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/*******************************************************************************
* Copyright (c) 2005, 2006 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.osgi.baseadaptor.bundlefile;
import java.io.IOException;
import org.eclipse.osgi.framework.eventmgr.*;
/**
* A simple/quick/small implementation of an MRU (Most Recently Used) list to keep
* track of open BundleFiles. The MRU will use the file limit specified by the property
* "osgi.bundlefile.limit" by default unless the MRU is constructed with a specific
* file limit.
* @since 3.2
*/
public class MRUBundleFileList implements EventDispatcher {
private static final String PROP_FILE_LIMIT = "osgi.bundlefile.limit"; //$NON-NLS-1$
private static final int MIN = 10;
// list of open bundle files
private BundleFile[] bundleFileList;
// list of open bundle files use stamps
private long[] useStampList;
// the current use stamp
private long curUseStamp = 0;
// the limit of open files to allow before least used bundle file is closed
private int fileLimit = 0; // value < MIN will disable MRU
// the current number of open bundle files
private int numOpen = 0;
private EventManager bundleFileCloserManager;
private EventListeners bundleFileCloser;
public MRUBundleFileList() {
try {
String prop = BundleFile.secureAction.getProperty(PROP_FILE_LIMIT);
if (prop != null)
init(Integer.parseInt(prop));
} catch (NumberFormatException e) {
//MRU will be disabled
}
}
public MRUBundleFileList(int fileLimit) {
init(fileLimit);
}
private void init(int initFileLimit) {
// only enable the MRU if the initFileLimit is > MIN
if (initFileLimit >= MIN) {
this.fileLimit = initFileLimit;
this.bundleFileList = new BundleFile[initFileLimit];
this.useStampList = new long[initFileLimit];
this.bundleFileCloserManager = new EventManager("Bundle File Closer"); //$NON-NLS-1$
this.bundleFileCloser = new EventListeners();
this.bundleFileCloser.addListener(this, this);
}
}
/**
* Adds a BundleFile which is about to be opened to the MRU list. If
* the number of open BundleFiles == the fileLimit then the least
* recently used BundleFile is closed.
* @param bundleFile the bundle file about to be opened.
* @throws IOException if an error occurs while closing the least recently used BundleFile
*/
public void add(BundleFile bundleFile) throws IOException {
if (fileLimit < MIN)
return; // MRU is disabled
BundleFile toRemove = null;
synchronized (bundleFileList) {
int index = 0; // default to the first slot
if (numOpen < fileLimit) {
// numOpen does not exceed the fileLimit
// find the first null slot to use in the MRU
for (int i = 0; i < fileLimit; i++)
if (bundleFileList[i] == null) {
index = i;
break;
}
} else {
// numOpen has reached the fileLimit
// find the least recently used bundleFile and close it
// and use it slot for the new bundleFile to be opened.
index = 0;
for (int i = 1; i < fileLimit; i++)
if (useStampList[i] < useStampList[index])
index = i;
toRemove = bundleFileList[index];
remove(toRemove);
}
// found an index to place to bundleFile to be opened
bundleFileList[index] = bundleFile;
bundleFile.setMruIndex(index);
incUseStamp(index);
numOpen++;
}
// must not close the toRemove bundle file while holding the lock of another bundle file (bug 161976)
// This queue the bundle file for close asynchronously.
closeBundleFile(toRemove);
}
/**
* Removes a bundle file which is about to be closed
* @param bundleFile the bundle file about to be closed
* @return true if the bundleFile existed in the MRU; false otherwise
*/
public boolean remove(BundleFile bundleFile) {
if (fileLimit < MIN)
return false; // MRU is disabled
synchronized (bundleFileList) {
int index = bundleFile.getMruIndex();
if ((index >= 0 && index < fileLimit) && bundleFileList[index] == bundleFile) {
bundleFile.setMruIndex(-1);
bundleFileList[index] = null;
useStampList[index] = -1;
numOpen--;
return true;
}
}
return false;
}
/**
* Increments the use stamp of a bundle file
* @param bundleFile the bundle file to increment the use stamp for
*/
public void use(BundleFile bundleFile) {
if (fileLimit < MIN)
return; // MRU is disabled
synchronized (bundleFileList) {
int index = bundleFile.getMruIndex();
if ((index >= 0 && index < fileLimit) && bundleFileList[index] == bundleFile)
incUseStamp(index);
}
}
private void incUseStamp(int index) {
if (curUseStamp == Long.MAX_VALUE) {
// we hit the curUseStamp max better reset all the stamps
for (int i = 0; i < fileLimit; i++)
useStampList[i] = 0;
curUseStamp = 0;
}
useStampList[index] = ++curUseStamp;
}
public final void dispatchEvent(Object eventListener, Object listenerObject, int eventAction, Object eventObject) {
try {
((BundleFile) eventObject).close();
} catch (IOException e) {
// TODO should log ??
}
}
private void closeBundleFile(BundleFile toRemove) {
if (toRemove == null)
return;
/* queue to hold set of listeners */
ListenerQueue queue = new ListenerQueue(bundleFileCloserManager);
/* add bundle file closer to the queue */
queue.queueListeners(bundleFileCloser, this);
/* dispatch event to set of listeners */
queue.dispatchEventAsynchronous(0, toRemove);
}
}
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