001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.kahadb.util;
018
019import java.util.ArrayList;
020
021/**
022 * Provides a list of LinkedNode objects. 
023 * 
024 * @author chirino
025 */
026public class LinkedNodeList<T extends LinkedNode<T>> {
027
028    T head;
029    int size;
030
031    public LinkedNodeList() {
032    }
033
034    public boolean isEmpty() {
035        return head == null;
036    }
037
038    public void addLast(T node) {
039        node.linkToTail(this);
040    }
041
042    public void addFirst(T node) {
043        node.linkToHead(this);
044    }
045
046    public T getHead() {
047        return head;
048    }
049
050    public T getTail() {
051        return head != null ? head.prev : null;
052    }
053    
054    public void clear() {
055        while (head != null) {
056            head.unlink();
057        }
058    }
059
060    public void addLast(LinkedNodeList<T> list) {
061        if (list.isEmpty()) {
062            return;
063        }
064        if (head == null) {
065            head = list.head;
066            reparent(list);
067        } else {
068            getTail().linkAfter(list);
069        }
070    }
071
072    public void addFirst(LinkedNodeList<T> list) {
073        if (list.isEmpty()) {
074            return;
075        }
076        if (head == null) {
077            reparent(list);
078            head = list.head;
079            list.head = null;
080        } else {
081            getHead().linkBefore(list);
082        }
083    }
084
085    public T reparent(LinkedNodeList<T> list) {
086        size += list.size;
087        T n = list.head;
088        do {
089            n.list = this;
090            n = n.next;
091        } while (n != list.head);
092        list.head = null;
093        list.size = 0;
094        return n;
095    }
096
097    /**
098     * Move the head to the tail and returns the new head node.
099     * 
100     * @return
101     */
102    public T rotate() {
103        if( head ==null )
104                return null;
105        return head = head.getNextCircular();
106    }
107
108    /**
109     * Move the head to the tail and returns the new head node.
110     * 
111     * @return
112     */
113    public void rotateTo(T head) {
114        assert head!=null: "Cannot rotate to a null head";
115        assert head.list == this : "Cannot rotate to a node not linked to this list";
116        this.head = head;
117    }
118
119    public int size() {
120        return size;
121    }
122
123    @Override
124    public String toString() {
125        StringBuilder sb = new StringBuilder();
126        sb.append("[");
127        boolean first=true;
128        T cur = getHead();
129        while( cur!=null ) {
130            if( !first ) {
131                sb.append(", ");
132            }
133            sb.append(cur);
134            first=false;
135            cur = cur.getNext();
136        }
137        sb.append("]");
138        return sb.toString();
139    }
140    
141    /**
142     * Copies the nodes of the LinkedNodeList to an ArrayList.
143     * @return
144     */
145    public ArrayList<T> toArrayList() {
146        ArrayList<T> rc = new ArrayList<T>(size);
147        T cur = head;
148        while( cur!=null ) {
149                rc.add(cur);
150                cur = cur.getNext();
151        }
152        return rc;
153    }
154}