PermissionsHash


1   /*******************************************************************************
2    * Copyright (c) 2003, 2005 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  
12  package org.eclipse.osgi.framework.internal.core;
13  
14  import java.security.Permission  ;
15  import java.security.PermissionCollection  ;
16  import java.util.Enumeration  ;
17  import java.util.Hashtable  ;
18  
19  /**
20   * A simple Hashtable based collection of Permission objects.
21   * <p>
22   * The class' .implies method simply scans each permission
23   * individually and asks if the permission should be granted.
24   * No addition semantics is provided by the collection, so it is
25   * not possible to grant permissions whose "grantedness" is
26   * split across multiple stored Permissions.
27   * <p>
28   * Instances of this class can be used to store heterogeneous
29   * collections of permissions, as long as it is not necessary
30   * to remember when multiple occurances of .equal permissions
31   * are added.
32   *
33   */
34  class PermissionsHash extends PermissionCollection   {
35      private static final long serialVersionUID = 3258408426341284153L;
36      /**
37       * A hashtable to store the elements of the collection.
38       */
39      Hashtable   perms = new Hashtable  (8);
40  
41      /**
42       * Constructs a new instance of this class.
43       *
44       */
45      public PermissionsHash() {
46          super();
47      }
48  
49      /**
50       * Adds the argument to the collection.
51       *
52       * @param       perm java.security.Permission
53       *                  the permission to add to the collection.
54       * @exception   IllegalStateException
55       *                  if the collection is read only.
56       */
57      public void add(Permission   perm) {
58          if (isReadOnly()) {
59              throw new SecurityException  ();
60          }
61  
62          perms.put(perm, perm);
63      }
64  
65      /**
66       * Answers an enumeration of the permissions
67       * in the receiver.
68       *
69       * @return      Enumeration
70       *                  the permissions in the receiver.
71       */
72      public Enumeration   elements() {
73          return perms.keys();
74      }
75  
76      /**
77       * Indicates whether the argument permission is implied
78       * by the permissions contained in the receiver.
79       *
80       * @return      boolean
81       *                  <code>true</code> if the argument permission
82       *                  is implied by the permissions in the receiver,
83       *                  and <code>false</code> if it is not.
84       * @param       perm java.security.Permission
85       *                  the permission to check
86       */
87      public boolean implies(Permission   perm) {
88          Permission   p = (Permission  ) perms.get(perm);
89  
90          if ((p != null) && p.implies(perm)) {
91              return true;
92          }
93  
94          Enumeration   permsEnum = elements();
95  
96          while (permsEnum.hasMoreElements()) {
97              if (((Permission  ) permsEnum.nextElement()).implies(perm)) {
98                  return true;
99              }
100         }
101 
102         return false;
103     }
104 }
105
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