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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.util;
    17
    18  import java.lang.reflect.Field;
    19  import java.lang.reflect.Modifier;
    20  import java.nio.ByteBuffer;
    21  import java.util.HashSet;
    22  import java.util.Set;
    23  import java.util.concurrent.ConcurrentMap;
    24
    25  import org.jboss.netty.buffer.ChannelBuffer;
    26  import org.jboss.netty.channel.MessageEvent;
    27  import org.jboss.netty.util.internal.ConcurrentIdentityWeakKeyHashMap;
    28
    29  /**
    30   * The default {@link ObjectSizeEstimator} implementation for general purpose.
    31   *
    32   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    33   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    34   *
    35   * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
    36   *
    37   */
    38  public class DefaultObjectSizeEstimator implements ObjectSizeEstimator {
    39
    40      private final ConcurrentMap<Class<?>, Integer> class2size =
    41          new ConcurrentIdentityWeakKeyHashMap<Class<?>, Integer>();
    42
    43      /**
    44       * Creates a new instance.
    45       */
    46      public DefaultObjectSizeEstimator() {
    47          class2size.put(boolean.class, 4); // Probably an integer.
    48          class2size.put(byte.class, 1);
    49          class2size.put(char.class, 2);
    50          class2size.put(int.class, 4);
    51          class2size.put(short.class, 2);
    52          class2size.put(long.class, 8);
    53          class2size.put(float.class, 4);
    54          class2size.put(double.class, 8);
    55          class2size.put(void.class, 0);
    56      }
    57
    58      public int estimateSize(Object o) {
    59          if (o == null) {
    60              return 8;
    61          }
    62
    63          int answer = 8 + estimateSize(o.getClass(), null);
    64
    65          if (o instanceof EstimatableObjectWrapper) {
    66              answer += estimateSize(((EstimatableObjectWrapper) o).unwrap());
    67          } else if (o instanceof MessageEvent) {
    68              answer += estimateSize(((MessageEvent) o).getMessage());
    69          } else if (o instanceof ChannelBuffer) {
    70              answer += ((ChannelBuffer) o).capacity();
    71          } else if (o instanceof byte[]) {
    72              answer += ((byte[]) o).length;
    73          } else if (o instanceof ByteBuffer) {
    74              answer += ((ByteBuffer) o).remaining();
    75          } else if (o instanceof CharSequence) {
    76              answer += ((CharSequence) o).length() << 1;
    77          } else if (o instanceof Iterable<?>) {
    78              for (Object m : (Iterable<?>) o) {
    79                  answer += estimateSize(m);
    80              }
    81          }
    82
    83          return align(answer);
    84      }
    85
    86      private int estimateSize(Class<?> clazz, Set<Class<?>> visitedClasses) {
    87          Integer objectSize = class2size.get(clazz);
    88          if (objectSize != null) {
    89              return objectSize;
    90          }
    91
    92          if (visitedClasses != null) {
    93              if (visitedClasses.contains(clazz)) {
    94                  return 0;
    95              }
    96          } else {
    97              visitedClasses = new HashSet<Class<?>>();
    98          }
    99
    100         visitedClasses.add(clazz);
    101
    102         int answer = 8; // Basic overhead.
    103         for (Class<?> c = clazz; c != null; c = c.getSuperclass()) {
    104             Field[] fields = c.getDeclaredFields();
    105             for (Field f : fields) {
    106                 if ((f.getModifiers() & Modifier.STATIC) != 0) {
    107                     // Ignore static fields.
    108                     continue;
    109                 }
    110
    111                 answer += estimateSize(f.getType(), visitedClasses);
    112             }
    113         }
    114
    115         visitedClasses.remove(clazz);
    116
    117         // Some alignment.
    118         answer = align(answer);
    119
    120         // Put the final answer.
    121         class2size.putIfAbsent(clazz, answer);
    122         return answer;
    123     }
    124
    125     private static int align(int size) {
    126         int r = size % 8;
    127         if (r != 0) {
    128             size += 8 - r;
    129         }
    130         return size;
    131     }
    132 }