src/java.base/share/classes/jdk/internal/loader/ResourceHelper.java

*** 1,7 ****
  /*
!  * Copyright (c) 2016, 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
--- 1,7 ----
  /*
!  * Copyright (c) 2016, 2017, 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
*** 22,42 ****
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  package jdk.internal.loader;
  
  import jdk.internal.module.Checks;
  
  /**
   * Helper class for Class#getResource, Module#getResourceAsStream, and other
   * methods that locate a resource in a module.
   */
  public final class ResourceHelper {
      private ResourceHelper() { }
  
      /**
!      * Returns the <em>package name</em> for a resource.
       */
      public static String getPackageName(String name) {
          int index = name.lastIndexOf('/');
          if (index != -1) {
              return name.substring(0, index).replace("/", ".");
--- 22,47 ----
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  package jdk.internal.loader;
  
+ import java.io.File;
+ import java.nio.file.Path;
+ import java.nio.file.Paths;
+ 
  import jdk.internal.module.Checks;
  
  /**
   * Helper class for Class#getResource, Module#getResourceAsStream, and other
   * methods that locate a resource in a module.
   */
  public final class ResourceHelper {
      private ResourceHelper() { }
  
      /**
!      * Returns the <em>package name</em> for a resource or the empty package if
!      * the resource name does not contain a slash.
       */
      public static String getPackageName(String name) {
          int index = name.lastIndexOf('/');
          if (index != -1) {
              return name.substring(0, index).replace("/", ".");
*** 44,64 ****
              return "";
          }
      }
  
      /**
!      * Returns true if the resource is a <em>simple resource</em> that can
!      * never be encapsulated. Resources ending in "{@code .class}" or where
!      * the package name is not a Java identifier are resources that can
!      * never be encapsulated.
       */
      public static boolean isSimpleResource(String name) {
          int len = name.length();
          if (len > 6 && name.endsWith(".class")) {
              return true;
          }
!         if (!Checks.isJavaIdentifier(getPackageName(name))) {
              return true;
          }
          return false;
      }
  }
--- 49,125 ----
              return "";
          }
      }
  
      /**
!      * Returns true if the resource is a <em>simple resource</em>. Simple
!      * resources can never be encapsulated. Resources ending in "{@code .class}"
!      * or where the package name is not a legal package name can not be
!      * encapsulated.
       */
      public static boolean isSimpleResource(String name) {
          int len = name.length();
          if (len > 6 && name.endsWith(".class")) {
              return true;
          }
!         if (!Checks.isPackageName(getPackageName(name))) {
              return true;
          }
          return false;
      }
+ 
+     /**
+      * Converts a resource name to a file path. Returns {@code null} if the
+      * resource name cannot be converted into a file path. Resource names
+      * with empty elements, or elements that are "." or ".." are rejected,
+      * as is a resource name that translates to a file path with a root
+      * component.
+      */
+     public static Path toFilePath(String name) {
+         // scan the resource name to eagerly reject obviously invalid names
+         int next;
+         int off = 0;
+         while ((next = name.indexOf('/', off)) != -1) {
+             int len = next - off;
+             if (!mayTranslate(name, off, len)) {
+                 return null;
+             }
+             off = next + 1;
+         }
+         int rem = name.length() - off;
+         if (!mayTranslate(name, off, rem)) {
+             return null;
+         }
+ 
+         // convert to file path
+         Path path;
+         if (File.separatorChar == '/') {
+             path = Paths.get(name);
+         } else {
+             // not allowed to embed file separators
+             if (name.contains(File.separator))
+                 return null;
+             path = Paths.get(name.replace('/', File.separatorChar));
+         }
+ 
+         // file path not allowed to have root component
+         return (path.getRoot() == null) ? path : null;
+     }
+ 
+     /**
+      * Returns {@code true} if the element in a resource name is a candidate
+      * to translate to the element of a file path.
+      */
+     private static boolean mayTranslate(String name, int off, int len) {
+         if (len <= 2) {
+             if (len == 0)
+                 return false;
+             boolean starsWithDot = (name.charAt(off) == '.');
+             if (len == 1 && starsWithDot)
+                 return false;
+             if (len == 2 && starsWithDot && (name.charAt(off+1) == '.'))
+                 return false;
+         }
+         return true;
+     }
+ 
  }