ReachableExcludesImpl.java revision 2224:2a8815d86b93 
1/*
2 * Copyright (c) 1997, 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
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
33package jdk.test.lib.hprof.model;
34
35import java.io.File;
36import java.io.FileInputStream;
37import java.io.InputStreamReader;
38import java.io.Reader;
39import java.io.BufferedReader;
40import java.io.IOException;
41
42import 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 */
53public 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}
104