1 /*
   2  * Copyright (c) 1997, 2015, 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 
  27 /*
  28  * The Original Code is HAT. The Initial Developer of the
  29  * Original Code is Bill Foote, with contributions from others
  30  * at JavaSoft/Sun.
  31  */
  32 
  33 package jdk.test.lib.hprof.model;
  34 
  35 import java.io.File;
  36 import java.io.FileInputStream;
  37 import java.io.InputStreamReader;
  38 import java.io.Reader;
  39 import java.io.BufferedReader;
  40 import java.io.IOException;
  41 
  42 import java.util.Hashtable;
  43 
  44 /**
  45  * This represents a set of data members that should be excluded from the
  46  * reachable objects query.
  47  * This is useful to exclude observers from the
  48  * transitive closure of objects reachable from a given object, allowing
  49  * some kind of real determination of the "size" of that object.
  50  *
  51  * @author      Bill Foote
  52  */
  53 public class ReachableExcludesImpl implements ReachableExcludes {
  54 
  55     private File excludesFile;
  56     private long lastModified;
  57     private Hashtable<String, String> methods;  // Used as a bag
  58 
  59     /**
  60      * Create a new ReachableExcludesImpl over the given file.  The file will be
  61      * re-read whenever the timestamp changes.
  62      */
  63     public ReachableExcludesImpl(File excludesFile) {
  64         this.excludesFile = excludesFile;
  65         readFile();
  66     }
  67 
  68     private void readFileIfNeeded() {
  69         if (excludesFile.lastModified() != lastModified) {
  70             synchronized(this) {
  71                 if (excludesFile.lastModified() != lastModified) {
  72                     readFile();
  73                 }
  74             }
  75         }
  76     }
  77 
  78     private void readFile() {
  79         long lm = excludesFile.lastModified();
  80         Hashtable<String, String> m = new Hashtable<String, String>();
  81 
  82         try (BufferedReader r = new BufferedReader(new InputStreamReader(
  83                 new FileInputStream(excludesFile)))) {
  84             String method;
  85             while ((method = r.readLine()) != null) {
  86                 m.put(method, method);
  87             }
  88             lastModified = lm;
  89             methods = m;        // We want this to be atomic
  90         } catch (IOException ex) {
  91             System.out.println("Error reading " + excludesFile + ":  " + ex);
  92         }
  93     }
  94 
  95     /**
  96      * @return true iff the given field is on the histlist of excluded
  97      *          fields.
  98      */
  99     public boolean isExcluded(String fieldName) {
 100         readFileIfNeeded();
 101         return methods.get(fieldName) != null;
 102     }
 103 }