org.entityfs.util.base
Class EmptyRandomAccess

java.lang.Object
  org.entityfs.util.base.EmptyRandomAccess

All Implemented Interfaces:

DataSink, DataSource, RandomAccess

public class EmptyRandomAccess
extends Object
implements RandomAccess

This object represents a read-only, empty RandomAccess file.

Since:

1.0

Author:

Karl Gustafsson

Constructor Summary

EmptyRandomAccess()

Method Summary

void	addCloseObserver(RandomAccessCloseObserver raco) Add an observer that is notified when this RandomAccess is closed.
int	available() Returns an estimate of the number of bytes that can be read from this data source without blocking by the next invocation of a method for this data source.
void	close() Close the sink and free all resources associated with it.
void	flush() Flush changes made to the sink to the underlying storage.
long	getFilePointer() Get the current offset in the file.
RandomAccessMode	getMode() Get the mode that this RandomAccess was opened in.
long	length() Get the file's current length.
int	read() Read a byte of data from the source.
int	read(byte[] barr) Read up to b.length bytes of data from the source into the array.
int	read(byte[] barr, int off, int len) Read up to len bytes of data from the source into the array.
void	seek(long pos) Set the file pointer offset, measured from the beginning of the file.
void	setLength(long l) Set the length of the file.
long	skipBytes(long n) Attempt to skip over n bytes in the source.
void	write(byte[] barr) Write the contents of the array to the sink, starting at the current file pointer.
void	write(byte[] barr, int off, int len) Write len bytes from the array, starting at the offset off to this sink.
void	write(int b) Write a byte to the sink.

Methods inherited from class java.lang.Object

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

Constructor Detail

EmptyRandomAccess

public EmptyRandomAccess()

Method Detail

getFilePointer

public long getFilePointer()

Description copied from interface: RandomAccess

Get the current offset in the file.

Specified by:

getFilePointer in interface RandomAccess

Returns:

The offset from the beginning of the file.

available

public int available()

Description copied from interface: DataSource

Returns an estimate of the number of bytes that can be read from this data source without blocking by the next invocation of a method for this data source.

Specified by:

available in interface DataSource

Returns:

0, always.

See Also:

InputStream.available()

length

public long length()

Description copied from interface: RandomAccess

Get the file's current length.

Specified by:

length in interface RandomAccess

Returns:

0, always.

read

public int read()

Description copied from interface: DataSource

Read a byte of data from the source. The byte is returned as an integer in the range 0 to 255 (0x00-0x0ff).

Specified by:

read in interface DataSource

Returns:

-1, always.

read

public int read(byte[] barr)

Description copied from interface: DataSource

Read up to b.length bytes of data from the source into the array.

Specified by:

read in interface DataSource

Parameters:

barr - The byte array into which data is read.

Returns:

-1, always.

read

public int read(byte[] barr,
                int off,
                int len)

Description copied from interface: DataSource

Read up to len bytes of data from the source into the array.

Specified by:

read in interface DataSource

Parameters:

barr - The byte array into which data is read.

off - The start offset in the array b at which data is written.

len - The maximum number of bytes to read.

Returns:

-1, always.

seek

public void seek(long pos)

Description copied from interface: RandomAccess

Set the file pointer offset, measured from the beginning of the file. If the offset is set beyond the end of the file does not change the file length until something is written to it.

Specified by:

seek in interface RandomAccess

Parameters:

pos - The new file pointer offset, measured from the beginning of the file.

See Also:

DataSource.skipBytes(long)

setLength

public void setLength(long l)
               throws ReadOnlyException

Description copied from interface: RandomAccess

Set the length of the file.

If the present length of the file is greater than the l argument, the file will be truncated.

If the new length is bigger than the current length of the file, the file will be extended. The contents of the extended portion of the file are not defined.

The current file pointer is not changed, unless the file pointer offset is greater than the new file length. If so, it will be set to the new length.

Specified by:

setLength in interface RandomAccess

Parameters:

l - The new length of the file.

Throws:

ReadOnlyException - Always.

skipBytes

public long skipBytes(long n)

Description copied from interface: DataSource

Attempt to skip over n bytes in the source. If n is negative, no bytes are skipped.

The pointer in the source cannot be moved beyond EOF using this method (unlike RandomAccess.seek(long)).

Specified by:

skipBytes in interface DataSource

Parameters:

n - The number of bytes to increment the source pointer with.

Returns:

0, always

See Also:

RandomAccess.seek(long)

write

public void write(byte[] barr)
           throws ReadOnlyException

Description copied from interface: DataSink

Write the contents of the array to the sink, starting at the current file pointer.

Specified by:

write in interface DataSink

Parameters:

barr - The array to write.

Throws:

ReadOnlyException - Always.

write

public void write(byte[] barr,
                  int off,
                  int len)
           throws ReadOnlyException

Description copied from interface: DataSink

Write len bytes from the array, starting at the offset off to this sink.

Specified by:

write in interface DataSink

Parameters:

barr - The byte array.

off - The starting offset in the array.

len - The number of bytes to write.

Throws:

ReadOnlyException - Always.

write

public void write(int b)
           throws ReadOnlyException

Description copied from interface: DataSink

Write a byte to the sink.

Specified by:

write in interface DataSink

Parameters:

b - The byte to write.

Throws:

ReadOnlyException - Always.

flush

public void flush()
           throws ReadOnlyException

Description copied from interface: DataSink

Flush changes made to the sink to the underlying storage. This is optional to implement, but read only sinks should always throw ReadOnlyException.

Specified by:

flush in interface DataSink

Throws:

ReadOnlyException - Always.

close

public void close()

Description copied from interface: DataSink

Close the sink and free all resources associated with it. If the object is already closed, this method does nothing.

Specified by:

close in interface DataSink

Specified by:

close in interface DataSource

addCloseObserver

public void addCloseObserver(RandomAccessCloseObserver raco)

Description copied from interface: RandomAccess

Add an observer that is notified when this RandomAccess is closed. The observers are called just after the RandomAccess has been closed.

Specified by:

addCloseObserver in interface RandomAccess

Parameters:

raco - The observer.

getMode

public RandomAccessMode getMode()

Description copied from interface: RandomAccess

Get the mode that this RandomAccess was opened in.

This method does not throw an IllegalStateException if it is called after the RandomAccess has been closed.

Specified by:

getMode in interface RandomAccess

Returns:

The mode that this RandomAccess was opened in.