Define codec interface for discrete resources

The codec defines how to encode the given resource into an integer and
to decode the given interger to a resource.

This is for ONOS-4281.

Change-Id: I5e9143c9f0285f588274f6649a146bbc1e13dcdb

+/*
+ * 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.net.resource;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Represents the common interface to encode a discrete resource to an integer,
+ * and to decode an integer to a discrete resource.
+ * This class is intended to be used only by the ResourceService implementation.
+ */
+@Beta
+public interface DiscreteResourceCodec {
+    /**
+     * Encodes the specified discrete resource to an integer.
+     *
+     * @param resource resource
+     * @return encoded integer
+     */
+    int encode(DiscreteResource resource);
+
+    /**
+     * Decodes the specified integer to a discrete resource.
+     *
+     * @param parent parent of the returned resource
+     * @param value encoded integer
+     * @return decoded discrete resource
+     */
+    DiscreteResource decode(DiscreteResourceId parent, int value);
+}

+/*
+ * 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.net.resource;
+
+import com.google.common.annotations.Beta;
+import org.onlab.packet.MplsLabel;
+
+import java.util.Optional;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Codec for MplsLabel.
+ */
+@Beta
+public final class MplsCodec implements DiscreteResourceCodec {
+    @Override
+    public int encode(DiscreteResource resource) {
+        Optional<MplsLabel> mpls = resource.valueAs(MplsLabel.class);
+        checkArgument(mpls.isPresent());
+        return mpls.map(MplsLabel::toInt).get();
+    }
+
+    @Override
+    public DiscreteResource decode(DiscreteResourceId parent, int value) {
+        return Resources.discrete(parent, MplsLabel.mplsLabel(value)).resource();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == this) {
+            return true;
+        }
+
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return MplsCodec.class.hashCode();
+    }
+}

+/*
+ * 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.net.resource;
+
+import com.google.common.annotations.Beta;
+import org.onlab.packet.VlanId;
+
+import java.util.Optional;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Codec for Vlan.
+ */
+@Beta
+public final class VlanCodec implements DiscreteResourceCodec {
+    @Override
+    public int encode(DiscreteResource resource) {
+        Optional<VlanId> vlan = resource.valueAs(VlanId.class);
+        checkArgument(vlan.isPresent());
+        return vlan.map(x -> (int) x.toShort()).get();
+    }
+
+    @Override
+    public DiscreteResource decode(DiscreteResourceId parent, int value) {
+        return Resources.discrete(parent, VlanId.vlanId((short) value)).resource();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == this) {
+            return true;
+        }
+
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return VlanCodec.class.hashCode();
+    }
+}