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 *
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24 */
25 package jdk.internal.jimage;
26
27 import java.io.IOException;
28 import java.nio.ByteBuffer;
29 import java.nio.ByteOrder;
30 import java.nio.IntBuffer;
31 import java.nio.file.Files;
32 import java.nio.file.Path;
33 import java.nio.file.attribute.BasicFileAttributes;
34 import java.util.ArrayList;
35 import java.util.Arrays;
36 import java.util.Collections;
37 import java.util.HashMap;
38 import java.util.HashSet;
39 import java.util.List;
40 import java.util.Map;
41 import java.util.Objects;
42 import java.util.Set;
43 import java.util.function.Function;
44 import java.util.function.Supplier;
45 import java.util.stream.Stream;
46
47 /**
48 * A view over the entries of a jimage file with a unified namespace suitable
49 * for file system use. The jimage entries (resources, module and package
50 * information) are mapped into a unified hierarchy of named nodes, which serve
51 * as the underlying structure for {@code JrtFileSystem} and other utilities.
52 *
53 * <p>Entries in jimage are expressed as one of three {@link Node} types;
54 * resource nodes, directory nodes and link nodes.
55 *
56 * <p>When remapping jimage entries, jimage location names (e.g. {@code
57 * "/java.base/java/lang/Integer.class"}) are prefixed with {@code "/modules"}
58 * to form the names of resource nodes. This aligns with the naming of module
59 * entries in jimage (e.g. "/modules/java.base/java/lang"), which appear as
60 * directory nodes in {@code ImageReader}.
61 *
62 * <p>Package entries (e.g. {@code "/packages/java.lang"} appear as directory
63 * nodes containing link nodes, which resolve back to the root directory of the
64 * module in which that package exists (e.g. {@code "/modules/java.base"}).
65 * Unlike other nodes, the jimage file does not contain explicit entries for
66 * link nodes, and their existence is derived only from the contents of the
67 * parent directory.
68 *
69 * <p>While similar to {@code BasicImageReader}, this class is not a conceptual
70 * subtype of it, and deliberately hides types such as {@code ImageLocation} to
71 * give a focused API based only on nodes.
72 *
73 * @implNote This class needs to maintain JDK 8 source compatibility.
74 *
75 * It is used internally in the JDK to implement jimage/jrtfs access,
76 * but also compiled and delivered as part of the jrtfs.jar to support access
77 * to the jimage file provided by the shipped JDK by tools running on JDK 8.
78 */
79 public final class ImageReader implements AutoCloseable {
80 private final SharedImageReader reader;
81
82 private volatile boolean closed;
83
84 private ImageReader(SharedImageReader reader) {
85 this.reader = reader;
86 }
87
88 /**
89 * Opens an image reader for a jimage file at the specified path, using the
90 * given byte order.
91 */
92 public static ImageReader open(Path imagePath, ByteOrder byteOrder) throws IOException {
93 Objects.requireNonNull(imagePath);
94 Objects.requireNonNull(byteOrder);
95
96 return SharedImageReader.open(imagePath, byteOrder);
97 }
98
99 /**
100 * Opens an image reader for a jimage file at the specified path, using the
101 * platform native byte order.
102 */
103 public static ImageReader open(Path imagePath) throws IOException {
104 return open(imagePath, ByteOrder.nativeOrder());
105 }
106
107 @Override
108 public void close() throws IOException {
109 if (closed) {
110 throw new IOException("image file already closed");
111 }
112 reader.close(this);
113 closed = true;
114 }
115
116 private void ensureOpen() throws IOException {
117 if (closed) {
118 throw new IOException("image file closed");
119 }
120 }
121
122 private void requireOpen() {
123 if (closed) {
124 throw new IllegalStateException("image file closed");
125 }
126 }
127
128 /**
129 * Finds the node with the given name.
130 *
131 * @param name a node name of the form {@code "/modules/<module>/...} or
132 * {@code "/packages/<package>/...}.
133 * @return a node representing a resource, directory or symbolic link.
