001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.io.filefilter; 018 019import java.io.File; 020import java.io.IOException; 021import java.io.RandomAccessFile; 022import java.io.Serializable; 023import java.nio.ByteBuffer; 024import java.nio.channels.FileChannel; 025import java.nio.charset.Charset; 026import java.nio.file.FileVisitResult; 027import java.nio.file.Files; 028import java.nio.file.Path; 029import java.nio.file.attribute.BasicFileAttributes; 030import java.util.Arrays; 031import java.util.Objects; 032 033import org.apache.commons.io.IOUtils; 034import org.apache.commons.io.RandomAccessFileMode; 035 036/** 037 * <p> 038 * File filter for matching files containing a "magic number". A magic number 039 * is a unique series of bytes common to all files of a specific file format. 040 * For instance, all Java class files begin with the bytes 041 * {@code 0xCAFEBABE}. 042 * </p> 043 * <h2>Using Classic IO</h2> 044 * <pre> 045 * File dir = FileUtils.current(); 046 * MagicNumberFileFilter javaClassFileFilter = 047 * MagicNumberFileFilter(new byte[] {(byte) 0xCA, (byte) 0xFE, 048 * (byte) 0xBA, (byte) 0xBE}); 049 * String[] javaClassFiles = dir.list(javaClassFileFilter); 050 * for (String javaClassFile : javaClassFiles) { 051 * System.out.println(javaClassFile); 052 * } 053 * </pre> 054 * 055 * <p> 056 * Sometimes, such as in the case of TAR files, the 057 * magic number will be offset by a certain number of bytes in the file. In the 058 * case of TAR archive files, this offset is 257 bytes. 059 * </p> 060 * 061 * <pre> 062 * File dir = FileUtils.current(); 063 * MagicNumberFileFilter tarFileFilter = 064 * MagicNumberFileFilter("ustar", 257); 065 * String[] tarFiles = dir.list(tarFileFilter); 066 * for (String tarFile : tarFiles) { 067 * System.out.println(tarFile); 068 * } 069 * </pre> 070 * <h2>Using NIO</h2> 071 * <pre> 072 * final Path dir = PathUtils.current(); 073 * final AccumulatorPathVisitor visitor = AccumulatorPathVisitor.withLongCounters(MagicNumberFileFilter("ustar", 257)); 074 * // 075 * // Walk one dir 076 * Files.<b>walkFileTree</b>(dir, Collections.emptySet(), 1, visitor); 077 * System.out.println(visitor.getPathCounters()); 078 * System.out.println(visitor.getFileList()); 079 * // 080 * visitor.getPathCounters().reset(); 081 * // 082 * // Walk dir tree 083 * Files.<b>walkFileTree</b>(dir, visitor); 084 * System.out.println(visitor.getPathCounters()); 085 * System.out.println(visitor.getDirList()); 086 * System.out.println(visitor.getFileList()); 087 * </pre> 088 * <h2>Deprecating Serialization</h2> 089 * <p> 090 * <em>Serialization is deprecated and will be removed in 3.0.</em> 091 * </p> 092 * 093 * @since 2.0 094 * @see FileFilterUtils#magicNumberFileFilter(byte[]) 095 * @see FileFilterUtils#magicNumberFileFilter(String) 096 * @see FileFilterUtils#magicNumberFileFilter(byte[], long) 097 * @see FileFilterUtils#magicNumberFileFilter(String, long) 098 */ 099public class MagicNumberFileFilter extends AbstractFileFilter implements 100 Serializable { 101 102 /** 103 * The serialization version unique identifier. 104 */ 105 private static final long serialVersionUID = -547733176983104172L; 106 107 /** 108 * The magic number to compare against the file's bytes at the provided 109 * offset. 110 */ 111 private final byte[] magicNumbers; 112 113 /** 114 * The offset (in bytes) within the files that the magic number's bytes 115 * should appear. 116 */ 117 private final long byteOffset; 118 119 /** 120 * <p> 121 * Constructs a new MagicNumberFileFilter and associates it with the magic 122 * number to test for in files. This constructor assumes a starting offset 123 * of {@code 0}. 124 * </p> 125 * 126 * <p> 127 * It is important to note that <em>the array is not cloned</em> and that 128 * any changes to the magic number array after construction will affect the 129 * behavior of this file filter. 130 * </p> 131 * 132 * <pre> 133 * MagicNumberFileFilter javaClassFileFilter = 134 * MagicNumberFileFilter(new byte[] {(byte) 0xCA, (byte) 0xFE, 135 * (byte) 0xBA, (byte) 0xBE}); 136 * </pre> 137 * 138 * @param magicNumber the magic number to look for in the file. 139 * 140 * @throws IllegalArgumentException if {@code magicNumber} is 141 * {@code null}, or contains no bytes. 142 */ 143 public MagicNumberFileFilter(final byte[] magicNumber) { 144 this(magicNumber, 0); 145 } 146 147 /** 148 * <p> 149 * Constructs a new MagicNumberFileFilter and associates it with the magic 150 * number to test for in files and the byte offset location in the file to 151 * to look for that magic number. 152 * </p> 153 * 154 * <pre> 155 * MagicNumberFileFilter tarFileFilter = 156 * MagicNumberFileFilter(new byte[] {0x75, 0x73, 0x74, 0x61, 0x72}, 257); 157 * </pre> 158 * 159 * <pre> 160 * MagicNumberFileFilter javaClassFileFilter = 161 * MagicNumberFileFilter(new byte[] {0xCA, 0xFE, 0xBA, 0xBE}, 0); 162 * </pre> 163 * 164 * @param magicNumbers the magic number to look for in the file. 165 * @param offset the byte offset in the file to start comparing bytes. 166 * 167 * @throws IllegalArgumentException if {@code magicNumber} 168 * contains no bytes, or {@code offset} 169 * is a negative number. 