1 /*
  2  * Copyright (c) 2015, 2024, 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 
 26 package jdk.internal.jimage;
 27 
 28 import java.io.IOException;
 29 import java.io.UncheckedIOException;
 30 import java.nio.file.FileSystem;
 31 import java.nio.file.FileSystems;
 32 import java.nio.file.Path;
 33 import java.util.concurrent.ConcurrentHashMap;
 34 import java.util.Map;
 35 import java.util.Objects;
 36 import java.util.function.Function;
 37 
 38 /**
 39  * Factory to get ImageReader
 40  *
 41  * @implNote This class needs to maintain JDK 8 source compatibility.
 42  *
 43  * It is used internally in the JDK to implement jimage/jrtfs access,
 44  * but also compiled and delivered as part of the jrtfs.jar to support access
 45  * to the jimage file provided by the shipped JDK by tools running on JDK 8.
 46  */
 47 public class ImageReaderFactory {
 48     private ImageReaderFactory() {}
 49 
 50     private static final String JAVA_HOME = System.getProperty("java.home");
 51     private static final Path BOOT_MODULES_JIMAGE;
 52 
 53     static {
 54         FileSystem fs;
 55         if (ImageReaderFactory.class.getClassLoader() == null) {
 56             try {
 57                 fs = (FileSystem) Class.forName("sun.nio.fs.DefaultFileSystemProvider")
 58                         .getMethod("theFileSystem")
 59                         .invoke(null);
 60             } catch (Exception e) {
 61                 throw new ExceptionInInitializerError(e);
 62             }
 63         } else {
 64             fs = FileSystems.getDefault();
 65         }
 66         BOOT_MODULES_JIMAGE = fs.getPath(JAVA_HOME, "lib", "modules");
 67     }
 68 
 69     private static final Map<Path, ImageReader> readers = new ConcurrentHashMap<>();
 70 
 71     /**
 72      * Returns an {@code ImageReader} to read from the given image file
 73      */
 74     public static ImageReader get(Path jimage) throws IOException {
 75         Objects.requireNonNull(jimage);
 76         try {
 77             return readers.computeIfAbsent(jimage, OPENER);
 78         } catch (UncheckedIOException io) {
 79             throw io.getCause();
 80         }
 81     }
 82 
 83     private static Function<Path, ImageReader> OPENER = new Function<Path, ImageReader>() {
 84         public ImageReader apply(Path path) {
 85             try {
 86                 return ImageReader.open(path);
 87             } catch (IOException io) {
 88                 throw new UncheckedIOException(io);
 89             }
 90         }
 91     };
 92 
 93     /**
 94      * Returns the {@code ImageReader} to read the image file in this
 95      * run-time image.
 96      *
 97      * @throws UncheckedIOException if an I/O error occurs
 98      */
 99     public static ImageReader getImageReader() {
100         try {
101             return get(BOOT_MODULES_JIMAGE);
102         } catch (IOException ioe) {
103             throw new UncheckedIOException(ioe);
104         }
105     }
106 }