    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.InputStreamStatistics;
    028import org.apache.commons.io.input.CountingInputStream;
    029
    030/**
    031 * Deflate decompressor.
    032 *
    033 * @since 1.9
    034 */
    035public class DeflateCompressorInputStream extends CompressorInputStream implements InputStreamStatistics {
    036
    037    private static final int MAGIC_1 = 0x78;
    038    private static final int MAGIC_2a = 0x01;
    039    private static final int MAGIC_2b = 0x5e;
    040    private static final int MAGIC_2c = 0x9c;
    041    private static final int MAGIC_2d = 0xda;
    042
    043    /**
    044     * Checks if the signature matches what is expected for a zlib / deflated file with the zlib header.
    045     *
    046     * @param signature the bytes to check
    047     * @param length    the number of bytes to check
    048     * @return true, if this stream is zlib / deflate compressed with a header stream, false otherwise
    049     *
    050     * @since 1.10
    051     */
    052    public static boolean matches(final byte[] signature, final int length) {
    053        return length > 3 && signature[0] == MAGIC_1
    054                && (signature[1] == (byte) MAGIC_2a || signature[1] == (byte) MAGIC_2b || signature[1] == (byte) MAGIC_2c || signature[1] == (byte) MAGIC_2d);
    055    }
    056
    057    private final CountingInputStream countingStream;
    058    private final InputStream in;
    059
    060    private final Inflater inflater;
    061
    062    /**
    063     * Creates a new input stream that decompresses Deflate-compressed data from the specified input stream.
    064     *
    065     * @param inputStream where to read the compressed data
    066     */
    067    public DeflateCompressorInputStream(final InputStream inputStream) {
    068        this(inputStream, new DeflateParameters());
    069    }
    070
    071    /**
    072     * Creates a new input stream that decompresses Deflate-compressed data from the specified input stream.
    073     *
    074     * @param inputStream where to read the compressed data
    075     * @param parameters  parameters
    076     */
    077    public DeflateCompressorInputStream(final InputStream inputStream, final DeflateParameters parameters) {
    078        inflater = new Inflater(!parameters.withZlibHeader());
    079        in = new InflaterInputStream(countingStream = new CountingInputStream(inputStream), inflater);
    080    }
    081
    082    /** {@inheritDoc} */
    083    @Override
    084    public int available() throws IOException {
    085        return in.available();
    086    }
    087
    088    /** {@inheritDoc} */
    089    @Override
    090    public void close() throws IOException {
    091        try {
    092            in.close();
    093        } finally {
    094            inflater.end();
    095        }
    096    }
    097
    098    /**
    099     * @since 1.17
    100     */
    101    @Override
    102    public long getCompressedCount() {
    103        return countingStream.getByteCount();
    104    }
    105
    106    /** {@inheritDoc} */
    107    @Override
    108    public int read() throws IOException {
    109        final int ret = in.read();
    110        count(ret == -1 ? 0 : 1);
    111        return ret;
    112    }
    113
    114    /** {@inheritDoc} */
    115    @Override
    116    public int read(final byte[] buf, final int off, final int len) throws IOException {
    117        if (len == 0) {
    118            return 0;
    119        }
    120        final int ret = in.read(buf, off, len);
    121        count(ret);
    122        return ret;
    123    }
    124
    125    /** {@inheritDoc} */
    126    @Override
    127    public long skip(final long n) throws IOException {
    128        return org.apache.commons.io.IOUtils.skip(in, n);
    129    }
    130}