SnappyCodec.java

/**
 * Copyright 2012 Twitter, 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 parquet.hadoop.codec;

import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.compress.*;
import parquet.hadoop.codec.buffers.CodecByteBufferFactory;
import parquet.hadoop.codec.buffers.CodecByteBufferFactory.BuffReuseOpt;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Snappy compression codec for Parquet.  We do not use the default hadoop
 * one since that codec adds a blocking structure around the base snappy compression
 * algorithm.  This is useful for hadoop to minimize the size of compression blocks
 * for their file formats (e.g. SequenceFile) but is undesirable for Parquet since
 * we already have the data page which provides that.
 */
public class SnappyCodec implements Configurable, CompressionCodec {
  private Configuration conf;
  // Hadoop config for how big to make intermediate buffers.
  private static final String BUFFER_SIZE_CONFIG = "io.file.buffer.size";

  // Whether to use onheap buffers or not
  public static final String REUSE_BUFFER_CONFIG = "org.apache.hadoop.io.compress.SnappyCodec.keepBuffersForReuse";

  @Override
  public void setConf(Configuration conf) {
    this.conf = conf;
  }

  @Override
  public Configuration getConf() {
    return conf;
  }

  private CodecByteBufferFactory getBufferFactory() {
    // by default maintain the existing behaviour of re-using directByteBuffers
    return conf.getBoolean(SnappyCodec.REUSE_BUFFER_CONFIG, true) ?
      new CodecByteBufferFactory(BuffReuseOpt.ReuseOnReset) :
      new CodecByteBufferFactory(BuffReuseOpt.FreeOnReset);
  }

  @Override
  public Compressor createCompressor() {
    final SnappyCompressor snappyCompressor = new SnappyCompressor();
    snappyCompressor.setByteBufferFactory( getBufferFactory() );
    return snappyCompressor;
  }

  @Override
  public Decompressor createDecompressor() {
    final SnappyDecompressor snappyDecompressor = new SnappyDecompressor();
    snappyDecompressor.setByteBufferFactory( getBufferFactory() );
    return snappyDecompressor;
  }

  @Override
  public CompressionInputStream createInputStream(InputStream stream)
      throws IOException {
    return createInputStream(stream, createDecompressor());
  }

  @Override
  public CompressionInputStream createInputStream(InputStream stream,
      Decompressor decompressor) throws IOException {
    return new NonBlockedDecompressorStream(stream, decompressor,
        conf.getInt(BUFFER_SIZE_CONFIG, 4*1024));
  }

  @Override
  public CompressionOutputStream createOutputStream(OutputStream stream)
      throws IOException {
    return createOutputStream(stream, createCompressor());
  }

  @Override
  public CompressionOutputStream createOutputStream(OutputStream stream,
      Compressor compressor) throws IOException {
    return new NonBlockedCompressorStream(stream, compressor, 
        conf.getInt(BUFFER_SIZE_CONFIG, 4*1024));
  }

  @Override
  public Class<? extends Compressor> getCompressorType() {
    return SnappyCompressor.class;
  }

  @Override
  public Class<? extends Decompressor> getDecompressorType() {
    return SnappyDecompressor.class;
  }

  @Override
  public String getDefaultExtension() {
    return ".snappy";
  }  
}