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/*
 * 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.compression;

import java.io.IOException;
import java.io.Serializable;
import java.util.concurrent.atomic.AtomicReference;

import org.xerial.snappy.Snappy;
import org.xerial.snappy.SnappyError;

import com.gemstone.gemfire.internal.compression.SnappyUtils;
import com.gemstone.gemfire.internal.i18n.LocalizedStrings;

import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;

/**
 * An implementation of {@link Compressor} for Google's Snappy compression
 * codec. Utilizes the xerial java-snappy wrapper.
 * 
 * @author rholmes
 * @author David Hoots
 * @author Kirk Lund
 * @since 7.5
 */
public final class SnappyCompressor implements Compressor, Serializable {
  private static final long serialVersionUID = 496609875302446099L;
  
  // It's possible to create more than one, but there only needs to be a single
  // instance in the VM.
  private static final AtomicReference defaultInstance = new AtomicReference();
  
  // Set to true when we've loaded the Snappy native library.
  private static boolean nativeLibraryLoaded = false;
  
  /**
   * Create a new instance of the SnappyCompressor.
   * 
   * @throws IllegaltStateException when the Snappy native library is unavailable
   */
  @SuppressFBWarnings(value="DMI_RANDOM_USED_ONLY_ONCE", justification="The native library is only used once so we only need to generate one random number")
  public SnappyCompressor() {
    synchronized (defaultInstance) {
      if (!nativeLibraryLoaded) {
        try {
          SnappyUtils.setSnappySystemProperties(SnappyUtils.getOrCreateLogWriter());
          Snappy.getNativeLibraryVersion();
        } catch (SnappyError se) {
          throw new IllegalStateException(LocalizedStrings.SnappyCompressor_UNABLE_TO_LOAD_NATIVE_SNAPPY_LIBRARY.toLocalizedString(), se);
        }
        nativeLibraryLoaded = true;
      }
    }
  }
  
  /**
   * Get the single, default instance of the SnappyCompressor.
   */
  public static final SnappyCompressor getDefaultInstance() {
    SnappyCompressor instance = defaultInstance.get();
    if (instance != null) {
      return instance;
    }

    defaultInstance.compareAndSet(null, new SnappyCompressor());
    return defaultInstance.get();
  }

  @Override
  public byte[] compress(byte[] input) {
    try {
      return Snappy.compress(input);
    } catch (IOException e) {
      throw new CompressionException(e);
    }
  }

  @Override
  public byte[] decompress(byte[] input) {
    try {
      return Snappy.uncompress(input);
    } catch (IOException e) {
      throw new CompressionException(e);
    }
  }
  
  @Override
  public int hashCode() {
    return this.getClass().getName().hashCode();
  }
  
  @Override
  public boolean equals (final Object other) {
    if (other == null) {
      return false;
    }
    
    return this.getClass().getName().equals(other.getClass().getName());
  }
}