1/*
2 * Copyright (c) 2005, 2012, 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 sun.misc;
27
28import java.io.BufferedReader;
29import java.io.FileReader;
30import java.io.File;
31import java.io.IOException;
32import java.util.ArrayList;
33import java.util.Collections;
34import java.util.HashMap;
35import java.util.List;
36import 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
50sun/
51# jce.jar
52javax/
53! jsse.jar
54sun/
55com/sun/net/
56javax/
57com/sun/security/
58@ resources.jar
59com/sun/xml/
60com/sun/rowset/
61com/sun/org/
62sun/
63com/sun/imageio/
64javax/
65com/sun/java/swing/
66META-INF/services/
67com/sun/java/util/jar/pack/
68com/sun/corba/
69com/sun/jndi/
70! rt.jar
71org/w3c/
72com/sun/imageio/
73javax/
74java/
75sun/
76...
77</PRE>
78 * <p> A few notes about the design of the meta-index:
79 *
80 * <UL>
81 *
82 * <LI> It contains entries for multiple jar files. This is
83 * intentional, to reduce the number of disk accesses that need to be
84 * performed during startup.
85 *
86 * <LI> It is only intended to act as a fast reject mechanism to
87 * prevent application and other classes from forcing all jar files on
88 * the boot and extension class paths to be opened. It is not intended
89 * as a precise index of the contents of the jar.
90 *
91 * <LI> It should be as small as possible to reduce the amount of time
92 * required to parse it during startup. For example, adding on the
93 * secondary package element to java/ and javax/ packages
94 * ("javax/swing/", for example) causes the meta-index to grow
95 * significantly. This is why substrings of the packages have been
96 * chosen as the principal contents.
97 *
98 * <LI> It is versioned, and optional, to prevent strong dependencies
99 * between the JVM and JDK. It is also potentially applicable to more
100 * than just the boot and extension class paths.
101 *
102 * <LI> Precisely speaking, it plays different role in JVM and J2SE
103 * side.  On the JVM side, meta-index file is used to speed up locating the
104 * class files only while on the J2SE side, meta-index file is used to speed
105 * up the resources file & class file.
106 * To help the JVM and J2SE code to better utilize the information in meta-index
107 * file, we mark the jar file differently. Here is the current rule we use.
108 * For jar file containing only class file, we put '!' before the jar file name;
109 * for jar file containing only resources file, we put '@' before the jar file name;
110 * for jar file containing both resources and class file, we put '#' before the
111 * jar name.
112 * Notice the fact that every jar file contains at least the manifest file, so when
113 * we say "jar file containing only class file", we don't include that file.
114 *
115 * </UL>
116 *
117 * <p> To avoid changing the behavior of the current application
118 * loader and other loaders, the current MetaIndex implementation in
119 * the JDK requires that the directory containing the meta-index be
120 * registered with the MetaIndex class before construction of the
121 * associated URLClassPath. This prevents the need for automatic
122 * searching for the meta-index in the URLClassPath code and potential
123 * changes in behavior for non-core ClassLoaders.
124 *
125 * This class depends on make/tools/MetaIndex/BuildMetaIndex.java and
126 * is used principally by sun.misc.URLClassPath.
127 */
128
129public class MetaIndex {
130    // Maps jar file names in registered directories to meta-indices
131    private static volatile Map<File, MetaIndex> jarMap;
132
133    // List of contents of this meta-index
134    private String[] contents;
135
136    // Indicate whether the coresponding jar file is a pure class jar file or not
137    private boolean isClassOnlyJar;
138
139    //----------------------------------------------------------------------
140    // Registration of directories (which can cause parsing of the
141    // meta-index file if it is present), and fetching of parsed
142    // meta-indices
143    // jarMap is not strictly thread-safe when the meta index mechanism
144    // is extended for user-provided jar files in future.
145
146    public static MetaIndex forJar(File jar) {
147        return getJarMap().get(jar);
148    }
149
150    // 'synchronized' is added to protect the jarMap from being modified
151    // by multiple threads.
