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<String, String> compressSuffix =
036            new HashMap<String, String>();
037    
038        /**
039         * Map from common filename suffixes of gzipped files to the corresponding
040         * suffixes of uncompressed files. For example: from ".tgz" to ".tar".
041         * <p>
042         * This map also contains gzip-specific suffixes like ".gz" and "-z".
043         * These suffixes are mapped to the empty string, as they should simply
044         * be removed from the filename when the file is uncompressed.
045         */
046        private static final Map<String, String> uncompressSuffix =
047            new HashMap<String, String>();
048    
049        static {
050            compressSuffix.put(".tar", ".tgz");
051            compressSuffix.put(".svg", ".svgz");
052            compressSuffix.put(".cpio", ".cpgz");
053            compressSuffix.put(".wmf", ".wmz");
054            compressSuffix.put(".emf", ".emz");
055    
056            uncompressSuffix.put(".tgz", ".tar");
057            uncompressSuffix.put(".taz", ".tar");
058            uncompressSuffix.put(".svgz", ".svg");
059            uncompressSuffix.put(".cpgz", ".cpio");
060            uncompressSuffix.put(".wmz", ".wmf");
061            uncompressSuffix.put(".emz", ".emf");
062            uncompressSuffix.put(".gz", "");
063            uncompressSuffix.put(".z", "");
064            uncompressSuffix.put("-gz", "");
065            uncompressSuffix.put("-z", "");
066            uncompressSuffix.put("_z", "");
067        }
068        // N.B. if any shorter or longer keys are added, ensure the for loop limits are changed
069    
070        /** Private constructor to prevent instantiation of this utility class. */
071        private GzipUtils() {
072        }
073    
074        /**
075         * Detects common gzip suffixes in the given filename.
076         *
077         * @param filename name of a file
078         * @return <code>true</code> if the filename has a common gzip suffix,
079         *         <code>false</code> otherwise
080         */
081        public static boolean isCompressedFilename(String filename) {
082            String lower = filename.toLowerCase(Locale.ENGLISH);
083            int n = lower.length();
084            // Shortest suffix is two letters (_z), longest is five (.svgz)
085            for (int i = 2; i <= 5 && i < n; i++) {
086                if (uncompressSuffix.containsKey(lower.substring(n - i))) {
087                    return true;
088                }
089            }
090            return false;
091        }
092    
093        /**
094         * Maps the given name of a gzip-compressed file to the name that the
095         * file should have after uncompression. Commonly used file type specific
096         * suffixes like ".tgz" or ".svgz" are automatically detected and
097         * correctly mapped. For example the name "package.tgz" is mapped to
098         * "package.tar". And any filenames with the generic ".gz" suffix
099         * (or any other generic gzip suffix) is mapped to a name without that
100         * suffix. If no gzip suffix is detected, then the filename is returned
101         * unmapped.
102         *
103         * @param filename name of a file
104         * @return name of the corresponding uncompressed file
105         */
106        public static String getUncompressedFilename(String filename) {
107            String lower = filename.toLowerCase(Locale.ENGLISH);
108            int n = lower.length();
109            // Shortest suffix is two letters (_z), longest is five (.svgz)
110            for (int i = 2; i <= 5 && i < n; i++) {
111                Object suffix = uncompressSuffix.get(lower.substring(n - i));
112                if (suffix != null) {
113                    return filename.substring(0, n - i) + suffix;
114                }
115            }
116            return filename;
117        }
118    
119        /**
120         * Maps the given filename to the name that the file should have after
121         * compression with gzip. Common file types with custom suffixes for
122         * compressed versions are automatically detected and correctly mapped.
123         * For example the name "package.tar" is mapped to "package.tgz". If no
124         * custom mapping is applicable, then the default ".gz" suffix is appended
125         * to the filename.
126         *
127         * @param filename name of a file
128         * @return name of the corresponding compressed file
129         */
130        public static String getCompressedFilename(String filename) {
131            String lower = filename.toLowerCase(Locale.ENGLISH);
132            int n = lower.length();
133            // Shortest suffix is four letters (.svg), longest is five (.cpio)
134            for (int i = 4; i <= 5 && i < n; i++) {
135                Object suffix = compressSuffix.get(lower.substring(n - i));
136                if (suffix != null) {
137                    return filename.substring(0, n - i) + suffix;
138                }
139            }
140            // No custom suffix found, just append the default .gz
141            return filename + ".gz";
142        }
143    
144    }