java.io
Class File

java.lang.Object
  java.io.File

public class File
extends Object

Implements a file system using pages of flash memory. Currently has limited functionality and only supports one file open at a time.

Author:

Brian Bagnall

Field Summary

static byte	MAX_FILES Number of files the file system can store.
static byte	totalFiles The total number of files in the file system.

Constructor Summary

File(String name)
Creates a new File object.

Method Summary

boolean	canRead()
boolean	canWrite()
boolean	createNewFile() Creates a new file entry in the flash memory.
static void	defrag() Defrag the file system.
boolean	delete() Deletes the file represented by this File object.
void	exec() If the file is a binary executable, begins running it.
boolean	exists() Indicates if the file exists in the flash memory.
static void	format() Essentially formats the file system by writing TABLE_ID characters to the first page of flash memory.
static int	freeMemory() Returns to total free memory in the flash file system.
int	getIndex() Returns location of file in the files[] array
String	getName() Returns the name of the file.
int	getPage() Internal method used to get the page number of the start of the file.
boolean	isHidden()
long	length() Returns the length of the file denoted by this file name.
static File[]	listFiles() Returns a list of files in the flash file system.
void	moveToTop() Move the file to become the last one in flash memory.
static void	reset() Reset the files array after an error.
boolean	setReadOnly()

Methods inherited from class java.lang.Object

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

Field Detail

MAX_FILES

public static final byte MAX_FILES

Number of files the file system can store. Defines the size of the files array. If leJOS gets a garbage collector we can get rid of this limitation.

See Also:

Constant Field Values

totalFiles

public static byte totalFiles

The total number of files in the file system. A negative value indicates this variable has not been initialized. Using byte, but if we expand past the 30 limit (garbage collector) we can use short.

Constructor Detail

File

public File(String name)

Creates a new File object. If this file exists on disk it will represent that file. If the file does not exist, you will need to use createNewFile() before writing to the file.

Parameters:

name -

Method Detail

delete

public boolean delete()

Deletes the file represented by this File object.

Returns:

true if the file is successfully deleted; false otherwise

exec

public void exec()

If the file is a binary executable, begins running it.

listFiles

public static File[] listFiles()

Returns a list of files in the flash file system. Because there are no directories, this is a static method in leJOS NXJ. The order of the files in the array goes from oldest (0) to newest (highest index array).

Returns:

An array of File objects representing files in the file system. The array will be empty if the directory is empty.

getName

public String getName()

Returns the name of the file.

Returns:

The name of the file, including the file extension. e.g. "mapdata.txt"

length

public long length()

Returns the length of the file denoted by this file name.

Returns:

The length, in bytes, of the file denoted by this file name, or 0 if the file does not exist.

exists

public boolean exists()

Indicates if the file exists in the flash memory.

Returns:

True indicates the file exists, false means it has not been created.

canRead

public boolean canRead()

canWrite

public boolean canWrite()

isHidden

public boolean isHidden()

setReadOnly

public boolean setReadOnly()

format

public static void format()

Essentially formats the file system by writing TABLE_ID characters to the first page of flash memory. Also writes 0 as the number of files in the file system, so it can be used to restart/erase all files.

createNewFile

public boolean createNewFile()
                      throws IOException

Creates a new file entry in the flash memory.

Returns:

True indicates file was created in flash. False means it already existed or the size is 0 or less.

Throws:

IOException

moveToTop

public void moveToTop()
               throws IOException

Move the file to become the last one in flash memory.

Throws:

IOException

freeMemory

public static int freeMemory()

Returns to total free memory in the flash file system.

getIndex

public int getIndex()

Returns location of file in the files[] array

Returns:

index of file in files[]

defrag

public static void defrag()
                   throws IOException

Defrag the file system. WARNING: should only be called from the startup menu. If called from a user program, can cause the current program to be moved resulting in a data abort of other firmware crash. Assumptions: the files[] array has no nulls, and is in increasing order by page_location. This scheme moves moves each file down to fill in the empty pages.

Throws:

IOException

getPage

public int getPage()

Internal method used to get the page number of the start of the file.

Returns:

page number

reset

public static void reset()

Reset the files array after an error. Forces listFiles to read from the file table.