    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 * http://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.commons.compress.compressors.deflate;
    020
    021import java.io.IOException;
    022import java.io.InputStream;
    023import java.util.zip.Inflater;
    024import java.util.zip.InflaterInputStream;
    025
    026import org.apache.commons.compress.compressors.CompressorInputStream;
    027import org.apache.commons.compress.utils.CountingInputStream;
    028import org.apache.commons.compress.utils.IOUtils;
    029import org.apache.commons.compress.utils.InputStreamStatistics;
    030
    031/**
    032 * Deflate decompressor.
    033 * @since 1.9
    034 */
    035public class DeflateCompressorInputStream extends CompressorInputStream
    036    implements InputStreamStatistics {
    037
    038    private static final int MAGIC_1 = 0x78;
    039    private static final int MAGIC_2a = 0x01;
    040    private static final int MAGIC_2b = 0x5e;
    041    private static final int MAGIC_2c = 0x9c;
    042    private static final int MAGIC_2d = 0xda;
    043
    044    private final CountingInputStream countingStream;
    045    private final InputStream in;
    046    private final Inflater inflater;
    047
    048    /**
    049     * Creates a new input stream that decompresses Deflate-compressed data
    050     * from the specified input stream.
    051     *
    052     * @param       inputStream where to read the compressed data
    053     *
    054     */
    055    public DeflateCompressorInputStream(final InputStream inputStream) {
    056        this(inputStream, new DeflateParameters());
    057    }
    058
    059    /**
    060     * Creates a new input stream that decompresses Deflate-compressed data
    061     * from the specified input stream.
    062     *
    063     * @param       inputStream where to read the compressed data
    064     * @param       parameters parameters
    065     */
    066    public DeflateCompressorInputStream(final InputStream inputStream,
    067                                        final DeflateParameters parameters) {
    068        inflater = new Inflater(!parameters.withZlibHeader());
    069        in = new InflaterInputStream(countingStream = new CountingInputStream(inputStream), inflater);
    070    }
    071
    072    /** {@inheritDoc} */
    073    @Override
    074    public int read() throws IOException {
    075        final int ret = in.read();
    076        count(ret == -1 ? 0 : 1);
    077        return ret;
    078    }
    079
    080    /** {@inheritDoc} */
    081    @Override
    082    public int read(final byte[] buf, final int off, final int len) throws IOException {
    083        if (len == 0) {
    084            return 0;
    085        }
    086        final int ret = in.read(buf, off, len);
    087        count(ret);
    088        return ret;
    089    }
    090
    091    /** {@inheritDoc} */
    092    @Override
    093    public long skip(final long n) throws IOException {
    094        return IOUtils.skip(in, n);
    095    }
    096
    097    /** {@inheritDoc} */
    098    @Override
    099    public int available() throws IOException {
    100        return in.available();
    101    }
    102
    103    /** {@inheritDoc} */
    104    @Override
    105    public void close() throws IOException {
    106        try {
    107            in.close();
    108        } finally {
    109            inflater.end();
    110        }
    111    }
    112
    113    /**
    114     * @since 1.17
    115     */
    116    @Override
    117    public long getCompressedCount() {
    118        return countingStream.getBytesRead();
    119    }
    120
    121    /**
    122     * Checks if the signature matches what is expected for a zlib / deflated file
    123     *  with the zlib header.
    124     *
    125     * @param signature
    126     *            the bytes to check
    127     * @param length
    128     *            the number of bytes to check
    129     * @return true, if this stream is zlib / deflate compressed with a header
    130     * stream, false otherwise
    131     *
    132     * @since 1.10
    133     */
    134    public static boolean matches(final byte[] signature, final int length) {
    135        return length > 3 && signature[0] == MAGIC_1 && (
    136                signature[1] == (byte) MAGIC_2a ||
    137                signature[1] == (byte) MAGIC_2b ||
    138                signature[1] == (byte) MAGIC_2c ||
    139                signature[1] == (byte) MAGIC_2d);
    140    }
    141}