    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.gzip;
    020
    021import java.nio.charset.Charset;
    022import java.nio.charset.StandardCharsets;
    023import java.util.LinkedHashMap;
    024import java.util.Map;
    025
    026import org.apache.commons.compress.compressors.FileNameUtil;
    027
    028/**
    029 * Utility code for the gzip compression format.
    030 * @ThreadSafe
    031 */
    032public class GzipUtils {
    033
    034    private static final FileNameUtil fileNameUtil;
    035
    036    static {
    037        // using LinkedHashMap so .tgz is preferred over .taz as
    038        // compressed extension of .tar as FileNameUtil will use the
    039        // first one found
    040        final Map<String, String> uncompressSuffix =
    041            new LinkedHashMap<>();
    042        uncompressSuffix.put(".tgz", ".tar");
    043        uncompressSuffix.put(".taz", ".tar");
    044        uncompressSuffix.put(".svgz", ".svg");
    045        uncompressSuffix.put(".cpgz", ".cpio");
    046        uncompressSuffix.put(".wmz", ".wmf");
    047        uncompressSuffix.put(".emz", ".emf");
    048        uncompressSuffix.put(".gz", "");
    049        uncompressSuffix.put(".z", "");
    050        uncompressSuffix.put("-gz", "");
    051        uncompressSuffix.put("-z", "");
    052        uncompressSuffix.put("_z", "");
    053        fileNameUtil = new FileNameUtil(uncompressSuffix, ".gz");
    054    }
    055
    056    /**
    057     * Encoding for file name and comments per the <a href="https://tools.ietf.org/html/rfc1952">GZIP File Format Specification</a>
    058     */
    059    static final Charset GZIP_ENCODING = StandardCharsets.ISO_8859_1;
    060
    061    /**
    062     * Maps the given file name to the name that the file should have after
    063     * compression with gzip. Common file types with custom suffixes for
    064     * compressed versions are automatically detected and correctly mapped.
    065     * For example the name "package.tar" is mapped to "package.tgz". If no
    066     * custom mapping is applicable, then the default ".gz" suffix is appended
    067     * to the file name.
    068     *
    069     * @param fileName name of a file
    070     * @return name of the corresponding compressed file
    071     */
    072    public static String getCompressedFilename(final String fileName) {
    073        return fileNameUtil.getCompressedFilename(fileName);
    074    }
    075
    076    /**
    077     * Maps the given name of a gzip-compressed file to the name that the
    078     * file should have after uncompression. Commonly used file type specific
    079     * suffixes like ".tgz" or ".svgz" are automatically detected and
    080     * correctly mapped. For example the name "package.tgz" is mapped to
    081     * "package.tar". And any file names with the generic ".gz" suffix
    082     * (or any other generic gzip suffix) is mapped to a name without that
    083     * suffix. If no gzip suffix is detected, then the file name is returned
    084     * unmapped.
    085     *
    086     * @param fileName name of a file
    087     * @return name of the corresponding uncompressed file
    088     */
    089    public static String getUncompressedFilename(final String fileName) {
    090        return fileNameUtil.getUncompressedFilename(fileName);
    091    }
    092
    093    /**
    094     * Detects common gzip suffixes in the given file name.
    095     *
    096     * @param fileName name of a file
    097     * @return {@code true} if the file name has a common gzip suffix,
    098     *         {@code false} otherwise
    099     */
    100    public static boolean isCompressedFilename(final String fileName) {
    101        return fileNameUtil.isCompressedFilename(fileName);
    102    }
    103
    104    /** Private constructor to prevent instantiation of this utility class. */
    105    private GzipUtils() {
    106    }
    107
    108}