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 }