/*******************************************************************************
* Copyright (c) 2008 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.internal.permadmin;
import java.security.Permission;
import java.security.PermissionCollection;
import java.util.Enumeration;
import java.util.Hashtable;
/**
* A simple Hashtable based collection of Permission objects.
* <p>
* The class' .implies method simply scans each permission
* individually and asks if the permission should be granted.
* No addition semantics is provided by the collection, so it is
* not possible to grant permissions whose "grantedness" is
* split across multiple stored Permissions.
* <p>
* Instances of this class can be used to store heterogeneous
* collections of permissions, as long as it is not necessary
* to remember when multiple occurances of .equal permissions
* are added.
*
*/
class PermissionsHash extends PermissionCollection {
private static final long serialVersionUID = 3258408426341284153L;
/**
* A hashtable to store the elements of the collection.
*/
Hashtable perms = new Hashtable(8);
/**
* Constructs a new instance of this class.
*
*/
public PermissionsHash() {
super();
}
/**
* Adds the argument to the collection.
*
* @param perm java.security.Permission
* the permission to add to the collection.
* @exception IllegalStateException
* if the collection is read only.
*/
public void add(Permission perm) {
if (isReadOnly()) {
throw new SecurityException();
}
perms.put(perm, perm);
}
/**
* Answers an enumeration of the permissions
* in the receiver.
*
* @return Enumeration
* the permissions in the receiver.
*/
public Enumeration elements() {
return perms.keys();
}
/**
* Indicates whether the argument permission is implied
* by the permissions contained in the receiver.
*
* @return boolean
* <code>true</code> if the argument permission
* is implied by the permissions in the receiver,
* and <code>false</code> if it is not.
* @param perm java.security.Permission
* the permission to check
*/
public boolean implies(Permission perm) {
Permission p = (Permission) perms.get(perm);
if ((p != null) && p.implies(perm)) {
return true;
}
Enumeration permsEnum = elements();
while (permsEnum.hasMoreElements()) {
if (((Permission) permsEnum.nextElement()).implies(perm)) {
return true;
}
}
return false;
}
}