//******************************************************************************
//
// File:    SharedInteger.java
// Package: edu.rit.pj.reduction
// Unit:    Class edu.rit.pj.reduction.SharedInteger
//
// This Java source file is copyright (C) 2007 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
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// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
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//******************************************************************************

package edu.rit.pj.reduction;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * Class SharedInteger provides a reduction variable for a value of type
 * <TT>int</TT>.
 * <P>
 * Class SharedInteger is multiple thread safe. The methods use lock-free atomic
 * compare-and-set.
 * <P>
 * <I>Note:</I> Class SharedInteger is implemented using class
 * java.util.concurrent.atomic.AtomicInteger.
 *
 * @author  Alan Kaminsky
 * @version 06-Jun-2007
 */
public class SharedInteger
	extends Number
	{

// Hidden data members.

	private AtomicInteger myValue;

// Exported constructors.

	/**
	 * Construct a new integer reduction variable with the initial value 0.
	 */
	public SharedInteger()
		{
		myValue = new AtomicInteger();
		}

	/**
	 * Construct a new integer reduction variable with the given initial
	 * value.
	 *
	 * @param  initialValue  Initial value.
	 */
	public SharedInteger
		(int initialValue)
		{
		myValue = new AtomicInteger (initialValue);
		}

// Exported operations.

	/**
	 * Returns this reduction variable's current value.
	 *
	 * @return  Current value.
	 */
	public int get()
		{
		return myValue.get();
		}

	/**
	 * Set this reduction variable to the given value.
	 *
	 * @param  value  New value.
	 */
	public void set
		(int value)
		{
		myValue.set (value);
		}

	/**
	 * Set this reduction variable to the given value and return the previous
	 * value.
	 *
	 * @param  value  New value.
	 *
	 * @return  Previous value.
	 */
	public int getAndSet
		(int value)
		{
		return myValue.getAndSet (value);
		}

	/**
	 * Atomically set this reduction variable to the given updated value if the
	 * current value equals the expected value.
	 *
	 * @param  expect  Expected value.
	 * @param  update  Updated value.
	 *
	 * @return  True if the update happened, false otherwise.
	 */
	public boolean compareAndSet
		(int expect,
		 int update)
		{
		return myValue.compareAndSet (expect, update);
		}

	/**
	 * Atomically set this reduction variable to the given updated value if the
	 * current value equals the expected value. May fail spuriously.
	 *
	 * @param  expect  Expected value.
	 * @param  update  Updated value.
	 *
	 * @return  True if the update happened, false otherwise.
	 */
	public boolean weakCompareAndSet
		(int expect,
		 int update)
		{
		return myValue.weakCompareAndSet (expect, update);
		}

	/**
	 * Add one to this reduction variable and return the previous value.
	 *
	 * @return  Previous value.
	 */
	public int getAndIncrement()
		{
		return myValue.getAndIncrement();
		}

	/**
	 * Subtract one from this reduction variable and return the previous value.
	 *
	 * @return  Previous value.
	 */
	public int getAndDecrement()
		{
		return myValue.getAndDecrement();
		}

	/**
	 * Add the given value to this reduction variable and return the previous
	 * value.
	 *
	 * @param  value  Value to add.
	 *
	 * @return  Previous value.
	 */
	public int getAndAdd
		(int value)
		{
		return myValue.getAndAdd (value);
		}

	/**
	 * Add one to this reduction variable and return the new value.
	 *
	 * @return  New value.
	 */
	public int incrementAndGet()
		{
		return myValue.incrementAndGet();
		}

	/**
	 * Subtract one from this reduction variable and return the new value.
	 *
	 * @return  New value.
	 */
	public int decrementAndGet()
		{
		return myValue.decrementAndGet();
		}

	/**
	 * Add the given value to this reduction variable and return the new value.
	 *
	 * @param  value  Value to add.
	 *
	 * @return  New value.
	 */
	public int addAndGet
		(int value)
		{
		return myValue.addAndGet (value);
		}

	/**
	 * Combine this reduction variable with the given value using the given
	 * operation. The result is stored back into this reduction variable and is
	 * returned.
	 *
	 * @param  value  Value.
	 * @param  op     Binary operation.
	 *
	 * @return  (This variable) <I>op</I> (<TT>value</TT>).
	 */
	public int reduce
		(int value,
		 IntegerOp op)
		{
		for (;;)
			{
			int oldvalue = myValue.get();
			int newvalue = op.op (oldvalue, value);
			if (myValue.compareAndSet (oldvalue, newvalue)) return newvalue;
			}
		}

	/**
	 * Returns a string version of this reduction variable.
	 *
	 * @return  String version.
	 */
	public String toString()
		{
		return Integer.toString (get());
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>int</TT>.
	 *
	 * @return  Current value.
	 */
	public int intValue()
		{
		return (int) get();
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>long</TT>.
	 *
	 * @return  Current value.
	 */
	public long longValue()
		{
		return (long) get();
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>float</TT>.
	 *
	 * @return  Current value.
	 */
	public float floatValue()
		{
		return (float) get();
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>double</TT>.
	 *
	 * @return  Current value.
	 */
	public double doubleValue()
		{
		return (double) get();
		}

	}