ClientStore.java

/* ClientStore.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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General Public License for more details.

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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.sasl.srp;

import java.util.HashMap;

/**
 * The client-side implementation of the SRP security context store.
 */
public class ClientStore
{
  /** The underlying singleton. */
  private static ClientStore singleton = null;
  /** The map of uid --> SASL Security Context record. */
  private static final HashMap uid2ssc = new HashMap();
  /** The map of sid --> Session timing record. */
  private static final HashMap uid2ttl = new HashMap();
  /** A synchronisation lock. */
  private static final Object lock = new Object();

  /** Private constructor to enforce Singleton pattern. */
  private ClientStore()
  {
    super();

    // TODO: add a cleaning timer thread
  }

  /**
   * Returns the classloader Singleton.
   * 
   * @return the classloader Singleton instance.
   */
  static synchronized final ClientStore instance()
  {
    if (singleton == null)
      singleton = new ClientStore();
    return singleton;
  }

  /**
   * Returns a boolean flag indicating if the designated client's session is
   * still alive or not.
   * 
   * @param uid the identifier of the client whose session to check.
   * @return <code>true</code> if the designated client's session is still
   *         alive. <code>false</code> otherwise.
   */
  boolean isAlive(final String uid)
  {
    final boolean result;
    synchronized (lock)
      {
        final Object obj = uid2ssc.get(uid);
        result = (obj != null);
        if (result) // is it still alive?
          {
            final StoreEntry sto = (StoreEntry) uid2ttl.get(uid);
            if (! sto.isAlive()) // invalidate it
              {
                uid2ssc.remove(uid);
                uid2ttl.remove(uid);
              }
          }
      }
    return result;
  }

  /**
   * Records a mapping between a client's unique identifier and its security
   * context.
   * 
   * @param uid the unique identifier of the SRP client for which the session is
   *          to be cached.
   * @param ttl the session's Time-To-Live indicator (in seconds).
   * @param ctx the client's security context.
   */
  void cacheSession(final String uid, final int ttl, final SecurityContext ctx)
  {
    synchronized (lock)
      {
        uid2ssc.put(uid, ctx);
        uid2ttl.put(uid, new StoreEntry(ttl));
      }
  }

  /**
   * Removes the mapping between the designated SRP client unique identifier and
   * the its session security context (and other timing information).
   * 
   * @param uid the identifier of the client whose session is to invalidate.
   */
  void invalidateSession(final String uid)
  {
    synchronized (lock)
      {
        uid2ssc.remove(uid);
        uid2ttl.remove(uid);
      }
  }

  /**
   * Returns an SRP client's security context record mapped by that client's
   * unique identifier.
   * 
   * @param uid the identifier of the client whose session is to restore.
   * @return the SRP client's security context.
   */
  SecurityContext restoreSession(final String uid)
  {
    final SecurityContext result;
    synchronized (lock)
      {
        result = (SecurityContext) uid2ssc.remove(uid);
        uid2ttl.remove(uid);
      }
    return result;
  }
}