gomp-20050608-branch/libjava/java/security/AccessControlContext.java

   1 /* AccessControlContext.java --- Access Control Context Class
   2    Copyright (C) 1999, 2004 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.security;
  39
  40 /**
  41  * AccessControlContext makes system resource access decsion
  42  * based on permission rights.
  43  *
  44  * It is used for a specific context and has only one method
  45  * checkPermission. It is similar to AccessController except
  46  * that it makes decsions based on the current context instead
  47  * of the the current thread.
  48  *
  49  * It is created by call AccessController.getContext method.
  50  *
  51  * @author Mark Benvenuto
  52  * @since 1.2
  53  */
  54 public final class AccessControlContext
  55 {
  56   private ProtectionDomain[] protectionDomains;
  57   private DomainCombiner combiner;
  58
  59   /**
  60    * Construct a new AccessControlContext with the specified
  61    * ProtectionDomains. <code>context</code> must not be
  62    * null and duplicates will be removed.
  63    *
  64    * @param context The ProtectionDomains to use
  65    */
  66   public AccessControlContext(ProtectionDomain[] context)
  67   {
  68     int i, j, k, count = context.length, count2 = 0;
  69     for (i = 0, j = 0; i < count; i++)
  70       {
  71         for (k = 0; k < i; k++)
  72           if (context[k] == protectionDomains[i])
  73             break;
  74         if (k != i)             //it means previous loop did not complete
  75           continue;
  76
  77         count2++;
  78       }
  79
  80     protectionDomains = new ProtectionDomain[count2];
  81     for (i = 0, j = 0; i < count2; i++)
  82       {
  83         for (k = 0; k < i; k++)
  84           if (context[k] == protectionDomains[i])
  85             break;
  86         if (k != i)             //it means previous loop did not complete
  87           continue;
  88
  89         protectionDomains[j++] = context[i];
  90       }
  91   }
  92
  93   /**
  94    * Construct a new AccessControlContext with the specified
  95    * ProtectionDomains and DomainCombiner
  96    *
  97    * @since 1.3
  98    */
  99   public AccessControlContext(AccessControlContext acc,
 100                               DomainCombiner combiner)
 101   {
 102     this(acc.protectionDomains);
 103     this.combiner = combiner;
 104   }
 105
 106   /**
 107    * Returns the Domain Combiner associated with the AccessControlContext
 108    *
 109    * @return the DomainCombiner
 110    */
 111   public DomainCombiner getDomainCombiner()
 112   {
 113     return combiner;
 114   }
 115
 116   /**
 117    * Determines whether or not the specific permission is granted
 118    * depending on the context it is within.
 119    *
 120    * @param perm a permission to check
 121    *
 122    * @throws AccessControlException if the permssion is not permitted
 123    */
 124   public void checkPermission(Permission perm) throws AccessControlException
 125   {
 126     for (int i = 0; i < protectionDomains.length; i++)
 127       if (protectionDomains[i].implies(perm) == true)
 128         return;
 129
 130     throw new AccessControlException("Permission not granted");
 131   }
 132
 133   /**
 134    * Checks if two AccessControlContexts are equal.
 135    *
 136    * It first checks if obj is an AccessControlContext class, and
 137    * then checks if each ProtectionDomain matches.
 138    *
 139    * @param obj The object to compare this class to
 140    *
 141    * @return true if equal, false otherwise
 142    */
 143   public boolean equals(Object obj)
 144   {
 145     if (obj instanceof AccessControlContext)
 146       {
 147         AccessControlContext acc = (AccessControlContext) obj;
 148
 149         if (acc.protectionDomains.length != protectionDomains.length)
 150           return false;
 151
 152         for (int i = 0; i < protectionDomains.length; i++)
 153           if (acc.protectionDomains[i] != protectionDomains[i])
 154             return false;
 155         return true;
 156       }
 157     return false;
 158   }
 159
 160   /**
 161    * Computes a hash code of this class
 162    *
 163    * @return a hash code representing this class
 164    */
 165   public int hashCode()
 166   {
 167     int h = 0;
 168     for (int i = 0; i < protectionDomains.length; i++)
 169       h ^= protectionDomains[i].hashCode();
 170
 171     return h;
 172   }
 173 }