[ONOS-7114] Meter Subsystem Refactoring

Changes:
- Moves meter counters in the store
- Uses atomic counter map for meter counters
- Implements atomic counter map adapter and test atomic counter map
- Introduces free meter id
- Changes allocate meter id
- Implements unit tests for MeterManager and MeterStore

Change-Id: I45e3debc0e43ca7edcf6e3b4065866634f76f9f7
diff --git a/core/api/src/test/java/org/onosproject/store/service/TestAtomicCounterMap.java b/core/api/src/test/java/org/onosproject/store/service/TestAtomicCounterMap.java
new file mode 100644
index 0000000..ef1769c
--- /dev/null
+++ b/core/api/src/test/java/org/onosproject/store/service/TestAtomicCounterMap.java
@@ -0,0 +1,177 @@
+/*
+ * 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.store.service;
+
+import com.google.common.util.concurrent.AtomicLongMap;
+
+/**
+ * Test implementation of the atomic counter map.
+ */
+public final class TestAtomicCounterMap<K> extends AtomicCounterMapAdapter<K> {
+
+    // Map name
+    private final String atomicCounterMapName;
+    // Atomic long map from guava
+    private AtomicLongMap<K> map;
+
+    private TestAtomicCounterMap(String name) {
+        // Init name, map using create
+        atomicCounterMapName = name;
+        map = AtomicLongMap.create();
+    }
+
+    @Override
+    public long incrementAndGet(K key) {
+        // Forward directly to the guava map
+        return map.incrementAndGet(key);
+    }
+
+    @Override
+    public long decrementAndGet(K key) {
+        // Forward directly to the guava map
+        return map.decrementAndGet(key);
+    }
+
+    @Override
+    public long getAndIncrement(K key) {
+        // Forward directly to the guava map
+        return map.getAndIncrement(key);
+    }
+
+    @Override
+    public long getAndDecrement(K key) {
+        // Forward directly to the guava map
+        return map.getAndDecrement(key);
+    }
+
+    @Override
+    public long addAndGet(K key, long delta) {
+        // Forward directly to the guava map
+        return map.addAndGet(key, delta);
+    }
+
+    @Override
+    public long getAndAdd(K key, long delta) {
+        // Forward directly to the guava map
+        return map.getAndAdd(key, delta);
+    }
+
+    @Override
+    public long get(K key) {
+        // Forward directly to the guava map
+        return map.get(key);
+    }
+
+    @Override
+    public long put(K key, long newValue) {
+        // Forward directly to the guava map
+        return map.put(key, newValue);
+    }
+
+    @Override
+    // Coarse implementation, should we take the lock ?
+    public long putIfAbsent(K key, long newValue) {
+        // If it does not exist
+        if (!map.containsKey(key)) {
+            // Just do a put
+            return map.put(key, newValue);
+        } else {
+            // Let's return the existing value
+            return map.get(key);
+        }
+    }
+
+    @Override
+    // Coarse implementation, should we take the lock ?
+    public boolean replace(K key, long expectedOldValue, long newValue) {
+        // If the value exists and it the expected one
+        if (map.containsKey(key) && map.get(key) == expectedOldValue) {
+            // Let's put the value
+            map.put(key, newValue);
+            // Done, return true
+            return true;
+
+        } else if (!map.containsKey(key) && expectedOldValue == 0) {
+            // If the value does not exist, and old value is 0
+            map.put(key, newValue);
+            // Done, return true
+            return true;
+        } else {
+            // replace is not possible, just return false
+            return false;
+        }
+    }
+
+    @Override
+    public long remove(K key) {
+        // Forward directly to the guava map
+        return map.remove(key);
+    }
+
+    @Override
+    // Coarse implementation, should we take the lock ?
+    public boolean remove(K key, long value) {
+        // If the value exists and it is equal to value
+        if (map.containsKey(key) && map.get(key) == value) {
+            // Let's remove the value
+            map.remove(key);
+            // Done, return true
+            return true;
+        } else {
+            // remove is not possible, just return false
+            return false;
+        }
+    }
+
+    @Override
+    public int size() {
+        return map.size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return map.isEmpty();
+    }
+
+    @Override
+    public void clear() {
+        map.clear();
+    }
+
+    @Override
+    public String name() {
+        return atomicCounterMapName;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static class Builder<K> extends AtomicCounterMapBuilder<K> {
+
+        @Override
+        public AtomicCounterMap<K> build() {
+            return new TestAtomicCounterMap<>(name());
+        }
+
+        @Override
+        public AsyncAtomicCounterMap<K> buildAsyncMap() {
+            return null;
+        }
+    }
+
+}