001/* 
002    Licensed to the Apache Software Foundation (ASF) under one
003    or more contributor license agreements.  See the NOTICE file
004    distributed with this work for additional information
005    regarding copyright ownership.  The ASF licenses this file
006    to you under the Apache License, Version 2.0 (the
007    "License"); you may not use this file except in compliance
008    with the License.  You may obtain a copy of the License at
009
010       http://www.apache.org/licenses/LICENSE-2.0
011
012    Unless required by applicable law or agreed to in writing,
013    software distributed under the License is distributed on an
014    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015    KIND, either express or implied.  See the License for the
016    specific language governing permissions and limitations
017    under the License.  
018 */
019package org.apache.wiki.auth.permissions;
020
021import org.apache.wiki.api.core.Page;
022
023import java.util.WeakHashMap;
024
025
026/**
027 *  Provides a factory for Permission objects.  Since the Permissions are immutable,
028 *  and creating them takes a bit of time, caching them makes sense.
029 *  <p>
030 *  This class stores the permissions in a static HashMap.
031 *  @since 2.5.54
032 */
033public final class PermissionFactory
034{
035    /**
036     *  Prevent instantiation.
037     */
038    private PermissionFactory() {}
039    
040    /**
041     *  This is a WeakHashMap<Integer,PagePermission>, which stores the
042     *  cached page permissions.
043     */
044    private static final WeakHashMap<Integer, PagePermission> c_cache = new WeakHashMap<>();
045    
046    /**
047     *  Get a permission object for a WikiPage and a set of actions.
048     *  
049     *  @param page The page object.
050     *  @param actions A list of actions.
051     *  @return A PagePermission object, presenting this page+actions combination.
052     */
053    public static PagePermission getPagePermission( final Page page, final String actions )
054    {
055        return getPagePermission( page.getWiki(), page.getName(), actions );
056    }
057    
058    /**
059     *  Get a permission object for a WikiPage and a set of actions.
060     *  
061     *  @param page The name of the page.
062     *  @param actions A list of actions.
063     *  @return A PagePermission object, presenting this page+actions combination.
064     */
065    public static PagePermission getPagePermission( final String page, final String actions )
066    {
067        return getPagePermission( "", page, actions );
068    }
069
070    /**
071     *  Get a page permission based on a wiki, page, and actions.
072     *  
073     *  @param wiki The name of the wiki. Can be an empty string, but must not be null.
074     *  @param page The page name
075     *  @param actions A list of actions.
076     *  @return A PagePermission object.
077     */
078    private static PagePermission getPagePermission( final String wiki, String page, final String actions )
079    {
080        PagePermission perm;
081        //
082        //  Since this is pretty speed-critical, we try to avoid the StringBuffer creation
083        //  overhead by XORring the hashcodes.  However, if page name length > 32 characters,
084        //  this might result in two same hashCodes.
085        //  FIXME: Make this work for page-name lengths > 32 characters (use the alt implementation
086        //         if page.length() > 32?)
087        // Alternative implementation below, but it does create an extra StringBuffer.
088        //String         key = wiki+":"+page+":"+actions;
089        
090        final Integer key = wiki.hashCode() ^ page.hashCode() ^ actions.hashCode();
091   
092        //
093        //  It's fine if two threads update the cache, since the objects mean the same
094        //  thing anyway.  And this avoids nasty blocking effects.
095        //
096        synchronized( c_cache )
097        {
098            perm = c_cache.get( key );
099        }
100        
101        if( perm == null )
102        {
103            if( !wiki.isEmpty() ) page = wiki+":"+page;
104            perm = new PagePermission( page, actions );
105            
106            synchronized( c_cache )
107            {
108                c_cache.put( key, perm );
109            }
110        }
111        
112        return perm;
113    }
114
115}