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    1   /*
    2    * Copyright (c) 2005, 2011, 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 com.sun.tools.javac.file;
   27   
   28   import java.io.File;
   29   import java.io.IOException;
   30   import java.util.List;
   31   import java.util.Map;
   32   import java.util.concurrent.ConcurrentHashMap;
   33   
   34   import com.sun.tools.javac.util.Context;
   35   
   36   /**
   37    * Caching implementation of FSInfo.
   38    *
   39    * <p><b>This is NOT part of any supported API.
   40    * If you write code that depends on this, you do so at your own risk.
   41    * This code and its internal interfaces are subject to change or
   42    * deletion without notice.</b>
   43    */
   44   public class CacheFSInfo extends FSInfo {
   45   
   46       /**
   47        * Register a Context.Factory to create a CacheFSInfo.
   48        */
   49       public static void preRegister(Context context) {
   50           context.put(FSInfo.class, new Context.Factory<FSInfo>() {
   51               public FSInfo make(Context c) {
   52                   FSInfo instance = new CacheFSInfo();
   53                   c.put(FSInfo.class, instance);
   54                   return instance;
   55               }
   56           });
   57       }
   58   
   59       public void clearCache() {
   60           cache.clear();
   61       }
   62   
   63       @Override
   64       public File getCanonicalFile(File file) {
   65           Entry e = getEntry(file);
   66           return e.canonicalFile;
   67       }
   68   
   69       @Override
   70       public boolean exists(File file) {
   71           Entry e = getEntry(file);
   72           return e.exists;
   73       }
   74   
   75       @Override
   76       public boolean isDirectory(File file) {
   77           Entry e = getEntry(file);
   78           return e.isDirectory;
   79       }
   80   
   81       @Override
   82       public boolean isFile(File file) {
   83           Entry e = getEntry(file);
   84           return e.isFile;
   85       }
   86   
   87       @Override
   88       public List<File> getJarClassPath(File file) throws IOException {
   89           // don't bother to lock the cache, because it is thread-safe, and
   90           // because the worst that can happen would be to create two identical
   91           // jar class paths together and have one overwrite the other.
   92           Entry e = getEntry(file);
   93           if (e.jarClassPath == null)
   94               e.jarClassPath = super.getJarClassPath(file);
   95           return e.jarClassPath;
   96       }
   97   
   98       private Entry getEntry(File file) {
   99           // don't bother to lock the cache, because it is thread-safe, and
  100           // because the worst that can happen would be to create two identical
  101           // entries together and have one overwrite the other.
  102           Entry e = cache.get(file);
  103           if (e == null) {
  104               e = new Entry();
  105               e.canonicalFile = super.getCanonicalFile(file);
  106               e.exists = super.exists(file);
  107               e.isDirectory = super.isDirectory(file);
  108               e.isFile = super.isFile(file);
  109               cache.put(file, e);
  110           }
  111           return e;
  112       }
  113   
  114       // could also be a Map<File,SoftReference<Entry>> ?
  115       private Map<File,Entry> cache = new ConcurrentHashMap<File,Entry>();
  116   
  117       private static class Entry {
  118           File canonicalFile;
  119           boolean exists;
  120           boolean isFile;
  121           boolean isDirectory;
  122           List<File> jarClassPath;
  123       }
  124   }

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