//******************************************************************************
//
// File:    SharedLongArrayBuf.java
// Package: edu.rit.mp.buf
// Unit:    Class edu.rit.mp.buf.SharedLongArrayBuf
//
// 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.
//
// 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.mp.buf;

import edu.rit.mp.Buf;
import edu.rit.mp.LongBuf;

import edu.rit.pj.reduction.LongOp;
import edu.rit.pj.reduction.Op;
import edu.rit.pj.reduction.SharedLongArray;

import edu.rit.util.Range;

import java.nio.ByteBuffer;

/**
 * Class SharedLongArrayBuf provides a buffer for a multiple thread safe
 * array of long items sent or received using the Message Protocol (MP).
 * The array element stride may be 1 or greater than 1. While an instance of
 * class SharedLongArrayBuf may be constructed directly, normally you will
 * use a factory method in class {@linkplain edu.rit.mp.LongBuf
 * LongBuf}. See that class for further information.
 *
 * @author  Alan Kaminsky
 * @version 26-Oct-2007
 */
public class SharedLongArrayBuf
	extends LongBuf
	{

// Hidden data members.

	SharedLongArray myArray;
	Range myRange;
	int myArrayOffset;
	int myStride;

// Exported constructors.

	/**
	 * Construct a new shared long array buffer.
	 *
	 * @param  theArray  Shared array.
	 * @param  theRange  Range of array elements to include in the buffer.
	 */
	public SharedLongArrayBuf
		(SharedLongArray theArray,
		 Range theRange)
		{
		super (theRange.length());
		myArray = theArray;
		myRange = theRange;
		myArrayOffset = theRange.lb();
		myStride = theRange.stride();
		}

// Exported operations.

	/**
	 * Obtain the given item from this buffer.
	 * 

	 * The get() 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 .. length()-1.
	 *
	 * @return  Item at index i.
	 */
	public long get
		(int i)
		{
		return myArray.get (myArrayOffset+i*myStride);
		}

	/**
	 * Store the given item in this buffer.
	 * 

	 * The put() 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 .. length()-1.
	 * @param  item  Item to be stored at index i.
	 */
	public void put
		(int i,
		 long item)
		{
		myArray.set (myArrayOffset+i*myStride, item);
		}

	/**
	 * Create a buffer for performing parallel reduction using the given binary
	 * operation. The results of the reduction are placed into this buffer.
	 *
	 * @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)
		{
		return new SharedLongArrayReductionBuf
			(myArray, myRange, (LongOp) op);
		}

// Hidden operations.

	/**
	 * Send as many items as possible from this buffer to the given byte
	 * buffer.
	 * 

	 * The sendItems() 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 ..
	 *                 length-1.
	 * @param  buffer  Byte buffer.
	 *
	 * @return  Number of items sent.
	 */
	protected int sendItems
		(int i,
		 ByteBuffer buffer)
		{
		int index = i;
		int off = myArrayOffset + i * myStride;
		while (index < myLength && buffer.remaining() >= 8)
			{
			buffer.putLong (myArray.get (off));
			++ index;
			off += myStride;
			}
		return index - i;
		}

	/**
	 * Receive as many items as possible from the given byte buffer to this
	 * buffer.
	 * 

	 * The receiveItems() 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 ..
	 *                 length-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 = i;
		int off = myArrayOffset + i * myStride;
		int max = Math.min (i + num, myLength);
		while (index < max && buffer.remaining() >= 8)
			{
			myArray.set (off, buffer.getLong());
			++ index;
			off += myStride;
			}
		return index - i;
		}

	}