134 */
135 public Node findNode(String name) throws IOException {
136 ensureOpen();
137 return reader.findNode(name);
138 }
139
140 /**
141 * Returns a resource node in the given module, or null if no resource of
142 * that name exists.
143 *
144 * <p>This is equivalent to:
145 * <pre>{@code
146 * findNode("/modules/" + moduleName + "/" + resourcePath)
147 * }</pre>
148 * but more performant, and returns {@code null} for directories.
149 *
150 * @param moduleName The module name of the requested resource.
151 * @param resourcePath Trailing module-relative resource path, not starting
152 * with {@code '/'}.
153 */
154 public Node findResourceNode(String moduleName, String resourcePath)
155 throws IOException {
156 ensureOpen();
157 return reader.findResourceNode(moduleName, resourcePath);
158 }
159
160 /**
161 * Returns whether a resource exists in the given module.
162 *
163 * <p>This is equivalent to:
164 * <pre>{@code
165 * findResourceNode(moduleName, resourcePath) != null
166 * }</pre>
167 * but more performant, and will not create or cache new nodes.
168 *
169 * @param moduleName The module name of the resource being tested for.
170 * @param resourcePath Trailing module-relative resource path, not starting
171 * with {@code '/'}.
172 */
173 public boolean containsResource(String moduleName, String resourcePath)
174 throws IOException {
175 ensureOpen();
176 return reader.containsResource(moduleName, resourcePath);
177 }
178
179 /**
180 * Returns a copy of the content of a resource node. The buffer returned by
181 * this method is not cached by the node, and each call returns a new array
182 * instance.
183 *
184 * @throws IOException if the content cannot be returned (including if the
185 * given node is not a resource node).
186 */
187 public byte[] getResource(Node node) throws IOException {
188 ensureOpen();
189 return reader.getResource(node);
190 }
191
192 /**
193 * Returns the content of a resource node in a newly allocated byte buffer.
194 */
195 public ByteBuffer getResourceBuffer(Node node) {
196 requireOpen();
197 if (!node.isResource()) {
198 throw new IllegalArgumentException("Not a resource node: " + node);
199 }
200 return reader.getResourceBuffer(node.getLocation());
201 }
202
203 private static final class SharedImageReader extends BasicImageReader {
204 private static final Map<Path, SharedImageReader> OPEN_FILES = new HashMap<>();
205 private static final String MODULES_ROOT = "/modules";
206 private static final String PACKAGES_ROOT = "/packages";
207 // There are >30,000 nodes in a complete jimage tree, and even relatively
208 // common tasks (e.g. starting up javac) load somewhere in the region of
209 // 1000 classes. Thus, an initial capacity of 2000 is a reasonable guess.
210 private static final int INITIAL_NODE_CACHE_CAPACITY = 2000;
211
212 // List of openers for this shared image.
213 private final Set<ImageReader> openers = new HashSet<>();
214
215 // Attributes of the jimage file. The jimage file does not contain
216 // attributes for the individual resources (yet). We use attributes
217 // of the jimage file itself (creation, modification, access times).
218 private final BasicFileAttributes imageFileAttributes;
219
220 // Cache of all user visible nodes, guarded by synchronizing 'this' instance.
221 private final Map<String, Node> nodes;
222 // Used to classify ImageLocation instances without string comparison.
223 private final int modulesStringOffset;
224 private final int packagesStringOffset;
225
226 private SharedImageReader(Path imagePath, ByteOrder byteOrder) throws IOException {
227 super(imagePath, byteOrder);
228 this.imageFileAttributes = Files.readAttributes(imagePath, BasicFileAttributes.class);
229 this.nodes = new HashMap<>(INITIAL_NODE_CACHE_CAPACITY);
230 // Pick stable jimage names from which to extract string offsets (we cannot
231 // use "/modules" or "/packages", since those have a module offset of zero).
