filebackedseekableiodevice.java

JPC: x86 PC Hardware Emulator. 牛津大学开发的一个纯JAVA的x86系统结构硬件模拟器。

/*
    JPC: A x86 PC Hardware Emulator for a pure Java Virtual Machine
    Release Version 2.0

    A project from the Physics Dept, The University of Oxford

    Copyright (C) 2007 Isis Innovation Limited

    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 for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
    Details (including contact information) can be found at: 

    www.physics.ox.ac.uk/jpc
*/

package org.jpc.support;

import java.io.*;

public class FileBackedSeekableIODevice implements SeekableIODevice
{
    private String fileName;
    private RandomAccessFile image;

    private boolean readOnly;

    public FileBackedSeekableIODevice()
    {
    }

    public void configure(String spec)
    {
	fileName = spec;
	
	try 
        {
	    image = new RandomAccessFile(spec, "rw");
	    readOnly = false;
	} 
        catch (IOException first) 
        {
	    try 
            {
		image = new RandomAccessFile(spec, "r");
		readOnly = true;
		System.err.println("Opened " + spec + " as read only");	    
	    } 
            catch (IOException last) 
            {
		System.err.println("Failed Opening Floppy Image");
		image = null;
		readOnly = false;
	    }
	}
    }

    public FileBackedSeekableIODevice(String file)
    {
       fileName = file;

	try 
        {
	    image = new RandomAccessFile(file, "rw");
	    readOnly = false;
	} 
        catch (IOException first) 
        {
	    try 
            {
		image = new RandomAccessFile(file, "r");
		readOnly = true;
		System.err.println("Opened " + file + " as read only");	    
	    } 
            catch (IOException last) 
            {
		System.err.println("Failed Opening Floppy Image");
		image = null;
		readOnly = false;
	    }
	}
    }

    public void seek(int offset) throws IOException
    {
        image.seek(offset);
    }

    public int write(byte[] data, int offset, int length) throws IOException
    {
        image.write(data, offset, length);
        return length;
    }

    public int read(byte[] data, int offset, int length) throws IOException
    {
        return image.read(data, offset, length);
    }

    public int length()
    {
        try
        {
            return (int) image.length();
        }
        catch (Exception e)
        {
            return -1;
        }
    }

    public boolean readOnly()
    {
	return readOnly;
    }

    public String toString()
    {
        return fileName;
    }
}