1 /*
2 * Copyright (c) 2014, 2025, 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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20 *
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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 * Releases a (possibly cached) {@link ByteBuffer} obtained via
194 * {@link #getResourceBuffer(Node)}.
195 *
196 * <p>Note that no testing is performed to check whether the buffer about
197 * to be released actually came from a call to {@code getResourceBuffer()}.
198 */
199 public static void releaseByteBuffer(ByteBuffer buffer) {
200 BasicImageReader.releaseByteBuffer(buffer);
201 }
202
203 /**
204 * Returns the content of a resource node in a possibly cached byte buffer.
205 * Callers of this method must call {@link #releaseByteBuffer(ByteBuffer)}
206 * when they are finished with it.
207 */
208 public ByteBuffer getResourceBuffer(Node node) {
209 requireOpen();
210 if (!node.isResource()) {
211 throw new IllegalArgumentException("Not a resource node: " + node);
212 }
213 return reader.getResourceBuffer(node.getLocation());
214 }
215
216 private static final class SharedImageReader extends BasicImageReader {
217 private static final Map<Path, SharedImageReader> OPEN_FILES = new HashMap<>();
218 private static final String MODULES_ROOT = "/modules";
219 private static final String PACKAGES_ROOT = "/packages";
220 // There are >30,000 nodes in a complete jimage tree, and even relatively
221 // common tasks (e.g. starting up javac) load somewhere in the region of
222 // 1000 classes. Thus, an initial capacity of 2000 is a reasonable guess.
223 private static final int INITIAL_NODE_CACHE_CAPACITY = 2000;
224
225 // List of openers for this shared image.
226 private final Set<ImageReader> openers = new HashSet<>();
227
228 // Attributes of the jimage file. The jimage file does not contain
229 // attributes for the individual resources (yet). We use attributes
230 // of the jimage file itself (creation, modification, access times).
231 private final BasicFileAttributes imageFileAttributes;
232
233 // Cache of all user visible nodes, guarded by synchronizing 'this' instance.
234 private final Map<String, Node> nodes;
235 // Used to classify ImageLocation instances without string comparison.
236 private final int modulesStringOffset;
237 private final int packagesStringOffset;
238
239 private SharedImageReader(Path imagePath, ByteOrder byteOrder) throws IOException {
240 super(imagePath, byteOrder);
241 this.imageFileAttributes = Files.readAttributes(imagePath, BasicFileAttributes.class);
242 this.nodes = new HashMap<>(INITIAL_NODE_CACHE_CAPACITY);
243 // Pick stable jimage names from which to extract string offsets (we cannot
244 // use "/modules" or "/packages", since those have a module offset of zero).
245 this.modulesStringOffset = getModuleOffset("/modules/java.base");
246 this.packagesStringOffset = getModuleOffset("/packages/java.lang");
247
248 // Node creation is very lazy, so we can just make the top-level directories
249 // now without the risk of triggering the building of lots of other nodes.
250 Directory packages = newDirectory(PACKAGES_ROOT);
251 nodes.put(packages.getName(), packages);
252 Directory modules = newDirectory(MODULES_ROOT);
253 nodes.put(modules.getName(), modules);
254
255 Directory root = newDirectory("/");
256 root.setChildren(Arrays.asList(packages, modules));
257 nodes.put(root.getName(), root);
258 }
259
260 /**
261 * Returns the offset of the string denoting the leading "module" segment in
262 * the given path (e.g. {@code <module>/<path>}). We can't just pass in the
263 * {@code /<module>} string here because that has a module offset of zero.
264 */
265 private int getModuleOffset(String path) {
266 ImageLocation location = findLocation(path);
267 assert location != null : "Cannot find expected jimage location: " + path;
268 int offset = location.getModuleOffset();
269 assert offset != 0 : "Invalid module offset for jimage location: " + path;
270 return offset;
271 }
272
273 private static ImageReader open(Path imagePath, ByteOrder byteOrder) throws IOException {
274 Objects.requireNonNull(imagePath);
275 Objects.requireNonNull(byteOrder);
276
277 synchronized (OPEN_FILES) {
278 SharedImageReader reader = OPEN_FILES.get(imagePath);
279
280 if (reader == null) {
281 // Will fail with an IOException if wrong byteOrder.
