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Diffstat (limited to 'tools/gnu/classpath/tools/rmid/PersistentBidiHashTable.java')
| -rw-r--r-- | tools/gnu/classpath/tools/rmid/PersistentBidiHashTable.java | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/tools/gnu/classpath/tools/rmid/PersistentBidiHashTable.java b/tools/gnu/classpath/tools/rmid/PersistentBidiHashTable.java new file mode 100644 index 000000000..d213373d5 --- /dev/null +++ b/tools/gnu/classpath/tools/rmid/PersistentBidiHashTable.java @@ -0,0 +1,269 @@ +/* PersistentBidiHasthable.java -- Bidirectional persistent hash table. + Copyright (C) 2006 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath 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 for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package gnu.classpath.tools.rmid; + +import gnu.classpath.tools.common.Persistent; +import gnu.classpath.tools.rmid.ActivationSystemImpl; +import gnu.java.rmi.activation.BidiTable; + +import java.io.BufferedInputStream; +import java.io.BufferedOutputStream; +import java.io.File; +import java.io.FileInputStream; +import java.io.FileOutputStream; +import java.io.IOException; +import java.io.InputStream; +import java.io.ObjectInputStream; +import java.io.ObjectOutputStream; +import java.util.Hashtable; +import java.util.Iterator; +import java.util.Map; +import java.util.TimerTask; + +/** + * The persistent bidirectional hash table, maps both a to b and b to a. The + * changes are written to dist after SAVE_AT_MOST_AFTER time from the latest + * database change or at most after ALWAYS_UPDATE, if the database is updated + * very frequently. To ensure that no information is lost, the shutdown method + * must be called before exit. + * + * @author Audrius Meskauskas (audriusa@bioinformatics.org) + */ +public class PersistentBidiHashTable extends BidiTable implements + Persistent +{ + class WriteToDiskTask extends TimerTask + { + /** + * Save the database. + */ + public void run() + { + writeContent(); + sheduled = null; + } + } + + /** + * Replaces instances of ActivationSystemImpl into the currently active + * instance of the ActivationSystemImpl + */ + class AdaptedReader extends ObjectInputStream + { + AdaptedReader(InputStream in) throws IOException + { + super(in); + enableResolveObject(true); + } + + protected Object resolveObject(Object obj) throws IOException + { + if (obj instanceof ActivationSystemImpl) + return ActivationSystemImpl.singleton2; + else + return obj; + } + } + + /** + * The database file. + */ + File database; + + /** + * The currently sheduled write to disk task, null if none. + */ + WriteToDiskTask sheduled = null; + + /** + * The time, when the disk database was last updated. + */ + long lastUpdated; + + /** + * Create the unitialised instance that must be initalised when + * ActivationSystemImpl.singleton2 is assigned. + */ + public PersistentBidiHashTable() + { + // Do not initalise the table fields - the initalise method must be + // called later. + super(0); + } + + /** + * Create a new persistent table that stores its information into the given + * file. The ActivationSystemImpl.singleton2 must be assigned. + * + * @param file + * the file, where the table stores its information. + * @param coldStart + * if true, the existing file with this name will be erased and + * ignored. Otherwise, it will be assumed that the file contains the + * persistent table information. + */ + public void init(File file, boolean coldStart) + { + try + { + database = file; + if (database.exists()) + { + if (coldStart) + { + k2v = new Hashtable(); + v2k = new Hashtable(); + database.delete(); + } + else + { + FileInputStream fi = new FileInputStream(file); + BufferedInputStream b = new BufferedInputStream(fi); + ObjectInputStream oin = new AdaptedReader(b); + + k2v = (Map) oin.readObject(); + oin.close(); + + v2k = new Hashtable(k2v.size()); + + // Reguild v2k from k2v: + Iterator en = k2v.keySet().iterator(); + Object key; + while (en.hasNext()) + { + key = en.next(); + v2k.put(k2v.get(key), key); + } + } + } + else + { + k2v = new Hashtable(); + v2k = new Hashtable(); + } + } + catch (Exception ioex) + { + InternalError ierr = new InternalError("Unable to intialize with file " + + file); + ierr.initCause(ioex); + throw ierr; + } + } + + /** + * Write the database content to the disk. + */ + public synchronized void writeContent() + { + try + { + FileOutputStream fou = new FileOutputStream(database); + BufferedOutputStream b = new BufferedOutputStream(fou); + ObjectOutputStream oout = new ObjectOutputStream(b); + oout.writeObject(k2v); + oout.close(); + } + catch (Exception ioex) + { + InternalError ierr = new InternalError( + "Failed to write database to disk: " + + database); + ierr.initCause(ioex); + throw ierr; + } + } + + /** + * Mark the modified database as modified. The database will be written after + * several seconds, unless another modification occurs. + */ + public void markDirty() + { + if (System.currentTimeMillis() - lastUpdated > ALWAYS_UPDATE) + { + // Force storing to disk under intensive operation. + writeContent(); + lastUpdated = System.currentTimeMillis(); + if (sheduled != null) + { + sheduled.cancel(); + sheduled = null; + } + } + else + { + // Otherwise coalesce the disk database copy update events. + if (sheduled != null) + sheduled.cancel(); + sheduled = new WriteToDiskTask(); + timer.schedule(sheduled, SAVE_AT_MOST_AFTER); + } + } + + /** + * Save the current database state to the disk before exit. + */ + public void shutdown() + { + if (sheduled != null) + { + writeContent(); + sheduled = null; + } + } + + /** + * Update the memory maps and mark as should be written to the disk. + */ + public void put(Object key, Object value) + { + super.put(key, value); + markDirty(); + } + + /** + * Update the memory maps and mark as should be written to the disk. + */ + public void removeKey(Object key) + { + super.removeKey(key); + markDirty(); + } + +} |