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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.gallery3d.util;
     18 
     19 
     20 public class LinkedNode {
     21     /* package */ LinkedNode mPrev;
     22     /* package */ LinkedNode mNext;
     23 
     24     public LinkedNode() {
     25         mPrev = mNext = this;
     26     }
     27 
     28     public void insert(LinkedNode node) {
     29         node.mNext = mNext;
     30         mNext.mPrev = node;
     31         node.mPrev = this;
     32         mNext = node;
     33     }
     34 
     35     public void remove() {
     36         if (mNext == this) throw new IllegalStateException();
     37         mPrev.mNext = mNext;
     38         mNext.mPrev = mPrev;
     39         mPrev = mNext = null;
     40     }
     41 
     42     @SuppressWarnings("unchecked")
     43     public static class List<T extends LinkedNode> {
     44         private LinkedNode mHead = new LinkedNode();
     45 
     46         public void insertLast(T node) {
     47             mHead.mPrev.insert(node);
     48         }
     49 
     50         public T getFirst() {
     51             return (T) (mHead.mNext == mHead ? null : mHead.mNext);
     52         }
     53 
     54         public T getLast() {
     55             return (T) (mHead.mPrev == mHead ? null : mHead.mPrev);
     56         }
     57 
     58         public T nextOf(T node) {
     59             return (T) (node.mNext == mHead ? null : node.mNext);
     60         }
     61 
     62         public T previousOf(T node) {
     63             return (T) (node.mPrev == mHead ? null : node.mPrev);
     64         }
     65 
     66     }
     67 
     68     public static <T extends LinkedNode> List<T> newList() {
     69         return new List<T>();
     70     }
     71 }
     72