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