catalog.java

pastry的java实现的2.0b版

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"FreePastry" Peer-to-Peer Application Development Substrate 

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package rice.persistence;

import java.util.*;
import rice.p2p.util.*;

/*
 *  @(#) Catalog.java
 *
 *  @author Ansley Post
 *  @author Alan Mislove
 *
 *  @version $Id: Catalog.java 2509 2005-05-26 17:59:07Z amislove $
 */
import java.io.*;

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

/**
 * This interface is the abstraction of something which holds objects which are
 * available for lookup. This interface does not, however, specify how the
 * objects are inserted, and makes NO guarantees as to whether objects available
 * at a given point in time will be available at a later time. Implementations
 * of the Catalog interface are designed to be interfaces which specify how
 * objects are inserted and stored, and are designed to include a cache and
 * persistent storage interface.
 *
 * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
 * @author jeffh
 */
public interface Catalog {

  /**
   * Returns whether or not an object is present in the location <code>id</code>
   * .
   *
   * @param id The id of the object in question.
   * @return Whether or not an object is present at id.
   */
  public boolean exists(Id id);

  /**
   * Returns the object identified by the given id, or <code>null</code> if
   * there is no cooresponding object (through receiveResult on c).
   *
   * @param id The id of the object in question.
   * @param c The command to run once the operation is complete
   */
  public void getObject(Id id, Continuation c);

  /**
   * Returns the metadata associated with the provided object, or null if no
   * metadata exists. The metadata must be stored in memory, so this operation
   * is guaranteed to be fast and non-blocking. The metadata returned from this
   * method must *NOT* be mutated in any way, as the actual reference to the
   * internal object is returned. Mutating this metadata may make the internal
   * indices incorrect, resulting in undefined behavior. Changing the metadata
   * should be done by creating a new metadata object and calling setMetadata().
   *
   * @param id The id for which the metadata is needed
   * @return The metadata, or null if none exists
   */
  public Serializable getMetadata(Id id);

  /**
   * Updates the metadata stored under the given key to be the provided value.
   * As this may require a disk access, the requestor must also provide a
   * continuation to return the result to.
   *
   * @param id The id for the metadata
   * @param metadata The metadata to store
   * @param command The new Metadata value
   */
  public void setMetadata(Id id, Serializable metadata, Continuation command);

  /**
   * Renames the given object to the new id. This method is potentially faster
   * than store/cache and unstore/uncache.
   *
   * @param oldId The id of the object in question.
   * @param newId The new id of the object in question.
   * @param c The command to run once the operation is complete
   */
  public void rename(Id oldId, Id newId, Continuation c);

  /**
   * Return the objects identified by the given range of ids. The IdSet returned
   * contains the Ids of the stored objects. The range is partially inclusive,
   * the lower range is inclusive, and the upper exclusive. NOTE: This method
   * blocks so if the behavior of this method changes and no longer stored in
   * memory, this method may be deprecated.
   *
   * @param range The range to query
   * @return The idset containg the keys
   */
  public IdSet scan(IdRange range);

  /**
   * Return all objects currently stored by this catalog NOTE: This method
   * blocks so if the behavior of this method changes and no longer stored in
   * memory, this method may be deprecated.
   *
   * @return The idset containg the keys
   */
  public IdSet scan();

  /**
   * Returns a map which contains keys mapping ids to the associated metadata.
   *
   * @param range The range to query
   * @return The map containg the keys
   */
  public SortedMap scanMetadata(IdRange range);

  /**
   * Returns a map which contains keys mapping ids to the associated metadata.
   *
   * @return The treemap mapping ids to metadata
   */
  public SortedMap scanMetadata();

  /**
   * Returns the submapping of ids which have metadata less than the provided
   * value.
   *
   * @param value The maximal metadata value
   * @return The submapping
   */
  public SortedMap scanMetadataValuesHead(Object value);

  /**
   * Returns the submapping of ids which have metadata null
   *
   * @return The submapping
   */
  public SortedMap scanMetadataValuesNull();

  /**
   * Returns the number of Ids currently stored in the catalog
   *
   * @return The number of ids in the catalog
   */
  public int getSize();

  /**
   * Returns the total size of the stored data in bytes.
   *
   * @return The total storage size
   */
  public long getTotalSize();

  /**
   * Method which is used to erase all data stored in the Catalog. Use this
   * method with care!
   *
   * @param c The command to run once done
   */
  public void flush(Continuation c);
}