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 */ 019package org.apache.commons.compress.compressors.xz; 020 021import java.util.HashMap; 022import java.util.Map; 023import org.apache.commons.compress.compressors.FileNameUtil; 024 025/** 026 * Utility code for the xz compression format. 027 * @ThreadSafe 028 * @since 1.4 029 */ 030public class XZUtils { 031 032 private static final FileNameUtil fileNameUtil; 033 034 /** 035 * XZ Header Magic Bytes begin a XZ file. 036 * 037 * <p>This is a copy of {@code org.tukaani.xz.XZ.HEADER_MAGIC} in 038 * XZ for Java version 1.5.</p> 039 */ 040 private static final byte[] HEADER_MAGIC = { 041 (byte) 0xFD, '7', 'z', 'X', 'Z', '\0' 042 }; 043 044 static enum CachedAvailability { 045 DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE 046 } 047 048 private static volatile CachedAvailability cachedXZAvailability; 049 050 static { 051 Map<String, String> uncompressSuffix = new HashMap<String, String>(); 052 uncompressSuffix.put(".txz", ".tar"); 053 uncompressSuffix.put(".xz", ""); 054 uncompressSuffix.put("-xz", ""); 055 fileNameUtil = new FileNameUtil(uncompressSuffix, ".xz"); 056 cachedXZAvailability = CachedAvailability.DONT_CACHE; 057 try { 058 Class.forName("org.osgi.framework.BundleEvent"); 059 } catch (Exception ex) { 060 setCacheXZAvailablity(true); 061 } 062 } 063 064 /** Private constructor to prevent instantiation of this utility class. */ 065 private XZUtils() { 066 } 067 068 /** 069 * Checks if the signature matches what is expected for a .xz file. 070 * 071 * <p>This is more or less a copy of the version found in {@link 072 * XZCompressorInputStream} but doesn't depend on the presence of 073 * XZ for Java.</p> 074 * 075 * @param signature the bytes to check 076 * @param length the number of bytes to check 077 * @return true if signature matches the .xz magic bytes, false otherwise 078 * @since 1.9 079 */ 080 public static boolean matches(byte[] signature, int length) { 081 if (length < HEADER_MAGIC.length) { 082 return false; 083 } 084 085 for (int i = 0; i < HEADER_MAGIC.length; ++i) { 086 if (signature[i] != HEADER_MAGIC[i]) { 087 return false; 088 } 089 } 090 091 return true; 092 } 093 094 /** 095 * Are the classes required to support XZ compression available? 096 * @since 1.5 097 */ 098 public static boolean isXZCompressionAvailable() { 099 final CachedAvailability cachedResult = cachedXZAvailability; 100 if (cachedResult != CachedAvailability.DONT_CACHE) { 101 return cachedResult == CachedAvailability.CACHED_AVAILABLE; 102 } 103 return internalIsXZCompressionAvailable(); 104 } 105 106 private static boolean internalIsXZCompressionAvailable() { 107 try { 108 XZCompressorInputStream.matches(null, 0); 109 return true; 110 } catch (NoClassDefFoundError error) { 111 return false; 112 } 113 } 114 115 /** 116 * Detects common xz suffixes in the given filename. 117 * 118 * @param filename name of a file 119 * @return {@code true} if the filename has a common xz suffix, 120 * {@code false} otherwise 121 */ 122 public static boolean isCompressedFilename(String filename) { 123 return fileNameUtil.isCompressedFilename(filename); 124 } 125 126 /** 127 * Maps the given name of a xz-compressed file to the name that the 128 * file should have after uncompression. Commonly used file type specific 129 * suffixes like ".txz" are automatically detected and 130 * correctly mapped. For example the name "package.txz" is mapped to 131 * "package.tar". And any filenames with the generic ".xz" suffix 132 * (or any other generic xz suffix) is mapped to a name without that 133 * suffix. If no xz suffix is detected, then the filename is returned 134 * unmapped. 135 * 136 * @param filename name of a file 137 * @return name of the corresponding uncompressed file 138 */ 139 public static String getUncompressedFilename(String filename) { 140 return fileNameUtil.getUncompressedFilename(filename); 141 } 142 143 /** 144 * Maps the given filename to the name that the file should have after 145 * compression with xz. Common file types with custom suffixes for 146 * compressed versions are automatically detected and correctly mapped. 147 * For example the name "package.tar" is mapped to "package.txz". If no 148 * custom mapping is applicable, then the default ".xz" suffix is appended 149 * to the filename. 150 * 151 * @param filename name of a file 152 * @return name of the corresponding compressed file 153 */ 154 public static String getCompressedFilename(String filename) { 155 return fileNameUtil.getCompressedFilename(filename); 156 } 157 158 /** 159 * Whether to cache the result of the XZ for Java check. 160 * 161 * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p> 162 * @param doCache whether to cache the result 163 * @since 1.9 164 */ 165 public static void setCacheXZAvailablity(boolean doCache) { 166 if (!doCache) { 167 cachedXZAvailability = CachedAvailability.DONT_CACHE; 168 } else if (cachedXZAvailability == CachedAvailability.DONT_CACHE) { 169 final boolean hasXz = internalIsXZCompressionAvailable(); 170 cachedXZAvailability = hasXz ? CachedAvailability.CACHED_AVAILABLE 171 : CachedAvailability.CACHED_UNAVAILABLE; 172 } 173 } 174 175 // only exists to support unit tests 176 static CachedAvailability getCachedXZAvailability() { 177 return cachedXZAvailability; 178 } 179}