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

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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

package rice.persistence;
/*
 *  @(#) Cache.java
 *
 *  @author Ansley Post
 *  @author Alan Mislove
 *  @version $Id: Cache.java 2682 2005-08-01 22:22:32Z 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 2682 2005-08-01 22:22:32Z jeffh $
 * @author 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 c The command to run once the operation is complete
   * @param id DESCRIBE THE PARAMETER
   */
  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.
   *
   * @return The MaximumSize value
   */
  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);
}
