1 /*
   2  * Copyright (c) 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.util.jar;
  27 
  28 import java.util.Objects;
  29 import java.util.jar.JarEntry;
  30 import java.util.jar.JarFile;
  31 import java.util.stream.Stream;
  32 
  33 public class VersionedStream {
  34     private static final String META_INF_VERSIONS = "META-INF/versions/";
  35 
  36     /**
  37      * Returns a stream of versioned entries, derived from the base names of
  38      * all entries in a multi-release {@code JarFile} that are present either in
  39      * the base directory or in any versioned directory with a version number
  40      * less than or equal to the {@code Runtime.Version::major} that the
  41      * {@code JarFile} was opened with.  These versioned entries are aliases
  42      * for the real entries -- i.e. the names are base names and the content
  43      * may come from a versioned directory entry.  If the {@code jarFile} is not
  44      * a multi-release jar, a stream of all entries is returned.
  45      *
  46      * @param jf the input JarFile
  47      * @return stream of entries
  48      * @since 9
  49      */
  50     public static Stream<JarEntry> stream(JarFile jf) {
  51         if (jf.isMultiRelease()) {
  52             int version = jf.getVersion().major();
  53             return jf.stream()
  54                     .map(je -> getBaseSuffix(je, version))
  55                     .filter(Objects::nonNull)
  56                     .distinct()
  57                     .map(jf::getJarEntry);
  58         }
  59         return jf.stream();
  60     }
  61 
  62     private static String getBaseSuffix(JarEntry je, int version) {
  63         String name = je.getName();
  64         if (name.startsWith(META_INF_VERSIONS)) {
  65             int len = META_INF_VERSIONS.length();
  66             int index = name.indexOf('/', len);
  67             if (index == -1 || index == (name.length() - 1)) {
  68                 // filter out META-INF/versions/* and META-INF/versions/*/
  69                 return null;
  70             }
  71             try {
  72                 if (Integer.parseInt(name, len, index, 10) > version) {
  73                     // not an integer
  74                     return null;
  75                 }
  76             } catch (NumberFormatException x) {
  77                 // silently remove malformed entries
  78                 return null;
  79             }
  80             // We know name looks like META-INF/versions/*/*
  81             return name.substring(index + 1);
  82         }
  83         return name;
  84     }
  85 }