232 this.modulesStringOffset = getModuleOffset("/modules/java.base");
233 this.packagesStringOffset = getModuleOffset("/packages/java.lang");
234
235 // Node creation is very lazy, so we can just make the top-level directories
236 // now without the risk of triggering the building of lots of other nodes.
237 Directory packages = newDirectory(PACKAGES_ROOT);
238 nodes.put(packages.getName(), packages);
239 Directory modules = newDirectory(MODULES_ROOT);
240 nodes.put(modules.getName(), modules);
241
242 Directory root = newDirectory("/");
243 root.setChildren(Arrays.asList(packages, modules));
244 nodes.put(root.getName(), root);
245 }
246
247 /**
248 * Returns the offset of the string denoting the leading "module" segment in
249 * the given path (e.g. {@code <module>/<path>}). We can't just pass in the
250 * {@code /<module>} string here because that has a module offset of zero.
251 */
252 private int getModuleOffset(String path) {
253 ImageLocation location = findLocation(path);
254 assert location != null : "Cannot find expected jimage location: " + path;
255 int offset = location.getModuleOffset();
256 assert offset != 0 : "Invalid module offset for jimage location: " + path;
257 return offset;
258 }
259
260 private static ImageReader open(Path imagePath, ByteOrder byteOrder) throws IOException {
261 Objects.requireNonNull(imagePath);
262 Objects.requireNonNull(byteOrder);
263
264 synchronized (OPEN_FILES) {
265 SharedImageReader reader = OPEN_FILES.get(imagePath);
266
267 if (reader == null) {
268 // Will fail with an IOException if wrong byteOrder.
269 reader = new SharedImageReader(imagePath, byteOrder);
270 OPEN_FILES.put(imagePath, reader);
271 } else if (reader.getByteOrder() != byteOrder) {
272 throw new IOException("\"" + reader.getName() + "\" is not an image file");
273 }
274
275 ImageReader image = new ImageReader(reader);
276 reader.openers.add(image);
277
278 return image;
279 }
280 }
281
282 public void close(ImageReader image) throws IOException {
283 Objects.requireNonNull(image);
284
285 synchronized (OPEN_FILES) {
286 if (!openers.remove(image)) {
287 throw new IOException("image file already closed");
288 }
289
290 if (openers.isEmpty()) {
291 close();
292 nodes.clear();
293
294 if (!OPEN_FILES.remove(this.getImagePath(), this)) {
295 throw new IOException("image file not found in open list");
296 }
297 }
298 }
299 }
300
301 /**
302 * Returns a node with the given name, or null if no resource or directory of
303 * that name exists.
304 *
305 * <p>Note that there is no reentrant calling back to this method from within
306 * the node handling code.
307 *
308 * @param name an absolute, {@code /}-separated path string, prefixed with either
309 * "/modules" or "/packages".
310 */
311 synchronized Node findNode(String name) {
312 Node node = nodes.get(name);
313 if (node == null) {
314 // We cannot get the root paths ("/modules" or "/packages") here
315 // because those nodes are already in the nodes cache.
316 if (name.startsWith(MODULES_ROOT + "/")) {
317 // This may perform two lookups, one for a directory (in
318 // "/modules/...") and one for a non-prefixed resource
319 // (with "/modules" removed).
320 node = buildModulesNode(name);
321 } else if (name.startsWith(PACKAGES_ROOT + "/")) {
322 node = buildPackagesNode(name);
323 }
324 if (node != null) {
325 nodes.put(node.getName(), node);
326 }
327 } else if (!node.isCompleted()) {
328 // Only directories can be incomplete.
329 assert node instanceof Directory : "Invalid incomplete node: " + node;
330 completeDirectory((Directory) node);
331 }
332 assert node == null || node.isCompleted() : "Incomplete node: " + node;
333 return node;
334 }
335
336 /**
337 * Returns a resource node in the given module, or null if no resource of
338 * that name exists.
339 *
340 * <p>Note that there is no reentrant calling back to this method from within
341 * the node handling code.
