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 * reserved comment block

 * DO NOT REMOVE OR ALTER!

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/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 *  Unless required by applicable law or agreed to in writing, software

 *  distributed under the License is distributed on an "AS IS" BASIS,

 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 *  See the License for the specific language governing permissions and

 *  limitations under the License.

 *

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package com.sun.org.apache.bcel.internal.util;

import java.io.Closeable;

import java.io.File;

import java.io.IOException;

import java.net.URI;

import java.net.URL;

import java.net.URLClassLoader;

import java.nio.file.DirectoryStream;

import java.nio.file.FileSystem;

import java.nio.file.FileSystems;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

/**

 * Wraps a Java 9 JEP 220 modular runtime image. Requires the JRT NIO file system.

 *

 * @since 6.3

 */

public class ModularRuntimeImage implements Closeable {

    static final String MODULES_PATH = File.separator + "modules";

    static final String PACKAGES_PATH = File.separator + "packages";

    private final URLClassLoader classLoader;

    private final FileSystem fileSystem;

    /**

     * Constructs a default instance.

     *

     * @throws IOException

     *             an I/O error occurs accessing the file system

     */

    public ModularRuntimeImage() throws IOException {

        this(null, FileSystems.getFileSystem(URI.create("jrt:/")));

    }

    /**

     * Constructs an instance using the JRT file system implementation from a specific Java Home.

     *

     * @param javaHome

     *            Path to a Java 9 or greater home.

     *

     * @throws IOException

     *             an I/O error occurs accessing the file system

     */

    public ModularRuntimeImage(final String javaHome) throws IOException {

        final Map<String, ?> emptyMap = Collections.emptyMap();

        final Path jrePath = Paths.get(javaHome);

        final Path jrtFsPath = jrePath.resolve("lib").resolve("jrt-fs.jar");

        this.classLoader = new URLClassLoader(new URL[] {jrtFsPath.toUri().toURL() });

        this.fileSystem = FileSystems.newFileSystem(URI.create("jrt:/"), emptyMap, classLoader);

    }

    private ModularRuntimeImage(final URLClassLoader cl, final FileSystem fs) {

        this.classLoader = cl;

        this.fileSystem = fs;

    }

    @Override

    public void close() throws IOException {

        if (classLoader != null) {

            classLoader.close();

        }

        if (fileSystem != null) {

            fileSystem.close();

        }

    }

    /**

     * Lists all entries in the given directory.

     *

     * @param dirPath

     *            directory path.

     * @return a list of dir entries if an I/O error occurs

     * @throws IOException

     *             an I/O error occurs accessing the file system

     */

    public List<Path> list(final Path dirPath) throws IOException {

        final List<Path> list = new ArrayList<>();

        try (DirectoryStream<Path> ds = Files.newDirectoryStream(dirPath)) {

            final Iterator<Path> iterator = ds.iterator();

            while (iterator.hasNext()) {

                list.add(iterator.next());

            }

        }

        return list;

    }

    /**

     * Lists all entries in the given directory.

     *

     * @param dirName

     *            directory path.

     * @return a list of dir entries if an I/O error occurs

     * @throws IOException

     *             an I/O error occurs accessing the file system

     */

    public List<Path> list(final String dirName) throws IOException {

        return list(fileSystem.getPath(dirName));

    }

    /**

     * Lists all modules.

     *

     * @return a list of modules

     * @throws IOException

     *             an I/O error occurs accessing the file system

     */

    public List<Path> modules() throws IOException {

        return list(MODULES_PATH);

    }

    /**

     * Lists all packages.

     *

     * @return a list of modules

     * @throws IOException

     *             an I/O error occurs accessing the file system

     */

    public List<Path> packages() throws IOException {

        return list(PACKAGES_PATH);

    }

    public FileSystem getFileSystem() {

        return fileSystem;

    }

}