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.bzip2;
020    
021    import java.util.HashMap;
022    import java.util.Map;
023    
024    /**
025     * Utility code for the BZip2 compression format.
026     * @ThreadSafe
027     * @since Commons Compress 1.1
028     */
029    public abstract class BZip2Utils {
030    
031        /**
032         * Map from common filename suffixes of bzip2ed files to the corresponding
033         * suffixes of uncompressed files. For example: from ".tbz2" to ".tar".
034         * <p>
035         * This map also contains bzip2-specific suffixes like ".bz2". These
036         * suffixes are mapped to the empty string, as they should simply be
037         * removed from the filename when the file is uncompressed.
038         */
039        private static final Map uncompressSuffix = new HashMap();
040    
041        static {
042            uncompressSuffix.put(".tbz2", ".tar");
043            uncompressSuffix.put(".tbz", ".tar");
044            uncompressSuffix.put(".bz2", "");
045            uncompressSuffix.put(".bz", "");
046        }
047        // N.B. if any shorter or longer keys are added, ensure the for loop limits are changed
048    
049        /** Private constructor to prevent instantiation of this utility class. */
050        private BZip2Utils() {
051        }
052    
053        /**
054         * Detects common bzip2 suffixes in the given filename.
055         *
056         * @param filename name of a file
057         * @return <code>true</code> if the filename has a common bzip2 suffix,
058         *         <code>false</code> otherwise
059         */
060        public static boolean isCompressedFilename(String filename) {
061            String lower = filename.toLowerCase();
062            int n = lower.length();
063            // Shortest suffix is three letters (.bz), longest is five (.tbz2)
064            for (int i = 3; i <= 5 && i < n; i++) {
065                if (uncompressSuffix.containsKey(lower.substring(n - i))) {
066                    return true;
067                }
068            }
069            return false;
070        }
071    
072        /**
073         * Maps the given name of a bzip2-compressed file to the name that the
074         * file should have after uncompression. Commonly used file type specific
075         * suffixes like ".tbz" or ".tbz2" are automatically detected and
076         * correctly mapped. For example the name "package.tbz2" is mapped to
077         * "package.tar". And any filenames with the generic ".bz2" suffix
078         * (or any other generic bzip2 suffix) is mapped to a name without that
079         * suffix. If no bzip2 suffix is detected, then the filename is returned
080         * unmapped.
081         *
082         * @param filename name of a file
083         * @return name of the corresponding uncompressed file
084         */
085        public static String getUncompressedFilename(String filename) {
086            String lower = filename.toLowerCase();
087            int n = lower.length();
088            // Shortest suffix is three letters (.bz), longest is five (.tbz2)
089            for (int i = 3; i <= 5 && i < n; i++) {
090                Object suffix = uncompressSuffix.get(lower.substring(n - i));
091                if (suffix != null) {
092                    return filename.substring(0, n - i) + suffix;
093                }
094            }
095            return filename;
096        }
097    
098        /**
099         * Maps the given filename to the name that the file should have after
100         * compression with bzip2. Currently this method simply appends the suffix
101         * ".bz2" to the filename based on the standard behaviour of the "bzip2"
102         * program, but a future version may implement a more complex mapping if
103         * a new widely used naming pattern emerges.
104         *
105         * @param filename name of a file
106         * @return name of the corresponding compressed file
107         */
108        public static String getCompressedFilename(String filename) {
109            return filename + ".bz2";
110        }
111    
112    }