342 */
343 Node findResourceNode(String moduleName, String resourcePath) {
344 // Unlike findNode(), this method makes only one lookup in the
345 // underlying jimage, but can only reliably return resource nodes.
346 if (moduleName.indexOf('/') >= 0) {
347 throw new IllegalArgumentException("invalid module name: " + moduleName);
348 }
349 String nodeName = MODULES_ROOT + "/" + moduleName + "/" + resourcePath;
350 // Synchronize as tightly as possible to reduce locking contention.
351 synchronized (this) {
352 Node node = nodes.get(nodeName);
353 if (node == null) {
354 ImageLocation loc = findLocation(moduleName, resourcePath);
355 if (loc != null && isResource(loc)) {
356 node = newResource(nodeName, loc);
357 nodes.put(node.getName(), node);
358 }
359 return node;
360 } else {
361 return node.isResource() ? node : null;
362 }
363 }
364 }
365
366 /**
367 * Returns whether a resource exists in the given module.
368 *
369 * <p>This method is expected to be called frequently for resources
370 * which do not exist in the given module (e.g. as part of classpath
371 * search). As such, it skips checking the nodes cache and only checks
372 * for an entry in the jimage file, as this is faster if the resource
373 * is not present. This also means it doesn't need synchronization.
374 */
375 boolean containsResource(String moduleName, String resourcePath) {
376 if (moduleName.indexOf('/') >= 0) {
377 throw new IllegalArgumentException("invalid module name: " + moduleName);
378 }
379 // If the given module name is 'modules', then 'isResource()'
380 // returns false to prevent false positives.
381 ImageLocation loc = findLocation(moduleName, resourcePath);
382 return loc != null && isResource(loc);
383 }
384
385 /**
386 * Builds a node in the "/modules/..." namespace.
387 *
388 * <p>Called by {@link #findNode(String)} if a {@code /modules/...} node
389 * is not present in the cache.
390 */
391 private Node buildModulesNode(String name) {
392 assert name.startsWith(MODULES_ROOT + "/") : "Invalid module node name: " + name;
393 // Returns null for non-directory resources, since the jimage name does not
394 // start with "/modules" (e.g. "/java.base/java/lang/Object.class").
395 ImageLocation loc = findLocation(name);
396 if (loc != null) {
397 assert name.equals(loc.getFullName()) : "Mismatched location for directory: " + name;
398 assert isModulesSubdirectory(loc) : "Invalid modules directory: " + name;
399 return completeModuleDirectory(newDirectory(name), loc);
400 }
401 // Now try the non-prefixed resource name, but be careful to avoid false
402 // positives for names like "/modules/modules/xxx" which could return a
403 // location of a directory entry.
404 loc = findLocation(name.substring(MODULES_ROOT.length()));
405 return loc != null && isResource(loc) ? newResource(name, loc) : null;
406 }
407
408 /**
409 * Builds a node in the "/packages/..." namespace.
410 *
411 * <p>Called by {@link #findNode(String)} if a {@code /packages/...} node
412 * is not present in the cache.
413 */
414 private Node buildPackagesNode(String name) {
415 // There are only locations for the root "/packages" or "/packages/xxx"
416 // directories, but not the symbolic links below them (the links can be
417 // entirely derived from the name information in the parent directory).
418 // However, unlike resources this means that we do not have a constant
419 // time lookup for link nodes when creating them.
420 int packageStart = PACKAGES_ROOT.length() + 1;
421 int packageEnd = name.indexOf('/', packageStart);
422 if (packageEnd == -1) {
423 ImageLocation loc = findLocation(name);
424 return loc != null ? completePackageDirectory(newDirectory(name), loc) : null;
425 } else {
426 // We cannot assume that the parent directory exists for a link node, since
427 // the given name is untrusted and could reference a non-existent link.
428 // However, if the parent directory is present, we can conclude that the
429 // given name was not a valid link (or else it would already be cached).
430 String dirName = name.substring(0, packageEnd);
431 if (!nodes.containsKey(dirName)) {
432 ImageLocation loc = findLocation(dirName);
433 // If the parent location doesn't exist, the link node cannot exist.
