org.apache.jena.dboe.base.file

Interface BufferChannel

All Superinterfaces:

org.apache.jena.atlas.lib.Closeable, org.apache.jena.atlas.lib.Sync

All Known Implementing Classes:

BufferChannelFile, BufferChannelMem

public interface BufferChannel
extends org.apache.jena.atlas.lib.Sync, org.apache.jena.atlas.lib.Closeable

Interface to storage : a simplified version of FileChannel. Read and write bytes, passed via ByteBuffers, addressed by file location. This interface is not suitable for memory mapped I/O - there is no ability to use slices of a memory mapped file. This interface does not insert size of ByteBuffer, the size of ByteBuffer passed to read controls the number of bytes read. Having our own abstraction enables us to implement memory-backed versions.

See Also:

BlockAccess, FileChannel

Method Summary

Modifier and Type	Method and Description
BufferChannel	duplicate() Return another channel to the same storage but with independent position.
String	getFilename() Filename for this BufferChannel (maybe null)
String	getLabel() useful display string
boolean	isEmpty() Is it empty?
long	position() return the position
void	position(long pos) set the position
int	read(ByteBuffer buffer) Read into a ByteBuffer.
int	read(ByteBuffer buffer, long loc) Read into a ByteBuffer, starting at position loc.
long	size() Length of storage, in bytes.
void	truncate(long size) Truncate the file.
int	write(ByteBuffer buffer) Write from ByteBuffer, starting at the current position.
int	write(ByteBuffer buffer, long loc) Write from ByteBuffer, starting at position loc.

Methods inherited from interface org.apache.jena.atlas.lib.Sync

sync

Methods inherited from interface org.apache.jena.atlas.lib.Closeable

close

Method Detail

duplicate

BufferChannel duplicate()

Return another channel to the same storage but with independent position. Chaos may result due to concurrent use.

position

long position()

return the position

position

void position(long pos)

set the position

read

int read(ByteBuffer buffer)

Read into a ByteBuffer. Returns the number of bytes read. -1 for end of file.

read

int read(ByteBuffer buffer,
         long loc)

Read into a ByteBuffer, starting at position loc. Return the number of bytes read. loc must be within the file.

write

int write(ByteBuffer buffer)

Write from ByteBuffer, starting at the current position. Return the number of bytes written

write

int write(ByteBuffer buffer,
          long loc)

Write from ByteBuffer, starting at position loc. Return the number of bytes written. loc must be within 0 to length - writing at length is append

truncate

void truncate(long size)

Truncate the file.

See Also:

FileChannel.truncate(long)

size

long size()

Length of storage, in bytes.

isEmpty

boolean isEmpty()

Is it empty?

getLabel

String getLabel()

useful display string

getFilename

String getFilename()

Filename for this BufferChannel (maybe null)