Make serialized resources more compact to omit redundant parent resource ID

Change-Id: Icafe92f35bded405dd39e57ad8380bca82a6d720
(cherry picked from commit d68739b5839e1d2be907d3806e2c742df9da95fd)
diff --git a/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EncodedDiscreteResources.java b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EncodedDiscreteResources.java
new file mode 100644
index 0000000..c79b23a
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onosproject/store/resource/impl/EncodedDiscreteResources.java
@@ -0,0 +1,73 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * 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.store.resource.impl;
+
+import org.onlab.util.Tools;
+import org.onosproject.net.resource.DiscreteResource;
+import org.onosproject.net.resource.DiscreteResourceCodec;
+import org.onosproject.net.resource.DiscreteResourceId;
+import org.onosproject.net.resource.Resources;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * Represents discrete resources encoded by a codec.
+ */
+final class EncodedDiscreteResources {
+    private final Set<Integer> rawValues;
+    private final DiscreteResourceCodec codec;
+
+    EncodedDiscreteResources(Set<Integer> rawValues, DiscreteResourceCodec codec) {
+        this.rawValues = rawValues;
+        this.codec = codec;
+    }
+
+    static EncodedDiscreteResources of(Set<DiscreteResource> resources, DiscreteResourceCodec codec) {
+        Set<Integer> rawValues = resources.stream()
+                .map(x -> x.valueAs(Object.class))
+                .flatMap(Tools::stream)
+                .map(x -> codec.encode(x))
+                .collect(Collectors.toCollection(LinkedHashSet::new));
+
+        return new EncodedDiscreteResources(rawValues, codec);
+    }
+
+    Set<Integer> rawValues() {
+        return rawValues;
+    }
+
+    DiscreteResourceCodec codec() {
+        return codec;
+    }
+
+    Set<DiscreteResource> resources(DiscreteResourceId parent) {
+        return rawValues.stream()
+                .map(x -> codec.decode(x))
+                .map(x -> Resources.discrete(parent, x).resource())
+                .collect(Collectors.toCollection(LinkedHashSet::new));
+    }
+
+    @SuppressWarnings("unchecked")
+    boolean contains(DiscreteResource resource) {
+        return rawValues.contains(codec.encode(resource));
+    }
+
+    boolean isEmpty() {
+        return rawValues.isEmpty();
+    }
+}