//******************************************************************************
//
// File:    SharedCharacterArray.java
// Package: edu.rit.pj.reduction
// Unit:    Class edu.rit.pj.reduction.SharedCharacterArray
//
// 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
// and conditions of the license of that module. An independent module is a
// 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.AtomicIntegerArray;

/**
 * Class SharedCharacterArray provides an array reduction variable with elements
 * of type <TT>char</TT>.
 * <P>
 * Class SharedCharacterArray is multiple thread safe. The methods use lock-free
 * atomic compare-and-set.
 * <P>
 * <I>Note:</I> Class SharedCharacterArray is implemented using class
 * java.util.concurrent.atomic.AtomicIntegerArray. Each character array element
 * is stored as an <TT>int</TT> whose values are restricted to the range of type
 * <TT>char</TT>.
 *
 * @author  Alan Kaminsky
 * @version 24-Aug-2007
 */
public class SharedCharacterArray
	{

// Hidden data members.

	private AtomicIntegerArray myArray;

// Exported constructors.

	/**
	 * Construct a new character array reduction variable with the given length.
	 * Each array element is initially 0.
	 *
	 * @param  len  Length.
	 *
	 * @exception  NegativeArraySizeException
	 *     (unchecked exception) Thrown if <TT>len</TT> &lt; 0.
	 */
	public SharedCharacterArray
		(int len)
		{
		myArray = new AtomicIntegerArray (len);
		}

	/**
	 * Construct a new character array reduction variable whose elements are
	 * copied from the given array.
	 *
	 * @param  array  Array to copy.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>array</TT> is null.
	 */
	public SharedCharacterArray
		(char[] array)
		{
		int n = array.length;
		int[] intarray = new int [n];
		for (int i = 0; i < n; ++ i) intarray[i] = array[i];
		myArray = new AtomicIntegerArray (intarray);
		}

// Exported operations.

	/**
	 * Returns this array reduction variable's length.
	 *
	 * @return  Length.
	 */
	public int length()
		{
		return myArray.length();
		}

	/**
	 * Returns this array reduction variable's current value at the given index.
	 *
	 * @param  i  Index.
	 *
	 * @return  Current value.
	 */
	public char get
		(int i)
		{
		return (char) myArray.get (i);
		}

	/**
	 * Set this array reduction variable at the given index to the given value.
	 *
	 * @param  i      Index.
	 * @param  value  New value.
	 */
	public void set
		(int i,
		 char value)
		{
		myArray.set (i, value);
		}

	/**
	 * Set this array reduction variable at the given index to the given value
	 * and return the previous value.
	 *
	 * @param  i      Index.
	 * @param  value  New value.
	 *
	 * @return  Previous value.
	 */
	public char getAndSet
		(int i,
		 char value)
		{
		return (char) myArray.getAndSet (i, value);
		}

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

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

	/**
	 * Add one to this array reduction variable at the given index and return
	 * the previous value.
	 *
	 * @param  i  Index.
	 *
	 * @return  Previous value.
	 */
	public char getAndIncrement
		(int i)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = (char) (oldvalue + 1);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return oldvalue;
			}
		}

	/**
	 * Subtract one from this array reduction variable at the given index and
	 * return the previous value.
	 *
	 * @param  i  Index.
	 *
	 * @return  Previous value.
	 */
	public char getAndDecrement
		(int i)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = (char) (oldvalue - 1);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return oldvalue;
			}
		}

	/**
	 * Add the given value to this array reduction variable at the given index
	 * and return the previous value.
	 *
	 * @param  i      Index.
	 * @param  value  Value to add.
	 *
	 * @return  Previous value.
	 */
	public char getAndAdd
		(int i,
		 char value)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = (char) (oldvalue + value);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return oldvalue;
			}
		}

	/**
	 * Add one to this array reduction variable at the given index and return
	 * the new value.
	 *
	 * @param  i  Index.
	 *
	 * @return  New value.
	 */
	public char incrementAndGet
		(int i)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = (char) (oldvalue + 1);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return newvalue;
			}
		}

	/**
	 * Subtract one from this array reduction variable at the given index and
	 * return the new value.
	 *
	 * @param  i  Index.
	 *
	 * @return  New value.
	 */
	public char decrementAndGet
		(int i)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = (char) (oldvalue - 1);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return newvalue;
			}
		}

