1 /*
2 * Copyright (c) 2014, 2026, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package jdk.internal.jimage;
26
27 import java.io.ByteArrayInputStream;
28 import java.io.IOException;
29 import java.io.InputStream;
30 import java.lang.reflect.InvocationTargetException;
31 import java.lang.reflect.Method;
32 import java.nio.ByteBuffer;
33 import java.nio.ByteOrder;
34 import java.nio.IntBuffer;
35 import java.nio.channels.FileChannel;
36 import java.nio.file.Path;
37 import java.nio.file.StandardOpenOption;
38 import java.security.AccessController;
39 import java.security.PrivilegedAction;
40 import java.util.NoSuchElementException;
41 import java.util.Objects;
42 import java.util.Random;
43 import java.util.stream.IntStream;
44 import java.util.stream.Stream;
45
46 import jdk.internal.jimage.decompressor.Decompressor;
47
48 /**
49 * @implNote This class needs to maintain JDK 8 source compatibility.
50 *
51 * It is used internally in the JDK to implement jimage/jrtfs access,
52 * but also compiled and delivered as part of the jrtfs.jar to support access
53 * to the jimage file provided by the shipped JDK by tools running on JDK 8.
54 */
55 public class BasicImageReader implements AutoCloseable {
56 @SuppressWarnings({ "removal", "suppression" })
57 private static boolean isSystemProperty(String key, String value, String def) {
58 // No lambdas during bootstrap
59 return AccessController.doPrivileged(
60 new PrivilegedAction<Boolean>() {
61 @Override
62 public Boolean run() {
63 return value.equals(System.getProperty(key, def));
64 }
65 });
66 }
67
68 private static final boolean IS_64_BIT =
69 isSystemProperty("sun.arch.data.model", "64", "32");
70 private static final boolean USE_JVM_MAP =
71 isSystemProperty("jdk.image.use.jvm.map", "true", "true");
72 private static final boolean MAP_ALL =
73 isSystemProperty("jdk.image.map.all", "true", IS_64_BIT ? "true" : "false");
74
75 private final Path imagePath;
76 private final ByteOrder byteOrder;
77 private final String name;
78 private final ByteBuffer memoryMap;
79 private final FileChannel channel;
80 private final ImageHeader header;
81 private final long indexSize;
82 private final IntBuffer redirect;
83 private final IntBuffer offsets;
84 private final ByteBuffer locations;
85 private final ByteBuffer strings;
86 private final ImageStringsReader stringsReader;
87 private final Decompressor decompressor;
88
89 @SuppressWarnings({ "removal", "this-escape", "suppression" })
90 protected BasicImageReader(Path path, ByteOrder byteOrder)
91 throws IOException {
92 this.imagePath = Objects.requireNonNull(path);
93 this.byteOrder = Objects.requireNonNull(byteOrder);
94 this.name = this.imagePath.toString();
95
96 ByteBuffer map;
97
98 if (USE_JVM_MAP && BasicImageReader.class.getClassLoader() == null) {
99 // Check to see if the jvm has opened the file using libjimage
100 // native entry when loading the image for this runtime
101 map = NativeImageBuffer.getNativeMap(name);
102 } else {
103 map = null;
104 }
105
106 // Open the file only if no memory map yet or is 32 bit jvm
107 if (map != null && MAP_ALL) {
108 channel = null;
109 } else {
110 channel = FileChannel.open(imagePath, StandardOpenOption.READ);
111 // No lambdas during bootstrap
112 AccessController.doPrivileged(new PrivilegedAction<Void>() {
113 @Override
114 public Void run() {
115 if (BasicImageReader.class.getClassLoader() == null) {
116 try {
117 Class<?> fileChannelImpl =
118 Class.forName("sun.nio.ch.FileChannelImpl");
119 Method setUninterruptible =
120 fileChannelImpl.getMethod("setUninterruptible");
121 setUninterruptible.invoke(channel);
122 } catch (ClassNotFoundException |
123 NoSuchMethodException |
124 IllegalAccessException |
125 InvocationTargetException ex) {
126 // fall thru - will only happen on JDK-8 systems where this code
127 // is only used by tools using jrt-fs (non-critical.)
