1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 */ 19 package org.apache.commons.compress.compressors.lzma; 20 21 import java.util.HashMap; 22 import java.util.Map; 23 import org.apache.commons.compress.compressors.FileNameUtil; 24 25 /** 26 * Utility code for the lzma compression format. 27 * @ThreadSafe 28 * @since 1.10 29 */ 30 public class LZMAUtils { 31 32 private static final FileNameUtil fileNameUtil; 33 34 /** 35 * LZMA Header Magic Bytes begin a LZMA file. 36 */ 37 private static final byte[] HEADER_MAGIC = { 38 (byte) 0x5D, 0, 0 39 }; 40 41 enum CachedAvailability { 42 DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE 43 } 44 45 private static volatile CachedAvailability cachedLZMAAvailability; 46 47 static { 48 final Map<String, String> uncompressSuffix = new HashMap<>(); 49 uncompressSuffix.put(".lzma", ""); 50 uncompressSuffix.put("-lzma", ""); 51 fileNameUtil = new FileNameUtil(uncompressSuffix, ".lzma"); 52 cachedLZMAAvailability = CachedAvailability.DONT_CACHE; 53 try { 54 Class.forName("org.osgi.framework.BundleEvent"); 55 } catch (final Exception ex) { 56 setCacheLZMAAvailablity(true); 57 } 58 } 59 60 /** Private constructor to prevent instantiation of this utility class. */ LZMAUtils()61 private LZMAUtils() { 62 } 63 64 /** 65 * Checks if the signature matches what is expected for a .lzma file. 66 * 67 * @param signature the bytes to check 68 * @param length the number of bytes to check 69 * @return true if signature matches the .lzma magic bytes, false otherwise 70 */ matches(final byte[] signature, final int length)71 public static boolean matches(final byte[] signature, final int length) { 72 if (length < HEADER_MAGIC.length) { 73 return false; 74 } 75 76 for (int i = 0; i < HEADER_MAGIC.length; ++i) { 77 if (signature[i] != HEADER_MAGIC[i]) { 78 return false; 79 } 80 } 81 82 return true; 83 } 84 85 /** 86 * Are the classes required to support LZMA compression available? 87 * @return true if the classes required to support LZMA 88 * compression are available 89 */ isLZMACompressionAvailable()90 public static boolean isLZMACompressionAvailable() { 91 final CachedAvailability cachedResult = cachedLZMAAvailability; 92 if (cachedResult != CachedAvailability.DONT_CACHE) { 93 return cachedResult == CachedAvailability.CACHED_AVAILABLE; 94 } 95 return internalIsLZMACompressionAvailable(); 96 } 97 internalIsLZMACompressionAvailable()98 private static boolean internalIsLZMACompressionAvailable() { 99 try { 100 LZMACompressorInputStream.matches(null, 0); 101 return true; 102 } catch (final NoClassDefFoundError error) { 103 return false; 104 } 105 } 106 107 /** 108 * Detects common lzma suffixes in the given filename. 109 * 110 * @param filename name of a file 111 * @return {@code true} if the filename has a common lzma suffix, 112 * {@code false} otherwise 113 */ isCompressedFilename(final String filename)114 public static boolean isCompressedFilename(final String filename) { 115 return fileNameUtil.isCompressedFilename(filename); 116 } 117 118 /** 119 * Maps the given name of a lzma-compressed file to the name that 120 * the file should have after uncompression. Any filenames with 121 * the generic ".lzma" suffix (or any other generic lzma suffix) 122 * is mapped to a name without that suffix. If no lzma suffix is 123 * detected, then the filename is returned unmapped. 124 * 125 * @param filename name of a file 126 * @return name of the corresponding uncompressed file 127 */ getUncompressedFilename(final String filename)128 public static String getUncompressedFilename(final String filename) { 129 return fileNameUtil.getUncompressedFilename(filename); 130 } 131 132 /** 133 * Maps the given filename to the name that the file should have after 134 * compression with lzma. 135 * 136 * @param filename name of a file 137 * @return name of the corresponding compressed file 138 */ getCompressedFilename(final String filename)139 public static String getCompressedFilename(final String filename) { 140 return fileNameUtil.getCompressedFilename(filename); 141 } 142 143 /** 144 * Whether to cache the result of the LZMA check. 145 * 146 * <p>This defaults to {@code false} in an OSGi environment and {@code true} otherwise.</p> 147 * @param doCache whether to cache the result 148 */ setCacheLZMAAvailablity(final boolean doCache)149 public static void setCacheLZMAAvailablity(final boolean doCache) { 150 if (!doCache) { 151 cachedLZMAAvailability = CachedAvailability.DONT_CACHE; 152 } else if (cachedLZMAAvailability == CachedAvailability.DONT_CACHE) { 153 final boolean hasLzma = internalIsLZMACompressionAvailable(); 154 cachedLZMAAvailability = hasLzma ? CachedAvailability.CACHED_AVAILABLE // NOSONAR 155 : CachedAvailability.CACHED_UNAVAILABLE; 156 } 157 } 158 159 // only exists to support unit tests getCachedLZMAAvailability()160 static CachedAvailability getCachedLZMAAvailability() { 161 return cachedLZMAAvailability; 162 } 163 } 164