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

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

Redistribution and use in source and binary forms, with or without
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- Redistributions of source code must retain the above copyright
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- Redistributions in binary form must reproduce the above copyright
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- Neither  the name  of Rice  University (RICE) nor  the names  of its
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This software is provided by RICE and the contributors on an "as is"
basis, without any representations or warranties of any kind, express
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********************************************************************************/

package rice.persistence;

/*
 *  @(#) Storage.java
 *
 *  @author Ansley Post
 *  @author Alan Mislove
 *
 *  @version $Id: Storage.java 2302 2005-03-11 00:58:26Z jeffh $
 */
import java.io.*;

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

/**
 * This interface is the abstraction of something which provides a local storage
 * service, such as a persistence storage service or an in-memory storage
 * service. Two implementations are provided, the PersistentStorage and
 * MemoryStorage, respsectively.
 *
 * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
 * @author jeffh
 */
public interface Storage extends Catalog {

  /**
   * Stores 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>unstore(id)</code> followed by <code>store(id, obj)</code>
   * . This method finishes by calling receiveResult() on the provided
   * continuation with the success or failure of the store. Returns <code>True</code>
   * if the action succeeds, else <code>False</code> (through receiveResult on
   * c).
   *
   * @param id The object's id.
   * @param metadata The object's metadata
   * @param obj The object to store.
   * @param c The command to run once the operation is complete
   */
  public void store(Id id, Serializable metadata, Serializable obj, Continuation c);

  /**
   * Removes the object from the list of stored objects. This method is
   * non-blocking. If the object was not in the stored 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 unstore(Id id, Continuation c);
}
