/**
 * edu.utexas.GeDBIT.mckoi.store.IOBufferedFile  27 Jan 2003
 *
 * Mckoi SQL Database ( http://www.mckoi.com/database )
 * Copyright (C) 2000, 2001, 2002  Diehl and Associates, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * Version 2 as published by the Free Software Foundation.
 *
 * This program 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 Version 2 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * Version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Change Log:
 * 2005.05.24: Two lines added to compute length of time to read pages in from disk, by Willard
 * 
 */

package GeDBIT.mckoi.store;

import java.io.RandomAccessFile;
import java.io.IOException;

/**
 * An implementation of AbstractBufferedFile that implements a paging strategy
 * that copies pages from the underlying RandomAccessFile into byte[] arrays in
 * memeory.
 * 
 * @author Tobias Downer
 */

class IOBufferedFile extends AbstractBufferedFile {

    /**
     * The constructor.
     */
    public IOBufferedFile(int unique_id, RandomAccessFile file,
	    BufferManager manager) {
	super(unique_id, file, manager);
    }

    // ---------- Implemented from AbstractBufferedFile ----------

    public PageBuffer createPageFor(long position, int len) {
	return new IOPageBuffer(position, len);
    }

    public void sizeChange(long old_size, long new_size) throws IOException {
	// This doesn't need to do anything for this implementation.
    }

    // ---------- Inner classes ----------

    /**
     * This implementation of a page buffer initializes the page by reading the
     * page into a byte[] array in memory.
     */
    class IOPageBuffer extends PageBuffer {

	private long position;
	private int length;
	private byte[] buf;

	public IOPageBuffer(long position, int length) {
	    this.position = position;
	    this.length = length;
	}

	public void initImpl() throws IOException {
	    buf = new byte[length];
	    synchronized (file) {
		// added by Willard 2005.05.24 to compute statistics on how long
		// it takes to read a page in from disk
		buffer_manager.addTime(System.currentTimeMillis());
		// Read the page from the file into memory.
		file.seek(position);
		file.read(buf, 0, length);
		// added by Willard 2005.05.24 to compute statistics on how long
		// it takes to read a page in from disk
		buffer_manager.addTime(System.currentTimeMillis());
	    }
	}

	public byte readImpl(int position) {
	    return buf[position];
	}

	public void readImpl(int position, byte[] b, int off, int len) {
	    System.arraycopy(buf, position, b, off, len);
	}

	public void writeImpl(int position, byte b) {
	    buf[position] = b;
	}

	public void writeImpl(int position, byte[] b, int off, int len) {
	    System.arraycopy(b, off, buf, position, len);
	}

	public void flushImpl(int p1, int p2) throws IOException {
	    synchronized (file) {
		// Read the page from the file into memory.
		file.seek(position + p1);
		file.write(buf, p1, p2 - p1);
	    }
	}

	public void disposeImpl() {
	    buf = null;
	}

    }

}