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