CacheFSInfo.java revision 2675:4be0e35f385a 
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
26package com.sun.tools.javac.file;
27
28import java.io.File;
29import java.io.IOException;
30import java.util.List;
31import java.util.Map;
32import java.util.concurrent.ConcurrentHashMap;
33
34import 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 */
44public 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<>();
116
117    private static class Entry {
118        File canonicalFile;
119        boolean exists;
120        boolean isFile;
121        boolean isDirectory;
122        List<File> jarClassPath;
123    }
124}
125