128 }
129 }
130
131 return null;
132 }
133 });
134 }
135
136 // If no memory map yet and 64 bit jvm then memory map entire file
137 if (MAP_ALL && map == null) {
138 map = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
139 }
140
141 // Assume we have a memory map to read image file header
142 ByteBuffer headerBuffer = map;
143 int headerSize = ImageHeader.getHeaderSize();
144
145 // If no memory map then read header from image file
146 if (headerBuffer == null) {
147 headerBuffer = ByteBuffer.allocateDirect(headerSize);
148 if (channel.read(headerBuffer, 0L) == headerSize) {
149 headerBuffer.rewind();
150 } else {
151 throw new IOException("\"" + name + "\" is not an image file");
152 }
153 } else if (headerBuffer.capacity() < headerSize) {
154 throw new IOException("\"" + name + "\" is not an image file");
155 }
156
157 // Interpret the image file header
158 header = readHeader(intBuffer(headerBuffer, 0, headerSize));
159 indexSize = header.getIndexSize();
160
161 // If no memory map yet then must be 32 bit jvm not previously mapped
162 if (map == null) {
163 // Just map the image index
164 map = channel.map(FileChannel.MapMode.READ_ONLY, 0, indexSize);
165 }
166
167 memoryMap = map.asReadOnlyBuffer();
168
169 // Interpret the image index
170 if (memoryMap.capacity() < indexSize) {
171 throw new IOException("The image file \"" + name + "\" is corrupted");
172 }
173 redirect = intBuffer(memoryMap, header.getRedirectOffset(), header.getRedirectSize());
174 offsets = intBuffer(memoryMap, header.getOffsetsOffset(), header.getOffsetsSize());
175 locations = slice(memoryMap, header.getLocationsOffset(), header.getLocationsSize());
176 strings = slice(memoryMap, header.getStringsOffset(), header.getStringsSize());
177
178 stringsReader = new ImageStringsReader(this);
179 decompressor = new Decompressor();
180 }
181
182 protected BasicImageReader(Path imagePath) throws IOException {
183 this(imagePath, ByteOrder.nativeOrder());
184 }
185
186 public static BasicImageReader open(Path imagePath) throws IOException {
187 return new BasicImageReader(imagePath, ByteOrder.nativeOrder());
188 }
189
190 public ImageHeader getHeader() {
191 return header;
192 }
193
194 private ImageHeader readHeader(IntBuffer buffer) throws IOException {
195 ImageHeader result = ImageHeader.readFrom(buffer);
196
197 if (result.getMagic() != ImageHeader.MAGIC) {
198 throw new IOException("\"" + name + "\" is not an image file");
199 }
200
201 if (result.getMajorVersion() != ImageHeader.MAJOR_VERSION ||
202 result.getMinorVersion() != ImageHeader.MINOR_VERSION) {
203 throw new IOException("The image file \"" + name + "\" is not " +
204 "the correct version. Major: " + result.getMajorVersion() +
205 ". Minor: " + result.getMinorVersion());
206 }
207
208 return result;
209 }
210
211 private static ByteBuffer slice(ByteBuffer buffer, int position, int capacity) {
212 // Note that this is the only limit and position manipulation of
213 // BasicImageReader private ByteBuffers. The synchronize could be avoided
214 // by cloning the buffer to make a local copy, but at the cost of creating
215 // a new object.
216 synchronized(buffer) {
217 buffer.limit(position + capacity);
218 buffer.position(position);
219 return buffer.slice();
220 }
221 }
222
223 private IntBuffer intBuffer(ByteBuffer buffer, int offset, int size) {
224 return slice(buffer, offset, size).order(byteOrder).asIntBuffer();
225 }
226
227 public String getName() {
228 return name;
229 }
230
231 public ByteOrder getByteOrder() {
232 return byteOrder;
233 }
234
235 public Path getImagePath() {
236 return imagePath;
237 }
238
239 @Override
240 public void close() throws IOException {
241 if (channel != null) {
242 channel.close();
243 }
244 }
245
246 public ImageStringsReader getStrings() {
247 return stringsReader;
248 }
249
250 public ImageLocation findLocation(String module, String name) {
251 int index = getLocationIndex(module, name);
252 if (index < 0) {
253 return null;
254 }
255 long[] attributes = getAttributes(offsets.get(index));
256 if (!ImageLocation.verify(module, name, attributes, stringsReader)) {
257 return null;
258 }
259 return new ImageLocation(attributes, stringsReader);
260 }
261
262 public ImageLocation findLocation(String name) {
263 int index = getLocationIndex(name);
264 if (index < 0) {
265 return null;
266 }
267 long[] attributes = getAttributes(offsets.get(index));
268 if (!ImageLocation.verify(name, attributes, stringsReader)) {
269 return null;
270 }
271 return new ImageLocation(attributes, stringsReader);
272 }
273
274 public boolean verifyLocation(String module, String name) {
275 int index = getLocationIndex(module, name);
276 if (index < 0) {
277 return false;
278 }
279 int locationOffset = offsets.get(index);
280 return ImageLocation.verify(module, name, locations, locationOffset, stringsReader);
281 }
282
283 // Details of the algorithm used here can be found in
284 // jdk.tools.jlink.internal.PerfectHashBuilder.