282 reader = new SharedImageReader(imagePath, byteOrder);
283 OPEN_FILES.put(imagePath, reader);
284 } else if (reader.getByteOrder() != byteOrder) {
285 throw new IOException("\"" + reader.getName() + "\" is not an image file");
286 }
287
288 ImageReader image = new ImageReader(reader);
289 reader.openers.add(image);
290
291 return image;
292 }
293 }
294
295 public void close(ImageReader image) throws IOException {
296 Objects.requireNonNull(image);
297
298 synchronized (OPEN_FILES) {
299 if (!openers.remove(image)) {
300 throw new IOException("image file already closed");
301 }
302
303 if (openers.isEmpty()) {
304 close();
305 nodes.clear();
306
307 if (!OPEN_FILES.remove(this.getImagePath(), this)) {
308 throw new IOException("image file not found in open list");
309 }
310 }
311 }
312 }
313
314 /**
315 * Returns a node with the given name, or null if no resource or directory of
316 * that name exists.
317 *
318 * <p>Note that there is no reentrant calling back to this method from within
319 * the node handling code.
320 *
321 * @param name an absolute, {@code /}-separated path string, prefixed with either
322 * "/modules" or "/packages".
323 */
324 synchronized Node findNode(String name) {
325 Node node = nodes.get(name);
326 if (node == null) {
327 // We cannot get the root paths ("/modules" or "/packages") here
328 // because those nodes are already in the nodes cache.
329 if (name.startsWith(MODULES_ROOT + "/")) {
330 // This may perform two lookups, one for a directory (in
331 // "/modules/...") and one for a non-prefixed resource
332 // (with "/modules" removed).
333 node = buildModulesNode(name);
334 } else if (name.startsWith(PACKAGES_ROOT + "/")) {
335 node = buildPackagesNode(name);
336 }
337 if (node != null) {
338 nodes.put(node.getName(), node);
339 }
340 } else if (!node.isCompleted()) {
341 // Only directories can be incomplete.
342 assert node instanceof Directory : "Invalid incomplete node: " + node;
343 completeDirectory((Directory) node);
344 }
345 assert node == null || node.isCompleted() : "Incomplete node: " + node;
346 return node;
347 }
348
349 /**
350 * Returns a resource node in the given module, or null if no resource of
351 * that name exists.
352 *
353 * <p>Note that there is no reentrant calling back to this method from within
354 * the node handling code.
355 */
356 Node findResourceNode(String moduleName, String resourcePath) {
357 // Unlike findNode(), this method makes only one lookup in the
358 // underlying jimage, but can only reliably return resource nodes.
359 if (moduleName.indexOf('/') >= 0) {
360 throw new IllegalArgumentException("invalid module name: " + moduleName);
361 }
362 String nodeName = MODULES_ROOT + "/" + moduleName + "/" + resourcePath;
363 // Synchronize as tightly as possible to reduce locking contention.
364 synchronized (this) {
365 Node node = nodes.get(nodeName);
366 if (node == null) {
367 ImageLocation loc = findLocation(moduleName, resourcePath);
368 if (loc != null && isResource(loc)) {
369 node = newResource(nodeName, loc);
370 nodes.put(node.getName(), node);
371 }
372 return node;
373 } else {
374 return node.isResource() ? node : null;
375 }
376 }
377 }
378
379 /**
380 * Returns whether a resource exists in the given module.
381 *
382 * <p>This method is expected to be called frequently for resources
383 * which do not exist in the given module (e.g. as part of classpath
384 * search). As such, it skips checking the nodes cache and only checks
385 * for an entry in the jimage file, as this is faster if the resource
386 * is not present. This also means it doesn't need synchronization.
387 */
388 boolean containsResource(String moduleName, String resourcePath) {
389 if (moduleName.indexOf('/') >= 0) {
390 throw new IllegalArgumentException("invalid module name: " + moduleName);
391 }
392 // If the given module name is 'modules', then 'isResource()'
393 // returns false to prevent false positives.
394 ImageLocation loc = findLocation(moduleName, resourcePath);
395 return loc != null && isResource(loc);
396 }
397
398 /**
399 * Builds a node in the "/modules/..." namespace.
400 *
401 * <p>Called by {@link #findNode(String)} if a {@code /modules/...} node
402 * is not present in the cache.
403 */
404 private Node buildModulesNode(String name) {
405 assert name.startsWith(MODULES_ROOT + "/") : "Invalid module node name: " + name;
406 // Returns null for non-directory resources, since the jimage name does not
407 // start with "/modules" (e.g. "/java.base/java/lang/Object.class").
