CacheList.java

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package org.gffs.cache;
 
/*
 * Copyright 2006 University of Virginia
 * 
 * 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.
 */
 
abstract class CacheList<KeyType, DataType>
{
  protected int _myRole;
 
  protected RoleBasedCacheNode<KeyType, DataType> _head;
  protected RoleBasedCacheNode<KeyType, DataType> _tail;
 
  protected CacheList(int role)
  {
    _myRole = role;
 
    _head = _tail = null;
  }
 
  public abstract void insert(RoleBasedCacheNode<KeyType, DataType> node);
 
  public RoleBasedCacheNode<KeyType, DataType> removeFirst()
  {
    if (_head == null)
      return null;
 
    RoleBasedCacheNode<KeyType, DataType> ret = _head;
 
    _head = _head.getNext(_myRole);
    if (_head != null)
      _head.setPrevious(_myRole, null);
    else
      _tail = null;
 
    ret.clearLinks(_myRole);
    return ret;
  }
 
  public RoleBasedCacheNode<KeyType, DataType> peekFirst()
  {
    if (_head == null)
      return null;
 
    return _head;
  }
 
  public void remove(RoleBasedCacheNode<KeyType, DataType> node)
  {
    if (node.getPrevious(_myRole) == null) // At the head of the list
      _head = node.getNext(_myRole);
    else
      node.getPrevious(_myRole).setNext(_myRole, node.getNext(_myRole));
 
    if (node.getNext(_myRole) == null) // At the tail of the list
      _tail = node.getPrevious(_myRole);
    else
      node.getNext(_myRole).setPrevious(_myRole, node.getPrevious(_myRole));
 
    node.clearLinks(_myRole);
  }
 
  public void clear()
  {
    _head = null;
    _tail = null;
  }
}