//******************************************************************************
//
// File:    Vector2DArrayDoubleBuf.java
// Package: edu.rit.vector
// Unit:    Class edu.rit.vector.Vector2DArrayDoubleBuf
//
// 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.
//
//******************************************************************************

package edu.rit.vector;

import edu.rit.mp.Buf;
import edu.rit.mp.DoubleBuf;

import edu.rit.pj.reduction.Op;

import edu.rit.util.Range;

import java.nio.ByteBuffer;

/**
 * Class Vector2DArrayDoubleBuf provides a buffer for an array of {@linkplain
 * Vector2D} items sent or received using the Message Protocol (MP). The array
 * element stride may be 1 or greater than 1. In a message, a vector is treated
 * as two double values (<I>x</I>,<I>y</I>), with each double value represented
 * as eight bytes, most significant byte first.
 * <P>
 * A buffer may be used to send one or more messages at the same time in
 * multiple threads. If a buffer is being used to send a message or messages,
 * the buffer must not be used to receive a message at the same time.
 * <P>
 * A buffer may be used to receive one message at a time. If a buffer is being
 * used to receive a message, the buffer must not be used to receive another
 * message in a different thread, and the buffer must not be used to send a
 * message or messages.
 * <P>
 * A buffer is a conduit for retrieving and storing data in some underlying data
 * structure. If the underlying data structure is multiple thread safe, then one
 * thread can be retrieving or storing data via the buffer at the same time as
 * other threads are accessing the data structure. If the underlying data
 * structure is not multiple thread safe, then other threads must not access the
 * data structure while one thread is retrieving or storing data via the buffer.
 *
 * @author  Alan Kaminsky
 * @version 27-Jun-2007
 */
class Vector2DArrayDoubleBuf
	extends DoubleBuf
	{

// Hidden data members.

	Vector2D[] myArray;
	Range myRange;
	int myArrayOffset;
	int myStride;

// Hidden constructors.

	/**
	 * Construct a new vector array buffer.
	 *
	 * @param  theArray  Array.
	 * @param  theRange  Range of elements to include.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if any argument is null.
	 * @exception  IndexOutOfBoundsException
	 *     (unchecked exception) Thrown if <TT>theArray</TT>'s allocation does
	 *     not include <TT>theRange</TT>.
	 */
	public Vector2DArrayDoubleBuf
		(Vector2D[] theArray,
		 Range theRange)
		{
		super (theRange.length() * 2);
		if (0 > theRange.lb() || theRange.ub() >= theArray.length)
			{
			throw new IndexOutOfBoundsException
				("Vector2DArrayDoubleBuf(): theArray index range = 0.." +
				 (theArray.length-1) + "1, theRange = " + theRange);
			}
		myArray = theArray;
		myRange = theRange;
		myArrayOffset = theRange.lb();
		myStride = theRange.stride();
		}

// Exported operations.

	/**
	 * Obtain the given item from this buffer.
	 * <P>
	 * The <TT>get()</TT> method must not block the calling thread; if it does,
	 * all message I/O in MP will be blocked.
	 *
	 * @param  i  Item index in the range 0 .. <TT>length()</TT>-1.
	 *
	 * @return  Item at index <TT>i</TT>.
	 */
	public double get
		(int i)
		{
		int index = myArrayOffset + (i >>> 1) * myStride;
		if ((i & 1) == 0)
			{
			return myArray[index].x;
			}
		else
			{
			return myArray[index].y;
			}
		}

	/**
	 * Store the given item in this buffer.
	 * <P>
	 * The <TT>put()</TT> method must not block the calling thread; if it does,
	 * all message I/O in MP will be blocked.
	 *
	 * @param  i     Item index in the range 0 .. <TT>length()</TT>-1.
	 * @param  item  Item to be stored at index <TT>i</TT>.
	 */
	public void put
		(int i,
		 double item)
		{
		int index = myArrayOffset + (i >>> 1) * myStride;
		if ((i & 1) == 0)
			{
			myArray[index].x = item;
			}
		else
			{
			myArray[index].y = item;
			}
		}