434 if (loc != null) {
435 nodes.put(dirName, completePackageDirectory(newDirectory(dirName), loc));
436 // When the parent is created its child nodes are created and cached,
437 // but this can still return null if given name wasn't a valid link.
438 return nodes.get(name);
439 }
440 }
441 }
442 return null;
443 }
444
445 /** Completes a directory by ensuring its child list is populated correctly. */
446 private void completeDirectory(Directory dir) {
447 String name = dir.getName();
448 // Since the node exists, we can assert that its name starts with
449 // either "/modules" or "/packages", making differentiation easy.
450 // It also means that the name is valid, so it must yield a location.
451 assert name.startsWith(MODULES_ROOT) || name.startsWith(PACKAGES_ROOT);
452 ImageLocation loc = findLocation(name);
453 assert loc != null && name.equals(loc.getFullName()) : "Invalid location for name: " + name;
454 // We cannot use 'isXxxSubdirectory()' methods here since we could
455 // be given a top-level directory (for which that test doesn't work).
456 // The string MUST start "/modules" or "/packages" here.
457 if (name.charAt(1) == 'm') {
458 completeModuleDirectory(dir, loc);
459 } else {
460 completePackageDirectory(dir, loc);
461 }
462 assert dir.isCompleted() : "Directory must be complete by now: " + dir;
463 }
464
465 /**
466 * Completes a modules directory by setting the list of child nodes.
467 *
468 * <p>The given directory can be the top level {@code /modules} directory,
469 * so it is NOT safe to use {@code isModulesSubdirectory(loc)} here.
470 */
471 private Directory completeModuleDirectory(Directory dir, ImageLocation loc) {
472 assert dir.getName().equals(loc.getFullName()) : "Mismatched location for directory: " + dir;
473 List<Node> children = createChildNodes(loc, childLoc -> {
474 if (isModulesSubdirectory(childLoc)) {
475 return nodes.computeIfAbsent(childLoc.getFullName(), this::newDirectory);
476 } else {
477 // Add "/modules" prefix to image location paths to get node names.
478 String resourceName = childLoc.getFullName(true);
479 return nodes.computeIfAbsent(resourceName, n -> newResource(n, childLoc));
480 }
481 });
482 dir.setChildren(children);
483 return dir;
484 }
485
486 /**
487 * Completes a package directory by setting the list of child nodes.
488 *
489 * <p>The given directory can be the top level {@code /packages} directory,
490 * so it is NOT safe to use {@code isPackagesSubdirectory(loc)} here.
491 */
492 private Directory completePackageDirectory(Directory dir, ImageLocation loc) {
493 assert dir.getName().equals(loc.getFullName()) : "Mismatched location for directory: " + dir;
494 // The only directories in the "/packages" namespace are "/packages" or
495 // "/packages/<package>". However, unlike "/modules" directories, the
496 // location offsets mean different things.
497 List<Node> children;
498 if (dir.getName().equals(PACKAGES_ROOT)) {
499 // Top-level directory just contains a list of subdirectories.
500 children = createChildNodes(loc, c -> nodes.computeIfAbsent(c.getFullName(), this::newDirectory));
501 } else {
502 // A package directory's content is array of offset PAIRS in the
503 // Strings table, but we only need the 2nd value of each pair.
504 IntBuffer intBuffer = getOffsetBuffer(loc);
505 int offsetCount = intBuffer.capacity();
506 assert (offsetCount & 0x1) == 0 : "Offset count must be even: " + offsetCount;
507 children = new ArrayList<>(offsetCount / 2);
508 // Iterate the 2nd offset in each pair (odd indices).
509 for (int i = 1; i < offsetCount; i += 2) {
510 String moduleName = getString(intBuffer.get(i));
511 children.add(nodes.computeIfAbsent(
512 dir.getName() + "/" + moduleName,
513 n -> newLinkNode(n, MODULES_ROOT + "/" + moduleName)));
514 }
515 }
516 // This only happens once and "completes" the directory.
