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.lzma; 020 021import java.util.HashMap; 022import java.util.Map; 023import org.apache.commons.compress.compressors.FileNameUtil; 024 025/** 026 * Utility code for the lzma compression format. 027 * @ThreadSafe 028 * @since 1.10 029 */ 030public class LZMAUtils { 031 032 private static final FileNameUtil fileNameUtil; 033 034 /** 035 * LZMA Header Magic Bytes begin a LZMA file. 036 */ 037 private static final byte[] HEADER_MAGIC = { 038 (byte) 0x5D, 0, 0 039 }; 040 041 static enum CachedAvailability { 042 DONT_CACHE, CACHED_AVAILABLE, CACHED_UNAVAILABLE 043 } 044 045 private static volatile CachedAvailability cachedLZMAAvailability; 046 047 static { 048 final Map<String, String> uncompressSuffix = new HashMap<>(); 049 uncompressSuffix.put(".lzma", ""); 050 uncompressSuffix.put("-lzma", ""); 051 fileNameUtil = new FileNameUtil(uncompressSuffix, ".lzma"); 052 cachedLZMAAvailability = CachedAvailability.DONT_CACHE; 053 try { 054 Class.forName("org.osgi.framework.BundleEvent"); 055 } catch (final Exception ex) { 056 setCacheLZMAAvailablity(true); 057 } 058 } 059 060 /** Private constructor to prevent instantiation of this utility class. */ 061 private LZMAUtils() { 062 } 063 064 /** 065 * Checks if the signature matches what is expected for a .lzma file. 066 * 067 * @param signature the bytes to check 068 * @param length the number of bytes to check 069 * @return true if signature matches the .lzma magic bytes, false otherwise 070 */ 071 public static boolean matches(final byte[] signature, final int length) { 072 if (length < HEADER_MAGIC.length) { 073 return false; 074 } 075 076 for (int i = 0; i < HEADER_MAGIC.length; ++i) { 077 if (signature[i] != HEADER_MAGIC[i]) { 078 return false; 079 } 080 } 081 082 return true; 083 } 084 085 /** 086 * Are the classes required to support LZMA compression available? 087 * @return true if the classes required to support LZMA 088 * compression are available 089 */ 090 public static boolean isLZMACompressionAvailable() { 091 final CachedAvailability cachedResult = cachedLZMAAvailability; 092 if (cachedResult != CachedAvailability.DONT_CACHE) { 093 return cachedResult == CachedAvailability.CACHED_AVAILABLE; 094 } 095 return internalIsLZMACompressionAvailable(); 096 } 097 098 private static boolean internalIsLZMACompressionAvailable() { 099 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 */ 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 */ 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 */ 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 */ 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 155 : CachedAvailability.CACHED_UNAVAILABLE; 156 } 157 } 158 159 // only exists to support unit tests 160 static CachedAvailability getCachedLZMAAvailability() { 161 return cachedLZMAAvailability; 162 } 163}