    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     */
    019    package org.apache.commons.compress.compressors.gzip;
    020
    021    import java.util.HashMap;
    022    import java.util.Locale;
    023    import java.util.Map;
    024
    025    /**
    026     * Utility code for the gzip compression format.
    027     * @ThreadSafe
    028     */
    029    public class GzipUtils {
    030
    031        /**
    032         * Map from common filename suffixes to the suffixes that identify gzipped
    033         * versions of those file types. For example: from ".tar" to ".tgz".
    034         */
    035        private static final Map compressSuffix = new HashMap();
    036
    037        /**
    038         * Map from common filename suffixes of gzipped files to the corresponding
    039         * suffixes of uncompressed files. For example: from ".tgz" to ".tar".
    040         * <p>
    041         * This map also contains gzip-specific suffixes like ".gz" and "-z".
    042         * These suffixes are mapped to the empty string, as they should simply
    043         * be removed from the filename when the file is uncompressed.
    044         */
    045        private static final Map uncompressSuffix = new HashMap();
    046
    047        static {
    048            compressSuffix.put(".tar", ".tgz");
    049            compressSuffix.put(".svg", ".svgz");
    050            compressSuffix.put(".cpio", ".cpgz");
    051            compressSuffix.put(".wmf", ".wmz");
    052            compressSuffix.put(".emf", ".emz");
    053
    054            uncompressSuffix.put(".tgz", ".tar");
    055            uncompressSuffix.put(".taz", ".tar");
    056            uncompressSuffix.put(".svgz", ".svg");
    057            uncompressSuffix.put(".cpgz", ".cpio");
    058            uncompressSuffix.put(".wmz", ".wmf");
    059            uncompressSuffix.put(".emz", ".emf");
    060            uncompressSuffix.put(".gz", "");
    061            uncompressSuffix.put(".z", "");
    062            uncompressSuffix.put("-gz", "");
    063            uncompressSuffix.put("-z", "");
    064            uncompressSuffix.put("_z", "");
    065        }
    066        // N.B. if any shorter or longer keys are added, ensure the for loop limits are changed
    067
    068        /** Private constructor to prevent instantiation of this utility class. */
    069        private GzipUtils() {
    070        }
    071
    072        /**
    073         * Detects common gzip suffixes in the given filename.
    074         *
    075         * @param filename name of a file
    076         * @return <code>true</code> if the filename has a common gzip suffix,
    077         *         <code>false</code> otherwise
    078         */
    079        public static boolean isCompressedFilename(String filename) {
    080            String lower = filename.toLowerCase(Locale.ENGLISH);
    081            int n = lower.length();
    082            // Shortest suffix is two letters (_z), longest is five (.svgz)
    083            for (int i = 2; i <= 5 && i < n; i++) {
    084                if (uncompressSuffix.containsKey(lower.substring(n - i))) {
    085                    return true;
    086                }
    087            }
    088            return false;
    089        }
    090
    091        /**
    092         * Maps the given name of a gzip-compressed file to the name that the
    093         * file should have after uncompression. Commonly used file type specific
    094         * suffixes like ".tgz" or ".svgz" are automatically detected and
    095         * correctly mapped. For example the name "package.tgz" is mapped to
    096         * "package.tar". And any filenames with the generic ".gz" suffix
    097         * (or any other generic gzip suffix) is mapped to a name without that
    098         * suffix. If no gzip suffix is detected, then the filename is returned
    099         * unmapped.
    100         *
    101         * @param filename name of a file
    102         * @return name of the corresponding uncompressed file
    103         */
    104        public static String getUncompressedFilename(String filename) {
    105            String lower = filename.toLowerCase(Locale.ENGLISH);
    106            int n = lower.length();
    107            // Shortest suffix is two letters (_z), longest is five (.svgz)
    108            for (int i = 2; i <= 5 && i < n; i++) {
    109                Object suffix = uncompressSuffix.get(lower.substring(n - i));
    110                if (suffix != null) {
    111                    return filename.substring(0, n - i) + suffix;
    112                }
    113            }
    114            return filename;
    115        }
    116
    117        /**
    118         * Maps the given filename to the name that the file should have after
    119         * compression with gzip. Common file types with custom suffixes for
    120         * compressed versions are automatically detected and correctly mapped.
    121         * For example the name "package.tar" is mapped to "package.tgz". If no
    122         * custom mapping is applicable, then the default ".gz" suffix is appended
    123         * to the filename.
    124         *
    125         * @param filename name of a file
    126         * @return name of the corresponding compressed file
    127         */
    128        public static String getCompressedFilename(String filename) {
    129            String lower = filename.toLowerCase(Locale.ENGLISH);
    130            int n = lower.length();
    131            // Shortest suffix is four letters (.svg), longest is five (.cpio)
    132            for (int i = 4; i <= 5 && i < n; i++) {
    133                Object suffix = compressSuffix.get(lower.substring(n - i));
    134                if (suffix != null) {
    135                    return filename.substring(0, n - i) + suffix;
    136                }
    137            }
    138            // No custom suffix found, just append the default .gz
    139            return filename + ".gz";
    140        }
    141
    142    }