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