libjava/java/security/AccessControlContext.java

   1 /* AccessControlContext.java --- Access Control Context Class
   2    Copyright (C) 1999 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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 JDK 1.2
  53  */
  54 public final class AccessControlContext
  55 {
  56   private ProtectionDomain protectionDomain[];
  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] == protectionDomain[i])
  73             break;
  74         if (k != i)             //it means previous loop did not complete
  75           continue;
  76
  77         count2++;
  78       }
  79
  80     protectionDomain = new ProtectionDomain[count2];
  81     for (i = 0, j = 0; i < count2; i++)
  82       {
  83         for (k = 0; k < i; k++)
  84           if (context[k] == protectionDomain[i])
  85             break;
  86         if (k != i)             //it means previous loop did not complete
  87           continue;
  88
  89         protectionDomain[j++] = context[i];
  90       }
  91   }
  92
  93   /**
  94      Construct a new AccessControlContext with the specified
  95      ProtectionDomains and DomainCombiner
  96
  97      @param context The ProtectionDomains to use
  98
  99      @since JDK 1.3
 100    */
 101   public AccessControlContext(AccessControlContext acc,
 102                               DomainCombiner combiner)
 103   {
 104     this(acc.protectionDomain);
 105     this.combiner = combiner;
 106   }
 107
 108   /**
 109      Returns the Domain Combiner associated with the AccessControlContext
 110
 111      @returns the DomainCombiner
 112    */
 113   public DomainCombiner getDomainCombiner()
 114   {
 115     return combiner;
 116   }
 117
 118   /**
 119      Determines whether or not the specific permission is granted
 120      depending on the context it is within.
 121
 122      @param perm a permission to check
 123
 124      @throws AccessControlException if the permssion is not permitted
 125    */
 126   public void checkPermission(Permission perm) throws AccessControlException
 127   {
 128     for (int i = 0; i < protectionDomain.length; i++)
 129       if (protectionDomain[i].implies(perm) == true)
 130         return;
 131
 132     throw new AccessControlException("Permission not granted");
 133   }
 134
 135   /**
 136      Checks if two AccessControlContexts are equal.
 137
 138      It first checks if obj is an AccessControlContext class, and
 139      then checks if each ProtectionDomain matches.
 140
 141      @param obj The object to compare this class to
 142
 143      @return true if equal, false otherwise
 144    */
 145   public boolean equals(Object obj)
 146   {
 147     if (obj instanceof AccessControlContext)
 148       {
 149         AccessControlContext acc = (AccessControlContext) obj;
 150
 151         if (acc.protectionDomain.length != protectionDomain.length)
 152           return false;
 153
 154         for (int i = 0; i < protectionDomain.length; i++)
 155           if (acc.protectionDomain[i] != protectionDomain[i])
 156             return false;
 157         return true;
 158       }
 159     return false;
 160   }
 161
 162   /**
 163      Computes a hash code of this class
 164
 165      @return a hash code representing this class
 166    */
 167   public int hashCode()
 168   {
 169     int h = 0;
 170     for (int i = 0; i < protectionDomain.length; i++)
 171       h ^= protectionDomain[i].hashCode();
 172
 173     return h;
 174   }
 175 }