1 /*
2 * Copyright 2009 Red Hat, Inc.
3 *
4 * Red Hat licenses this file to you under the Apache License, version 2.0
5 * (the "License"); you may not use this file except in compliance with the
6 * License. You may obtain a copy of the License at:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package org.jboss.netty.handler.ssl;
17
18 import java.nio.ByteBuffer;
19
20 import javax.net.ssl.SSLEngine;
21
22 /**
23 * A {@link ByteBuffer} pool dedicated for {@link SslHandler} performance
24 * improvement.
25 * <p>
26 * In most cases, you won't need to create a new pool instance because
27 * {@link SslHandler} has a default pool instance internally.
28 * <p>
29 * The reason why {@link SslHandler} requires a buffer pool is because the
30 * current {@link SSLEngine} implementation always requires a 17KiB buffer for
31 * every 'wrap' and 'unwrap' operation. In most cases, the actual size of the
32 * required buffer is much smaller than that, and therefore allocating a 17KiB
33 * buffer for every 'wrap' and 'unwrap' operation wastes a lot of memory
34 * bandwidth, resulting in the application performance degradation.
35 *
36 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
37 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
38 *
39 * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
40 */
41 public class SslBufferPool {
42
43 // Add 1024 as a room for compressed data and another 1024 for Apache Harmony compatibility.
44 private static final int MAX_PACKET_SIZE = 16665 + 2048;
45 private static final int DEFAULT_POOL_SIZE = MAX_PACKET_SIZE * 1024;
46
47 private final ByteBuffer[] pool;
48 private final int maxBufferCount;
49 private int index;
50
51 /**
52 * Creates a new buffer pool whose size is {@code 18113536}, which can
53 * hold {@code 1024} buffers.
54 */
55 public SslBufferPool() {
56 this(DEFAULT_POOL_SIZE);
57 }
58
59 /**
60 * Creates a new buffer pool.
61 *
62 * @param maxPoolSize the maximum number of bytes that this pool can hold
63 */
64 public SslBufferPool(int maxPoolSize) {
65 if (maxPoolSize <= 0) {
66 throw new IllegalArgumentException("maxPoolSize: " + maxPoolSize);
67 }
68
69 int maxBufferCount = maxPoolSize / MAX_PACKET_SIZE;
70 if (maxPoolSize % MAX_PACKET_SIZE != 0) {
71 maxBufferCount ++;
72 }
73
74 pool = new ByteBuffer[maxBufferCount];
75 this.maxBufferCount = maxBufferCount;
76 }
77
78 /**
79 * Returns the maximum size of this pool in byte unit. The returned value
80 * can be somewhat different from what was specified in the constructor.
81 */
82 public int getMaxPoolSize() {
83 return maxBufferCount * MAX_PACKET_SIZE;
84 }
85
86 /**
87 * Returns the number of bytes which were allocated but have not been
88 * acquired yet. You can estimate how optimal the specified maximum pool
89 * size is from this value. If it keeps returning {@code 0}, it means the
90 * pool is getting exhausted. If it keeps returns a unnecessarily big
91 * value, it means the pool is wasting the heap space.
92 */
93 public synchronized int getUnacquiredPoolSize() {
94 return index * MAX_PACKET_SIZE;
95 }
96
97 synchronized ByteBuffer acquire() {
98 if (index == 0) {
99 return ByteBuffer.allocate(MAX_PACKET_SIZE);
100 } else {
101 return (ByteBuffer) pool[-- index].clear();
102 }
103 }
104
105 synchronized void release(ByteBuffer buffer) {
106 if (index < maxBufferCount) {
107 pool[index ++] = buffer;
108 }
109 }
110 }