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}