152    public static synchronized void registerDirectory(File dir) {
153        // Note that this does not currently check to see whether the
154        // directory has previously been registered, since the meta-index
155        // in a particular directory creates multiple entries in the
156        // jarMap. If this mechanism is extended beyond the boot and
157        // extension class paths (for example, automatically searching for
158        // meta-index files in directories containing jars which have been
159        // explicitly opened) then this code should be generalized.
160        //
161        // This method must be called from a privileged context.
162        File indexFile = new File(dir, "meta-index");
163        if (indexFile.exists()) {
164            try {
165                BufferedReader reader = new BufferedReader(new FileReader(indexFile));
166                String line = null;
167                String curJarName = null;
168                boolean isCurJarContainClassOnly = false;
169                List<String> contents = new ArrayList<String>();
170                Map<File, MetaIndex> map = getJarMap();
171
172                /* Convert dir into canonical form. */
173                dir = dir.getCanonicalFile();
174                /* Note: The first line should contain the version of
175                 * the meta-index file. We have to match the right version
176                 * before trying to parse this file. */
177                line = reader.readLine();
178                if (line == null ||
179                    !line.equals("% VERSION 2")) {
180                    reader.close();
181                    return;
182                }
183                while ((line = reader.readLine()) != null) {
184                    switch (line.charAt(0)) {
185                    case '!':
186                    case '#':
187                    case '@': {
188                        // Store away current contents, if any
189                        if ((curJarName != null) && (contents.size() > 0)) {
190                            map.put(new File(dir, curJarName),
191                                    new MetaIndex(contents,
192                                                  isCurJarContainClassOnly));
193
194                            contents.clear();
195                        }
196                        // Fetch new current jar file name
197                        curJarName = line.substring(2);
198                        if (line.charAt(0) == '!') {
199                            isCurJarContainClassOnly = true;
200                        } else if (isCurJarContainClassOnly) {
201                            isCurJarContainClassOnly = false;
202                        }
203
204                        break;
205                    }
206                    case '%':
207                        break;
208                    default: {
209                        contents.add(line);
210                    }
211                    }
212                }
213                // Store away current contents, if any
214                if ((curJarName != null) && (contents.size() > 0)) {
215                    map.put(new File(dir, curJarName),
216                            new MetaIndex(contents, isCurJarContainClassOnly));
217                }
218
219                reader.close();
220
221            } catch (IOException e) {
222                // Silently fail for now (similar behavior to elsewhere in
223                // extension and core loaders)
224            }
225        }
226    }
227
228    //----------------------------------------------------------------------
229    // Public APIs
230    //
231
232    public boolean mayContain(String entry) {
233        // Ask non-class file from class only jar returns false
234        // This check is important to avoid some class only jar
235        // files such as rt.jar are opened for resource request.
236        if  (isClassOnlyJar && !entry.endsWith(".class")){
237            return false;
238        }
239
240        String[] conts = contents;
241        for (int i = 0; i < conts.length; i++) {
242            if (entry.startsWith(conts[i])) {
243                return true;
244            }
245        }
246        return false;
247    }
248
249
250    //----------------------------------------------------------------------
251    // Implementation only below this point
252    // @IllegalArgumentException if entries is null.
253    private MetaIndex(List<String> entries, boolean isClassOnlyJar)
254        throws IllegalArgumentException {
255        if (entries == null) {
256            throw new IllegalArgumentException();
257        }
258
259        contents = entries.toArray(new String[0]);
260        this.isClassOnlyJar = isClassOnlyJar;
261    }
262
263    private static Map<File, MetaIndex> getJarMap() {
264        if (jarMap == null) {
265            synchronized (MetaIndex.class) {
266                if (jarMap == null) {
267                    jarMap = new HashMap<File, MetaIndex>();
268                }
269            }
270        }
271        assert jarMap != null;
272        return jarMap;
273    }
274}
275