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| 1 | /* | ||
| 2 | * Copyright (c) 2005, 2009, 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 | package sun.nio.ch; | ||
| 27 | |||
| 28 | import java.nio.channels.*; | ||
| 29 | import java.util.*; | ||
| 30 | import java.util.concurrent.ConcurrentHashMap; | ||
| 31 | import java.lang.ref.*; | ||
| 32 | import java.io.FileDescriptor; | ||
| 33 | import java.io.IOException; | ||
| 34 | |||
| 35 | abstract class FileLockTable { | ||
| 36 | protected FileLockTable() { | ||
| 37 | } | ||
| 38 | |||
| 39 | /** | ||
| 40 | * Creates and returns a file lock table for a channel that is connected to | ||
| 41 | * the a system-wide map of all file locks for the Java virtual machine. | ||
| 42 | */ | ||
| 43 | public static FileLockTable newSharedFileLockTable(Channel channel, | ||
| 44 | FileDescriptor fd) | ||
| 45 | throws IOException | ||
| 46 | { | ||
| 47 | return new SharedFileLockTable(channel, fd); | ||
| 48 | } | ||
| 49 | |||
| 50 | /** | ||
| 51 | * Adds a file lock to the table. | ||
| 52 | * | ||
| 53 | * @throws OverlappingFileLockException if the file lock overlaps | ||
| 54 | * with an existing file lock in the table | ||
| 55 | */ | ||
| 56 | public abstract void add(FileLock fl) throws OverlappingFileLockException; | ||
| 57 | |||
| 58 | /** | ||
| 59 | * Remove an existing file lock from the table. | ||
| 60 | */ | ||
| 61 | public abstract void remove(FileLock fl); | ||
| 62 | |||
| 63 | /** | ||
| 64 | * Removes all file locks from the table. | ||
| 65 | * | ||
| 66 | * @return The list of file locks removed | ||
| 67 | */ | ||
| 68 | public abstract List<FileLock> removeAll(); | ||
| 69 | |||
| 70 | /** | ||
| 71 | * Replaces an existing file lock in the table. | ||
| 72 | */ | ||
| 73 | public abstract void replace(FileLock fl1, FileLock fl2); | ||
| 74 | } | ||
| 75 | |||
| 76 | |||
| 77 | /** | ||
| 78 | * A file lock table that is over a system-wide map of all file locks. | ||
| 79 | */ | ||
| 80 | class SharedFileLockTable extends FileLockTable { | ||
| 81 | |||
| 82 | /** | ||
| 83 | * A weak reference to a FileLock. | ||
| 84 | * <p> | ||
| 85 | * SharedFileLockTable uses a list of file lock references to avoid keeping the | ||
| 86 | * FileLock (and FileChannel) alive. | ||
| 87 | */ | ||
| 88 | private static class FileLockReference extends WeakReference<FileLock> { | ||
| 89 | private FileKey fileKey; | ||
| 90 | |||
| 91 | FileLockReference(FileLock referent, | ||
| 92 | ReferenceQueue<FileLock> queue, | ||
| 93 | FileKey key) { | ||
| 94 | super(referent, queue); | ||
| 95 | this.fileKey = key; | ||
| 96 | } | ||
| 97 | |||
| 98 | FileKey fileKey() { | ||
| 99 | return fileKey; | ||
| 100 | } | ||
| 101 | } | ||
| 102 | |||
| 103 | // The system-wide map is a ConcurrentHashMap that is keyed on the FileKey. | ||
| 104 | // The map value is a list of file locks represented by FileLockReferences. | ||
| 105 | // All access to the list must be synchronized on the list. | ||
| 106 | private static ConcurrentHashMap<FileKey, List<FileLockReference>> lockMap = | ||
| 107 | new ConcurrentHashMap<FileKey, List<FileLockReference>>(); | ||
| 108 | |||
| 109 | // reference queue for cleared refs | ||
| 110 | private static ReferenceQueue<FileLock> queue = new ReferenceQueue<FileLock>(); | ||
| 111 | |||
| 112 | // The connection to which this table is connected | ||
| 113 | private final Channel channel; | ||
| 114 | |||
| 115 | // File key for the file that this channel is connected to | ||
| 116 | private final FileKey fileKey; | ||
| 117 | |||
| 118 | SharedFileLockTable(Channel channel, FileDescriptor fd) throws IOException { | ||
| 119 | this.channel = channel; | ||
| 120 | this.fileKey = FileKey.create(fd); | ||
| 121 | } | ||
| 122 | |||
| 123 | @Override | ||
| 124 | public void add(FileLock fl) throws OverlappingFileLockException { | ||
| 125 | List<FileLockReference> list = lockMap.get(fileKey); | ||
| 126 | |||
| 127 | for (;;) { | ||
| 128 | |||
| 129 | // The key isn't in the map so we try to create it atomically | ||
| 130 | if (list == null) { | ||
| 131 | list = new ArrayList<FileLockReference>(2); | ||
| 132 | List<FileLockReference> prev; | ||
| 133 | synchronized (list) { | ||
| 134 | prev = lockMap.putIfAbsent(fileKey, list); | ||
| 135 | if (prev == null) { | ||
| 136 | // we successfully created the key so we add the file lock | ||
| 137 | list.add(new FileLockReference(fl, queue, fileKey)); | ||
| 138 | break; | ||
| 139 | } | ||
| 140 | } | ||
| 141 | // someone else got there first | ||
| 142 | list = prev; | ||
| 143 | } | ||