408 ImageLocation loc = findLocation(name);
409 if (loc != null) {
410 assert name.equals(loc.getFullName()) : "Mismatched location for directory: " + name;
411 assert isModulesSubdirectory(loc) : "Invalid modules directory: " + name;
412 return completeModuleDirectory(newDirectory(name), loc);
413 }
414 // Now try the non-prefixed resource name, but be careful to avoid false
415 // positives for names like "/modules/modules/xxx" which could return a
416 // location of a directory entry.
417 loc = findLocation(name.substring(MODULES_ROOT.length()));
418 return loc != null && isResource(loc) ? newResource(name, loc) : null;
419 }
420
421 /**
422 * Builds a node in the "/packages/..." namespace.
423 *
424 * <p>Called by {@link #findNode(String)} if a {@code /packages/...} node
425 * is not present in the cache.
426 */
427 private Node buildPackagesNode(String name) {
428 // There are only locations for the root "/packages" or "/packages/xxx"
429 // directories, but not the symbolic links below them (the links can be
430 // entirely derived from the name information in the parent directory).
431 // However, unlike resources this means that we do not have a constant
432 // time lookup for link nodes when creating them.
433 int packageStart = PACKAGES_ROOT.length() + 1;
434 int packageEnd = name.indexOf('/', packageStart);
435 if (packageEnd == -1) {
436 ImageLocation loc = findLocation(name);
437 return loc != null ? completePackageDirectory(newDirectory(name), loc) : null;
438 } else {
439 // We cannot assume that the parent directory exists for a link node, since
440 // the given name is untrusted and could reference a non-existent link.
441 // However, if the parent directory is present, we can conclude that the
442 // given name was not a valid link (or else it would already be cached).
443 String dirName = name.substring(0, packageEnd);
444 if (!nodes.containsKey(dirName)) {
445 ImageLocation loc = findLocation(dirName);
446 // If the parent location doesn't exist, the link node cannot exist.
447 if (loc != null) {
448 nodes.put(dirName, completePackageDirectory(newDirectory(dirName), loc));
449 // When the parent is created its child nodes are created and cached,
450 // but this can still return null if given name wasn't a valid link.
451 return nodes.get(name);
452 }
453 }
454 }
455 return null;
456 }
457
458 /** Completes a directory by ensuring its child list is populated correctly. */
459 private void completeDirectory(Directory dir) {
460 String name = dir.getName();
461 // Since the node exists, we can assert that its name starts with
462 // either "/modules" or "/packages", making differentiation easy.
463 // It also means that the name is valid, so it must yield a location.
464 assert name.startsWith(MODULES_ROOT) || name.startsWith(PACKAGES_ROOT);
465 ImageLocation loc = findLocation(name);
466 assert loc != null && name.equals(loc.getFullName()) : "Invalid location for name: " + name;
467 // We cannot use 'isXxxSubdirectory()' methods here since we could
468 // be given a top-level directory (for which that test doesn't work).
469 // The string MUST start "/modules" or "/packages" here.
470 if (name.charAt(1) == 'm') {
471 completeModuleDirectory(dir, loc);
472 } else {
473 completePackageDirectory(dir, loc);
474 }
475 assert dir.isCompleted() : "Directory must be complete by now: " + dir;
476 }
477
478 /**
479 * Completes a modules directory by setting the list of child nodes.
480 *
481 * <p>The given directory can be the top level {@code /modules} directory,
482 * so it is NOT safe to use {@code isModulesSubdirectory(loc)} here.
483 */
484 private Directory completeModuleDirectory(Directory dir, ImageLocation loc) {
485 assert dir.getName().equals(loc.getFullName()) : "Mismatched location for directory: " + dir;
486 List<Node> children = createChildNodes(loc, childLoc -> {
487 if (isModulesSubdirectory(childLoc)) {
488 return nodes.computeIfAbsent(childLoc.getFullName(), this::newDirectory);
489 } else {
490 // Add "/modules" prefix to image location paths to get node names.
491 String resourceName = childLoc.getFullName(true);
492 return nodes.computeIfAbsent(resourceName, n -> newResource(n, childLoc));
493 }
494 });
495 dir.setChildren(children);
496 return dir;
497 }
498
499 /**
500 * Completes a package directory by setting the list of child nodes.
501 *
502 * <p>The given directory can be the top level {@code /packages} directory,
503 * so it is NOT safe to use {@code isPackagesSubdirectory(loc)} here.
