| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.hadoop.io; |
| |
| import com.google.common.collect.ComparisonChain; |
| import org.apache.commons.lang.builder.HashCodeBuilder; |
| |
| import java.nio.ByteBuffer; |
| import java.util.Map; |
| import java.util.TreeMap; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * This is a simple ByteBufferPool which just creates ByteBuffers as needed. |
| * It also caches ByteBuffers after they're released. It will always return |
| * the smallest cached buffer with at least the capacity you request. |
| * We don't try to do anything clever here like try to limit the maximum cache |
| * size. |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public final class ElasticByteBufferPool implements ByteBufferPool { |
| private static final class Key implements Comparable<Key> { |
| private final int capacity; |
| private final long insertionTime; |
| |
| Key(int capacity, long insertionTime) { |
| this.capacity = capacity; |
| this.insertionTime = insertionTime; |
| } |
| |
| @Override |
| public int compareTo(Key other) { |
| return ComparisonChain.start(). |
| compare(capacity, other.capacity). |
| compare(insertionTime, other.insertionTime). |
| result(); |
| } |
| |
| @Override |
| public boolean equals(Object rhs) { |
| if (rhs == null) { |
| return false; |
| } |
| try { |
| Key o = (Key)rhs; |
| return (compareTo(o) == 0); |
| } catch (ClassCastException e) { |
| return false; |
| } |
| } |
| |
| @Override |
| public int hashCode() { |
| return new HashCodeBuilder(). |
| append(capacity). |
| append(insertionTime). |
| toHashCode(); |
| } |
| } |
| |
| private final TreeMap<Key, ByteBuffer> buffers = |
| new TreeMap<Key, ByteBuffer>(); |
| |
| private final TreeMap<Key, ByteBuffer> directBuffers = |
| new TreeMap<Key, ByteBuffer>(); |
| |
| private final TreeMap<Key, ByteBuffer> getBufferTree(boolean direct) { |
| return direct ? directBuffers : buffers; |
| } |
| |
| @Override |
| public synchronized ByteBuffer getBuffer(boolean direct, int length) { |
| TreeMap<Key, ByteBuffer> tree = getBufferTree(direct); |
| Map.Entry<Key, ByteBuffer> entry = |
| tree.ceilingEntry(new Key(length, 0)); |
| if (entry == null) { |
| return direct ? ByteBuffer.allocateDirect(length) : |
| ByteBuffer.allocate(length); |
| } |
| tree.remove(entry.getKey()); |
| return entry.getValue(); |
| } |
| |
| @Override |
| public synchronized void putBuffer(ByteBuffer buffer) { |
| buffer.clear(); |
| TreeMap<Key, ByteBuffer> tree = getBufferTree(buffer.isDirect()); |
| while (true) { |
| Key key = new Key(buffer.capacity(), System.nanoTime()); |
| if (!tree.containsKey(key)) { |
| tree.put(key, buffer); |
| return; |
| } |
| // Buffers are indexed by (capacity, time). |
| // If our key is not unique on the first try, we try again, since the |
| // time will be different. Since we use nanoseconds, it's pretty |
| // unlikely that we'll loop even once, unless the system clock has a |
| // poor granularity. |
| } |
| } |
| } |