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    }