Decision.java

/*
** Module   : Decision.java
** Abstract : Helpers to manage/search cached access decisions.
**
** Copyright (c) 2004-2021, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- ----------------------------------Description-----------------------------------
** 001 NVS 20050322   @20454 Created the initial version. This class represents cached access decisions.
** 002 ECF 20080704   @39142 Minor memory optimization. Use Boolean constants instead of instantiating new
**                           Boolean objects.
** 003 GES 20210917          Removed dead code, implemented generics, improved documentation, encapsulated
**                           the cache itself. 
*/

/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
** 
** Additional terms under GNU Affero GPL version 3 section 7:
** 
**   Under Section 7 of the GNU Affero GPL version 3, the following additional
**   terms apply to the works covered under the License.  These additional terms
**   are non-permissive additional terms allowed under Section 7 of the GNU
**   Affero GPL version 3 and may not be removed by you.
** 
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*/

package com.goldencode.p2j.security;

import java.util.*;

/**
 * Cache and helpers to lookup cached decisions.  Each decision associates a resource instance name, access
 * mode (the rights being requested, which is an integer) and the resulting access decision (a boolean).  
 * This allows repeated accesses to reuse the previously calculated decisions.
 * <p>
 * Access decisions are cached in maps. The top level map contains second level maps and has the instance
 * name for the key. Second level maps have access mode as the key and contain a boolean value bearing the
 * decision.  Instances of this cache are specific to a given resource type and are held by the respective
 * security contexts.
 */
class Decision
{
   /** Cache storage. */
   private Map<String, Map<Integer, Boolean>> cache = new HashMap<String, Map<Integer, Boolean>>();
   
   /**
    * Searches the instance's cached decisions to find the decision for the requested access mode.
    *
    * @param    instance
    *           The resource instance name. 
    * @param    mode
    *           The requested access mode (rights level). 
    *
    * @return   The cached decision or {@code null} if no matching decision exists.
    */
   Boolean search(String instance, int mode)
   {
      Map<Integer, Boolean> internal = cache.get(instance);
      
      if (internal == null)
      {
         return null;
      }

      return internal.get(mode);
   }

   /**
    * Removes the access decision from the cache. 
    *
    * @param    instance
    *           The resource instance name. 
    * @param    mode
    *           The requested access mode (rights level). 
    */
   void remove(String instance, int mode)
   {
      Map<Integer, Boolean> internal = cache.get(instance);
      
      if (internal == null)
      {
         return;
      }

      internal.remove(mode);
   }

   /**
    * Puts the access decision into the cache. 
    *
    * @param    instance
    *           The resource instance name. 
    * @param    mode
    *           The requested access mode (rights level). 
    * @param    decision
    *           The value to cache. 
    */
   void cache(String instance, int mode, boolean decision)
   {
      Map<Integer, Boolean> internal = cache.get(instance);
      
      if (internal == null)
      {
         internal = new HashMap<Integer, Boolean>();
         cache.put(instance, internal);
      }

      internal.put(mode, (decision ? Boolean.TRUE : Boolean.FALSE));
   }
}