/*******************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate

Copyright 2002-2007, Rice University. Copyright 2006-2007, Max Planck Institute 
for Software Systems.  All rights reserved.

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modification, are permitted provided that the following conditions are
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- Redistributions of source code must retain the above copyright
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- Neither the name of Rice  University (RICE), Max Planck Institute for Software 
Systems (MPI-SWS) nor the names of its contributors may be used to endorse or 
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This software is provided by RICE, MPI-SWS and the contributors on an "as is" 
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*******************************************************************************/ 

package rice.persistence;
/*
 * @(#) Cache.java
 *
 * @author Ansley Post
 * @author Alan Mislove
 * @version $Id: Cache.java 3524 2007-01-09 14:09:27Z jeffh $
 */
import java.io.*;

import rice.*;
import rice.p2p.commonapi.*;

/**
 * This interface is the abstraction of something which provides a
 * caching service.  Implementations should take in parameters specific
 * to the cache algorithm.  Two implementations are provided,
 * the LRUCache and GDSCache. This interface extends the Catalog
 * interface, as the cache provides a Catalog service.
 *
 * @version $Id: Cache.java 3524 2007-01-09 14:09:27Z jeffh $
 */
public interface Cache extends Catalog {
  
  /**
   * Caches an object in this storage. This method is non-blocking.
   * If the object has already been stored at the location id, this
   * method has the effect of calling <code>uncache(id)</code> followed
   * by <code>cache(id, obj)</code>. This method finishes by calling
   * receiveResult() on the provided continuation with whether or not
   * the object was cached.  Note that the object may not actually be
   * cached due to the cache replacement policy.
   *
   * Returns <code>True</code> if the cache actaully stores the object, else
   * <code>False</code> (through receiveResult on c).
   *
   * @param id The object's id.
   * @param metadata The object's metdatadata
   * @param obj The object to cache.
   * @param c The command to run once the operation is complete
   */
  public void cache(Id id, Serializable metadata, Serializable obj, Continuation c);

  /**
   * Removes the object from the list of cached objects. This method is
   * non-blocking. If the object was not in the cached list in the first place,
   * nothing happens and <code>False</code> is returned.
   *
   * Returns <code>True</code> if the action succeeds, else
   * <code>False</code>  (through receiveResult on c).
   *
   * @param pid The object's id
   * @param c The command to run once the operation is complete
   */
  public void uncache(Id id, Continuation c);

  /**
   * Returns the maximum size of the cache, in bytes. The result
   * is returned via the receiveResult method on the provided
   * Continuation with an Integer representing the size.
   *
   * @param c The command to run once the operation is complete
   */
  public long getMaximumSize();

  /**
   * Sets the maximum size of the cache, in bytes. Setting this
   * value to a smaller value than the current value may result in
   * object being evicted from the cache.
   *
   * Returns the success or failure of the setSize operation
   * (through receiveResult on c).
   *
   * @param size The new maximum size, in bytes, of the cache.
   * @param c The command to run once the operation is complete
   */
  public void setMaximumSize(int size, Continuation c);  
}
