationProto.newBuilder()
+                    .setConnectPoint(ConnectPointProto.newBuilder()
+                                             .setDeviceId(hostLocation.deviceId().toString())
+                                             .setPortNumber(hostLocation.port().toString()))
+                    .setTime(hostLocation.time())
+                    .build();
+        }
+
+        return HostLocationProto.getDefaultInstance();
+    }
+
+    // Utility class not intended for instantiation.
+    private HostLocationProtoTranslator() {}
+}