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/* Glazed Lists (c) 2003-2006 */
/* http://publicobject.com/glazedlists/ publicobject.com,*/
/* O'Dell Engineering Ltd.*/
package ca.odell.glazedlists.io;
// the core Glazed Lists packages
import ca.odell.glazedlists.BasicEventList;
import ca.odell.glazedlists.EventList;
import ca.odell.glazedlists.TransformedList;
import ca.odell.glazedlists.event.ListEvent;
import ca.odell.glazedlists.impl.io.Bufferlo;
import ca.odell.glazedlists.impl.io.ListEventToBytes;
import ca.odell.glazedlists.impl.pmap.Chunk;
import ca.odell.glazedlists.impl.pmap.PersistentMap;
import ca.odell.glazedlists.util.concurrent.ReadWriteLock;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.SortedMap;
import java.util.TreeMap;
/**
* An {@link EventList} that is persisted to disk.
*
* <p><font size="5"><strong><font color="#FF0000">Warning:</font></strong> This
* class is a technology preview and is subject to API changes.</font>
*
* <p><table border="1" width="100%" cellpadding="3" cellspacing="0">
* <tr class="TableHeadingColor"><td colspan=2><font size="+2"><b>EventList Overview</b></font></td></tr>
* <tr><td class="TableSubHeadingColor"><b>Writable:</b></td><td>yes</td></tr>
* <tr><td class="TableSubHeadingColor"><b>Concurrency:</b></td><td>Requires {@link ReadWriteLock} for every access, even for single-threaded use</td></tr>
* <tr><td class="TableSubHeadingColor"><b>Performance:</b></td><td>N/A</td></tr>
* <tr><td class="TableSubHeadingColor"><b>Memory:</b></td><td>O(N)</td></tr>
* <tr><td class="TableSubHeadingColor"><b>Unit Tests:</b></td><td>N/A</td></tr>
* <tr><td class="TableSubHeadingColor"><b>Issues:</b></td><td>N/A</td></tr>
* </table>
*
* @author <a href="mailto:jesse@swank.ca">Jesse Wilson</a>
*/
public final class FileList extends TransformedList {
/** the destination file, just for user convenience */
private File file = null;
/** how bytes are encoded and decoded */
private ByteCoder byteCoder;
/** the underlying storage of ListEvents */
private PersistentMap storage = null;
/** the ID of the next update to write to disc */
private int nextUpdateId = 81;
/** whether this list can be modified */
private boolean writable = true;
/**
* Create a {@link FileList} that stores its data in the specified file.
*/
public FileList(File file, ByteCoder byteCoder) throws IOException {
super(new BasicEventList());
this.file = file;
this.byteCoder = byteCoder;
// store the updates in a persistent map
storage = new PersistentMap(file);
// sequence the updates
SortedMap sequentialUpdates = new TreeMap();
for(Iterator k = storage.keySet().iterator(); k.hasNext(); ) {
Integer key = (Integer)k.next();
Bufferlo valueBuffer = ((Chunk)storage.get(key)).getValue();
sequentialUpdates.put(key, valueBuffer);
}
// replay all the updates from the file
for(Iterator u = sequentialUpdates.keySet().iterator(); u.hasNext(); ) {
Integer key = (Integer)u.next();
Bufferlo update = (Bufferlo)sequentialUpdates.get(key);
ListEventToBytes.toListEvent(update, this, byteCoder);
}
// prepare the next update id to use
if(!sequentialUpdates.isEmpty()) {
nextUpdateId = ((Integer)sequentialUpdates.lastKey()).intValue() + 1;
}
// now that we're up-to-date, listen for further events
source.addListEventListener(this);
}
/** {@inheritDoc} */
@Override
public boolean isWritable() {
return writable;
}
/** {@inheritDoc} */
@Override
public void listChanged(ListEvent listChanges) {
// write the change to disc
try {
ListEvent listChangesCopy = listChanges.copy();
Bufferlo listChangesBytes = ListEventToBytes.toBytes(listChangesCopy, byteCoder);
storage.put(new Integer(nextUpdateId), new Chunk(listChangesBytes));
nextUpdateId++;
} catch(IOException e) {
throw new IllegalStateException(e.getMessage());
}
// forward the event to interested listeners
updates.forwardEvent(listChanges);
}
/**
* Closes this FileList so that it consumes no disc resources. The list may
* continue to be read until it is {@link #dispose() disposed}.
*/
public void close() {
if(storage != null) storage.close();
storage = null;
writable = false;
}
/** {@inheritDoc} */
@Override
public void dispose() {
close();
super.dispose();
}
}
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