/* 
 * $Id: GenericCache.java 124053 2005-01-04 01:24:35Z dfs $
 *
 * Copyright 2000-2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.oro.util;

import j2me.util.*;

/**
 * This is the base class for all cache implementations provided in the
 * org.apache.oro.util package.  To derive a subclass from GenericCache
 * only the ... methods
 * need be overridden.
 * Although 4 subclasses of GenericCache are provided with this
 * package, users may not derive subclasses from this class.
 * Rather, users should create their own implmentations of the
 * {@link Cache} interface.
 *
 * @version @version@
 * @since 1.0
 * @see Cache
 * @see CacheLRU
 * @see CacheFIFO
 * @see CacheFIFO2
 * @see CacheRandom
 */
public abstract class GenericCache implements Cache {//, java.io.Serializable {
  /**
   * The default capacity to be used by the GenericCache subclasses
   * provided with this package.  Its value is 20.
   */
  public static final int DEFAULT_CAPACITY = 20;

  int _numEntries;
  GenericCacheEntry[] _cache;
  HashMap _table;

  /**
   * The primary constructor for GenericCache.  It has default
   * access so it will only be used within the package.  It initializes
   * _table to a Hashtable of capacity equal to the capacity argument,
   * _cache to an array of size equal to the capacity argument, and
   * _numEntries to 0.
   * <p>
   * @param capacity The maximum capacity of the cache.
   */
  GenericCache(int capacity) {
    _numEntries = 0;
    _table    = new HashMap(capacity);
    _cache    = new GenericCacheEntry[capacity];

    while(--capacity >= 0)
      _cache[capacity] = new GenericCacheEntry(capacity);
  }

  public abstract void addElement(Object key, Object value);

  public synchronized Object getElement(Object key) { 
    Object obj;

    obj = _table.get(key);

    if(obj != null)
      return ((GenericCacheEntry)obj)._value;

    return null;
  }

  public final Iterator keys() {
    return _table.keySet().iterator();
  }

  /**
   * Returns the number of elements in the cache, not to be confused with
   * the {@link #capacity()} which returns the number
   * of elements that can be held in the cache at one time.
   * <p>
   * @return  The current size of the cache (i.e., the number of elements
   *          currently cached).
   */
  public final int size() { return _numEntries; }

  /**
   * Returns the maximum number of elements that can be cached at one time.
   * <p>
   * @return The maximum number of elements that can be cached at one time.
   */
  public final int capacity() { return _cache.length; }

  public final boolean isFull() { return (_numEntries >= _cache.length); }
}