DistributedPrimitives updates:
    Adds a ferderated distributed primitive creator
    Adds a DistributedPrimitives utility class
    Adds a transcoding async consistent map for transcoding between map types

Change-Id: I7bc30e4a8aee9d4286175d7081bbbd0f28b9928f
diff --git a/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/FederatedDistributedPrimitiveCreator.java b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/FederatedDistributedPrimitiveCreator.java
new file mode 100644
index 0000000..20c2a98
--- /dev/null
+++ b/core/store/primitives/src/main/java/org/onosproject/store/primitives/impl/FederatedDistributedPrimitiveCreator.java
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2016 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.primitives.impl;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+
+import org.apache.commons.lang.StringUtils;
+import org.onlab.util.Tools;
+import org.onosproject.cluster.PartitionId;
+import org.onosproject.store.primitives.DistributedPrimitiveCreator;
+import org.onosproject.store.service.AsyncAtomicCounter;
+import org.onosproject.store.service.AsyncAtomicValue;
+import org.onosproject.store.service.AsyncConsistentMap;
+import org.onosproject.store.service.AsyncDistributedSet;
+import org.onosproject.store.service.AsyncLeaderElector;
+import org.onosproject.store.service.DistributedQueue;
+import org.onosproject.store.service.Serializer;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.google.common.hash.HashCode;
+import com.google.common.hash.Hashing;
+import com.google.common.primitives.Bytes;
+
+/**
+ * {@code DistributedPrimitiveCreator} that federates responsibility for creating
+ * distributed primitives to a collection of other {@link DistributedPrimitiveCreator creators}.
+ */
+public class FederatedDistributedPrimitiveCreator implements DistributedPrimitiveCreator {
+
+    private final TreeMap<PartitionId, DistributedPrimitiveCreator> members;
+    private final List<PartitionId> sortedMemberPartitionIds;
+
+    public FederatedDistributedPrimitiveCreator(Map<PartitionId, DistributedPrimitiveCreator> members) {
+        this.members = Maps.newTreeMap();
+        this.members.putAll(checkNotNull(members));
+        this.sortedMemberPartitionIds = Lists.newArrayList(members.keySet());
+    }
+
+    @Override
+    public <K, V> AsyncConsistentMap<K, V> newAsyncConsistentMap(String name, Serializer serializer) {
+        checkNotNull(name);
+        checkNotNull(serializer);
+        Map<PartitionId, AsyncConsistentMap<K, V>> maps =
+                Maps.transformValues(members,
+                                     partition -> partition.newAsyncConsistentMap(name, serializer));
+        Hasher<K> hasher = key -> {
+            long hashCode = HashCode.fromBytes(Bytes.ensureCapacity(serializer.encode(key), 8, 0)).asLong();
+            return sortedMemberPartitionIds.get(Hashing.consistentHash(hashCode, members.size()));
+        };
+        return new PartitionedAsyncConsistentMap<>(name, maps, hasher);
+    }
+
+    @Override
+    public <E> AsyncDistributedSet<E> newAsyncDistributedSet(String name, Serializer serializer) {
+        return DistributedPrimitives.newSetFromMap(newAsyncConsistentMap(name, serializer));
+    }
+
+    @Override
+    public AsyncAtomicCounter newAsyncCounter(String name) {
+        return getCreator(name).newAsyncCounter(name);
+    }
+
+    @Override
+    public <V> AsyncAtomicValue<V> newAsyncAtomicValue(String name, Serializer serializer) {
+        return getCreator(name).newAsyncAtomicValue(name, serializer);
+    }
+
+    @Override
+    public <E> DistributedQueue<E> newDistributedQueue(String name, Serializer serializer) {
+        return getCreator(name).newDistributedQueue(name, serializer);
+    }
+
+    @Override
+    public AsyncLeaderElector newAsyncLeaderElector(String name) {
+        return getCreator(name).newAsyncLeaderElector(name);
+    }
+
+    /**
+     * Returns the {@code DistributedPrimitiveCreator} to use for hosting a primitive.
+     * @param name primitive name
+     * @return primitive creator
+     */
+    private DistributedPrimitiveCreator getCreator(String name) {
+        long hashCode = HashCode.fromBytes(Tools.getBytesUtf8(StringUtils.leftPad(name, 8))).asLong();
+        int index = Hashing.consistentHash(hashCode, members.size());
+        return members.get(sortedMemberPartitionIds.get(index));
+    }
+}