| 144 | |||
| 145 | // There is already a key. It is possible that some other thread | ||
| 146 | // is removing it so we re-fetch the value from the map. If it | ||
| 147 | // hasn't changed then we check the list for overlapping locks | ||
| 148 | // and add the new lock to the list. | ||
| 149 | synchronized (list) { | ||
| 150 | List<FileLockReference> current = lockMap.get(fileKey); | ||
| 151 | if (list == current) { | ||
| 152 | checkList(list, fl.position(), fl.size()); | ||
| 153 | list.add(new FileLockReference(fl, queue, fileKey)); | ||
| 154 | break; | ||
| 155 | } | ||
| 156 | list = current; | ||
| 157 | } | ||
| 158 | |||
| 159 | } | ||
| 160 | |||
| 161 | // process any stale entries pending in the reference queue | ||
| 162 | removeStaleEntries(); | ||
| 163 | } | ||
| 164 | |||
| 165 | private void removeKeyIfEmpty(FileKey fk, List<FileLockReference> list) { | ||
| 166 | assert Thread.holdsLock(list); | ||
| 167 | assert lockMap.get(fk) == list; | ||
| 168 | if (list.isEmpty()) { | ||
| 169 | lockMap.remove(fk); | ||
| 170 | } | ||
| 171 | } | ||
| 172 | |||
| 173 | @Override | ||
| 174 | public void remove(FileLock fl) { | ||
| 175 | assert fl != null; | ||
| 176 | |||
| 177 | // the lock must exist so the list of locks must be present | ||
| 178 | List<FileLockReference> list = lockMap.get(fileKey); | ||
| 179 | if (list == null) return; | ||
| 180 | |||
| 181 | synchronized (list) { | ||
| 182 | int index = 0; | ||
| 183 | while (index < list.size()) { | ||
| 184 | FileLockReference ref = list.get(index); | ||
| 185 | FileLock lock = ref.get(); | ||
| 186 | if (lock == fl) { | ||
| 187 | assert (lock != null) && (lock.acquiredBy() == channel); | ||
| 188 | ref.clear(); | ||
| 189 | list.remove(index); | ||
| 190 | break; | ||
| 191 | } | ||
| 192 | index++; | ||
| 193 | } | ||
| 194 | } | ||
| 195 | } | ||
| 196 | |||
| 197 | @Override | ||
| 198 | public List<FileLock> removeAll() { | ||
| 199 | List<FileLock> result = new ArrayList<FileLock>(); | ||
| 200 | List<FileLockReference> list = lockMap.get(fileKey); | ||
| 201 | if (list != null) { | ||
| 202 | synchronized (list) { | ||
| 203 | int index = 0; | ||
| 204 | while (index < list.size()) { | ||
| 205 | FileLockReference ref = list.get(index); | ||
| 206 | FileLock lock = ref.get(); | ||
| 207 | |||
| 208 | // remove locks obtained by this channel | ||
| 209 | if (lock != null && lock.acquiredBy() == channel) { | ||
| 210 | // remove the lock from the list | ||
| 211 | ref.clear(); | ||
| 212 | list.remove(index); | ||
| 213 | |||
| 214 | // add to result | ||
| 215 | result.add(lock); | ||
| 216 | } else { | ||
| 217 | index++; | ||
| 218 | } | ||
| 219 | } | ||
| 220 | |||
| 221 | // once the lock list is empty we remove it from the map | ||
| 222 | removeKeyIfEmpty(fileKey, list); | ||
| 223 | } | ||
| 224 | } | ||
| 225 | return result; | ||
| 226 | } | ||
| 227 | |||
| 228 | @Override | ||
| 229 | public void replace(FileLock fromLock, FileLock toLock) { | ||
| 230 | // the lock must exist so there must be a list | ||
| 231 | List<FileLockReference> list = lockMap.get(fileKey); | ||
| 232 | assert list != null; | ||
| 233 | |||
| 234 | synchronized (list) { | ||
| 235 | for (int index=0; index<list.size(); index++) { | ||
| 236 | FileLockReference ref = list.get(index); | ||
| 237 | FileLock lock = ref.get(); | ||
| 238 | if (lock == fromLock) { | ||
| 239 | ref.clear(); | ||
| 240 | list.set(index, new FileLockReference(toLock, queue, fileKey)); | ||
| 241 | break; | ||
| 242 | } | ||
| 243 | } | ||
| 244 | } | ||
| 245 | } | ||
| 246 | |||
| 247 | // Check for overlapping file locks | ||
| 248 | private void checkList(List<FileLockReference> list, long position, long size) | ||
| 249 | throws OverlappingFileLockException | ||
| 250 | { | ||
| 251 | assert Thread.holdsLock(list); | ||
| 252 | for (FileLockReference ref: list) { | ||
| 253 | FileLock fl = ref.get(); | ||
| 254 | if (fl != null && fl.overlaps(position, size)) | ||
| 255 | throw new OverlappingFileLockException(); | ||
| 256 | } | ||
| 257 | } | ||
| 258 | |||
| 259 | // Process the reference queue | ||
| 260 | private void removeStaleEntries() { | ||
| 261 | FileLockReference ref; | ||
| 262 | while ((ref = (FileLockReference)queue.poll()) != null) { | ||
| 263 | FileKey fk = ref.fileKey(); | ||
| 264 | List<FileLockReference> list = lockMap.get(fk); | ||
| 265 | if (list != null) { | ||
| 266 | synchronized (list) { | ||
| 267 | list.remove(ref); | ||
| 268 | removeKeyIfEmpty(fk, list); | ||
| 269 | } | ||
| 270 | } | ||
| 271 | } | ||
| 272 | } | ||
| 273 | } | ||