channelmanager.java

支持并发访问的B+树

/*
 * Created on Nov 19, 2004
 *
 * TODO To change the template for this generated file go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
package com.nay0648.ds.bplustree;
import java.io.*;
import java.nio.channels.*;

/**
 * 
 * @author nay0648
 *
 * this is used to manage file channle.all file operation to the B+ tree
 * get the file channel by this class
 */
class ChannelManager
{
private static final String FILE_OPEN_MODE="rw";//open tree file in rw mode
private String path;

	/**
	 * @param path the tree file path
	 */
	public ChannelManager(String path)
	{
		this.path=path;
	}
	
	/**
	 * get a new channel of the tree file
	 * @return return null if field
	 */
	public FileChannel getChannel()
	{
		FileChannel ch=null;
		
		try
		{
			ch=(new RandomAccessFile(path,FILE_OPEN_MODE)).getChannel();
		}
		catch(IOException exc)
		{
			exc.printStackTrace();
		}
		return ch;
	}
	
	/**
	 * recycle a channel
	 * @param ch the channel of the tree file
	 */
	public void recycle(Channel ch)
	{
		try
		{
			if(ch.isOpen()) ch.close();
		}
		catch(IOException exc)
		{
			exc.printStackTrace();
		}
	}

	/*
	public static void main(String[] args)
	{}
	*/
}