org.garret.perst
Class NullFile

java.lang.Object
  org.garret.perst.NullFile

All Implemented Interfaces:

IFile

public class NullFile
extends java.lang.Object
implements IFile

This implementation of IFile interface can be used to make Perst an main-memory database. It should be used when pagePoolSize is set to Storage.INFINITE_PAGE_POOL. In this case all pages are cached in memory and NullFile is used just as a stub.

NullFile should be used only when data is transient - i.e. it should not be saved between database sessions. If you need in-memory database but which provide data persistency, you should use normal file and infinite page pool size.

Constructor Summary

NullFile()

Method Summary

void	close() Close file
long	length() Length of the file
void	lock(boolean shared) Lock file
int	read(long pos, byte[] buf) Read data from the file
void	sync() Flush all fiels changes to the disk
boolean	tryLock(boolean shared) Try lock file
void	unlock() Unlock file
void	write(long pos, byte[] buf) Write data to the file

Methods inherited from class java.lang.Object

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

Constructor Detail

NullFile

public NullFile()

Method Detail

close

public void close()

Description copied from interface: IFile

Close file

Specified by:

close in interface IFile

length

public long length()

Description copied from interface: IFile

Length of the file

Specified by:

length in interface IFile

lock

public void lock(boolean shared)

Description copied from interface: IFile

Lock file

Specified by:

lock in interface IFile

Parameters:

shared - if lock is shared

read

public int read(long pos,
                byte[] buf)

Description copied from interface: IFile

Read data from the file

Specified by:

read in interface IFile

Parameters:

pos - offset in the file

buf - array to receive readen data (size is always equal to database page size)

Returns:

number of bytes actually readen

sync

public void sync()

Description copied from interface: IFile

Flush all fiels changes to the disk

Specified by:

sync in interface IFile

tryLock

public boolean tryLock(boolean shared)

Description copied from interface: IFile

Try lock file

Specified by:

tryLock in interface IFile

Parameters:

shared - if lock is shared

Returns:

true if file was successfully locked or locking in not implemented, false if file is locked by some other applciation

unlock

public void unlock()

Description copied from interface: IFile

Unlock file

Specified by:

unlock in interface IFile

write

public void write(long pos,
                  byte[] buf)

Description copied from interface: IFile

Write data to the file

Specified by:

write in interface IFile

Parameters:

pos - offset in the file

buf - array with data to be writter (size is always equal to database page size)