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    1   /*
    2    * Copyright (c) 2005, 2006, 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 sun.misc;
   27   
   28   import java.io.BufferedReader;
   29   import java.io.FileReader;
   30   import java.io.File;
   31   import java.io.IOException;
   32   import java.util.ArrayList;
   33   import java.util.Collections;
   34   import java.util.HashMap;
   35   import java.util.List;
   36   import java.util.Map;
   37   
   38   /*
   39    * MetaIndex is intended to decrease startup time (in particular cold
   40    * start, when files are not yet in the disk cache) by providing a
   41    * quick reject mechanism for probes into jar files. The on-disk
   42    * representation of the meta-index is a flat text file with per-jar
   43    * entries indicating (generally speaking) prefixes of package names
   44    * contained in the jar. As an example, here is an edited excerpt of
   45    * the meta-index generated for jre/lib in the current build:
   46    *
   47   <PRE>
   48   % VERSION 1
   49   # charsets.jar
   50   sun/
   51   # jce.jar
   52   javax/
   53   ! jsse.jar
   54   sun/
   55   com/sun/net/
   56   javax/
   57   com/sun/security/
   58   @ resources.jar
   59   com/sun/xml/
   60   com/sun/rowset/
   61   com/sun/org/
   62   sun/
   63   com/sun/imageio/
   64   javax/
   65   com/sun/java/swing/
   66   META-INF/services/
   67   com/sun/java/util/jar/pack/
   68   com/sun/corba/
   69   com/sun/jndi/
   70   ! rt.jar
   71   org/w3c/
   72   com/sun/imageio/
   73   javax/
   74   sunw/util/
   75   java/
   76   sun/
   77   ...
   78   </PRE>
   79    * <p> A few notes about the design of the meta-index:
   80    *
   81    * <UL>
   82    *
   83    * <LI> It contains entries for multiple jar files. This is
   84    * intentional, to reduce the number of disk accesses that need to be
   85    * performed during startup.
   86    *
   87    * <LI> It is only intended to act as a fast reject mechanism to
   88    * prevent application and other classes from forcing all jar files on
   89    * the boot and extension class paths to be opened. It is not intended
   90    * as a precise index of the contents of the jar.
   91    *
   92    * <LI> It should be as small as possible to reduce the amount of time
   93    * required to parse it during startup. For example, adding on the
   94    * secondary package element to java/ and javax/ packages
   95    * ("javax/swing/", for example) causes the meta-index to grow
   96    * significantly. This is why substrings of the packages have been
   97    * chosen as the principal contents.
   98    *
   99    * <LI> It is versioned, and optional, to prevent strong dependencies
  100    * between the JVM and JDK. It is also potentially applicable to more
  101    * than just the boot and extension class paths.
  102    *
  103    * <LI> Precisely speaking, it plays different role in JVM and J2SE
  104    * side.  On the JVM side, meta-index file is used to speed up locating the
  105    * class files only while on the J2SE side, meta-index file is used to speed
  106    * up the resources file & class file.
  107    * To help the JVM and J2SE code to better utilize the information in meta-index
  108    * file, we mark the jar file differently. Here is the current rule we use.
  109    * For jar file containing only class file, we put '!' before the jar file name;
  110    * for jar file containing only resources file, we put '@' before the jar file name;
  111    * for jar file containing both resources and class file, we put '#' before the
  112    * jar name.
  113    * Notice the fact that every jar file contains at least the manifest file, so when
  114    * we say "jar file containing only class file", we don't include that file.
  115    *
  116    * </UL>
  117    *
  118    * <p> To avoid changing the behavior of the current application
  119    * loader and other loaders, the current MetaIndex implementation in
  120    * the JDK requires that the directory containing the meta-index be
  121    * registered with the MetaIndex class before construction of the
  122    * associated URLClassPath. This prevents the need for automatic
  123    * searching for the meta-index in the URLClassPath code and potential
  124    * changes in behavior for non-core ClassLoaders.
  125    *
  126    * This class depends on make/tools/MetaIndex/BuildMetaIndex.java and
  127    * is used principally by sun.misc.URLClassPath.
  128    */
  129   
  130   public class MetaIndex {
  131       // Maps jar file names in registered directories to meta-indices
  132       private static volatile Map<File, MetaIndex> jarMap;
  133   
  134       // List of contents of this meta-index
  135       private String[] contents;
  136   
  137       // Indicate whether the coresponding jar file is a pure class jar file or not
  138       private boolean isClassOnlyJar;
  139   
  140       //----------------------------------------------------------------------
  141       // Registration of directories (which can cause parsing of the
  142       // meta-index file if it is present), and fetching of parsed
  143       // meta-indices
  144       // jarMap is not strictly thread-safe when the meta index mechanism
  145       // is extended for user-provided jar files in future.
