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;
027
028/**
029 * Deflate decompressor.
030 * @since 1.9
031 */
032public class DeflateCompressorInputStream extends CompressorInputStream {
033    private static final int MAGIC_1 = 0x78;
034    private static final int MAGIC_2a = 0x01;
035    private static final int MAGIC_2b = 0x5e;
036    private static final int MAGIC_2c = 0x9c;
037    private static final int MAGIC_2d = 0xda;
038
039    private final InputStream in;
040    private final Inflater inflater;
041
042    /**
043     * Creates a new input stream that decompresses Deflate-compressed data
044     * from the specified input stream.
045     *
046     * @param       inputStream where to read the compressed data
047     *
048     */
049    public DeflateCompressorInputStream(final InputStream inputStream) {
050        this(inputStream, new DeflateParameters());
051    }
052
053    /**
054     * Creates a new input stream that decompresses Deflate-compressed data
055     * from the specified input stream.
056     *
057     * @param       inputStream where to read the compressed data
058     * @param       parameters parameters
059     */
060    public DeflateCompressorInputStream(final InputStream inputStream,
061                                        final DeflateParameters parameters) {
062        inflater = new Inflater(!parameters.withZlibHeader());
063        in = new InflaterInputStream(inputStream, inflater);
064    }
065
066    /** {@inheritDoc} */
067    @Override
068    public int read() throws IOException {
069        final int ret = in.read();
070        count(ret == -1 ? 0 : 1);
071        return ret;
072    }
073
074    /** {@inheritDoc} */
075    @Override
076    public int read(final byte[] buf, final int off, final int len) throws IOException {
077        final int ret = in.read(buf, off, len);
078        count(ret);
079        return ret;
080    }
081
082    /** {@inheritDoc} */
083    @Override
084    public long skip(final long n) throws IOException {
085        return in.skip(n);
086    }
087
088    /** {@inheritDoc} */
089    @Override
090    public int available() throws IOException {
091        return in.available();
092    }
093
094    /** {@inheritDoc} */
095    @Override
096    public void close() throws IOException {
097        try {
098            in.close();
099        } finally {
100            inflater.end();
101        }
102    }
103
104    /**
105     * Checks if the signature matches what is expected for a zlib / deflated file
106     *  with the zlib header.
107     *
108     * @param signature
109     *            the bytes to check
110     * @param length
111     *            the number of bytes to check
112     * @return true, if this stream is zlib / deflate compressed with a header
113     * stream, false otherwise
114     *
115     * @since 1.10
116     */
117    public static boolean matches(final byte[] signature, final int length) {
118        return length > 3 && signature[0] == MAGIC_1 && (
119                signature[1] == (byte) MAGIC_2a ||
120                signature[1] == (byte) MAGIC_2b ||
121                signature[1] == (byte) MAGIC_2c ||
122                signature[1] == (byte) MAGIC_2d);
123    }
124}