1 /* 2 * Copyright (c) 2015, 2016, 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.Path; 31 import java.nio.file.Paths; 32 import java.util.concurrent.ConcurrentHashMap; 33 import java.util.Map; 34 import java.util.Objects; 35 36 /** 37 * Factory to get ImageReader 38 * 39 * @implNote This class needs to maintain JDK 8 source compatibility. 40 * 41 * It is used internally in the JDK to implement jimage/jrtfs access, 42 * but also compiled and delivered as part of the jrtfs.jar to support access 43 * to the jimage file provided by the shipped JDK by tools running on JDK 8. 44 */ 45 public class ImageReaderFactory { 46 private ImageReaderFactory() {} 47 48 private static final String JAVA_HOME = System.getProperty("java.home"); 49 private static final Path BOOT_MODULES_JIMAGE = 50 Paths.get(JAVA_HOME, "lib", "modules"); 51 52 private static final Map<Path, ImageReader> readers = new ConcurrentHashMap<>(); 53 54 /** 55 * Returns an {@code ImageReader} to read from the given image file 56 */ 57 public static ImageReader get(Path jimage) throws IOException { 58 Objects.requireNonNull(jimage); 59 ImageReader reader = readers.get(jimage); 60 if (reader != null) { 61 return reader; 62 } 63 reader = ImageReader.open(jimage); 64 // potential race with other threads opening the same URL 65 ImageReader r = readers.putIfAbsent(jimage, reader); 66 if (r == null) { 67 return reader; 68 } else { 69 reader.close(); 70 return r; 71 } 72 } 73 74 /** 75 * Returns the {@code ImageReader} to read the image file in this 76 * run-time image. 77 * 78 * @throws UncheckedIOException if an I/O error occurs 79 */ 80 public static ImageReader getImageReader() { 81 try { 82 return get(BOOT_MODULES_JIMAGE); 83 } catch (IOException ioe) { 84 throw new UncheckedIOException(ioe); 85 } 86 } 87 }