org.eclipse.smila.connectivity.framework.crawler.web.util.GZIPUtils.java Source code

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/***********************************************************************************************************************
 * Copyright (c) 2008 empolis GmbH and brox IT Solutions GmbH. All rights reserved. This program and the accompanying
 * materials are made available under the terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors: Dmitry Hazin (brox IT Solutions GmbH) - initial creator Sebastian Voigt (brox IT Solutions GmbH)
 * 
 * This File is based on the src/java/org/apache/nutch/util/GZIPUtils.java from Nutch 0.8.1 (see below the licene). The
 * original File was modified by the Smila Team
 **********************************************************************************************************************/
/**
 * Copyright 2005 The Apache Software Foundation
 * 
 * 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 org.eclipse.smila.connectivity.framework.crawler.web.util;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * A collection of utility methods for working on GZIPed data.
 */
public final class GZIPUtils {

    /** The Constant LOG. */
    private static final Log LOG = LogFactory.getLog(GZIPUtils.class);

    /** The Constant EXPECTED_COMPRESSION_RATIO. */
    private static final int EXPECTED_COMPRESSION_RATIO = 5;

    /** The Constant BUF_SIZE. */
    private static final int BUF_SIZE = 4096;

    /**
     * Dummy constructor.
     */
    private GZIPUtils() {

    }

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

    /**
     * Returns an gunzipped copy of the input array, truncated to <code>sizeLimit</code> bytes, if necessary. If the
     * gzipped input has been truncated or corrupted, a best-effort attempt is made to unzip as much as possible. If no
     * data can be extracted <code>null</code> is returned.
     * 
     * @param in
     *          input byte array
     * @param sizeLimit
     *          value in bytes to truncate gunzziped copy of the input array
     * @return gunzipped byte array
     */
    public static byte[] unzipBestEffort(byte[] in, int sizeLimit) {
        try {
            // decompress using GZIPInputStream
            final ByteArrayOutputStream outStream = new ByteArrayOutputStream(
                    EXPECTED_COMPRESSION_RATIO * in.length);

            final GZIPInputStream inStream = new GZIPInputStream(new ByteArrayInputStream(in));

            final byte[] buf = new byte[BUF_SIZE];
            int written = 0;
            while (true) {
                try {
                    final int size = inStream.read(buf);
                    if (size <= 0) {
                        break;
                    }
                    if (sizeLimit > 0) {
                        if ((written + size) > sizeLimit) {
                            outStream.write(buf, 0, sizeLimit - written);
                            break;
                        }
                    }
                    outStream.write(buf, 0, size);
                    written += size;
                } catch (IOException e) {
                    break;
                }
            }
            try {
                outStream.close();
            } catch (IOException exception) {
                // don't matter
                ;
            }

            return outStream.toByteArray();

        } catch (IOException e) {
            return null;
        }
    }

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

        final GZIPInputStream inStream = new GZIPInputStream(new ByteArrayInputStream(in));

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

        return outStream.toByteArray();
    }

    /**
     * Returns an gzipped copy of the input array.
     * 
     * @param in
     *          input byte array
     * @return byte gzipped copy of the input array
     */
    public static byte[] zip(byte[] in) {
        try {
            // compress using GZIPOutputStream
            final ByteArrayOutputStream byteOut = new ByteArrayOutputStream(in.length / EXPECTED_COMPRESSION_RATIO);

            final GZIPOutputStream outStream = new GZIPOutputStream(byteOut);

            try {
                outStream.write(in);
            } catch (Exception exception) {
                LOG.error(exception.getMessage());
            }

            try {
                outStream.close();
            } catch (IOException e) {
                LOG.error(e.getMessage());
            }

            return byteOut.toByteArray();

        } catch (IOException e) {
            LOG.error(e.getMessage());
            return null;
        }
    }

}