PathManager.java

/*
    Priha - A JSR-170 implementation library.

    Copyright (C) 2007-2009 Janne Jalkanen (Janne.Jalkanen@iki.fi)

    Licensed under the Apache License, Version 2.0 (the "License"); 
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at 
    
      http://www.apache.org/licenses/LICENSE-2.0 
      
    Unless required by applicable law or agreed to in writing, software 
    distributed under the License is distributed on an "AS IS" BASIS, 
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
    See the License for the specific language governing permissions and 
    limitations under the License. 
 */
package org.priha.path;

import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.WeakHashMap;

import javax.jcr.PathNotFoundException;


/**
 *  PathManager stores all the Paths within a Session.
 */
public class PathManager
{
    private WeakHashMap<PathRef,Path> m_pathMap = new WeakHashMap<PathRef,Path>(128);
    private HashMap<Path,WeakPathRef> m_reversePathMap = new HashMap<Path,WeakPathRef>(128);
    private ReferenceQueue<PathRef> m_queue = new ReferenceQueue<PathRef>();
    
    public PathManager()
    {   
    }
        
    public synchronized Path getPath(PathRef p) throws PathNotFoundException
    {
        emptyStaleEntries();
        Path path = m_pathMap.get( p );
        
        if( path == null )
        {
            throw new PathNotFoundException("Path not found for reference "+p);
        }
        
        return path;
    }
    
    public synchronized PathRef getPathRef( Path path )
    {
        emptyStaleEntries();
        PathRef ref;
        WeakReference<PathRef> w = m_reversePathMap.get( path );
        
        if( w != null ) 
        {
            ref = w.get();
            
            if( ref != null ) return ref; 
        }
        
        ref = makeReference(path);
        
        m_reversePathMap.put( path, new WeakPathRef(ref,path,m_queue) );
        m_pathMap.put( ref, path );

        return ref;
    }

    public synchronized void move( Path oldPath, Path newPath )
    {
        PathRef pr = getPathRef( oldPath );
        if( pr != null )
        {
            m_pathMap.put( pr, newPath );
            m_reversePathMap.put( newPath, new WeakPathRef(pr,newPath,m_queue) );
            m_reversePathMap.remove( oldPath );
        }
        else
        {
            throw new RuntimeException("Oldpath does not exist!?! "+oldPath);
        }
    }
    
    private void emptyStaleEntries()
    {
        /*
        System.out.println("-------------");
        System.out.println("pathMap.size() "+m_pathMap.size());
        System.out.println("reversePathMap.size() "+m_reversePathMap.size());
         */
        WeakPathRef r;
        while( (r = (WeakPathRef)m_queue.poll()) != null )
        {
            Path p = r.getPath();
            
            m_reversePathMap.remove( p );
            
//            System.out.println("   Expunged "+p);
        }
        /*
        System.out.println("pathMap.size() "+m_pathMap.size());
        System.out.println("reversePathMap.size() "+m_reversePathMap.size());
        */
    }
    
    // FIXME: I don't quite know what happens when this overflows...
    private static int c_counter = Integer.MIN_VALUE;
    
    private PathRef makeReference(Path path)
    {
        return new PathRef(c_counter++);
    }
    
    private static class WeakPathRef extends WeakReference<PathRef>
    {
        private Path m_path;
        
        public WeakPathRef( PathRef referent,Path path, ReferenceQueue<PathRef> queue )
        {
            super( referent, queue );
            m_path = path;
        }
        
        public final Path getPath()
        {
            return m_path;
        }
    }

    public void close()
    {
        m_pathMap.clear();
        m_reversePathMap.clear();
    }
}