    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.Locale;
    023    import java.util.Map;
    024
    025    /**
    026     * Utility code for the BZip2 compression format.
    027     * @ThreadSafe
    028     * @since Commons Compress 1.1
    029     */
    030    public abstract class BZip2Utils {
    031
    032        /**
    033         * Map from common filename suffixes of bzip2ed files to the corresponding
    034         * suffixes of uncompressed files. For example: from ".tbz2" to ".tar".
    035         * <p>
    036         * This map also contains bzip2-specific suffixes like ".bz2". These
    037         * suffixes are mapped to the empty string, as they should simply be
    038         * removed from the filename when the file is uncompressed.
    039         */
    040        private static final Map<String, String> uncompressSuffix =
    041            new HashMap<String, String>();
    042
    043        static {
    044            uncompressSuffix.put(".tbz2", ".tar");
    045            uncompressSuffix.put(".tbz", ".tar");
    046            uncompressSuffix.put(".bz2", "");
    047            uncompressSuffix.put(".bz", "");
    048        }
    049        // N.B. if any shorter or longer keys are added, ensure the for loop limits are changed
    050
    051        /** Private constructor to prevent instantiation of this utility class. */
    052        private BZip2Utils() {
    053        }
    054
    055        /**
    056         * Detects common bzip2 suffixes in the given filename.
    057         *
    058         * @param filename name of a file
    059         * @return <code>true</code> if the filename has a common bzip2 suffix,
    060         *         <code>false</code> otherwise
    061         */
    062        public static boolean isCompressedFilename(String filename) {
    063            String lower = filename.toLowerCase(Locale.ENGLISH);
    064            int n = lower.length();
    065            // Shortest suffix is three letters (.bz), longest is five (.tbz2)
    066            for (int i = 3; i <= 5 && i < n; i++) {
    067                if (uncompressSuffix.containsKey(lower.substring(n - i))) {
    068                    return true;
    069                }
    070            }
    071            return false;
    072        }
    073
    074        /**
    075         * Maps the given name of a bzip2-compressed file to the name that the
    076         * file should have after uncompression. Commonly used file type specific
    077         * suffixes like ".tbz" or ".tbz2" are automatically detected and
    078         * correctly mapped. For example the name "package.tbz2" is mapped to
    079         * "package.tar". And any filenames with the generic ".bz2" suffix
    080         * (or any other generic bzip2 suffix) is mapped to a name without that
    081         * suffix. If no bzip2 suffix is detected, then the filename is returned
    082         * unmapped.
    083         *
    084         * @param filename name of a file
    085         * @return name of the corresponding uncompressed file
    086         */
    087        public static String getUncompressedFilename(String filename) {
    088            String lower = filename.toLowerCase(Locale.ENGLISH);
    089            int n = lower.length();
    090            // Shortest suffix is three letters (.bz), longest is five (.tbz2)
    091            for (int i = 3; i <= 5 && i < n; i++) {
    092                Object suffix = uncompressSuffix.get(lower.substring(n - i));
    093                if (suffix != null) {
    094                    return filename.substring(0, n - i) + suffix;
    095                }
    096            }
    097            return filename;
    098        }
    099
    100        /**
    101         * Maps the given filename to the name that the file should have after
    102         * compression with bzip2. Currently this method simply appends the suffix
    103         * ".bz2" to the filename based on the standard behaviour of the "bzip2"
    104         * program, but a future version may implement a more complex mapping if
    105         * a new widely used naming pattern emerges.
    106         *
    107         * @param filename name of a file
    108         * @return name of the corresponding compressed file
    109         */
    110        public static String getCompressedFilename(String filename) {
    111            return filename + ".bz2";
    112        }
    113
    114    }