/**************************************************************************
* Copyright (c) 2001 by Punch Telematix. All rights reserved. *
* *
* Redistribution and use in source and binary forms, with or without *
* modification, are permitted provided that the following conditions *
* are met: *
* 1. Redistributions of source code must retain the above copyright *
* notice, this list of conditions and the following disclaimer. *
* 2. Redistributions in binary form must reproduce the above copyright *
* notice, this list of conditions and the following disclaimer in the *
* documentation and/or other materials provided with the distribution. *
* 3. Neither the name of Punch Telematix nor the names of *
* other contributors may be used to endorse or promote products *
* derived from this software without specific prior written permission.*
* *
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED *
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF *
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. *
* IN NO EVENT SHALL PUNCH TELEMATIX OR OTHER CONTRIBUTORS BE LIABLE *
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR *
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF *
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR *
* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, *
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE *
* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN *
* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. *
**************************************************************************/
package wonka.security;
import java.security.Permission;
import java.util.Hashtable;
import java.util.Vector;
public class SocketPermissionCollection extends DefaultPermissionCollection {
private final static long LIFETIME_MILLIS = 300000;
private Hashtable cache;
private Vector ageing_fifo;
private long next_deletion;
private static final int INITIAL_TABSIZE=11;
/**
** Constructor SocketPermissionCollection() builds an empty Hashtable.
*/
public SocketPermissionCollection() {
cache = new Hashtable(INITIAL_TABSIZE);
ageing_fifo = new Vector();
next_deletion = System.currentTimeMillis();
}
/**
* Method 'implies' tests whether a given permission is implied by any
* of the Permissions in this collection. Since we know nothing about
* the semantics of the Permissions, we iterate over the collection
* until we find a match (or fail).
*/
public synchronized boolean implies (Permission permission) {
performPreAgeing();
Boolean cached_result = (Boolean)cache.get(permission);
if (cached_result != null) {
return cached_result.booleanValue();
}
ageing_fifo.addElement(permission);
performPostAgeing();
if (super.implies(permission)) {
cache.put(permission, new Boolean(true));
return true;
}
cache.put(permission, new Boolean(false));
return false;
}
/**
** A very rough-and-ready ageing algorithm.
*/
private void performPreAgeing() {
long now = System.currentTimeMillis();
while (ageing_fifo.size() > 0 && now > next_deletion) {
cache.remove(ageing_fifo.elementAt(0));
ageing_fifo.removeElementAt(0);
if (ageing_fifo.size() == 0) {
next_deletion = Long.MAX_VALUE;
}
else {
next_deletion += LIFETIME_MILLIS / ageing_fifo.size();
}
}
}
private void performPostAgeing() {
if (next_deletion == Long.MAX_VALUE) {
next_deletion = System.currentTimeMillis() + LIFETIME_MILLIS;
}
else {
int n = ageing_fifo.size();
if ( n > 1) {
next_deletion -= LIFETIME_MILLIS/n - LIFETIME_MILLIS/(n-1);
}
}
}
}