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	/*
	* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package jdk.internal.jrtfs;

	import java.io.IOException;
	import java.io.UncheckedIOException;
	import java.nio.file.DirectoryStream;
	import java.nio.file.FileSystem;
	import java.nio.file.FileSystemException;
	import java.nio.file.FileSystems;
	import java.nio.file.Files;
	import java.nio.file.Path;
	import java.nio.file.attribute.BasicFileAttributes;
	import java.util.ArrayList;
	import java.util.Collections;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;

	import jdk.internal.jimage.ImageReader.Node;

	/**
	* A jrt file system built on $JAVA_HOME/modules directory ('exploded modules
	* build')
	*
	* @implNote This class needs to maintain JDK 8 source compatibility.
	*
	* It is used internally in the JDK to implement jimage/jrtfs access,
	* but also compiled and delivered as part of the jrtfs.jar to support access
	* to the jimage file provided by the shipped JDK by tools running on JDK 8.
	*/
	class ExplodedImage extends SystemImage {

	private static final String MODULES = "/modules/";
	private static final String PACKAGES = "/packages/";
	private static final int PACKAGES_LEN = PACKAGES.length();

	private final FileSystem defaultFS;
	private final String separator;
	private final Map<String, PathNode> nodes = Collections.synchronizedMap(new HashMap<>());
	private final BasicFileAttributes modulesDirAttrs;

	ExplodedImage(Path modulesDir) throws IOException {
	defaultFS = FileSystems.getDefault();
	String str = defaultFS.getSeparator();
	separator = str.equals("/") ? null : str;
	modulesDirAttrs = Files.readAttributes(modulesDir, BasicFileAttributes.class);
	initNodes();
	}

	// A Node that is backed by actual default file system Path
	private final class PathNode extends Node {

	// Path in underlying default file system
	private Path path;
	private PathNode link;
	private List<Node> children;

	PathNode(String name, Path path, BasicFileAttributes attrs) { // path
	super(name, attrs);
	this.path = path;
	}

	PathNode(String name, Node link) { // link
	super(name, link.getFileAttributes());
	this.link = (PathNode)link;
	}

	PathNode(String name, List<Node> children) { // dir
	super(name, modulesDirAttrs);
	this.children = children;
	}

	@Override
	public boolean isDirectory() {
	return children != null \|\|
	(link == null && getFileAttributes().isDirectory());
	}

	@Override
	public boolean isLink() {
	return link != null;
	}

	@Override
	public PathNode resolveLink(boolean recursive) {
	if (link == null)
	return this;
	return recursive && link.isLink() ? link.resolveLink(true) : link;
	}

	byte[] getContent() throws IOException {
	if (!getFileAttributes().isRegularFile())
	throw new FileSystemException(getName() + " is not file");
	return Files.readAllBytes(path);
	}

	@Override
	public List<Node> getChildren() {
	if (!isDirectory())
	throw new IllegalArgumentException("not a directory: " + getNameString());
	if (children == null) {
	List<Node> list = new ArrayList<>();
	try (DirectoryStream<Path> stream = Files.newDirectoryStream(path)) {
	for (Path p : stream) {
	p = explodedModulesDir.relativize(p);
	String pName = MODULES + nativeSlashToFrontSlash(p.toString());
	Node node = findNode(pName);
	if (node != null) { // findNode may choose to hide certain files!
	list.add(node);
	}
	}
	} catch (IOException x) {
	return null;
	}
	children = list;
	}
	return children;
	}

	@Override
	public long size() {
	try {
	return isDirectory() ? 0 : Files.size(path);
	} catch (IOException ex) {
	throw new UncheckedIOException(ex);
	}
	}
	}

	@Override
	public void close() throws IOException {
	nodes.clear();
	}

	@Override
	public byte[] getResource(Node node) throws IOException {
	return ((PathNode)node).getContent();
	}

	// find Node for the given Path
	@Override
	public synchronized Node findNode(String str) {
	Node node = findModulesNode(str);
	if (node != null) {
	return node;
	}
	// lazily created for paths like /packages/<package>/<module>/xyz
	// For example /packages/java.lang/java.base/java/lang/
	if (str.startsWith(PACKAGES)) {
	// pkgEndIdx marks end of <package> part
	int pkgEndIdx = str.indexOf('/', PACKAGES_LEN);
	if (pkgEndIdx != -1) {
	// modEndIdx marks end of <module> part
	int modEndIdx = str.indexOf('/', pkgEndIdx + 1);
	if (modEndIdx != -1) {
	// make sure we have such module link!
	// ie., /packages/<package>/<module> is valid
	Node linkNode = nodes.get(str.substring(0, modEndIdx));
	if (linkNode == null \|\| !linkNode.isLink()) {
	return null;
	}
	// map to "/modules/zyz" path and return that node
	// For example, "/modules/java.base/java/lang" for
	// "/packages/java.lang/java.base/java/lang".
	String mod = MODULES + str.substring(pkgEndIdx + 1);
	return findModulesNode(mod);
	}
	}
	}
	return null;
	}

