Java tutorial
/* * Copyright 2014 Sameer Wadkar * * 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.largecollections; import static org.fusesource.leveldbjni.JniDBFactory.bytes; import static org.fusesource.leveldbjni.JniDBFactory.factory; import java.io.Closeable; import java.io.File; import java.io.IOException; import java.io.Serializable; import java.util.Collection; import java.util.Map; import java.util.Random; import java.util.Set; import org.apache.commons.lang.StringUtils; import org.iq80.leveldb.DB; import org.iq80.leveldb.DBIterator; import org.iq80.leveldb.Options; import org.iq80.leveldb.Range; import org.iq80.leveldb.WriteBatch; import utils.DBUtils; import utils.SerializationUtils; import com.google.common.base.Preconditions; import com.google.common.base.Throwables; import com.google.common.hash.BloomFilter; import com.google.common.hash.Funnel; import com.google.common.hash.PrimitiveSink; /** * FastHashMap is an implementation of java.util.Map. FastHashMap provides a heuristic value for size which is compensated by its * faster performance. If you want a true implementation of Map which returns the most accurate value for size() use CacheMap or * LargeCacheMap * * It differs from CacheMap in that it provides a lsize() function which is longer version of size(). In this respect it deviates from a * typical Map implementation. In return it allows LargeCacheMap to have size higher than Integer.MAX_VALUE * */ public class FastCacheMap<K, V> implements Map<K, V>, IDb, Serializable, Closeable { public static final long serialVersionUID = 2l; private final static Random rnd = new Random(); protected String folder = Constants.DEFAULT_FOLDER; protected int cacheSize = Constants.DEFAULT_CACHE_SIZE; protected String name = null; protected transient DB db; protected transient Options options; protected transient File dbFile; private SerializationUtils<K, V> serdeUtils = new SerializationUtils<K, V>(); private int bloomFilterSize = 10000000; protected transient Funnel<K> myFunnel = null; private BloomFilter<K> bloomFilter = null; private void initializeBloomFilter() { this.myFunnel = new Funnel<K>() { public void funnel(K obj, PrimitiveSink into) { into.putInt(Math.abs(obj.hashCode())); } }; this.bloomFilter = BloomFilter.create(myFunnel, this.bloomFilterSize); } public FastCacheMap(String folder, String name, int cacheSize) { try { if (!StringUtils.isEmpty(name)) { this.name = name; } if (!StringUtils.isEmpty(folder)) { this.folder = folder; } if (cacheSize > 0) this.cacheSize = cacheSize; Map m = DBUtils.createDB(this.folder, this.name, this.cacheSize); this.db = (DB) m.get(Constants.DB_KEY); this.options = (Options) m.get(Constants.DB_OPTIONS_KEY); this.dbFile = (File) m.get(Constants.DB_FILE_KEY); this.initializeBloomFilter(); } catch (Exception ex) { Throwables.propagate(ex); } } public FastCacheMap(String folder, String name) { this(folder, name, Constants.DEFAULT_CACHE_SIZE); } public FastCacheMap(String folder) { this(folder, "TMP" + rnd.nextInt(1000000), Constants.DEFAULT_CACHE_SIZE); } public FastCacheMap() { this(Constants.DEFAULT_FOLDER, "TMP" + rnd.nextInt(1000000), Constants.DEFAULT_CACHE_SIZE); } public void setBloomFilterSize(int bFilterSize) { Preconditions.checkState(this.size() == 0, "Cannot reset bloom filter size when the map has non-zero size"); Preconditions.checkArgument(bFilterSize <= 0, "Bloom Filter must have a non-zero estimated size"); this.bloomFilterSize = bFilterSize; this.initializeBloomFilter(); } public boolean containsKey(Object key) { byte[] valBytes = null; if (bloomFilter.mightContain((K) key)) { byte[] keyBytes = this.serdeUtils.serializeKey((K) key); valBytes = db.get(keyBytes); } return valBytes != null; } public boolean containsValue(Object value) { throw new UnsupportedOperationException(); } public V get(Object key) { if (key == null) { throw new RuntimeException("Nulls are not allowed as key"); } if (bloomFilter.mightContain((K) key)) { byte[] keyArr = serdeUtils.serializeKey((K) key); byte[] vbytes = db.get(keyArr); if (vbytes == null) { return null; } else { return serdeUtils.deserializeValue(vbytes); } } else { return null; } } public int size() { // Not reliable. Only an approximation Range r = new Range(bytes(Character.toString(Character.MIN_VALUE)), bytes(Character.toString(Character.MAX_VALUE))); long[] l = this.db.getApproximateSizes(r); if (l != null && l.length > 0) { return (int) l[0]; } return 0; } public boolean isEmpty() { return !this.keySet().iterator().hasNext(); } public V put(K key, V value) { db.put(serdeUtils.serializeKey(key), serdeUtils.serializeValue(value)); bloomFilter.put(key); return value; } public V remove(Object key) { db.delete(serdeUtils.serializeKey((K) key)); return null;//Breaks the interface a little but fast } public void putAll(Map<? extends K, ? extends V> m) { try { WriteBatch batch = db.createWriteBatch(); int counter = 0; for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) { byte[] keyArr = serdeUtils.serializeKey(e.getKey()); bloomFilter.put(e.getKey()); batch.put(keyArr, serdeUtils.serializeValue(e.getValue())); counter++; if (counter % 1000 == 0) { db.write(batch); batch.close(); batch = db.createWriteBatch(); } } } catch (Exception ex) { Throwables.propagate(ex); } } private void writeObject(java.io.ObjectOutputStream stream) throws IOException { stream.writeObject(this.folder); stream.writeObject(this.name); stream.writeInt(this.cacheSize); stream.writeObject(this.serdeUtils); stream.writeInt(this.bloomFilterSize); stream.writeObject(this.bloomFilter); this.db.close(); } private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException { this.folder = (String) in.readObject(); this.name = (String) in.readObject(); this.cacheSize = in.readInt(); this.serdeUtils = (SerializationUtils<K, V>) in.readObject(); this.bloomFilterSize = in.readInt(); this.bloomFilter = (BloomFilter<K>) in.readObject(); Map m = DBUtils.createDB(this.folder, this.name, this.cacheSize); this.db = (DB) m.get(Constants.DB_KEY); this.options = (Options) m.get(Constants.DB_OPTIONS_KEY); this.dbFile = (File) m.get(Constants.DB_FILE_KEY); } public void clear() { DBIterator iter = this.db.iterator(); iter.seekToFirst(); while (iter.hasNext()) { Entry<byte[], byte[]> e = iter.next(); this.db.delete(e.getKey()); } this.initializeBloomFilter(); } public Set<K> keySet() { return new MapKeySet<K>(this); } public Collection<V> values() { return new MapCollection<V>(this); } public Set<java.util.Map.Entry<K, V>> entrySet() { return new MapEntrySet<K, V>(this); } public void close() throws IOException { try { this.initializeBloomFilter(); this.db.close(); factory.destroy(this.dbFile, this.options); } catch (Exception ex) { throw Throwables.propagate(ex); } } public DB getDB() { return this.db; } }