	/**
	 * Add the given value to this array reduction variable at the given index
	 * and return the new value.
	 *
	 * @param  i      Index.
	 * @param  value  Value to add.
	 *
	 * @return  New value.
	 */
	public char addAndGet
		(int i,
		 char value)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = (char) (oldvalue + value);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return newvalue;
			}
		}

	/**
	 * Combine this array reduction variable at the given index with the given
	 * value using the given operation. (This array <TT>[i]</TT>) is set to
	 * (this array <TT>[i]</TT>) <I>op</I> (<TT>value</TT>), then (this array
	 * <TT>[i]</TT>) is returned.
	 *
	 * @param  i      Index.
	 * @param  value  Value.
	 * @param  op     Binary operation.
	 *
	 * @return  (This array <TT>[i]</TT>) <I>op</I> (<TT>value</TT>).
	 */
	public char reduce
		(int i,
		 char value,
		 CharacterOp op)
		{
		for (;;)
			{
			char oldvalue = (char) myArray.get (i);
			char newvalue = op.op (oldvalue, value);
			if (myArray.compareAndSet (i, oldvalue, newvalue)) return newvalue;
			}
		}

	/**
	 * Combine this array reduction variable with the given array using the
	 * given operation. For each index <TT>i</TT> from 0 to this array's
	 * length-1, (this array <TT>[i]</TT>) is set to (this array <TT>[i]</TT>)
	 * <I>op</I> (<TT>src[i]</TT>).
	 * <P>
	 * The <TT>reduce()</TT> method is multiple thread safe <I>on a per-element
	 * basis.</I> Each individual array element is updated atomically, but the
	 * array as a whole is not updated atomically.
	 *
	 * @param  src  Source array.
	 * @param  op   Binary operation.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>src</TT> is null. Thrown if
	 *     <TT>op</TT> is null.
	 * @exception  IndexOutOfBoundsException
	 *     (unchecked exception) Thrown if any array index would be out of
	 *     bounds.
	 */
	public void reduce
		(char[] src,
		 CharacterOp op)
		{
		reduce (0, src, 0, myArray.length(), op);
		}

	/**
	 * Combine a portion of this array reduction variable with a portion of the
	 * given array using the given operation. For each index <TT>i</TT> from 0
	 * to <TT>len</TT>-1, (this array <TT>[dstoff+i]</TT>) is set to (this array
	 * <TT>[dstoff+i]</TT>) <I>op</I> (<TT>src[srcoff+i]</TT>).
	 * <P>
	 * The <TT>reduce()</TT> method is multiple thread safe <I>on a per-element
	 * basis.</I> Each individual array element is updated atomically, but the
	 * array as a whole is not updated atomically.
	 *
	 * @param  dstoff  Index of first element to update in this array.
	 * @param  src     Source array.
	 * @param  srcoff  Index of first element to update from in the source
	 *                 array.
	 * @param  len     Number of array elements to update.
	 * @param  op      Binary operation.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>src</TT> is null. Thrown if
	 *     <TT>op</TT> is null.
	 * @exception  IndexOutOfBoundsException
	 *     (unchecked exception) Thrown if <TT>len</TT> &lt; 0. Thrown if any
	 *     array index would be out of bounds.
	 */
	public void reduce
		(int dstoff,
		 char[] src,
		 int srcoff,
		 int len,
		 CharacterOp op)
		{
		if
			(len < 0 ||
			 dstoff < 0 || dstoff+len > myArray.length() ||
			 srcoff < 0 || srcoff+len > src.length)
			{
			throw new IndexOutOfBoundsException();
			}
		while (len > 0)
			{
			updateLoop: for (;;)
				{
				char oldvalue = (char) myArray.get (dstoff);
				char newvalue = op.op (oldvalue, src[srcoff]);
				if (myArray.compareAndSet (dstoff, oldvalue, newvalue))
					break updateLoop;
				}
			++ dstoff;
			++ srcoff;
			-- len;
			}
		}

	/**
	 * Returns a string version of this array reduction variable.
	 *
	 * @return  String version.
	 */
	public String toString()
		{
		StringBuilder b = new StringBuilder();
		b.append ('[');
		int n = myArray.length();
		for (int i = 0; i < n; ++ i)
			{
			if (i > 0) b.append (", ");
			b.append (get (i));
			}
		b.append (']');
		return b.toString();
		}

	}
