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