Class BaseFileSystem

java.lang.Object
  BaseFileSystem

public class BaseFileSystem

extends java.lang.Object

A BaseFileSystem represents a low-level file system in which files are referenced by file number. This is intended as a general low-level file system interface that could be implemented for many different file system structures. In UNIX, inode numbers play the role of file numbers.

Field Summary

private java.util.BitSet	allBits allBits is a bit set of all valid file numbers.
private int	capacity capacity is the number of files in this base file system.
private java.util.List	files files is the list of file accessors for this base file system.
private java.util.BitSet	freeBits freeBits is a bit set of the file numbers that are not in use.
private java.lang.String	name name is the name of this base file system.
static int	NO_FILE BaseFileSystem.NO_FILE is the file number for nonexistent files.

Constructor Summary

private	BaseFileSystem() This constructor is disabled.
	BaseFileSystem(java.lang.String nm, int cap) new BaseFileSystem(nm, cap) returns a new base file system with a capacity of cap files.

Method Summary

int	create(File f) fs.create(f) returns the file number assigned to a new file f.
int	delete(int fn) fs.delete(fn) removes the file with file number fn from fs and returns fn.
java.util.Iterator	files() fs.files() returns an iterator for the files in fs.
java.lang.String	fileSet() fs.fileSet() returns a string describing the set of files in fs.
int	getCapacity() fs.getCapacity() returns the maximum number of files for fs.
java.lang.String	getName() fs.getName() returns the file system name of fs as a string.
static void	main(java.lang.String[] args) main(args) is a test program for the BaseFileSystem class.
File	open(int fn) fs.open(fn) returns an accessor for the file with file number fn, or null if there is no such file.
java.lang.String	toString() fs.toString() returns the class name and file system name of fs as a string.

Methods inherited from class java.lang.Object

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

Field Detail

NO_FILE

public static final int NO_FILE

BaseFileSystem.NO_FILE is the file number for nonexistent files.

See Also:

Constant Field Values

name

private java.lang.String name

name is the name of this base file system.

capacity

private int capacity

capacity is the number of files in this base file system.

files

private java.util.List files

files is the list of file accessors for this base file system. Here, the simulation departs from reality. In a real file system, file accessors are constructed as needed.

allBits

private java.util.BitSet allBits

allBits is a bit set of all valid file numbers.

freeBits

private java.util.BitSet freeBits

freeBits is a bit set of the file numbers that are not in use.

Constructor Detail

BaseFileSystem

private BaseFileSystem()

This constructor is disabled.

BaseFileSystem

public BaseFileSystem(java.lang.String nm,
                      int cap)

new BaseFileSystem(nm, cap) returns a new base file system with a capacity of cap files.

Method Detail

create

public int create(File f)

fs.create(f) returns the file number assigned to a new file f. If there is no space in fs for a new file then the return value is File.NULL;

delete

public int delete(int fn)

fs.delete(fn) removes the file with file number fn from fs and returns fn. If there is no such file then no action is taken and File.NULL is returned.

open

public File open(int fn)

fs.open(fn) returns an accessor for the file with file number fn, or null if there is no such file.

getCapacity

public int getCapacity()

fs.getCapacity() returns the maximum number of files for fs.

files

public java.util.Iterator files()

fs.files() returns an iterator for the files in fs.

fileSet

public java.lang.String fileSet()

fs.fileSet() returns a string describing the set of files in fs.

getName

public java.lang.String getName()

fs.getName() returns the file system name of fs as a string.

toString

public java.lang.String toString()

fs.toString() returns the class name and file system name of fs as a string.

main

public static void main(java.lang.String[] args)

main(args) is a test program for the BaseFileSystem class.