com.mucommander.commons.file.impl.bzip2.Bzip2ArchiveFile.java Source code

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Here is the source code for com.mucommander.commons.file.impl.bzip2.Bzip2ArchiveFile.java

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/**
 * This file is part of muCommander, http://www.mucommander.com
 * Copyright (C) 2002-2010 Maxence Bernard
 *
 * muCommander is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * muCommander is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.mucommander.commons.file.impl.bzip2;

import com.mucommander.commons.file.*;
import org.apache.hadoop.io.compress.bzip2.CBZip2InputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Bzip2ArchiveFile provides read-only access to archives in the Bzip2 format.
 *
 * <p>The actual decompression work is performed by the <code>Apache Ant</code> library under the terms of the
 * Apache Software License.</p>
 *
 * @see com.mucommander.commons.file.impl.bzip2.Bzip2FormatProvider
 * @author Maxence Bernard
 */
public class Bzip2ArchiveFile extends AbstractROArchiveFile {
    private static final Logger LOGGER = LoggerFactory.getLogger(Bzip2ArchiveFile.class);

    /**
     * Creates a BzipArchiveFile on top of the given file.
     *
     * @param file the underlying file to wrap this archive file around
     */
    public Bzip2ArchiveFile(AbstractFile file) {
        super(file);
    }

    ////////////////////////////////////////
    // AbstractArchiveFile implementation //
    ////////////////////////////////////////

    @Override
    public ArchiveEntryIterator getEntryIterator() throws IOException {
        String extension = getExtension();
        String name = getName();

        if (extension != null) {
            extension = extension.toLowerCase();

            // Remove the 'bz2' or 'tbz2' extension from the entry's name
            if (extension.equals("tbz2"))
                name = name.substring(0, name.length() - 4) + "tar";
            else if (extension.equals("bz2"))
                name = name.substring(0, name.length() - 4);
        }

        return new SingleArchiveEntryIterator(new ArchiveEntry("/" + name, false, getDate(), -1, true));
    }

    @Override
    public InputStream getEntryInputStream(ArchiveEntry entry, ArchiveEntryIterator entryIterator)
            throws IOException {
        try {
            InputStream in = getInputStream();

            // Skips the 2 magic bytes 'BZ', as required by CBZip2InputStream. Quoted from CBZip2InputStream's Javadoc:
            // "Although BZip2 headers are marked with the magic 'Bz'. this constructor expects the next byte in the
            // stream to be the first one after the magic.  Thus callers have to skip the first two bytes. Otherwise
            // this constructor will throw an exception."
            // Note: the return value of read() is unchecked. In the unlikely event that EOF is reached in the first
            // 2 bytes, CBZip2InputStream will throw an IOException.
            in.read();
            in.read();

            // Quoted from CBZip2InputStream's Javadoc:
            // "CBZip2InputStream reads bytes from the compressed source stream via the single byte {@link java.io.InputStream#read()
            // read()} method exclusively. Thus you should consider to use a buffered source stream."
            return new CBZip2InputStream(new BufferedInputStream(in));
        } catch (Exception e) {
            // CBZip2InputStream is known to throw NullPointerException if file is not properly Bzip2-encoded
            // so we need to catch those and throw them as IOException
            LOGGER.info("Exception caught while creating CBZip2InputStream, throwing IOException", e);

            throw new IOException();
        }
    }
}