  146   
  147       public static MetaIndex forJar(File jar) {
  148           return getJarMap().get(jar);
  149       }
  150   
  151       // 'synchronized' is added to protect the jarMap from being modified
  152       // by multiple threads.
  153       public static synchronized void registerDirectory(File dir) {
  154           // Note that this does not currently check to see whether the
  155           // directory has previously been registered, since the meta-index
  156           // in a particular directory creates multiple entries in the
  157           // jarMap. If this mechanism is extended beyond the boot and
  158           // extension class paths (for example, automatically searching for
  159           // meta-index files in directories containing jars which have been
  160           // explicitly opened) then this code should be generalized.
  161           //
  162           // This method must be called from a privileged context.
  163           File indexFile = new File(dir, "meta-index");
  164           if (indexFile.exists()) {
  165               try {
  166                   BufferedReader reader = new BufferedReader(new FileReader(indexFile));
  167                   String line = null;
  168                   String curJarName = null;
  169                   boolean isCurJarContainClassOnly = false;
  170                   List<String> contents = new ArrayList<String>();
  171                   Map<File, MetaIndex> map = getJarMap();
  172   
  173                   /* Convert dir into canonical form. */
  174                   dir = dir.getCanonicalFile();
  175                   /* Note: The first line should contain the version of
  176                    * the meta-index file. We have to match the right version
  177                    * before trying to parse this file. */
  178                   line = reader.readLine();
  179                   if (line == null ||
  180                       !line.equals("% VERSION 2")) {
  181                       reader.close();
  182                       return;
  183                   }
  184                   while ((line = reader.readLine()) != null) {
  185                       switch (line.charAt(0)) {
  186                       case '!':
  187                       case '#':
  188                       case '@': {
  189                           // Store away current contents, if any
  190                           if ((curJarName != null) && (contents.size() > 0)) {
  191                               map.put(new File(dir, curJarName),
  192                                       new MetaIndex(contents,
  193                                                     isCurJarContainClassOnly));
  194   
  195                               contents.clear();
  196                           }
  197                           // Fetch new current jar file name
  198                           curJarName = line.substring(2);
  199                           if (line.charAt(0) == '!') {
  200                               isCurJarContainClassOnly = true;
  201                           } else if (isCurJarContainClassOnly) {
  202                               isCurJarContainClassOnly = false;
  203                           }
  204   
  205                           break;
  206                       }
  207                       case '%':
  208                           break;
  209                       default: {
  210                           contents.add(line);
  211                       }
  212                       }
  213                   }
  214                   // Store away current contents, if any
  215                   if ((curJarName != null) && (contents.size() > 0)) {
  216                       map.put(new File(dir, curJarName),
  217                               new MetaIndex(contents, isCurJarContainClassOnly));
  218                   }
  219   
  220                   reader.close();
  221   
  222               } catch (IOException e) {
  223                   // Silently fail for now (similar behavior to elsewhere in
  224                   // extension and core loaders)
  225               }
  226           }
  227       }
  228   
  229       //----------------------------------------------------------------------
  230       // Public APIs
  231       //
  232   
  233       public boolean mayContain(String entry) {
  234           // Ask non-class file from class only jar returns false
  235           // This check is important to avoid some class only jar
  236           // files such as rt.jar are opened for resource request.
  237           if  (isClassOnlyJar && !entry.endsWith(".class")){
  238               return false;
  239           }
  240   
  241           String[] conts = contents;
  242           for (int i = 0; i < conts.length; i++) {
  243               if (entry.startsWith(conts[i])) {
  244                   return true;
  245               }
  246           }
  247           return false;
  248       }
  249   
  250   
  251       //----------------------------------------------------------------------
  252       // Implementation only below this point
  253       // @IllegalArgumentException if entries is null.
  254       private MetaIndex(List<String> entries, boolean isClassOnlyJar)
  255           throws IllegalArgumentException {
  256           if (entries == null) {
  257               throw new IllegalArgumentException();
  258           }
  259   
  260           contents = entries.toArray(new String[0]);
  261           this.isClassOnlyJar = isClassOnlyJar;
  262       }
  263   
  264       private static Map<File, MetaIndex> getJarMap() {
  265           if (jarMap == null) {
  266               synchronized (MetaIndex.class) {
  267                   if (jarMap == null) {
  268                       jarMap = new HashMap<File, MetaIndex>();
  269                   }
  270               }
  271           }
  272           assert jarMap != null;
  273           return jarMap;
  274       }
  275   }

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