	// find a Node for a path that starts like "/modules/..."
	Node findModulesNode(String str) {
	PathNode node = nodes.get(str);
	if (node != null) {
	return node;
	}
	// lazily created "/modules/xyz/abc/" Node
	// This is mapped to default file system path "<JDK_MODULES_DIR>/xyz/abc"
	Path p = underlyingPath(str);
	if (p != null) {
	try {
	BasicFileAttributes attrs = Files.readAttributes(p, BasicFileAttributes.class);
	if (attrs.isRegularFile()) {
	Path f = p.getFileName();
	if (f.toString().startsWith("_the."))
	return null;
	}
	node = new PathNode(str, p, attrs);
	nodes.put(str, node);
	return node;
	} catch (IOException x) {
	// does not exists or unable to determine
	}
	}
	return null;
	}

	Path underlyingPath(String str) {
	if (str.startsWith(MODULES)) {
	str = frontSlashToNativeSlash(str.substring("/modules".length()));
	return defaultFS.getPath(explodedModulesDir.toString(), str);
	}
	return null;
	}

	// convert "/" to platform path separator
	private String frontSlashToNativeSlash(String str) {
	return separator == null ? str : str.replace("/", separator);
	}

	// convert platform path separator to "/"
	private String nativeSlashToFrontSlash(String str) {
	return separator == null ? str : str.replace(separator, "/");
	}

	// convert "/"s to "."s
	private String slashesToDots(String str) {
	return str.replace(separator != null ? separator : "/", ".");
	}

	// initialize file system Nodes
	private void initNodes() throws IOException {
	// same package prefix may exist in mutliple modules. This Map
	// is filled by walking "jdk modules" directory recursively!
	Map<String, List<String>> packageToModules = new HashMap<>();
	try (DirectoryStream<Path> stream = Files.newDirectoryStream(explodedModulesDir)) {
	for (Path module : stream) {
	if (Files.isDirectory(module)) {
	String moduleName = module.getFileName().toString();
	// make sure "/modules/<moduleName>" is created
	findModulesNode(MODULES + moduleName);
	Files.walk(module).filter(Files::isDirectory).forEach((p) -> {
	p = module.relativize(p);
	String pkgName = slashesToDots(p.toString());
	// skip META-INFO and empty strings
	if (!pkgName.isEmpty() && !pkgName.startsWith("META-INF")) {
	List<String> moduleNames = packageToModules.get(pkgName);
	if (moduleNames == null) {
	moduleNames = new ArrayList<>();
	packageToModules.put(pkgName, moduleNames);
	}
	moduleNames.add(moduleName);
	}
	});
	}
	}
	}
	// create "/modules" directory
	// "nodes" map contains only /modules/<foo> nodes only so far and so add all as children of /modules
	PathNode modulesDir = new PathNode("/modules", new ArrayList<>(nodes.values()));
	nodes.put(modulesDir.getName(), modulesDir);

	// create children under "/packages"
	List<Node> packagesChildren = new ArrayList<>(packageToModules.size());
	for (Map.Entry<String, List<String>> entry : packageToModules.entrySet()) {
	String pkgName = entry.getKey();
	List<String> moduleNameList = entry.getValue();
	List<Node> moduleLinkNodes = new ArrayList<>(moduleNameList.size());
	for (String moduleName : moduleNameList) {
	Node moduleNode = findModulesNode(MODULES + moduleName);
	PathNode linkNode = new PathNode(PACKAGES + pkgName + "/" + moduleName, moduleNode);
	nodes.put(linkNode.getName(), linkNode);
	moduleLinkNodes.add(linkNode);
	}
	PathNode pkgDir = new PathNode(PACKAGES + pkgName, moduleLinkNodes);
	nodes.put(pkgDir.getName(), pkgDir);
	packagesChildren.add(pkgDir);
	}
	// "/packages" dir
	PathNode packagesDir = new PathNode("/packages", packagesChildren);
	nodes.put(packagesDir.getName(), packagesDir);

	// finally "/" dir!
	List<Node> rootChildren = new ArrayList<>();
	rootChildren.add(packagesDir);
	rootChildren.add(modulesDir);
	PathNode root = new PathNode("/", rootChildren);
	nodes.put(root.getName(), root);
	}
	}

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