1 /*
   2  * Copyright (c) 2016, 2017, 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.loader;
  26 
  27 import java.io.File;
  28 import java.nio.file.Path;
  29 import java.nio.file.Paths;
  30 
  31 import jdk.internal.module.Checks;
  32 
  33 /**
  34  * Helper class for Class#getResource, Module#getResourceAsStream, and other
  35  * methods that locate a resource in a module.
  36  */
  37 public final class ResourceHelper {
  38     private ResourceHelper() { }
  39 
  40     /**
  41      * Returns the <em>package name</em> for a resource or the empty package if
  42      * the resource name does not contain a slash.
  43      */
  44     public static String getPackageName(String name) {
  45         int index = name.lastIndexOf('/');
  46         if (index != -1) {
  47             return name.substring(0, index).replace("/", ".");
  48         } else {
  49             return "";
  50         }
  51     }
  52 
  53     /**
  54      * Returns true if the resource is a <em>simple resource</em>. Simple
  55      * resources can never be encapsulated. Resources ending in "{@code .class}"
  56      * or where the package name is not a legal package name can not be
  57      * encapsulated.
  58      */
  59     public static boolean isSimpleResource(String name) {
  60         int len = name.length();
  61         if (len > 6 && name.endsWith(".class")) {
  62             return true;
  63         }
  64         if (!Checks.isPackageName(getPackageName(name))) {
  65             return true;
  66         }
  67         return false;
  68     }
  69 
  70     /**
  71      * Converts a resource name to a file path. Returns {@code null} if the
  72      * resource name cannot be converted into a file path. Resource names
  73      * with empty elements, or elements that are "." or ".." are rejected,
  74      * as is a resource name that translates to a file path with a root
  75      * component.
  76      */
  77     public static Path toFilePath(String name) {
  78         // scan the resource name to eagerly reject obviously invalid names
  79         int next;
  80         int off = 0;
  81         while ((next = name.indexOf('/', off)) != -1) {
  82             int len = next - off;
  83             if (!mayTranslate(name, off, len)) {
  84                 return null;
  85             }
  86             off = next + 1;
  87         }
  88         int rem = name.length() - off;
  89         if (!mayTranslate(name, off, rem)) {
  90             return null;
  91         }
  92 
  93         // convert to file path
  94         Path path;
  95         if (File.separatorChar == '/') {
  96             path = Paths.get(name);
  97         } else {
  98             // not allowed to embed file separators
  99             if (name.contains(File.separator))
 100                 return null;
 101             path = Paths.get(name.replace('/', File.separatorChar));
 102         }
 103 
 104         // file path not allowed to have root component
 105         return (path.getRoot() == null) ? path : null;
 106     }
 107 
 108     /**
 109      * Returns {@code true} if the element in a resource name is a candidate
 110      * to translate to the element of a file path.
 111      */
 112     private static boolean mayTranslate(String name, int off, int len) {
 113         if (len <= 2) {
 114             if (len == 0)
 115                 return false;
 116             boolean starsWithDot = (name.charAt(off) == '.');
 117             if (len == 1 && starsWithDot)
 118                 return false;
 119             if (len == 2 && starsWithDot && (name.charAt(off+1) == '.'))
 120                 return false;
 121         }
 122         return true;
 123     }
 124 
 125 }