com.gemstone.gemfire.internal.memcached.ValueWrapper Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of gemfire-core Show documentation
SnappyData store based off Pivotal GemFireXD
There is a newer version: 2.0-BETA
/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.internal.memcached;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.concurrent.atomic.AtomicLong;

import com.gemstone.gemfire.DataSerializable;
import com.gemstone.gemfire.DataSerializer;

/**
 * For CAS operation, we have to store a unique long with all
 * the values being stored. This class encapsulates the
 * version and the value. Instances of this class can be
 * obtained by using {@link #getWrappedValue(byte[], int)}
 * 
 * @author Swapnil Bawaskar
 *
 */
public class ValueWrapper implements DataSerializable {

  private static final long serialVersionUID = 7931598505833835569L;

  /**
   * used to uniquely identify the value.
   * used for "cas" operation
   */
  private long casVersion;
  
  /**
   * the value being wrapped
   */
  private byte[] value;
  

  /**
   * the flags sent by the client
   */
  private int flags;

  /**
   * used to generate the version while constructing an instance.
   */
  private static final AtomicLong versionGenerator = new AtomicLong();
  
  public ValueWrapper() {
  }

  private ValueWrapper(byte[] value, long version, int flags) {
    this.value = value;
    this.casVersion = version;
    this.flags = flags;
  }
  
  /**
   * This method should be used to obtain instances of ValueWrapper.
   * @param value the value to be wrapped
   * @param flags the flags sent by the client
   * @return an instance of ValueWrapper that includes a version along
   * with the given value.
   */
  public static ValueWrapper getWrappedValue(byte[] value, int flags) {
    return new ValueWrapper(value, versionGenerator.incrementAndGet(), flags);
  }

  /**
   * For binary protocol we always have to compare the cas version.
   * To avoid turning each put into a get and replace, use ValueWrapper
   * instances from this method which only uses cas version. note that
   * equals and hashCode of this class have also been changed to
   * only use the cas version. 
   * 
   * @param cas
   * @return an instance with null value
   */
  public static ValueWrapper getDummyValue(long cas) {
    return new ValueWrapper(null, cas, 0);
  }

  /**
   * @return the encapsulated value
   */
  public byte[] getValue() {
    return this.value;
  }
  
  /**
   * @return the unique version for the encapsulated value
   */
  public long getVersion() {
    return this.casVersion;
  }
  
  /**
   * @return the flags
   */
  public int getFlags() {
	return this.flags;  
  }
  
  @Override
  public boolean equals(Object obj) {
    if (obj instanceof ValueWrapper) {
      ValueWrapper other = (ValueWrapper) obj;
      if (this.casVersion == other.casVersion) {
        return true;
      }
    }
    return false;
  }
  
  @Override
  public int hashCode() {
    return Long.valueOf(casVersion).hashCode();
  }
  
  public void fromData(DataInput in) throws IOException,
      ClassNotFoundException {
    this.casVersion = in.readLong();
    this.value = DataSerializer.readByteArray(in);
    this.flags = in.readInt();
  }

  public void toData(DataOutput out) throws IOException {
    out.writeLong(this.casVersion);
    DataSerializer.writeByteArray(value, out);
    out.writeInt(flags);
  }

}