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    1   /*
    2    *  Licensed to the Apache Software Foundation (ASF) under one
    3    *  or more contributor license agreements.  See the NOTICE file
    4    *  distributed with this work for additional information
    5    *  regarding copyright ownership.  The ASF licenses this file
    6    *  to you under the Apache License, Version 2.0 (the
    7    *  "License"); you may not use this file except in compliance
    8    *  with the License.  You may obtain a copy of the License at
    9    *
    10   *    http://www.apache.org/licenses/LICENSE-2.0
    11   *
    12   *  Unless required by applicable law or agreed to in writing,
    13   *  software distributed under the License is distributed on an
    14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    15   *  KIND, either express or implied.  See the License for the
    16   *  specific language governing permissions and limitations
    17   *  under the License.
    18   *
    19   */
    20  package org.apache.mina.common.support;
    21
    22  import java.util.ArrayList;
    23  import java.util.List;
    24
    25  import org.apache.mina.common.ExceptionMonitor;
    26  import org.apache.mina.common.IoFuture;
    27  import org.apache.mina.common.IoFutureListener;
    28  import org.apache.mina.common.IoSession;
    29
    30  /**
    31   * A default implementation of {@link IoFuture}.
    32   *
    33   * @author The Apache MINA Project (dev@mina.apache.org)
    34   * @version $Rev: 599822 $, $Date: 2007-11-30 22:54:07 +0900 (Fri, 30 Nov 2007) $
    35   */
    36  public class DefaultIoFuture implements IoFuture {
    37
    38      private final IoSession session;
    39      private final Object lock;
    40      private IoFutureListener firstListener;
    41      private List<IoFutureListener> otherListeners;
    42      private Object result;
    43      private boolean ready;
    44      private int waiters;
    45
    46      /**
    47       * Creates a new instance.
    48       *
    49       * @param session an {@link IoSession} which is associated with this future
    50       */
    51      public DefaultIoFuture(IoSession session) {
    52          this.session = session;
    53          this.lock = this;
    54      }
    55
    56      /**
    57       * Creates a new instance.
    58       *
    59       * @param session an {@link IoSession} which is associated with this future
    60       */
    61      public DefaultIoFuture(IoSession session, Object lock) {
    62          this.session = session;
    63          this.lock = lock;
    64      }
    65
    66      public IoSession getSession() {
    67          return session;
    68      }
    69
    70      public Object getLock() {
    71          return lock;
    72      }
    73
    74      public void join() {
    75          awaitUninterruptibly();
    76      }
    77
    78      public boolean join(long timeoutMillis) {
    79          return awaitUninterruptibly(timeoutMillis);
    80      }
    81
    82      private IoFuture awaitUninterruptibly() {
    83          synchronized (lock) {
    84              while (!ready) {
    85                  waiters++;
    86                  try {
    87                      lock.wait();
    88                  } catch (InterruptedException e) {
    89                  } finally {
    90                      waiters--;
    91                  }
    92              }
    93          }
    94
    95          return this;
    96      }
    97
    98      private boolean awaitUninterruptibly(long timeoutMillis) {
    99          try {
    100             return await0(timeoutMillis, false);
    101         } catch (InterruptedException e) {
    102             throw new InternalError();
    103         }
    104     }
    105
    106     private boolean await0(long timeoutMillis, boolean interruptable) throws InterruptedException {
    107         long startTime = timeoutMillis <= 0 ? 0 : System.currentTimeMillis();
    108         long waitTime = timeoutMillis;
    109
    110         synchronized (lock) {
    111             if (ready) {
    112                 return ready;
    113             } else if (waitTime <= 0) {
    114                 return ready;
    115             }
    116
    117             waiters++;
    118             try {
    119                 for (;;) {
    120                     try {
    121                         lock.wait(waitTime);
    122                     } catch (InterruptedException e) {
    123                         if (interruptable) {
    124                             throw e;
    125                         }
    126                     }
    127
    128                     if (ready) {
    129                         return true;
    130                     } else {
    131                         waitTime = timeoutMillis
    132                                 - (System.currentTimeMillis() - startTime);
    133                         if (waitTime <= 0) {
    134                             return ready;
    135                         }
    136                     }
    137                 }
    138             } finally {
    139                 waiters--;
    140             }
    141         }
    142     }
    143
    144     public boolean isReady() {
    145         synchronized (lock) {
    146             return ready;
    147         }
    148     }
    149
    150     /**
    151      * Sets the result of the asynchronous operation, and mark it as finished.
    152      */
    153     protected void setValue(Object newValue) {
    154         synchronized (lock) {
    155             // Allow only once.
    156             if (ready) {
    157                 return;
    158             }
    159
    160             result = newValue;
    161             ready = true;
    162             if (waiters > 0) {
    163                 lock.notifyAll();
    164             }
    165         }
    166
    167         notifyListeners();
    168     }
    169
    170     /**
    171      * Returns the result of the asynchronous operation.
    172      */
    173     protected Object getValue() {
    174         synchronized (lock) {
    175             return result;
    176         }
    177     }
    178
    179     public void addListener(IoFutureListener listener) {
    180         if (listener == null) {
    181             throw new NullPointerException("listener");
    182         }
    183
    184         boolean notifyNow = false;
    185         synchronized (lock) {
    186             if (ready) {
    187                 notifyNow = true;
    188             } else {
    189                 if (firstListener == null) {
    190                     firstListener = listener;
    191                 } else {
    192                     if (otherListeners == null) {
    193                         otherListeners = new ArrayList<IoFutureListener>(1);
    194                     }
    195                     otherListeners.add(listener);
    196                 }
    197             }
    198         }
    199
    200         if (notifyNow) {
    201             notifyListener(listener);
    202         }
    203     }
    204
    205     public void removeListener(IoFutureListener listener) {
    206         if (listener == null) {
    207             throw new NullPointerException("listener");
    208         }
    209
    210         synchronized (lock) {
    211             if (!ready) {
    212                 if (listener == firstListener) {
    213                     if (otherListeners != null && !otherListeners.isEmpty()) {
    214                         firstListener = otherListeners.remove(0);
    215                     } else {
    216                         firstListener = null;
    217                     }
    218                 } else if (otherListeners != null) {
    219                     otherListeners.remove(listener);
    220                 }
    221             }
    222         }
    223     }
    224
    225     private void notifyListeners() {
    226         // There won't be any visibility problem or concurrent modification
    227         // because 'ready' flag will be checked against both addListener and
    228         // removeListener calls.
    229         if (firstListener != null) {
    230             notifyListener(firstListener);
    231             firstListener = null;
    232
    233             if (otherListeners != null) {
    234                 for (IoFutureListener l : otherListeners) {
    235                     notifyListener(l);
    236                 }
    237                 otherListeners = null;
    238             }
    239         }
    240     }
    241
    242     @SuppressWarnings("unchecked")
    243     private void notifyListener(IoFutureListener l) {
    244         try {
    245             l.operationComplete(this);
    246         } catch (Throwable t) {
    247             ExceptionMonitor.getInstance().exceptionCaught(t);
    248         }
    249     }
    250 }