517 dir.setChildren(children);
518 return dir;
519 }
520
521 /**
522 * Creates the list of child nodes for a {@code Directory} based on a given
523 *
524 * <p>Note: This cannot be used for package subdirectories as they have
525 * child offsets stored differently to other directories.
526 */
527 private List<Node> createChildNodes(ImageLocation loc, Function<ImageLocation, Node> newChildFn) {
528 IntBuffer offsets = getOffsetBuffer(loc);
529 int childCount = offsets.capacity();
530 List<Node> children = new ArrayList<>(childCount);
531 for (int i = 0; i < childCount; i++) {
532 children.add(newChildFn.apply(getLocation(offsets.get(i))));
533 }
534 return children;
535 }
536
537 /** Helper to extract the integer offset buffer from a directory location. */
538 private IntBuffer getOffsetBuffer(ImageLocation dir) {
539 assert !isResource(dir) : "Not a directory: " + dir.getFullName();
540 byte[] offsets = getResource(dir);
541 ByteBuffer buffer = ByteBuffer.wrap(offsets);
542 buffer.order(getByteOrder());
543 return buffer.asIntBuffer();
544 }
545
546 /**
547 * Efficiently determines if an image location is a resource.
548 *
549 * <p>A resource must have a valid module associated with it, so its
550 * module offset must be non-zero, and not equal to the offsets for
551 * "/modules/..." or "/packages/..." entries.
552 */
553 private boolean isResource(ImageLocation loc) {
554 int moduleOffset = loc.getModuleOffset();
555 return moduleOffset != 0
556 && moduleOffset != modulesStringOffset
557 && moduleOffset != packagesStringOffset;
558 }
559
560 /**
561 * Determines if an image location is a directory in the {@code /modules}
562 * namespace (if so, the location name is the node name).
563 *
564 * <p>In jimage, every {@code ImageLocation} under {@code /modules/} is a
565 * directory and has the same value for {@code getModule()}, and {@code
566 * getModuleOffset()}.
567 */
568 private boolean isModulesSubdirectory(ImageLocation loc) {
569 return loc.getModuleOffset() == modulesStringOffset;
570 }
571
572 /**
573 * Creates an "incomplete" directory node with no child nodes set.
574 * Directories need to be "completed" before they are returned by
575 * {@link #findNode(String)}.
576 */
577 private Directory newDirectory(String name) {
578 return new Directory(name, imageFileAttributes);
579 }
580
581 /**
582 * Creates a new resource from an image location. This is the only case
583 * where the image location name does not match the requested node name.
584 * In image files, resource locations are NOT prefixed by {@code /modules}.
585 */
586 private Resource newResource(String name, ImageLocation loc) {
587 assert name.equals(loc.getFullName(true)) : "Mismatched location for resource: " + name;
588 return new Resource(name, loc, imageFileAttributes);
589 }
590
591 /**
592 * Creates a new link node pointing at the given target name.
593 *
594 * <p>Note that target node is resolved each time {@code resolve()} is called,
595 * so if a link node is retained after its reader is closed, it will fail.
596 */
597 private LinkNode newLinkNode(String name, String targetName) {
598 return new LinkNode(name, () -> findNode(targetName), imageFileAttributes);
599 }
600
601 /** Returns the content of a resource node. */
602 private byte[] getResource(Node node) throws IOException {
603 // We could have been given a non-resource node here.
604 if (node.isResource()) {
605 return super.getResource(node.getLocation());
606 }
607 throw new IOException("Not a resource: " + node);
608 }
609 }
610
611 /**
612 * A directory, resource or symbolic link.
613 *
614 * <h3 id="node_equality">Node Equality</h3>
615 *
616 * Nodes are identified solely by their name, and it is not valid to attempt
617 * to compare nodes from different reader instances. Different readers may
618 * produce nodes with the same names, but different contents.