	/**
	 * Copy items from the given buffer to this buffer. The number of items
	 * copied is this buffer's length or <TT>theSrc</TT>'s length, whichever is
	 * smaller.
	 *
	 * @param  theSrc  Source of items to copy into this buffer.
	 *
	 * @exception  ClassCastException
	 *     (unchecked exception) Thrown if <TT>theSrc</TT>'s item data type is
	 *     not the same as this buffer's item data type.
	 */
	public void copy
		(Buf theSrc)
		{
		if (theSrc == this)
			{
			}
		else if (theSrc instanceof Vector2DArrayDoubleBuf)
			{
			Vector2DArrayDoubleBuf src = (Vector2DArrayDoubleBuf) theSrc;
			if (src.myArray != this.myArray ||
						src.myArrayOffset > this.myArrayOffset)
				{
				int n = Math.min (src.myLength/2, this.myLength/2);
				int srcindex = src.myArrayOffset;
				int thisindex = this.myArrayOffset;
				for (int i = 0; i < n; ++ i)
					{
					this.myArray[thisindex].assign (src.myArray[srcindex]);
					srcindex += src.myStride;
					thisindex += this.myStride;
					}
				}
			else if (src.myArrayOffset < this.myArrayOffset)
				{
				int n = Math.min (src.myLength/2, this.myLength/2);
				int srcindex = src.myArrayOffset + (n-1) * src.myStride;
				int thisindex = this.myArrayOffset + (n-1) * this.myStride;
				for (int i = n-1; i >= 0; -- i)
					{
					this.myArray[thisindex].assign (src.myArray[srcindex]);
					srcindex -= src.myStride;
					thisindex -= this.myStride;
					}
				}
			}
		else
			{
			DoubleBuf.defaultCopy ((DoubleBuf) theSrc, this);
			}
		}

	/**
	 * Create a buffer for performing parallel reduction using the given binary
	 * operation. The results of the reduction are placed into this buffer.
	 * <P>
	 * <I>Note:</I> Class Vector2DArrayBuf does not support reduction. The
	 * <TT>getReductionBuf()</TT> method throws an
	 * UnsupportedOperationException.
	 *
	 * @param  op  Binary operation.
	 *
	 * @exception  ClassCastException
	 *     (unchecked exception) Thrown if this buffer's element data type and
	 *     the given binary operation's argument data type are not the same.
	 */
	public Buf getReductionBuf
		(Op op)
		{
		throw new UnsupportedOperationException();
		}

// Hidden operations.

	/**
	 * Send as many items as possible from this buffer to the given byte
	 * buffer.
	 * <P>
	 * The <TT>sendItems()</TT> method must not block the calling thread; if it
	 * does, all message I/O in MP will be blocked.
	 *
	 * @param  i       Index of first item to send, in the range 0 ..
	 *                 <TT>length</TT>-1.
	 * @param  buffer  Byte buffer.
	 *
	 * @return  Number of items sent.
	 */
	protected int sendItems
		(int i,
		 ByteBuffer buffer)
		{
		int index = myArrayOffset + (i >>> 1) * myStride;
		int off = i;
		while (off < myLength && buffer.remaining() >= 16)
			{
			Vector2D item = myArray[index];
			buffer.putDouble (item.x);
			buffer.putDouble (item.y);
			index += myStride;
			off += 2;
			}
		return off - i;
		}

	/**
	 * Receive as many items as possible from the given byte buffer to this
	 * buffer.
	 * <P>
	 * The <TT>receiveItems()</TT> method must not block the calling thread; if
	 * it does, all message I/O in MP will be blocked.
	 *
	 * @param  i       Index of first item to receive, in the range 0 ..
	 *                 <TT>length</TT>-1.
	 * @param  num     Maximum number of items to receive.
	 * @param  buffer  Byte buffer.
	 *
	 * @return  Number of items received.
	 */
	protected int receiveItems
		(int i,
		 int num,
		 ByteBuffer buffer)
		{
		int index = myArrayOffset + (i >>> 1) * myStride;
		int off = i;
		int max = Math.min (i + num, myLength);
		while (off < max && buffer.remaining() >= 16)
			{
			Vector2D item = myArray[index];
			item.x = buffer.getDouble();
			item.y = buffer.getDouble();
			index += myStride;
			off += 2;
			}
		return off - i;
		}

	}