285 public int getLocationIndex(String name) {
286 int count = header.getTableLength();
287 int index = redirect.get(ImageStringsReader.hashCode(name) % count);
288 if (index < 0) {
289 // index is twos complement of location attributes index.
290 return -index - 1;
291 } else if (index > 0) {
292 // index is hash seed needed to compute location attributes index.
293 return ImageStringsReader.hashCode(name, index) % count;
294 } else {
295 // No entry.
296 return -1;
297 }
298 }
299
300 private int getLocationIndex(String module, String name) {
301 int count = header.getTableLength();
302 int index = redirect.get(ImageStringsReader.hashCode(module, name) % count);
303 if (index < 0) {
304 // index is twos complement of location attributes index.
305 return -index - 1;
306 } else if (index > 0) {
307 // index is hash seed needed to compute location attributes index.
308 return ImageStringsReader.hashCode(module, name, index) % count;
309 } else {
310 // No entry.
311 return -1;
312 }
313 }
314
315 public String[] getEntryNames() {
316 return IntStream.range(0, offsets.capacity())
317 .map(offsets::get)
318 .filter(o -> o != 0)
319 .mapToObj(o -> ImageLocation.readFrom(this, o).getFullName())
320 .sorted()
321 .toArray(String[]::new);
322 }
323
324 /**
325 * Returns the "raw" API for accessing underlying jimage resource entries.
326 *
327 * <p>This is only meaningful for use by code dealing directly with jimage
328 * files, and cannot be used to reliably lookup resources used at runtime.
329 *
330 * <p>This API remains valid until the image reader from which it was
331 * obtained is closed.
332 */
333 // Package visible for use by ImageReader.
334 ResourceEntries getResourceEntries() {
335 return new ResourceEntries() {
336 @Override
337 public Stream<String> getEntryNames(String module) {
338 if (module.isEmpty() || module.equals("modules") || module.equals("packages")) {
339 throw new IllegalArgumentException("Invalid module name: " + module);
340 }
341 return IntStream.range(0, offsets.capacity())
342 .map(offsets::get)
343 .filter(offset -> offset != 0)
344 // Reusing a location instance or getting the module
345 // offset directly would save a lot of allocations here.
346 .mapToObj(offset -> ImageLocation.readFrom(BasicImageReader.this, offset))
347 // Reverse lookup of module offset would be faster here.
