| /** |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.activemq.kaha.impl.index; |
| |
| import org.apache.activemq.kaha.StoreEntry; |
| |
| /** |
| * A linked list used by IndexItems |
| * |
| * |
| */ |
| public final class VMIndexLinkedList implements Cloneable, IndexLinkedList { |
| private transient IndexItem root; |
| private transient int size; |
| |
| /** |
| * Constructs an empty list. |
| * @param header |
| */ |
| public VMIndexLinkedList(IndexItem header) { |
| this.root = header; |
| this.root.next=this.root.prev=this.root; |
| } |
| |
| public void setRoot(IndexItem newRoot) { |
| this.root=newRoot; |
| } |
| |
| public synchronized IndexItem getRoot() { |
| return root; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#getFirst() |
| */ |
| public synchronized IndexItem getFirst() { |
| if (size == 0) { |
| return null; |
| } |
| return root.next; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#getLast() |
| */ |
| public synchronized IndexItem getLast() { |
| if (size == 0) { |
| return null; |
| } |
| return root.prev; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#removeFirst() |
| */ |
| public synchronized StoreEntry removeFirst() { |
| if (size == 0) { |
| return null; |
| } |
| StoreEntry result = root.next; |
| remove(root.next); |
| return result; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#removeLast() |
| */ |
| public synchronized Object removeLast() { |
| if (size == 0) { |
| return null; |
| } |
| StoreEntry result = root.prev; |
| remove(root.prev); |
| return result; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#addFirst(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized void addFirst(IndexItem item) { |
| addBefore(item, root.next); |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#addLast(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized void addLast(IndexItem item) { |
| addBefore(item, root); |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#size() |
| */ |
| public synchronized int size() { |
| return size; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#isEmpty() |
| */ |
| public synchronized boolean isEmpty() { |
| return size == 0; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#add(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized boolean add(IndexItem item) { |
| addBefore(item, root); |
| return true; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#clear() |
| */ |
| public synchronized void clear() { |
| root.next=root.prev=root; |
| size = 0; |
| } |
| |
| // Positional Access Operations |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#get(int) |
| */ |
| public synchronized IndexItem get(int index) { |
| return entry(index); |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#add(int, |
| * org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized void add(int index, IndexItem element) { |
| addBefore(element, index == size ? root : entry(index)); |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#remove(int) |
| */ |
| public synchronized Object remove(int index) { |
| IndexItem e = entry(index); |
| remove(e); |
| return e; |
| } |
| |
| /** |
| * Return the indexed entry. |
| */ |
| private IndexItem entry(int index) { |
| if (index < 0 || index >= size) { |
| throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size); |
| } |
| IndexItem e = root; |
| if (index < size / 2) { |
| for (int i = 0; i <= index; i++) { |
| e = e.next; |
| } |
| } else { |
| for (int i = size; i > index; i--) { |
| e = e.prev; |
| } |
| } |
| return e; |
| } |
| |
| // Search Operations |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#indexOf(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized int indexOf(StoreEntry o) { |
| int index = 0; |
| for (IndexItem e = root.next; e != root; e = e.next) { |
| if (o == e) { |
| return index; |
| } |
| index++; |
| } |
| return -1; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#getNextEntry(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized IndexItem getNextEntry(IndexItem entry) { |
| return entry.next != root ? entry.next : null; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#getPrevEntry(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized IndexItem getPrevEntry(IndexItem entry) { |
| return entry.prev != root ? entry.prev : null; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#addBefore(org.apache.activemq.kaha.impl.IndexItem, |
| * org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized void addBefore(IndexItem insert, IndexItem e) { |
| insert.next = e; |
| insert.prev = e.prev; |
| insert.prev.next = insert; |
| insert.next.prev = insert; |
| size++; |
| } |
| |
| /* |
| * (non-Javadoc) |
| * |
| * @see org.apache.activemq.kaha.impl.IndexLinkedList#remove(org.apache.activemq.kaha.impl.IndexItem) |
| */ |
| public synchronized void remove(IndexItem e) { |
| if (e == root || e.equals(root)) { |
| return; |
| } |
| |
| e.prev.next = e.next; |
| e.next.prev = e.prev; |
| size--; |
| } |
| |
| /** |
| * @return clone |
| */ |
| public synchronized Object clone() { |
| IndexLinkedList clone = new VMIndexLinkedList(this.root); |
| for (IndexItem e = root.next; e != root; e = e.next) { |
| clone.add(e); |
| } |
| return clone; |
| } |
| |
| public synchronized StoreEntry getEntry(StoreEntry current) { |
| return current; |
| } |
| |
| /** |
| * Update the indexes of a StoreEntry |
| * |
| * @param current |
| */ |
| public synchronized StoreEntry refreshEntry(StoreEntry current) { |
| return current; |
| } |
| } |