com.iflytek.spider.util.DeflateUtils.java Source code

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Here is the source code for com.iflytek.spider.util.DeflateUtils.java

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/**
 * 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 com.iflytek.spider.util;

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

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
// Commons Logging imports

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

    private static final Log LOG = LogFactory.getLog(DeflateUtils.class);
    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.printStackTrace(LogUtil.getWarnStream(LOG));
                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) {
            e.printStackTrace(LogUtil.getWarnStream(LOG));
        }

        try {
            outStream.close();
        } catch (IOException e) {
            e.printStackTrace(LogUtil.getWarnStream(LOG));
        }

        return byteOut.toByteArray();
    }
}