619 *
620 * <p>Furthermore, since a {@link ImageReader} provides "perfect" caching of
621 * nodes, equality of nodes from the same reader is equivalent to instance
622 * identity.
623 */
624 public abstract static class Node {
625 private final String name;
626 private final BasicFileAttributes fileAttrs;
627
628 /**
629 * Creates an abstract {@code Node}, which is either a resource, directory
630 * or symbolic link.
631 *
632 * <p>This constructor is only non-private so it can be used by the
633 * {@code ExplodedImage} class, and must not be used otherwise.
634 */
635 protected Node(String name, BasicFileAttributes fileAttrs) {
636 this.name = Objects.requireNonNull(name);
637 this.fileAttrs = Objects.requireNonNull(fileAttrs);
638 }
639
640 // A node is completed when all its direct children have been built.
641 // As such, non-directory nodes are always complete.
642 boolean isCompleted() {
643 return true;
644 }
645
646 // Only resources can return a location.
647 ImageLocation getLocation() {
648 throw new IllegalStateException("not a resource: " + getName());
649 }
650
651 /**
652 * Returns the name of this node (e.g. {@code
653 * "/modules/java.base/java/lang/Object.class"} or {@code
654 * "/packages/java.lang"}).
655 *
656 * <p>Note that for resource nodes this is NOT the underlying jimage
657 * resource name (it is prefixed with {@code "/modules"}).
658 */
659 public final String getName() {
660 return name;
661 }
662
663 /**
664 * Returns file attributes for this node. The value returned may be the
665 * same for all nodes, and should not be relied upon for accuracy.
666 */
667 public final BasicFileAttributes getFileAttributes() {
668 return fileAttrs;
669 }
670
671 /**
672 * Resolves a symbolic link to its target node. If this code is not a
673 * symbolic link, then it resolves to itself.
674 */
675 public final Node resolveLink() {
676 return resolveLink(false);
677 }
678
679 /**
680 * Resolves a symbolic link to its target node. If this code is not a
681 * symbolic link, then it resolves to itself.
682 */
683 public Node resolveLink(boolean recursive) {
684 return this;
685 }
686
687 /** Returns whether this node is a symbolic link. */
688 public boolean isLink() {
689 return false;
690 }
691
692 /**
693 * Returns whether this node is a directory. Directory nodes can have
694 * {@link #getChildNames()} invoked to get the fully qualified names
695 * of any child nodes.
696 */
697 public boolean isDirectory() {
698 return false;
699 }
700
701 /**
702 * Returns whether this node is a resource. Resource nodes can have
703 * their contents obtained via {@link ImageReader#getResource(Node)}
704 * or {@link ImageReader#getResourceBuffer(Node)}.
705 */
706 public boolean isResource() {
707 return false;
708 }
709
710 /**
711 * Returns the fully qualified names of any child nodes for a directory.
712 *
713 * <p>By default, this method throws {@link IllegalStateException} and
714 * is overridden for directories.
715 */
716 public Stream<String> getChildNames() {
717 throw new IllegalStateException("not a directory: " + getName());
718 }
719
720 /**
721 * Returns the uncompressed size of this node's content. If this node is
722 * not a resource, this method returns zero.
723 */
724 public long size() {
725 return 0L;
726 }
727
728 /**
729 * Returns the compressed size of this node's content. If this node is
730 * not a resource, this method returns zero.
731 */
732 public long compressedSize() {
733 return 0L;
734 }
735
736 /**
737 * Returns the extension string of a resource node. If this node is not
738 * a resource, this method returns null.
739 */
740 public String extension() {
741 return null;
742 }
743
744 @Override
745 public final String toString() {
746 return getName();
747 }
748
749 /** See <a href="#node_equality">Node Equality</a>. */
750 @Override
751 public final int hashCode() {
752 return name.hashCode();
753 }
754
755 /** See <a href="#node_equality">Node Equality</a>. */
756 @Override
757 public final boolean equals(Object other) {
758 if (this == other) {
759 return true;
760 }
761
762 if (other instanceof Node) {
763 return name.equals(((Node) other).name);
764 }
765
766 return false;
767 }
768 }
769
770 /**
771 * Directory node (referenced from a full path, without a trailing '/').
