kona/src/org/gffs/cache/CacheList.java

   1 package org.gffs.cache;
   2
   3 /*
   4  * Copyright 2006 University of Virginia
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may
   7  * obtain a copy of the License at
   8  *
   9  * http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
  13  * and limitations under the License.
  14  */
  15
  16 abstract class CacheList<KeyType, DataType>
  17 {
  18         protected int _myRole;
  19
  20         protected RoleBasedCacheNode<KeyType, DataType> _head;
  21         protected RoleBasedCacheNode<KeyType, DataType> _tail;
  22
  23         protected CacheList(int role)
  24         {
  25                 _myRole = role;
  26
  27                 _head = _tail = null;
  28         }
  29
  30         public abstract void insert(RoleBasedCacheNode<KeyType, DataType> node);
  31
  32         public RoleBasedCacheNode<KeyType, DataType> removeFirst()
  33         {
  34                 if (_head == null)
  35                         return null;
  36
  37                 RoleBasedCacheNode<KeyType, DataType> ret = _head;
  38
  39                 _head = _head.getNext(_myRole);
  40                 if (_head != null)
  41                         _head.setPrevious(_myRole, null);
  42                 else
  43                         _tail = null;
  44
  45                 ret.clearLinks(_myRole);
  46                 return ret;
  47         }
  48
  49         public RoleBasedCacheNode<KeyType, DataType> peekFirst()
  50         {
  51                 if (_head == null)
  52                         return null;
  53
  54                 return _head;
  55         }
  56
  57         public void remove(RoleBasedCacheNode<KeyType, DataType> node)
  58         {
  59                 if (node.getPrevious(_myRole) == null) // At the head of the list
  60                         _head = node.getNext(_myRole);
  61                 else
  62                         node.getPrevious(_myRole).setNext(_myRole, node.getNext(_myRole));
  63
  64                 if (node.getNext(_myRole) == null) // At the tail of the list
  65                         _tail = node.getPrevious(_myRole);
  66                 else
  67                         node.getNext(_myRole).setPrevious(_myRole, node.getPrevious(_myRole));
  68
  69                 node.clearLinks(_myRole);
  70         }
  71
  72         public void clear()
  73         {
  74                 _head = null;
  75                 _tail = null;
  76         }
  77 }