J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2005-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package sun.misc; |
| 27 | |
| 28 | import java.io.BufferedReader; |
| 29 | import java.io.FileReader; |
| 30 | import java.io.File; |
| 31 | import java.io.IOException; |
| 32 | import java.util.ArrayList; |
| 33 | import java.util.Collections; |
| 34 | import java.util.HashMap; |
| 35 | import java.util.List; |
| 36 | import 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 |
| 50 | sun/ |
| 51 | # jce.jar |
| 52 | javax/ |
| 53 | ! jsse.jar |
| 54 | sun/ |
| 55 | com/sun/net/ |
| 56 | javax/ |
| 57 | com/sun/security/ |
| 58 | @ resources.jar |
| 59 | com/sun/xml/ |
| 60 | com/sun/rowset/ |
| 61 | com/sun/org/ |
| 62 | sun/ |
| 63 | com/sun/imageio/ |
| 64 | javax/ |
| 65 | com/sun/java/swing/ |
| 66 | META-INF/services/ |
| 67 | com/sun/java/util/jar/pack/ |
| 68 | com/sun/corba/ |
| 69 | com/sun/jndi/ |
| 70 | ! rt.jar |
| 71 | org/w3c/ |
| 72 | com/sun/imageio/ |
| 73 | javax/ |
| 74 | sunw/util/ |
| 75 | java/ |
| 76 | sun/ |
| 77 | ... |
| 78 | </PRE> |
| 79 | * <p> A few notes about the design of the meta-index: |
| 80 | * |
| 81 | * <UL> |
| 82 | * |
| 83 | * <LI> It contains entries for multiple jar files. This is |
| 84 | * intentional, to reduce the number of disk accesses that need to be |
| 85 | * performed during startup. |
| 86 | * |
| 87 | * <LI> It is only intended to act as a fast reject mechanism to |
| 88 | * prevent application and other classes from forcing all jar files on |
| 89 | * the boot and extension class paths to be opened. It is not intended |
| 90 | * as a precise index of the contents of the jar. |
| 91 | * |
| 92 | * <LI> It should be as small as possible to reduce the amount of time |
| 93 | * required to parse it during startup. For example, adding on the |
| 94 | * secondary package element to java/ and javax/ packages |
| 95 | * ("javax/swing/", for example) causes the meta-index to grow |
| 96 | * significantly. This is why substrings of the packages have been |
| 97 | * chosen as the principal contents. |
| 98 | * |
| 99 | * <LI> It is versioned, and optional, to prevent strong dependencies |
| 100 | * between the JVM and JDK. It is also potentially applicable to more |
| 101 | * than just the boot and extension class paths. |
| 102 | * |
| 103 | * <LI> Precisely speaking, it plays different role in JVM and J2SE |
| 104 | * side. On the JVM side, meta-index file is used to speed up locating the |
| 105 | * class files only while on the J2SE side, meta-index file is used to speed |
| 106 | * up the resources file & class file. |
| 107 | * To help the JVM and J2SE code to better utilize the information in meta-index |
| 108 | * file, we mark the jar file differently. Here is the current rule we use. |
| 109 | * For jar file containing only class file, we put '!' before the jar file name; |
| 110 | * for jar file containing only resources file, we put '@' before the jar file name; |
| 111 | * for jar file containing both resources and class file, we put '#' before the |
| 112 | * jar name. |
| 113 | * Notice the fact that every jar file contains at least the manifest file, so when |
| 114 | * we say "jar file containing only class file", we don't include that file. |
| 115 | * |
| 116 | * </UL> |
| 117 | * |
| 118 | * <p> To avoid changing the behavior of the current application |
| 119 | * loader and other loaders, the current MetaIndex implementation in |
| 120 | * the JDK requires that the directory containing the meta-index be |
| 121 | * registered with the MetaIndex class before construction of the |
| 122 | * associated URLClassPath. This prevents the need for automatic |
| 123 | * searching for the meta-index in the URLClassPath code and potential |
| 124 | * changes in behavior for non-core ClassLoaders. |
| 125 | * |
| 126 | * This class depends on make/tools/MetaIndex/BuildMetaIndex.java and |
| 127 | * is used principally by sun.misc.URLClassPath. |
| 128 | */ |
| 129 | |
| 130 | public class MetaIndex { |
| 131 | // Maps jar file names in registered directories to meta-indices |
| 132 | private static volatile Map<File, MetaIndex> jarMap; |
| 133 | |
| 134 | // List of contents of this meta-index |
| 135 | private String[] contents; |
| 136 | |
| 137 | // Indicate whether the coresponding jar file is a pure class jar file or not |
| 138 | private boolean isClassOnlyJar; |
| 139 | |
| 140 | //---------------------------------------------------------------------- |
| 141 | // Registration of directories (which can cause parsing of the |
| 142 | // meta-index file if it is present), and fetching of parsed |
| 143 | // meta-indices |
| 144 | // jarMap is not strictly thread-safe when the meta index mechanism |
