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// ========================================================================
// Copyright (c) 2004-2009 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
package org.eclipse.jetty.util;
import java.util.AbstractList;
import java.util.NoSuchElementException;
import java.util.Queue;
/* ------------------------------------------------------------ */
/** Queue backed by circular array.
*
* This partial Queue implementation (also with {@link #remove()} for stack operation)
* is backed by a growable circular array.
*
* @param
*/
public class ArrayQueue extends AbstractList implements Queue
{
public final int DEFAULT_CAPACITY=64;
public final int DEFAULT_GROWTH=32;
protected Object _lock=this;
protected Object[] _elements;
protected int _nextE;
protected int _nextSlot;
protected volatile int _size;
protected int _growCapacity;
/* ------------------------------------------------------------ */
public ArrayQueue()
{
_elements=new Object[64];
_growCapacity=32;
}
/* ------------------------------------------------------------ */
public ArrayQueue(int capacity)
{
_elements=new Object[capacity];
_growCapacity=-1;
}
/* ------------------------------------------------------------ */
public ArrayQueue(int initCapacity,int growBy)
{
_elements=new Object[initCapacity];
_growCapacity=growBy;
}
/* ------------------------------------------------------------ */
public ArrayQueue(int initCapacity,int growBy,Object lock)
{
_elements=new Object[initCapacity];
_growCapacity=growBy;
_lock=lock;
}
/* ------------------------------------------------------------ */
public int getCapacity()
{
return _elements.length;
}
/* ------------------------------------------------------------ */
@Override
public boolean add(E e)
{
if (!offer(e))
throw new IllegalStateException("Full");
return true;
}
/* ------------------------------------------------------------ */
public boolean offer(E e)
{
synchronized(_lock)
{
if (_size==_elements.length && !grow())
return false;
_size++;
_elements[_nextSlot++]=e;
if (_nextSlot==_elements.length)
_nextSlot=0;
}
return true;
}
/* ------------------------------------------------------------ */
/**
* Add without synchronization or bounds checking
* @see #add(Object)
*/
public void addUnsafe(E e)
{
if (_size==_elements.length && !grow())
throw new IllegalStateException("Full");
_size++;
_elements[_nextSlot++]=e;
if (_nextSlot==_elements.length)
_nextSlot=0;
}
/* ------------------------------------------------------------ */
public E element()
{
synchronized(_lock)
{
if (_size==0)
throw new NoSuchElementException();
return (E)_elements[_nextE];
}
}
/* ------------------------------------------------------------ */
public E peek()
{
synchronized(_lock)
{
if (_size==0)
return null;
return (E)_elements[_nextE];
}
}
/* ------------------------------------------------------------ */
public E poll()
{
synchronized(_lock)
{
if (_size==0)
return null;
E e = (E)_elements[_nextE];
_elements[_nextE]=null;
_size--;
if (++_nextE==_elements.length)
_nextE=0;
return e;
}
}
/* ------------------------------------------------------------ */
public E remove()
{
synchronized(_lock)
{
if (_size==0)
throw new NoSuchElementException();
E e = (E)_elements[_nextE];
_elements[_nextE]=null;
_size--;
if (++_nextE==_elements.length)
_nextE=0;
return e;
}
}
/* ------------------------------------------------------------ */
@Override
public void clear()
{
synchronized(_lock)
{
_size=0;
_nextE=0;
_nextSlot=0;
}
}
/* ------------------------------------------------------------ */
@Override
public boolean isEmpty()
{
synchronized(_lock)
{
return _size==0;
}
}
/* ------------------------------------------------------------ */
@Override
public int size()
{
return _size;
}
/* ------------------------------------------------------------ */
@Override
public E get(int index)
{
synchronized(_lock)
{
if (index<0 || index>=_size)
throw new IndexOutOfBoundsException("!("+0+"<"+index+"<="+_size+")");
int i = (_nextE+index)%_elements.length;
return (E)_elements[i];
}
}
/* ------------------------------------------------------------ */
/**
* Get without synchronization or bounds checking.
* @see #get(int)
*/
public E getUnsafe(int index)
{
int i = (_nextE+index)%_elements.length;
return (E)_elements[i];
}
/* ------------------------------------------------------------ */
@Override
public E remove(int index)
{
synchronized(_lock)
{
if (index<0 || index>=_size)
throw new IndexOutOfBoundsException("!("+0+"<"+index+"<="+_size+")");
int i = (_nextE+index)%_elements.length;
E old=(E)_elements[i];
if (i<_nextSlot)
{
// 0 _elements.length
// _nextE........._nextSlot
System.arraycopy(_elements,i+1,_elements,i,_nextSlot-i);
_nextSlot--;
_size--;
}
else
{
// 0 _elements.length
// ......_nextSlot _nextE..........
System.arraycopy(_elements,i+1,_elements,i,_elements.length-i-1);
if (_nextSlot>0)
{
_elements[_elements.length-1]=_elements[0];
System.arraycopy(_elements,1,_elements,0,_nextSlot-1);
_nextSlot--;
}
else
_nextSlot=_elements.length-1;
_size--;
}
return old;
}
}
/* ------------------------------------------------------------ */
@Override
public E set(int index, E element)
{
synchronized(_lock)
{
if (index<0 || index>=_size)
throw new IndexOutOfBoundsException("!("+0+"<"+index+"<="+_size+")");
int i = _nextE+index;
if (i>=_elements.length)
i-=_elements.length;
E old=(E)_elements[i];
_elements[i]=element;
return old;
}
}
/* ------------------------------------------------------------ */
@Override
public void add(int index, E element)
{
synchronized(_lock)
{
if (index<0 || index>_size)
throw new IndexOutOfBoundsException("!("+0+"<"+index+"<="+_size+")");
if (_size==_elements.length && !grow())
throw new IllegalStateException("Full");
if (index==_size)
{
add(element);
}
else
{
int i = _nextE+index;
if (i>=_elements.length)
i-=_elements.length;
_size++;
_nextSlot++;
if (_nextSlot==_elements.length)
_nextSlot=0;
if (i<_nextSlot)
{
// 0 _elements.length
// _nextE.....i..._nextSlot
// 0 _elements.length
// ..i..._nextSlot _nextE..........
System.arraycopy(_elements,i,_elements,i+1,_nextSlot-i);
_elements[i]=element;
}
else
{
// 0 _elements.length
// ......_nextSlot _nextE.....i....
if (_nextSlot>0)
{
System.arraycopy(_elements,0,_elements,1,_nextSlot);
_elements[0]=_elements[_elements.length-1];
}
System.arraycopy(_elements,i,_elements,i+1,_elements.length-i-1);
_elements[i]=element;
}
}
}
}
protected boolean grow()
{
if (_growCapacity<=0)
return false;
Object[] elements=new Object[_elements.length+_growCapacity];
int split=_elements.length-_nextE;
if (split>0)
System.arraycopy(_elements,_nextE,elements,0,split);
if (_nextE!=0)
System.arraycopy(_elements,0,elements,split,_nextSlot);
_elements=elements;
_nextE=0;
_nextSlot=_size;
return true;
}
}
