/**
* Copyright 2005 JBoss Inc
*
* 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.
*/
package org.drools.core.util;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
public class PrimitiveLongStack
implements
Externalizable {
/**
*
*/
private static final long serialVersionUID = 510l;
private int tableSize;
private int currentPageId;
private Page currentPage;
public PrimitiveLongStack() {
this( 256 );
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
tableSize = in.readInt();
currentPageId = in.readInt();
currentPage = (Page)in.readObject();
}
public void writeExternal(ObjectOutput out) throws IOException {
out.writeInt(tableSize);
out.writeInt(currentPageId);
out.writeObject(currentPage);
}
public PrimitiveLongStack(final int tableSize) {
this.tableSize = tableSize;
this.currentPageId = 0;
// instantiate the first node
// previous sibling of first node is null
// next sibling of last node is null
this.currentPage = new Page( null,
this.currentPageId,
this.tableSize );
}
public void push(final long value) {
if ( this.currentPage.getPosition() == this.tableSize - 1 ) {
final Page node = new Page( this.currentPage,
++this.currentPageId,
this.tableSize );
this.currentPage = node;
}
this.currentPage.push( value );
}
public long pop() {
if ( this.currentPage.getPosition() == -1 ) {
if ( this.currentPageId == 0 ) {
throw new RuntimeException( "Unable to pop" );
}
final Page node = this.currentPage;
this.currentPage = node.getPreviousSibling();
this.currentPageId--;
node.remove();
}
return this.currentPage.pop();
}
public boolean isEmpty() {
return this.currentPageId == 0 && this.currentPage.getPosition() == -1;
}
public static final class Page
implements
Externalizable {
/**
*
*/
private static final long serialVersionUID = 510l;
private int pageId;
private Page nextSibling;
private Page previousSibling;
private long[] table;
private int lastKey;
public Page() {
}
Page(final Page previousSibling,
final int nodeId,
final int tableSize) {
// create bi-directional link
this.previousSibling = previousSibling;
if ( this.previousSibling != null ) {
this.previousSibling.setNextSibling( this );
}
this.pageId = nodeId;
this.lastKey = -1;
// initiate tree;
this.table = new long[tableSize];
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
pageId = in.readInt();
nextSibling = (Page)in.readObject();
previousSibling = (Page)in.readObject();
table = (long[])in.readObject();
lastKey = in.readInt();
}
public void writeExternal(ObjectOutput out) throws IOException {
out.writeInt(pageId);
out.writeObject(nextSibling);
out.writeObject(previousSibling);
out.writeObject(table);
out.writeInt(lastKey);
}
public int getNodeId() {
return this.pageId;
}
void setNextSibling(final Page nextSibling) {
this.nextSibling = nextSibling;
}
public Page getNextSibling() {
return this.nextSibling;
}
public Page getPreviousSibling() {
return this.previousSibling;
}
public long pop() {
return this.table[this.lastKey--];
}
public void push(final long value) {
this.table[++this.lastKey] = value;
}
public int getPosition() {
return this.lastKey;
}
void remove() {
this.previousSibling.setNextSibling( null );
this.previousSibling = null;
this.table = null;
}
}
}