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    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.
    44      private static final int MAX_PACKET_SIZE = 16665 + 1024;
    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 }