DeflateCodec.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.avro.file;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.zip.Deflater;
import java.util.zip.DeflaterOutputStream;
import java.util.zip.Inflater;
import java.util.zip.InflaterOutputStream;

/**
 * Implements DEFLATE (RFC1951) compression and decompression.
 *
 * Note that there is a distinction between RFC1951 (deflate)
 * and RFC1950 (zlib).  zlib adds an extra 2-byte header
 * at the front, and a 4-byte checksum at the end.  The
 * code here, by passing "true" as the "nowrap" option to
 * {@link Inflater} and {@link Deflater}, is using
 * RFC1951.
 */
class DeflateCodec extends Codec {

  static class Option extends CodecFactory {
    private int compressionLevel;

    Option(int compressionLevel) {
      this.compressionLevel = compressionLevel;
    }

    @Override
    protected Codec createInstance() {
      return new DeflateCodec(compressionLevel);
    }
  }

  private ByteArrayOutputStream outputBuffer;
  private Deflater deflater;
  private Inflater inflater;
  //currently only do 'nowrap' -- RFC 1951, not zlib
  private boolean nowrap = true;
  private int compressionLevel;

  public DeflateCodec(int compressionLevel) {
    this.compressionLevel = compressionLevel;
  }

  @Override
  public String getName() {
    return DataFileConstants.DEFLATE_CODEC;
  }

  @Override
  public ByteBuffer compress(ByteBuffer data) throws IOException {
    ByteArrayOutputStream baos = getOutputBuffer(data.remaining());
    DeflaterOutputStream ios = new DeflaterOutputStream(baos, getDeflater());
    writeAndClose(data, ios);
    ByteBuffer result = ByteBuffer.wrap(baos.toByteArray());
    return result;
  }

  @Override
  public ByteBuffer decompress(ByteBuffer data) throws IOException {
    ByteArrayOutputStream baos = getOutputBuffer(data.remaining());
    InflaterOutputStream ios = new InflaterOutputStream(baos, getInflater());
    writeAndClose(data, ios);
    ByteBuffer result = ByteBuffer.wrap(baos.toByteArray());
    return result;
  }

  private void writeAndClose(ByteBuffer data, OutputStream to) throws IOException {
    byte[] input = data.array();
    int offset = data.arrayOffset() + data.position();
    int length = data.remaining();
    try {
      to.write(input, offset, length);
    } finally {
      to.close();
    }
  }

  // get and initialize the inflater for use.
  private Inflater getInflater() {
    if (null == inflater) {
      inflater = new Inflater(nowrap);
    }
    inflater.reset();
    return inflater;
  }

  // get and initialize the deflater for use.
  private Deflater getDeflater() {
    if (null == deflater) {
      deflater = new Deflater(compressionLevel, nowrap);
    }
    deflater.reset();
    return deflater;
  }

  // get and initialize the output buffer for use.
  private ByteArrayOutputStream getOutputBuffer(int suggestedLength) {
    if (null == outputBuffer) {
      outputBuffer = new ByteArrayOutputStream(suggestedLength);
    }
    outputBuffer.reset();
    return outputBuffer;
  }

  @Override
  public int hashCode() {
    return nowrap ? 0 : 1;
  }

  @Override
  public boolean equals(Object obj) {
    if (this == obj)
      return true;
    if (obj == null || obj.getClass() != getClass())
      return false;
    DeflateCodec other = (DeflateCodec)obj;
    return (this.nowrap == other.nowrap);
  }

  @Override
  public String toString() {
    return getName() + "-" + compressionLevel;
  }
}