504 */
505 private Directory completePackageDirectory(Directory dir, ImageLocation loc) {
506 assert dir.getName().equals(loc.getFullName()) : "Mismatched location for directory: " + dir;
507 // The only directories in the "/packages" namespace are "/packages" or
508 // "/packages/<package>". However, unlike "/modules" directories, the
509 // location offsets mean different things.
510 List<Node> children;
511 if (dir.getName().equals(PACKAGES_ROOT)) {
512 // Top-level directory just contains a list of subdirectories.
513 children = createChildNodes(loc, c -> nodes.computeIfAbsent(c.getFullName(), this::newDirectory));
514 } else {
515 // A package directory's content is array of offset PAIRS in the
516 // Strings table, but we only need the 2nd value of each pair.
517 IntBuffer intBuffer = getOffsetBuffer(loc);
518 int offsetCount = intBuffer.capacity();
519 assert (offsetCount & 0x1) == 0 : "Offset count must be even: " + offsetCount;
520 children = new ArrayList<>(offsetCount / 2);
521 // Iterate the 2nd offset in each pair (odd indices).
522 for (int i = 1; i < offsetCount; i += 2) {
523 String moduleName = getString(intBuffer.get(i));
524 children.add(nodes.computeIfAbsent(
525 dir.getName() + "/" + moduleName,
526 n -> newLinkNode(n, MODULES_ROOT + "/" + moduleName)));
527 }
528 }
529 // This only happens once and "completes" the directory.
530 dir.setChildren(children);
531 return dir;
532 }
533
534 /**
535 * Creates the list of child nodes for a {@code Directory} based on a given
536 *
537 * <p>Note: This cannot be used for package subdirectories as they have
538 * child offsets stored differently to other directories.
539 */
540 private List<Node> createChildNodes(ImageLocation loc, Function<ImageLocation, Node> newChildFn) {
541 IntBuffer offsets = getOffsetBuffer(loc);
542 int childCount = offsets.capacity();
543 List<Node> children = new ArrayList<>(childCount);
544 for (int i = 0; i < childCount; i++) {
545 children.add(newChildFn.apply(getLocation(offsets.get(i))));
546 }
547 return children;
548 }
549
550 /** Helper to extract the integer offset buffer from a directory location. */
551 private IntBuffer getOffsetBuffer(ImageLocation dir) {
552 assert !isResource(dir) : "Not a directory: " + dir.getFullName();
553 byte[] offsets = getResource(dir);
554 ByteBuffer buffer = ByteBuffer.wrap(offsets);
555 buffer.order(getByteOrder());
556 return buffer.asIntBuffer();
557 }
558
559 /**
560 * Efficiently determines if an image location is a resource.
561 *
562 * <p>A resource must have a valid module associated with it, so its
563 * module offset must be non-zero, and not equal to the offsets for
564 * "/modules/..." or "/packages/..." entries.
565 */
566 private boolean isResource(ImageLocation loc) {
567 int moduleOffset = loc.getModuleOffset();
568 return moduleOffset != 0
569 && moduleOffset != modulesStringOffset
570 && moduleOffset != packagesStringOffset;
571 }
572
573 /**
574 * Determines if an image location is a directory in the {@code /modules}
575 * namespace (if so, the location name is the node name).
576 *
577 * <p>In jimage, every {@code ImageLocation} under {@code /modules/} is a
578 * directory and has the same value for {@code getModule()}, and {@code
579 * getModuleOffset()}.
580 */
581 private boolean isModulesSubdirectory(ImageLocation loc) {
582 return loc.getModuleOffset() == modulesStringOffset;
583 }
584
585 /**
586 * Creates an "incomplete" directory node with no child nodes set.
587 * Directories need to be "completed" before they are returned by
588 * {@link #findNode(String)}.
589 */
590 private Directory newDirectory(String name) {
591 return new Directory(name, imageFileAttributes);
592 }
593
594 /**
595 * Creates a new resource from an image location. This is the only case
596 * where the image location name does not match the requested node name.
597 * In image files, resource locations are NOT prefixed by {@code /modules}.
598 */
599 private Resource newResource(String name, ImageLocation loc) {
600 assert name.equals(loc.getFullName(true)) : "Mismatched location for resource: " + name;
601 return new Resource(name, loc, imageFileAttributes);
602 }
603
604 /**
605 * Creates a new link node pointing at the given target name.
606 *
607 * <p>Note that target node is resolved each time {@code resolve()} is called,
608 * so if a link node is retained after its reader is closed, it will fail.
