src/java/org/apache/nutch/util/DeflateUtils.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.nutch.util;

import java.io.ByteArrayOutputStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.lang.invoke.MethodHandles;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import java.util.zip.DeflaterOutputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A collection of utility methods for working on deflated data.
 */
public class DeflateUtils {

  private static final Logger LOG = LoggerFactory
      .getLogger(MethodHandles.lookup().lookupClass());
  private static final int EXPECTED_COMPRESSION_RATIO = 5;
  private static final int BUF_SIZE = 4096;

  /**
   * Returns an inflated copy of the input array. If the deflated input has been
   * truncated or corrupted, a best-effort attempt is made to inflate as much as
   * possible. If no data can be extracted <code>null</code> is returned.
   */
  public static final byte[] inflateBestEffort(byte[] in) {
    return inflateBestEffort(in, Integer.MAX_VALUE);
  }

  /**
   * Returns an inflated copy of the input array, truncated to
   * <code>sizeLimit</code> bytes, if necessary. If the deflated input has been
   * truncated or corrupted, a best-effort attempt is made to inflate as much as
   * possible. If no data can be extracted <code>null</code> is returned.
   */
  public static final byte[] inflateBestEffort(byte[] in, int sizeLimit) {
    // decompress using InflaterInputStream
    ByteArrayOutputStream outStream = new ByteArrayOutputStream(
        EXPECTED_COMPRESSION_RATIO * in.length);

    // "true" because HTTP does not provide zlib headers
    Inflater inflater = new Inflater(true);
    InflaterInputStream inStream = new InflaterInputStream(
        new ByteArrayInputStream(in), inflater);

    byte[] buf = new byte[BUF_SIZE];
    int written = 0;
    while (true) {
      try {
        int size = inStream.read(buf);
        if (size <= 0)
          break;
        if ((written + size) > sizeLimit) {
          outStream.write(buf, 0, sizeLimit - written);
          break;
        }
        outStream.write(buf, 0, size);
        written += size;
      } catch (Exception e) {
        LOG.info("Caught Exception in inflateBestEffort", e);
        break;
      }
    }
    try {
      outStream.close();
    } catch (IOException e) {
    }

    return outStream.toByteArray();
  }

  /**
   * Returns an inflated copy of the input array.
   * 
   * @throws IOException
   *           if the input cannot be properly decompressed
   */
  public static final byte[] inflate(byte[] in) throws IOException {
    // decompress using InflaterInputStream
    ByteArrayOutputStream outStream = new ByteArrayOutputStream(
        EXPECTED_COMPRESSION_RATIO * in.length);

    InflaterInputStream inStream = new InflaterInputStream(
        new ByteArrayInputStream(in));

    byte[] buf = new byte[BUF_SIZE];
    while (true) {
      int size = inStream.read(buf);
      if (size <= 0)
        break;
      outStream.write(buf, 0, size);
    }
    outStream.close();

    return outStream.toByteArray();
  }

  /**
   * Returns a deflated copy of the input array.
   */
  public static final byte[] deflate(byte[] in) {
    // compress using DeflaterOutputStream
    ByteArrayOutputStream byteOut = new ByteArrayOutputStream(in.length
        / EXPECTED_COMPRESSION_RATIO);

    DeflaterOutputStream outStream = new DeflaterOutputStream(byteOut);

    try {
      outStream.write(in);
    } catch (Exception e) {
      LOG.error("Error compressing: ", e);
    }

    try {
      outStream.close();
    } catch (IOException e) {
      LOG.error("Error closing: ", e);
    }

    return byteOut.toByteArray();
  }
}