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    1   /*
    2    * Copyright 2012 The Netty Project
    3    *
    4    * The Netty Project licenses this file to you under the Apache License,
    5    * version 2.0 (the "License"); you may not use this file except in compliance
    6    * with the 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  public class DefaultObjectSizeEstimator implements ObjectSizeEstimator {
    33
    34      private final ConcurrentMap<Class<?>, Integer> class2size =
    35          new ConcurrentIdentityWeakKeyHashMap<Class<?>, Integer>();
    36
    37      /**
    38       * Creates a new instance.
    39       */
    40      public DefaultObjectSizeEstimator() {
    41          class2size.put(boolean.class, 4); // Probably an integer.
    42          class2size.put(byte.class, 1);
    43          class2size.put(char.class, 2);
    44          class2size.put(int.class, 4);
    45          class2size.put(short.class, 2);
    46          class2size.put(long.class, 8);
    47          class2size.put(float.class, 4);
    48          class2size.put(double.class, 8);
    49          class2size.put(void.class, 0);
    50      }
    51
    52      public int estimateSize(Object o) {
    53          if (o == null) {
    54              return 8;
    55          }
    56
    57          int answer = 8 + estimateSize(o.getClass(), null);
    58
    59          if (o instanceof EstimatableObjectWrapper) {
    60              answer += estimateSize(((EstimatableObjectWrapper) o).unwrap());
    61          } else if (o instanceof MessageEvent) {
    62              answer += estimateSize(((MessageEvent) o).getMessage());
    63          } else if (o instanceof ChannelBuffer) {
    64              answer += ((ChannelBuffer) o).capacity();
    65          } else if (o instanceof byte[]) {
    66              answer += ((byte[]) o).length;
    67          } else if (o instanceof ByteBuffer) {
    68              answer += ((ByteBuffer) o).remaining();
    69          } else if (o instanceof CharSequence) {
    70              answer += ((CharSequence) o).length() << 1;
    71          } else if (o instanceof Iterable<?>) {
    72              for (Object m : (Iterable<?>) o) {
    73                  answer += estimateSize(m);
    74              }
    75          }
    76
    77          return align(answer);
    78      }
    79
    80      private int estimateSize(Class<?> clazz, Set<Class<?>> visitedClasses) {
    81          Integer objectSize = class2size.get(clazz);
    82          if (objectSize != null) {
    83              return objectSize;
    84          }
    85
    86          if (visitedClasses != null) {
    87              if (visitedClasses.contains(clazz)) {
    88                  return 0;
    89              }
    90          } else {
    91              visitedClasses = new HashSet<Class<?>>();
    92          }
    93
    94          visitedClasses.add(clazz);
    95
    96          int answer = 8; // Basic overhead.
    97          for (Class<?> c = clazz; c != null; c = c.getSuperclass()) {
    98              Field[] fields = c.getDeclaredFields();
    99              for (Field f : fields) {
    100                 if ((f.getModifiers() & Modifier.STATIC) != 0) {
    101                     // Ignore static fields.
    102                     continue;
    103                 }
    104
    105                 answer += estimateSize(f.getType(), visitedClasses);
    106             }
    107         }
    108
    109         visitedClasses.remove(clazz);
    110
    111         // Some alignment.
    112         answer = align(answer);
    113
    114         // Put the final answer.
    115         class2size.putIfAbsent(clazz, answer);
    116         return answer;
    117     }
    118
    119     private static int align(int size) {
    120         int r = size % 8;
    121         if (r != 0) {
    122             size += 8 - r;
    123         }
    124         return size;
    125     }
    126 }