348 .filter(loc -> module.equals(loc.getModule()))
349 .map(ImageLocation::getFullName);
350 }
351
352 private ImageLocation getResourceLocation(String name) {
353 if (!name.startsWith("/modules/") && !name.startsWith("/packages/")) {
354 ImageLocation location = BasicImageReader.this.findLocation(name);
355 if (location != null) {
356 return location;
357 }
358 }
359 throw new NoSuchElementException("No such resource entry: " + name);
360 }
361
362 @Override
363 public long getSize(String name) {
364 return getResourceLocation(name).getUncompressedSize();
365 }
366
367 @Override
368 public byte[] getBytes(String name) {
369 return BasicImageReader.this.getResource(getResourceLocation(name));
370 }
371 };
372 }
373
374 ImageLocation getLocation(int offset) {
375 return ImageLocation.readFrom(this, offset);
376 }
377
378 public long[] getAttributes(int offset) {
379 if (offset < 0 || offset >= locations.limit()) {
380 throw new IndexOutOfBoundsException("offset");
381 }
382 return ImageLocation.decompress(locations, offset);
383 }
384
385 public String getString(int offset) {
386 if (offset < 0 || offset >= strings.limit()) {
387 throw new IndexOutOfBoundsException("offset");
388 }
389 return ImageStringsReader.stringFromByteBuffer(strings, offset);
390 }
391
392 public int match(int offset, String string, int stringOffset) {
393 if (offset < 0 || offset >= strings.limit()) {
394 throw new IndexOutOfBoundsException("offset");
395 }
396 return ImageStringsReader.stringFromByteBufferMatches(strings, offset, string, stringOffset);
397 }
398
399 private byte[] getBufferBytes(ByteBuffer buffer) {
400 Objects.requireNonNull(buffer);
401 byte[] bytes = new byte[buffer.limit()];
402 buffer.get(bytes);
403
404 return bytes;
405 }
406
407 private ByteBuffer readBuffer(long offset, long size) {
408 if (offset < 0 || Integer.MAX_VALUE <= offset) {
409 throw new IndexOutOfBoundsException("Bad offset: " + offset);
410 }
411 int checkedOffset = (int) offset;
412
413 if (size < 0 || Integer.MAX_VALUE <= size) {
414 throw new IllegalArgumentException("Bad size: " + size);
415 }
416 int checkedSize = (int) size;
417
418 if (MAP_ALL) {
419 ByteBuffer buffer = slice(memoryMap, checkedOffset, checkedSize);
420 buffer.order(ByteOrder.BIG_ENDIAN);
421
422 return buffer;
423 } else {
424 if (channel == null) {
425 throw new InternalError("Image file channel not open");
426 }
427 ByteBuffer buffer = ByteBuffer.allocate(checkedSize);
428 int read;
429 try {
430 read = channel.read(buffer, checkedOffset);
431 buffer.rewind();
432 } catch (IOException ex) {
433 throw new RuntimeException(ex);
434 }
435
436 if (read != checkedSize) {
437 throw new RuntimeException("Short read: " + read +
438 " instead of " + checkedSize + " bytes");
439 }
440
441 return buffer;
442 }
443 }
444
445 public byte[] getResource(String name) {
446 Objects.requireNonNull(name);
447 ImageLocation location = findLocation(name);
448
449 return location != null ? getResource(location) : null;
450 }
451
452 public byte[] getResource(ImageLocation loc) {
453 ByteBuffer buffer = getResourceBuffer(loc);
454 return buffer != null ? getBufferBytes(buffer) : null;
455 }
456
457 /**
458 * Returns the content of jimage location in a newly allocated byte buffer.
459 */
460 public ByteBuffer getResourceBuffer(ImageLocation loc) {
461 Objects.requireNonNull(loc);
462 long offset = loc.getContentOffset() + indexSize;
463 long compressedSize = loc.getCompressedSize();
464 long uncompressedSize = loc.getUncompressedSize();
465
466 if (compressedSize < 0 || Integer.MAX_VALUE < compressedSize) {
467 throw new IndexOutOfBoundsException(
468 "Bad compressed size: " + compressedSize);
469 }
470
471 if (uncompressedSize < 0 || Integer.MAX_VALUE < uncompressedSize) {
472 throw new IndexOutOfBoundsException(
473 "Bad uncompressed size: " + uncompressedSize);
474 }
475
476 if (compressedSize == 0) {
477 return readBuffer(offset, uncompressedSize);
478 } else {
479 ByteBuffer buffer = readBuffer(offset, compressedSize);
480 if (buffer != null) {
481 byte[] bytesIn = getBufferBytes(buffer);
482 byte[] bytesOut;
483
484 try {
485 bytesOut = decompressor.decompressResource(byteOrder,
486 (int strOffset) -> getString(strOffset), bytesIn);
487 } catch (IOException ex) {
488 throw new RuntimeException(ex);
489 }
490
491 return ByteBuffer.wrap(bytesOut);
492 }
493 }
494
495 return null;
496 }
497
498 public InputStream getResourceStream(ImageLocation loc) {
499 Objects.requireNonNull(loc);
500 byte[] bytes = getResource(loc);
501
502 return new ByteArrayInputStream(bytes);
503 }
504 }