1 /*
   2  * Copyright (c) 2014, 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 package jdk.internal.jrtfs;
  26 
  27 import java.net.URISyntaxException;
  28 import java.net.URL;
  29 import java.nio.file.Files;
  30 import java.nio.file.FileSystem;
  31 import java.nio.file.FileSystems;
  32 import java.nio.file.Path;
  33 import java.nio.file.Paths;
  34 import java.security.AccessController;
  35 import java.security.CodeSource;
  36 import java.security.PrivilegedAction;
  37 
  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 final class SystemImages {
  46     private SystemImages() {}
  47 
  48 
  49     static final String RUNTIME_HOME;
  50     // "modules" jimage file Path
  51     private static final Path moduleImageFile;
  52     // "modules" jimage exists or not?
  53     private static final boolean modulesImageExists;
  54     // <JAVA_HOME>/modules directory Path
  55     private static final Path explodedModulesDir;
  56 
  57     static {
  58         PrivilegedAction<String> pa = SystemImages::findHome;
  59         RUNTIME_HOME = AccessController.doPrivileged(pa);
  60 
  61         FileSystem fs = FileSystems.getDefault();
  62         moduleImageFile = fs.getPath(RUNTIME_HOME, "lib", "modules");
  63         explodedModulesDir = fs.getPath(RUNTIME_HOME, "modules");
  64 
  65         modulesImageExists = AccessController.doPrivileged(
  66             new PrivilegedAction<Boolean>() {
  67                 @Override
  68                 public Boolean run() {
  69                     return Files.isRegularFile(moduleImageFile);
  70                 }
  71             });
  72     }
  73 
  74     static boolean hasModulesImage() {
  75         return modulesImageExists;
  76     }
  77 
  78     static Path moduleImageFile() {
  79         return moduleImageFile;
  80     }
  81 
  82     static Path explodedModulesDir() {
  83         return explodedModulesDir;
  84     }
  85 
  86     /**
  87      * Returns the appropriate JDK home for this usage of the FileSystemProvider.
  88      * When the CodeSource is null (null loader) then jrt:/ is the current runtime,
  89      * otherwise the JDK home is located relative to jrt-fs.jar.
  90      */
  91     private static String findHome() {
  92         CodeSource cs = SystemImages.class.getProtectionDomain().getCodeSource();
  93         if (cs == null)
  94             return System.getProperty("java.home");
  95 
  96         // assume loaded from $TARGETJDK/jrt-fs.jar
  97         URL url = cs.getLocation();
  98         if (!url.getProtocol().equalsIgnoreCase("file"))
  99             throw new RuntimeException(url + " loaded in unexpected way");
 100         try {
 101             return Paths.get(url.toURI()).getParent().toString();
 102         } catch (URISyntaxException e) {
 103             throw new InternalError(e);
 104         }
 105     }
 106 }