772 *
773 * <p>Directory nodes have two distinct states:
774 * <ul>
775 * <li>Incomplete: The child list has not been set.
776 * <li>Complete: The child list has been set.
777 * </ul>
778 *
779 * <p>When a directory node is returned by {@link ImageReader#findNode(String)}
780 * it is always complete, but this DOES NOT mean that its child nodes are
781 * complete yet.
782 *
783 * <p>To avoid users being able to access incomplete child nodes, the
784 * {@code Node} API offers only a way to obtain child node names, forcing
785 * callers to invoke {@code findNode()} if they need to access the child
786 * node itself.
787 *
788 * <p>This approach allows directories to be implemented lazily with respect
789 * to child nodes, while retaining efficiency when child nodes are accessed
790 * (since any incomplete nodes will be created and placed in the node cache
791 * when the parent was first returned to the user).
792 */
793 private static final class Directory extends Node {
794 // Monotonic reference, will be set to the unmodifiable child list exactly once.
795 private List<Node> children = null;
796
797 private Directory(String name, BasicFileAttributes fileAttrs) {
798 super(name, fileAttrs);
799 }
800
801 @Override
802 boolean isCompleted() {
803 return children != null;
804 }
805
806 @Override
807 public boolean isDirectory() {
808 return true;
809 }
810
811 @Override
812 public Stream<String> getChildNames() {
813 if (children != null) {
814 return children.stream().map(Node::getName);
815 }
816 throw new IllegalStateException("Cannot get child nodes of an incomplete directory: " + getName());
817 }
818
819 private void setChildren(List<Node> children) {
820 assert this.children == null : this + ": Cannot set child nodes twice!";
821 this.children = Collections.unmodifiableList(children);
822 }
823 }
824 /**
825 * Resource node (e.g. a ".class" entry, or any other data resource).
826 *
827 * <p>Resources are leaf nodes referencing an underlying image location. They
828 * are lightweight, and do not cache their contents.
829 *
830 * <p>Unlike directories (where the node name matches the jimage path for the
831 * corresponding {@code ImageLocation}), resource node names are NOT the same
832 * as the corresponding jimage path. The difference is that node names for
833 * resources are prefixed with "/modules", which is missing from the
834 * equivalent jimage path.
835 */
836 private static class Resource extends Node {
837 private final ImageLocation loc;
838
839 private Resource(String name, ImageLocation loc, BasicFileAttributes fileAttrs) {
840 super(name, fileAttrs);
841 this.loc = loc;
842 }
843
844 @Override
845 ImageLocation getLocation() {
846 return loc;
847 }
848
849 @Override
850 public boolean isResource() {
851 return true;
852 }
853
854 @Override
855 public long size() {
856 return loc.getUncompressedSize();
857 }
858
859 @Override
860 public long compressedSize() {
861 return loc.getCompressedSize();
862 }
863
864 @Override
865 public String extension() {
866 return loc.getExtension();
867 }
868 }
869
870 /**
871 * Link node (a symbolic link to a top-level modules directory).
872 *
873 * <p>Link nodes resolve their target by invoking a given supplier, and do
874 * not cache the result. Since nodes are cached by the {@code ImageReader},
875 * this means that only the first call to {@link #resolveLink(boolean)}
876 * could do any significant work.
877 */
878 private static class LinkNode extends Node {
879 private final Supplier<Node> link;
880
881 private LinkNode(String name, Supplier<Node> link, BasicFileAttributes fileAttrs) {
882 super(name, fileAttrs);
883 this.link = link;
884 }
885
886 @Override
887 public Node resolveLink(boolean recursive) {
888 // No need to use or propagate the recursive flag, since the target
889 // cannot possibly be a link node (links only point to directories).
890 return link.get();
891 }
892
893 @Override
894 public boolean isLink() {
895 return true;
896 }
897 }
898 }