nachos.machine
Class OpenFileWithPosition

java.lang.Object
  nachos.machine.OpenFile
      nachos.machine.OpenFileWithPosition

Direct Known Subclasses:

ArrayFile

public abstract class OpenFileWithPosition
extends OpenFile

An OpenFile that maintains a current file position.

Field Summary

protected int

position The current value of the file pointer.

Constructor Summary

OpenFileWithPosition()
Allocate a new unnamed OpenFileWithPosition that is not associated with any file system.

OpenFileWithPosition(FileSystem fileSystem, String name)
Allocate a new OpenFileWithPosition with the specified name on the specified file system.

Method Summary

int	read(byte[] buf, int offset, int length) Read this file starting at the current file pointer and return the number of bytes successfully read.
void	seek(int position) Set the value of the current file pointer.
int	tell() Get the value of the current file pointer, or -1 if this file has no pointer.
int	write(byte[] buf, int offset, int length) Write this file starting at the current file pointer and return the number of bytes successfully written.

Methods inherited from class nachos.machine.OpenFile

close, getFileSystem, getName, length, read, write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

position

protected int position

The current value of the file pointer.

Constructor Detail

OpenFileWithPosition

public OpenFileWithPosition(FileSystem fileSystem,
                            String name)

Allocate a new OpenFileWithPosition with the specified name on the specified file system.

Parameters:

fileSystem - the file system to which this file belongs.

name - the name of the file, on that file system.

OpenFileWithPosition

public OpenFileWithPosition()

Allocate a new unnamed OpenFileWithPosition that is not associated with any file system.

Method Detail

seek

public void seek(int position)

Description copied from class: OpenFile

Set the value of the current file pointer.

Overrides:

seek in class OpenFile

tell

public int tell()

Description copied from class: OpenFile

Get the value of the current file pointer, or -1 if this file has no pointer.

Overrides:

tell in class OpenFile

read

public int read(byte[] buf,
                int offset,
                int length)

Description copied from class: OpenFile

Read this file starting at the current file pointer and return the number of bytes successfully read. Advances the file pointer by this amount. If no bytes could be* read because of a fatal error, returns -1.

Overrides:

read in class OpenFile

Parameters:

buf - the buffer to store the bytes in.

offset - the offset in the buffer to start storing bytes.

length - the number of bytes to read.

Returns:

the actual number of bytes successfully read, or -1 on failure.

write

public int write(byte[] buf,
                 int offset,
                 int length)

Description copied from class: OpenFile

Write this file starting at the current file pointer and return the number of bytes successfully written. Advances the file pointer by this amount. If no bytes could be written because of a fatal error, returns -1.

Overrides:

write in class OpenFile

Parameters:

buf - the buffer to get the bytes from.

offset - the offset in the buffer to start getting.

length - the number of bytes to write.

Returns:

the actual number of bytes successfully written, or -1 on failure.