CMap: wrapper around DatabaseService

Change-Id: I55c534567b99d6bb7e95045c8100226c0b515a99

+/*
+ * Copyright 2014 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.onlab.onos.store.service.impl;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Predicates.notNull;
+
+import java.util.Map;
+
+import org.onlab.onos.store.serializers.StoreSerializer;
+import org.onlab.onos.store.service.DatabaseAdminService;
+import org.onlab.onos.store.service.DatabaseService;
+import org.onlab.onos.store.service.VersionedValue;
+
+import com.google.common.base.Function;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import com.google.common.collect.FluentIterable;
+
+/**
+ * Map like interface wrapper around DatabaseService.
+ *
+ * @param <K> Key type of the map.
+ *       The type must have toString(), which can uniquely identify the entry.
+ * @param <V> Value type
+ */
+public class CMap<K, V> {
+
+    @SuppressWarnings("unused")
+    private final DatabaseAdminService dbAdminService;
+
+    private final DatabaseService dbService;
+
+    private final String tableName;
+    private final StoreSerializer serializer;
+
+    private final LoadingCache<K, String> keyCache;
+
+    /**
+     * Creates a CMap instance.
+     * It will create the table if necessary.
+     *
+     * @param dbAdminService
+     * @param dbService
+     * @param tableName table which this Map corresponds to
+     * @param serializer Value serializer
+     */
+    public CMap(DatabaseAdminService dbAdminService,
+                DatabaseService dbService,
+                String tableName,
+                StoreSerializer serializer) {
+
+        this.dbAdminService = checkNotNull(dbAdminService);
+        this.dbService = checkNotNull(dbService);
+        this.tableName = checkNotNull(tableName);
+        this.serializer = checkNotNull(serializer);
+
+        if (!dbAdminService.listTables().contains(tableName)) {
+            dbAdminService.createTable(tableName);
+        }
+
+        keyCache = CacheBuilder.newBuilder()
+                    .softValues()
+                    .build(new CacheLoader<K, String>() {
+
+                        @Override
+                        public String load(K key) {
+                            return key.toString();
+                        }
+                    });
+    }
+
+    protected String sK(K key) {
+        return keyCache.getUnchecked(key);
+    }
+
+    protected byte[] sV(V val) {
+        return serializer.encode(val);
+    }
+
+    protected V dV(byte[] valBytes) {
+        return serializer.decode(valBytes);
+    }
+
+    /**
+     * Puts an entry to the map, if not already present.
+     *
+     * @param key the key of the value to put if absent
+     * @param value the value to be put if previous value does not exist
+     * @return true if put was successful.
+     */
+    public boolean putIfAbsent(K key, V value) {
+        return dbService.putIfAbsent(tableName, sK(key), sV(value));
+    }
+
+    /**
+     * Removes an entry associated to specified key.
+     *
+     * @param key key of the value to remove
+     * @return previous value in the map for the key
+     */
+    public V remove(K key) {
+        VersionedValue removed = dbService.remove(tableName, sK(key));
+        if (removed == null) {
+            return null;
+        }
+        return dV(removed.value());
+    }
+
+    /**
+     * Returns the size of the map.
+     *
+     * @return size of the map
+     */
+    public long size() {
+        // TODO this is very inefficient
+        return dbService.getAll(tableName).size();
+    }
+
+    /**
+     * Returns all the values contained in the map.
+     *
+     * @return values containd in this map
+     */
+    public Iterable<V> values() {
+        Map<String, VersionedValue> all = dbService.getAll(tableName);
+        return FluentIterable.from(all.values())
+                .transform(new Function<VersionedValue, V>() {
+
+                    @Override
+                    public V apply(VersionedValue input) {
+                        if (input == null) {
+                            return null;
+                        }
+                        return dV(input.value());
+                    }
+                })
+                .filter(notNull());
+    }
+
+    /**
+     * Gets the value in the map.
+     *
+     * @param key to get from the map
+     * @return value associated with the key, null if not such entry
+     */
+    public V get(K key) {
+        VersionedValue vv = dbService.get(tableName, sK(key));
+        if (vv == null) {
+            return null;
+        }
+        return dV(vv.value());
+    }
+
+    /**
+     * Replaces the value in the map if the value matches the expected.
+     *
+     * @param key of the entry to replace
+     * @param oldVal value expected to be in the map
+     * @param newVal value to be replaced with
+     * @return true if successfully replaced
+     */
+    public boolean replace(K key, V oldVal, V newVal) {
+        return dbService.putIfValueMatches(tableName, sK(key), sV(oldVal), sV(newVal));
+    }
+
+    /**
+     * Puts a value int the map.
+     *
+     * @param key key with which the specified value is to be associated
+     * @param value value to be associated with the specified key
+     * @return previous value or null if not such entry
+     */
+    public V put(K key, V value) {
+        VersionedValue vv = dbService.put(tableName, sK(key), sV(value));
+        if (vv == null) {
+            return null;
+        }
+        return dV(vv.value());
+    }
+}
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