| 145 | // is extended for user-provided jar files in future. |
| 146 | |
| 147 | public static MetaIndex forJar(File jar) { |
| 148 | return getJarMap().get(jar); |
| 149 | } |
| 150 | |
| 151 | // 'synchronized' is added to protect the jarMap from being modified |
| 152 | // by multiple threads. |
| 153 | public static synchronized void registerDirectory(File dir) { |
| 154 | // Note that this does not currently check to see whether the |
| 155 | // directory has previously been registered, since the meta-index |
| 156 | // in a particular directory creates multiple entries in the |
| 157 | // jarMap. If this mechanism is extended beyond the boot and |
| 158 | // extension class paths (for example, automatically searching for |
| 159 | // meta-index files in directories containing jars which have been |
| 160 | // explicitly opened) then this code should be generalized. |
| 161 | // |
| 162 | // This method must be called from a privileged context. |
| 163 | File indexFile = new File(dir, "meta-index"); |
| 164 | if (indexFile.exists()) { |
| 165 | try { |
| 166 | BufferedReader reader = new BufferedReader(new FileReader(indexFile)); |
| 167 | String line = null; |
| 168 | String curJarName = null; |
| 169 | boolean isCurJarContainClassOnly = false; |
| 170 | List<String> contents = new ArrayList<String>(); |
| 171 | Map<File, MetaIndex> map = getJarMap(); |
| 172 | |
| 173 | /* Convert dir into canonical form. */ |
| 174 | dir = dir.getCanonicalFile(); |
| 175 | /* Note: The first line should contain the version of |
| 176 | * the meta-index file. We have to match the right version |
| 177 | * before trying to parse this file. */ |
| 178 | line = reader.readLine(); |
| 179 | if (line == null || |
| 180 | !line.equals("% VERSION 2")) { |
| 181 | reader.close(); |
| 182 | return; |
| 183 | } |
| 184 | while ((line = reader.readLine()) != null) { |
| 185 | switch (line.charAt(0)) { |
| 186 | case '!': |
| 187 | case '#': |
| 188 | case '@': { |
| 189 | // Store away current contents, if any |
| 190 | if ((curJarName != null) && (contents.size() > 0)) { |
| 191 | map.put(new File(dir, curJarName), |
| 192 | new MetaIndex(contents, |
| 193 | isCurJarContainClassOnly)); |
| 194 | |
| 195 | contents.clear(); |
| 196 | } |
| 197 | // Fetch new current jar file name |
| 198 | curJarName = line.substring(2); |
| 199 | if (line.charAt(0) == '!') { |
| 200 | isCurJarContainClassOnly = true; |
| 201 | } else if (isCurJarContainClassOnly) { |
| 202 | isCurJarContainClassOnly = false; |
| 203 | } |
| 204 | |
| 205 | break; |
| 206 | } |
| 207 | case '%': |
| 208 | break; |
| 209 | default: { |
| 210 | contents.add(line); |
| 211 | } |
| 212 | } |
| 213 | } |
| 214 | // Store away current contents, if any |
| 215 | if ((curJarName != null) && (contents.size() > 0)) { |
| 216 | map.put(new File(dir, curJarName), |
| 217 | new MetaIndex(contents, isCurJarContainClassOnly)); |
| 218 | } |
| 219 | |
| 220 | reader.close(); |
| 221 | |
| 222 | } catch (IOException e) { |
| 223 | // Silently fail for now (similar behavior to elsewhere in |
| 224 | // extension and core loaders) |
| 225 | } |
| 226 | } |
| 227 | } |
| 228 | |
| 229 | //---------------------------------------------------------------------- |
| 230 | // Public APIs |
| 231 | // |
| 232 | |
| 233 | public boolean mayContain(String entry) { |
| 234 | // Ask non-class file from class only jar returns false |
| 235 | // This check is important to avoid some class only jar |
| 236 | // files such as rt.jar are opened for resource request. |
| 237 | if (isClassOnlyJar && !entry.endsWith(".class")){ |
| 238 | return false; |
| 239 | } |
| 240 | |
| 241 | String[] conts = contents; |
| 242 | for (int i = 0; i < conts.length; i++) { |
| 243 | if (entry.startsWith(conts[i])) { |
| 244 | return true; |
| 245 | } |
| 246 | } |
| 247 | return false; |
| 248 | } |
| 249 | |
| 250 | |
| 251 | //---------------------------------------------------------------------- |
| 252 | // Implementation only below this point |
| 253 | // @IllegalArgumentException if entries is null. |
| 254 | private MetaIndex(List<String> entries, boolean isClassOnlyJar) |
| 255 | throws IllegalArgumentException { |
| 256 | if (entries == null) { |
| 257 | throw new IllegalArgumentException(); |
| 258 | } |
| 259 | |
| 260 | contents = entries.toArray(new String[0]); |
| 261 | this.isClassOnlyJar = isClassOnlyJar; |
| 262 | } |
| 263 | |
| 264 | private static Map<File, MetaIndex> getJarMap() { |
| 265 | if (jarMap == null) { |
| 266 | synchronized (MetaIndex.class) { |
| 267 | if (jarMap == null) { |
| 268 | jarMap = new HashMap<File, MetaIndex>(); |
| 269 | } |
| 270 | } |
| 271 | } |
| 272 | assert jarMap != null; |
| 273 | return jarMap; |
| 274 | } |
| 275 | } |