/*
* Copyright (c) 2005, 2012, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package sun.misc;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/*
* MetaIndex is intended to decrease startup time (in particular cold
* start, when files are not yet in the disk cache) by providing a
* quick reject mechanism for probes into jar files. The on-disk
* representation of the meta-index is a flat text file with per-jar
* entries indicating (generally speaking) prefixes of package names
* contained in the jar. As an example, here is an edited excerpt of
* the meta-index generated for jre/lib in the current build:
*
% VERSION 1
# charsets.jar
sun/
# jce.jar
javax/
! jsse.jar
sun/
com/sun/net/
javax/
com/sun/security/
@ resources.jar
com/sun/xml/
com/sun/rowset/
com/sun/org/
sun/
com/sun/imageio/
javax/
com/sun/java/swing/
META-INF/services/
com/sun/java/util/jar/pack/
com/sun/corba/
com/sun/jndi/
! rt.jar
org/w3c/
com/sun/imageio/
javax/
java/
sun/
...
* A few notes about the design of the meta-index:
*
*
*
* - It contains entries for multiple jar files. This is
* intentional, to reduce the number of disk accesses that need to be
* performed during startup.
*
*
- It is only intended to act as a fast reject mechanism to
* prevent application and other classes from forcing all jar files on
* the boot and extension class paths to be opened. It is not intended
* as a precise index of the contents of the jar.
*
*
- It should be as small as possible to reduce the amount of time
* required to parse it during startup. For example, adding on the
* secondary package element to java/ and javax/ packages
* ("javax/swing/", for example) causes the meta-index to grow
* significantly. This is why substrings of the packages have been
* chosen as the principal contents.
*
*
- It is versioned, and optional, to prevent strong dependencies
* between the JVM and JDK. It is also potentially applicable to more
* than just the boot and extension class paths.
*
*
- Precisely speaking, it plays different role in JVM and J2SE
* side. On the JVM side, meta-index file is used to speed up locating the
* class files only while on the J2SE side, meta-index file is used to speed
* up the resources file & class file.
* To help the JVM and J2SE code to better utilize the information in meta-index
* file, we mark the jar file differently. Here is the current rule we use.
* For jar file containing only class file, we put '!' before the jar file name;
* for jar file containing only resources file, we put '@' before the jar file name;
* for jar file containing both resources and class file, we put '#' before the
* jar name.
* Notice the fact that every jar file contains at least the manifest file, so when
* we say "jar file containing only class file", we don't include that file.
*
*
*
* To avoid changing the behavior of the current application
* loader and other loaders, the current MetaIndex implementation in
* the JDK requires that the directory containing the meta-index be
* registered with the MetaIndex class before construction of the
* associated URLClassPath. This prevents the need for automatic
* searching for the meta-index in the URLClassPath code and potential
* changes in behavior for non-core ClassLoaders.
*
* This class depends on make/tools/MetaIndex/BuildMetaIndex.java and
* is used principally by sun.misc.URLClassPath.
*/
public class MetaIndex {
// Maps jar file names in registered directories to meta-indices
private static volatile Map jarMap;
// List of contents of this meta-index
private String[] contents;
// Indicate whether the coresponding jar file is a pure class jar file or not
private boolean isClassOnlyJar;
//----------------------------------------------------------------------
// Registration of directories (which can cause parsing of the
// meta-index file if it is present), and fetching of parsed
// meta-indices
// jarMap is not strictly thread-safe when the meta index mechanism
// is extended for user-provided jar files in future.
public static MetaIndex forJar(File jar) {
return getJarMap().get(jar);
}
// 'synchronized' is added to protect the jarMap from being modified
// by multiple threads.
public static synchronized void registerDirectory(File dir) {
// Note that this does not currently check to see whether the
// directory has previously been registered, since the meta-index
// in a particular directory creates multiple entries in the
// jarMap. If this mechanism is extended beyond the boot and
// extension class paths (for example, automatically searching for
// meta-index files in directories containing jars which have been
// explicitly opened) then this code should be generalized.
//
// This method must be called from a privileged context.
File indexFile = new File(dir, "meta-index");
if (indexFile.exists()) {
try {
BufferedReader reader = new BufferedReader(new FileReader(indexFile));
String line = null;
String curJarName = null;
boolean isCurJarContainClassOnly = false;
List contents = new ArrayList();
Map map = getJarMap();
/* Convert dir into canonical form. */
dir = dir.getCanonicalFile();
/* Note: The first line should contain the version of
* the meta-index file. We have to match the right version
* before trying to parse this file. */
line = reader.readLine();
if (line == null ||
!line.equals("% VERSION 2")) {
reader.close();
return;
}
while ((line = reader.readLine()) != null) {
switch (line.charAt(0)) {
case '!':
case '#':
case '@': {
// Store away current contents, if any
if ((curJarName != null) && (contents.size() > 0)) {
map.put(new File(dir, curJarName),
new MetaIndex(contents,
isCurJarContainClassOnly));
contents.clear();
}
// Fetch new current jar file name
curJarName = line.substring(2);
if (line.charAt(0) == '!') {
isCurJarContainClassOnly = true;
} else if (isCurJarContainClassOnly) {
isCurJarContainClassOnly = false;
}
break;
}
case '%':
break;
default: {
contents.add(line);
}
}
}
// Store away current contents, if any
if ((curJarName != null) && (contents.size() > 0)) {
map.put(new File(dir, curJarName),
new MetaIndex(contents, isCurJarContainClassOnly));
}
reader.close();
} catch (IOException e) {
// Silently fail for now (similar behavior to elsewhere in
// extension and core loaders)
}
}
}
//----------------------------------------------------------------------
// Public APIs
//
public boolean mayContain(String entry) {
// Ask non-class file from class only jar returns false
// This check is important to avoid some class only jar
// files such as rt.jar are opened for resource request.
if (isClassOnlyJar && !entry.endsWith(".class")){
return false;
}
String[] conts = contents;
for (int i = 0; i < conts.length; i++) {
if (entry.startsWith(conts[i])) {
return true;
}
}
return false;
}
//----------------------------------------------------------------------
// Implementation only below this point
// @IllegalArgumentException if entries is null.
private MetaIndex(List entries, boolean isClassOnlyJar)
throws IllegalArgumentException {
if (entries == null) {
throw new IllegalArgumentException();
}
contents = entries.toArray(new String[0]);
this.isClassOnlyJar = isClassOnlyJar;
}
private static Map getJarMap() {
if (jarMap == null) {
synchronized (MetaIndex.class) {
if (jarMap == null) {
jarMap = new HashMap();
}
}
}
assert jarMap != null;
return jarMap;
}
}