170 */ 171 public MagicNumberFileFilter(final byte[] magicNumbers, final long offset) { 172 Objects.requireNonNull(magicNumbers, "magicNumbers"); 173 if (magicNumbers.length == 0) { 174 throw new IllegalArgumentException("The magic number must contain at least one byte"); 175 } 176 if (offset < 0) { 177 throw new IllegalArgumentException("The offset cannot be negative"); 178 } 179 180 this.magicNumbers = magicNumbers.clone(); 181 this.byteOffset = offset; 182 } 183 184 /** 185 * <p> 186 * Constructs a new MagicNumberFileFilter and associates it with the magic 187 * number to test for in files. This constructor assumes a starting offset 188 * of {@code 0}. 189 * </p> 190 * 191 * Example usage: 192 * <pre> 193 * {@code 194 * MagicNumberFileFilter xmlFileFilter = 195 * MagicNumberFileFilter("<?xml"); 196 * } 197 * </pre> 198 * 199 * @param magicNumber the magic number to look for in the file. 200 * The string is converted to bytes using the platform default charset. 201 * 202 * @throws IllegalArgumentException if {@code magicNumber} is 203 * {@code null} or the empty String. 204 */ 205 public MagicNumberFileFilter(final String magicNumber) { 206 this(magicNumber, 0); 207 } 208 209 /** 210 * <p> 211 * Constructs a new MagicNumberFileFilter and associates it with the magic 212 * number to test for in files and the byte offset location in the file to 213 * to look for that magic number. 214 * </p> 215 * 216 * <pre> 217 * MagicNumberFileFilter tarFileFilter = 218 * MagicNumberFileFilter("ustar", 257); 219 * </pre> 220 * 221 * @param magicNumber the magic number to look for in the file. 222 * The string is converted to bytes using the platform default charset. 223 * @param offset the byte offset in the file to start comparing bytes. 224 * 225 * @throws IllegalArgumentException if {@code magicNumber} is 226 * the empty String, or {@code offset} is 227 * a negative number. 228 */ 229 public MagicNumberFileFilter(final String magicNumber, final long offset) { 230 Objects.requireNonNull(magicNumber, "magicNumber"); 231 if (magicNumber.isEmpty()) { 232 throw new IllegalArgumentException("The magic number must contain at least one byte"); 233 } 234 if (offset < 0) { 235 throw new IllegalArgumentException("The offset cannot be negative"); 236 } 237 238 this.magicNumbers = magicNumber.getBytes(Charset.defaultCharset()); // explicitly uses the platform default charset 239 this.byteOffset = offset; 240 } 241 242 /** 243 * <p> 244 * Accepts the provided file if the file contains the file filter's magic 245 * number at the specified offset. 246 * </p> 247 * 248 * <p> 249 * If any {@link IOException}s occur while reading the file, the file will 250 * be rejected. 251 * </p> 252 * 253 * @param file the file to accept or reject. 254 * 255 * @return {@code true} if the file contains the filter's magic number 256 * at the specified offset, {@code false} otherwise. 257 */ 258 @Override 259 public boolean accept(final File file) { 260 if (file != null && file.isFile() && file.canRead()) { 261 try { 262 try (RandomAccessFile randomAccessFile = RandomAccessFileMode.READ_ONLY.create(file)) { 263 final byte[] fileBytes = IOUtils.byteArray(this.magicNumbers.length); 264 randomAccessFile.seek(byteOffset); 265 final int read = randomAccessFile.read(fileBytes); 266 if (read != magicNumbers.length) { 267 return false; 268 } 269 return Arrays.equals(this.magicNumbers, fileBytes); 270 } 271 } 272 catch (final IOException ignored) { 273 // Do nothing, fall through and do not accept file 274 } 275 } 276 277 return false; 278 } 279 280 /** 281 * <p> 282 * Accepts the provided file if the file contains the file filter's magic 283 * number at the specified offset. 284 * </p> 285 * 286 * <p> 287 * If any {@link IOException}s occur while reading the file, the file will 288 * be rejected. 289 * </p> 290 * @param file the file to accept or reject. 291 * 292 * @return {@code true} if the file contains the filter's magic number 293 * at the specified offset, {@code false} otherwise. 294 * @since 2.9.0 295 */ 296 @Override 297 public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) { 298 if (file != null && Files.isRegularFile(file) && Files.isReadable(file)) { 299 try { 300 try (FileChannel fileChannel = FileChannel.open(file)) { 301 final ByteBuffer byteBuffer = ByteBuffer.allocate(this.magicNumbers.length); 302 final int read = fileChannel.read(byteBuffer); 303 if (read != magicNumbers.length) { 304 return FileVisitResult.TERMINATE; 305 } 306 return toFileVisitResult(Arrays.equals(this.magicNumbers, byteBuffer.array())); 307 } 308 } 309 catch (final IOException ignored) { 310 // Do nothing, fall through and do not accept file 311 } 312 } 313 return FileVisitResult.TERMINATE; 314 } 315 316 /** 317 * Returns a String representation of the file filter, which includes the 318 * magic number bytes and byte offset. 319 * 320 * @return a String representation of the file filter. 321 */ 322 @Override 323 public String toString() { 324 final StringBuilder builder = new StringBuilder(super.toString()); 325 builder.append("("); 326 builder.append(new String(magicNumbers, Charset.defaultCharset()));// TODO perhaps use hex if value is not 327 // printable 328 builder.append(","); 329 builder.append(this.byteOffset); 330 builder.append(")"); 331 return builder.toString(); 332 } 333}