609 */
610 private LinkNode newLinkNode(String name, String targetName) {
611 return new LinkNode(name, () -> findNode(targetName), imageFileAttributes);
612 }
613
614 /** Returns the content of a resource node. */
615 private byte[] getResource(Node node) throws IOException {
616 // We could have been given a non-resource node here.
617 if (node.isResource()) {
618 return super.getResource(node.getLocation());
619 }
620 throw new IOException("Not a resource: " + node);
621 }
622 }
623
624 /**
625 * A directory, resource or symbolic link.
626 *
627 * <h3 id="node_equality">Node Equality</h3>
628 *
629 * Nodes are identified solely by their name, and it is not valid to attempt
630 * to compare nodes from different reader instances. Different readers may
631 * produce nodes with the same names, but different contents.
632 *
633 * <p>Furthermore, since a {@link ImageReader} provides "perfect" caching of
634 * nodes, equality of nodes from the same reader is equivalent to instance
635 * identity.
636 */
637 public abstract static class Node {
638 private final String name;
639 private final BasicFileAttributes fileAttrs;
640
641 /**
642 * Creates an abstract {@code Node}, which is either a resource, directory
643 * or symbolic link.
644 *
645 * <p>This constructor is only non-private so it can be used by the
646 * {@code ExplodedImage} class, and must not be used otherwise.
647 */
648 protected Node(String name, BasicFileAttributes fileAttrs) {
649 this.name = Objects.requireNonNull(name);
650 this.fileAttrs = Objects.requireNonNull(fileAttrs);
651 }
652
653 // A node is completed when all its direct children have been built.
654 // As such, non-directory nodes are always complete.
655 boolean isCompleted() {
656 return true;
657 }
658
659 // Only resources can return a location.
660 ImageLocation getLocation() {
661 throw new IllegalStateException("not a resource: " + getName());
662 }
663
664 /**
665 * Returns the name of this node (e.g. {@code
666 * "/modules/java.base/java/lang/Object.class"} or {@code
667 * "/packages/java.lang"}).
668 *
669 * <p>Note that for resource nodes this is NOT the underlying jimage
670 * resource name (it is prefixed with {@code "/modules"}).
671 */
672 public final String getName() {
673 return name;
674 }
675
676 /**
677 * Returns file attributes for this node. The value returned may be the
678 * same for all nodes, and should not be relied upon for accuracy.
679 */
680 public final BasicFileAttributes getFileAttributes() {
681 return fileAttrs;
682 }
683
684 /**
685 * Resolves a symbolic link to its target node. If this code is not a
686 * symbolic link, then it resolves to itself.
687 */
688 public final Node resolveLink() {
689 return resolveLink(false);
690 }
691
692 /**
693 * Resolves a symbolic link to its target node. If this code is not a
694 * symbolic link, then it resolves to itself.
695 */
696 public Node resolveLink(boolean recursive) {
697 return this;
698 }
699
700 /** Returns whether this node is a symbolic link. */
701 public boolean isLink() {
702 return false;
703 }
704
705 /**
706 * Returns whether this node is a directory. Directory nodes can have
707 * {@link #getChildNames()} invoked to get the fully qualified names
708 * of any child nodes.
709 */
710 public boolean isDirectory() {
711 return false;
712 }
713
714 /**
715 * Returns whether this node is a resource. Resource nodes can have
716 * their contents obtained via {@link ImageReader#getResource(Node)}
717 * or {@link ImageReader#getResourceBuffer(Node)}.
718 */
719 public boolean isResource() {
720 return false;
721 }
722
723 /**
724 * Returns the fully qualified names of any child nodes for a directory.
725 *
726 * <p>By default, this method throws {@link IllegalStateException} and
727 * is overridden for directories.
728 */
729 public Stream<String> getChildNames() {
730 throw new IllegalStateException("not a directory: " + getName());
731 }
732
733 /**
734 * Returns the uncompressed size of this node's content. If this node is
735 * not a resource, this method returns zero.
736 */
737 public long size() {
738 return 0L;
739 }
740
741 /**
742 * Returns the compressed size of this node's content. If this node is
743 * not a resource, this method returns zero.
744 */
745 public long compressedSize() {
746 return 0L;
747 }
748
749 /**
750 * Returns the extension string of a resource node. If this node is not
751 * a resource, this method returns null.
