LazyMessage.java

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/*
 * Copyright (C) 2012 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.ros.internal.transport.queue;

import com.google.common.annotations.VisibleForTesting;

import org.jboss.netty.buffer.ChannelBuffer;
import org.ros.message.MessageDeserializer;

public class LazyMessage<T> {

  private final ChannelBuffer buffer;
  private final MessageDeserializer<T> deserializer;
  private final Object mutex;

  private T message;

  public LazyMessage(ChannelBuffer buffer, MessageDeserializer<T> deserializer) {
    this.buffer = buffer;
    this.deserializer = deserializer;
    mutex = new Object();
  }

  @VisibleForTesting
  LazyMessage(T message) {
    this(null, null);
    this.message = message;
  }

  public T get() {
    synchronized (mutex) {
      if (message != null) {
        return message;
      }
      message = deserializer.deserialize(buffer);
    }
    return message;
  }
}