Copyright (c) 2008, 2016 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2008, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * 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.

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.

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.
/**
 * 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.
/**
	 * A hashtable to store the elements of the collection.
	 */
	Hashtable<Permission, Permission> perms = new Hashtable<>(8);

	
Constructs a new instance of this class.
/**
	 * Constructs a new instance of this class.
	 *
	 */
	public PermissionsHash() {
		super();
	}

	
Adds the argument to the collection.
Params:
perm – java.security.Permission
				the permission to add to the collection.
Throws:
IllegalStateException – 
				if the collection is read only./**
	 * 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.
	 */
	@Override
	public void add(Permission perm) {
		if (isReadOnly()) {
			throw new SecurityException();
		}

		perms.put(perm, perm);
	}

	
Answers an enumeration of the permissions
in the receiver.
Returns:
		Enumeration
				the permissions in the receiver./**
	 * Answers an enumeration of the permissions
	 * in the receiver.
	 *
	 * @return		Enumeration
	 *					the permissions in the receiver.
	 */
	@Override
	public Enumeration<Permission> elements() {
		return perms.keys();
	}

	
Indicates whether the argument permission is implied
by the permissions contained in the receiver.
Params:
perm – java.security.Permission
				the permission to check
Returns:
		boolean
				true if the argument permission
				is implied by the permissions in the receiver,
				and false if it is not./**
	 * 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
	 */
	@Override
	public boolean implies(Permission perm) {
		Permission p = perms.get(perm);

		if ((p != null) && p.implies(perm)) {
			return true;
		}

		Enumeration<Permission> permsEnum = elements();

		while (permsEnum.hasMoreElements()) {
			if (permsEnum.nextElement().implies(perm)) {
				return true;
			}
		}

		return false;
	}
}