752 */
753 public String extension() {
754 return null;
755 }
756
757 @Override
758 public final String toString() {
759 return getName();
760 }
761
762 /** See <a href="#node_equality">Node Equality</a>. */
763 @Override
764 public final int hashCode() {
765 return name.hashCode();
766 }
767
768 /** See <a href="#node_equality">Node Equality</a>. */
769 @Override
770 public final boolean equals(Object other) {
771 if (this == other) {
772 return true;
773 }
774
775 if (other instanceof Node) {
776 return name.equals(((Node) other).name);
777 }
778
779 return false;
780 }
781 }
782
783 /**
784 * Directory node (referenced from a full path, without a trailing '/').
785 *
786 * <p>Directory nodes have two distinct states:
787 * <ul>
788 * <li>Incomplete: The child list has not been set.
789 * <li>Complete: The child list has been set.
790 * </ul>
791 *
792 * <p>When a directory node is returned by {@link ImageReader#findNode(String)}
793 * it is always complete, but this DOES NOT mean that its child nodes are
794 * complete yet.
795 *
796 * <p>To avoid users being able to access incomplete child nodes, the
797 * {@code Node} API offers only a way to obtain child node names, forcing
798 * callers to invoke {@code findNode()} if they need to access the child
799 * node itself.
800 *
801 * <p>This approach allows directories to be implemented lazily with respect
802 * to child nodes, while retaining efficiency when child nodes are accessed
803 * (since any incomplete nodes will be created and placed in the node cache
804 * when the parent was first returned to the user).
805 */
806 private static final class Directory extends Node {
807 // Monotonic reference, will be set to the unmodifiable child list exactly once.
808 private List<Node> children = null;
809
810 private Directory(String name, BasicFileAttributes fileAttrs) {
811 super(name, fileAttrs);
812 }
813
814 @Override
815 boolean isCompleted() {
816 return children != null;
817 }
818
819 @Override
820 public boolean isDirectory() {
821 return true;
822 }
823
824 @Override
825 public Stream<String> getChildNames() {
826 if (children != null) {
827 return children.stream().map(Node::getName);
828 }
829 throw new IllegalStateException("Cannot get child nodes of an incomplete directory: " + getName());
830 }
831
832 private void setChildren(List<Node> children) {
833 assert this.children == null : this + ": Cannot set child nodes twice!";
834 this.children = Collections.unmodifiableList(children);
835 }
836 }
837 /**
838 * Resource node (e.g. a ".class" entry, or any other data resource).
839 *
840 * <p>Resources are leaf nodes referencing an underlying image location. They
841 * are lightweight, and do not cache their contents.
842 *
843 * <p>Unlike directories (where the node name matches the jimage path for the
844 * corresponding {@code ImageLocation}), resource node names are NOT the same
845 * as the corresponding jimage path. The difference is that node names for
846 * resources are prefixed with "/modules", which is missing from the
847 * equivalent jimage path.
848 */
849 private static class Resource extends Node {
850 private final ImageLocation loc;
851
852 private Resource(String name, ImageLocation loc, BasicFileAttributes fileAttrs) {
853 super(name, fileAttrs);
854 this.loc = loc;
855 }
856
857 @Override
858 ImageLocation getLocation() {
859 return loc;
860 }
861
862 @Override
863 public boolean isResource() {
864 return true;
865 }
866
867 @Override
868 public long size() {
869 return loc.getUncompressedSize();
870 }
871
872 @Override
873 public long compressedSize() {
874 return loc.getCompressedSize();
875 }
876
877 @Override
878 public String extension() {
879 return loc.getExtension();
880 }
881 }
882
883 /**
884 * Link node (a symbolic link to a top-level modules directory).
885 *
886 * <p>Link nodes resolve their target by invoking a given supplier, and do
887 * not cache the result. Since nodes are cached by the {@code ImageReader},
888 * this means that only the first call to {@link #resolveLink(boolean)}
889 * could do any significant work.
890 */
891 private static class LinkNode extends Node {
892 private final Supplier<Node> link;
893
894 private LinkNode(String name, Supplier<Node> link, BasicFileAttributes fileAttrs) {
895 super(name, fileAttrs);
896 this.link = link;
897 }
898
899 @Override
900 public Node resolveLink(boolean recursive) {
901 // No need to use or propagate the recursive flag, since the target
902 // cannot possibly be a link node (links only point to directories).
903 return link.get();
904 }
905
906 @Override
907 public boolean isLink() {
908 return true;
909 }
910 }
911 }