com.faunos.util.io
Class SubFileChannel

java.lang.Object
  java.nio.channels.spi.AbstractInterruptibleChannel
      java.nio.channels.FileChannel
          com.faunos.util.io.FilterFileChannel
              com.faunos.util.io.CloseProtectedFileChannel
                  com.faunos.util.io.SubFileChannel

All Implemented Interfaces:

Closeable, ByteChannel, Channel, GatheringByteChannel, InterruptibleChannel, ReadableByteChannel, ScatteringByteChannel, WritableByteChannel

public class SubFileChannel
extends CloseProtectedFileChannel

A view of a region of an underlying FileChannel. The position of the this view is independent of that of the underlying FileChannel, except for the case involving truncation.

Access modes

Three access modes are supported. They are

1. READ_ONLY. The instance can only read from the channel.
2. BOUNDED_UPDATE. The instance can read and write to the channel, but may not change the file size.
3. WRITE. The instance can read and write to to the channel, may grow the file size, or alternatively truncate it. This is the least protected view of the underlying FileChannel.

Author:

Babak Farhang

Nested Class Summary

static class

SubFileChannel.AccessMode Defines the access modes supported by SubFileChannel.

Nested classes/interfaces inherited from class com.faunos.util.io.FilterFileChannel

FilterFileChannel.FilterFileLock

Nested classes/interfaces inherited from class java.nio.channels.FileChannel

FileChannel.MapMode

Field Summary

Fields inherited from class com.faunos.util.io.FilterFileChannel

inner

Constructor Summary

SubFileChannel(FileChannel file, SubFileChannel.AccessMode mode, long startPosition, long endPosition)
Creates a new instance with the specified underlying file channel, access mode, and view boundaries.

Method Summary

protected void	checkAccess() Checks that the instance has read access.
protected void	checkWriteAccess() Checks that the instance has write access.
void	force(boolean metaData)
protected FilterFileChannel.FilterFileLock	implCreateFileLock(FileLock innerLock) Creates and returns a position-shifted FileLock.
FileLock	lock(long position, long size, boolean shared)
MappedByteBuffer	map(FileChannel.MapMode mode, long position, long size)
static SubFileChannel	newReadOnlyView(FileChannel file, long startPosition, long endPosition)
long	position()
FileChannel	position(long newPosition)
int	read(ByteBuffer dst)
long	read(ByteBuffer[] dsts, int offset, int length)
int	read(ByteBuffer dst, long position)
long	size()
long	transferFrom(ReadableByteChannel src, long position, long count)
long	transferTo(long position, long count, WritableByteChannel target)
FileChannel	truncate(long size)
FileLock	tryLock(long position, long size, boolean shared)
int	write(ByteBuffer src)
long	write(ByteBuffer[] srcs, int offset, int length)
int	write(ByteBuffer src, long position)

Methods inherited from class com.faunos.util.io.CloseProtectedFileChannel

implCloseChannel

Methods inherited from class com.faunos.util.io.FilterFileChannel

checkReadAccess

Methods inherited from class java.nio.channels.FileChannel

lock, read, tryLock, write

Methods inherited from class java.nio.channels.spi.AbstractInterruptibleChannel

begin, close, end, isOpen

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.nio.channels.Channel

close, isOpen

Methods inherited from interface java.nio.channels.Channel

close, isOpen

Methods inherited from interface java.nio.channels.Channel

close, isOpen

Methods inherited from interface java.nio.channels.Channel

close, isOpen

Constructor Detail

SubFileChannel

public SubFileChannel(FileChannel file,
                      SubFileChannel.AccessMode mode,
                      long startPosition,
                      long endPosition)
               throws IOException

Creates a new instance with the specified underlying file channel, access mode, and view boundaries.

Parameters:

startPosition - the lower bounds of the view

endPosition - the upper bounds of the view

Throws:

IOException

Method Detail

newReadOnlyView

public static SubFileChannel newReadOnlyView(FileChannel file,
                                             long startPosition,
                                             long endPosition)
                                      throws IOException

Throws:

IOException

force

public void force(boolean metaData)
           throws IOException

Overrides:

force in class FilterFileChannel

Throws:

IOException

lock

public FileLock lock(long position,
                     long size,
                     boolean shared)
              throws IOException

Overrides:

lock in class FilterFileChannel

Throws:

IOException

map

public MappedByteBuffer map(FileChannel.MapMode mode,
                            long position,
                            long size)
                     throws IOException

Overrides:

map in class FilterFileChannel

Throws:

IOException

position

public long position()
              throws IOException

Overrides:

position in class FilterFileChannel

Throws:

IOException

position

public FileChannel position(long newPosition)
                     throws IOException

Overrides:

position in class FilterFileChannel

Throws:

IOException

read

public int read(ByteBuffer dst,
                long position)
         throws IOException

Overrides:

read in class FilterFileChannel

Throws:

IOException

read

public int read(ByteBuffer dst)
         throws IOException

Specified by:

read in interface ReadableByteChannel

Overrides:

read in class FilterFileChannel

Throws:

IOException

read

public long read(ByteBuffer[] dsts,
                 int offset,
                 int length)
          throws IOException

Specified by:

read in interface ScatteringByteChannel

Overrides:

read in class FilterFileChannel

Throws:

IOException

size

public long size()
          throws IOException

Overrides:

size in class FilterFileChannel

Throws:

IOException

transferFrom

public long transferFrom(ReadableByteChannel src,
                         long position,
                         long count)
                  throws IOException

Overrides:

transferFrom in class FilterFileChannel

Throws:

IOException

transferTo

public long transferTo(long position,
                       long count,
                       WritableByteChannel target)
                throws IOException

Overrides:

transferTo in class FilterFileChannel

Throws:

IOException

truncate

public FileChannel truncate(long size)
                     throws IOException

Overrides:

truncate in class FilterFileChannel

Throws:

IOException

tryLock

public FileLock tryLock(long position,
                        long size,
                        boolean shared)
                 throws IOException

Overrides:

tryLock in class FilterFileChannel

Throws:

IOException

write

public int write(ByteBuffer src,
                 long position)
          throws IOException

Overrides:

write in class FilterFileChannel

Throws:

IOException

write

public int write(ByteBuffer src)
          throws IOException

Specified by:

write in interface WritableByteChannel

Overrides:

write in class FilterFileChannel

Throws:

IOException

write

public long write(ByteBuffer[] srcs,
                  int offset,
                  int length)
           throws IOException

Specified by:

write in interface GatheringByteChannel

Overrides:

write in class FilterFileChannel

Throws:

IOException

implCreateFileLock

protected FilterFileChannel.FilterFileLock implCreateFileLock(FileLock innerLock)
                                                       throws IOException

Creates and returns a position-shifted FileLock.

Overrides:

implCreateFileLock in class FilterFileChannel

Throws:

IOException

checkWriteAccess

protected void checkWriteAccess()
                         throws IOException

Checks that the instance has write access. Called on methods that may attempt to change the contents of the channel.

This implementation simply checks that the access mode at instantiation was not SubFileChannel.AccessMode.READ_ONLY; o.w. an java.io.IOException is thrown.

Overrides:

checkWriteAccess in class FilterFileChannel

Throws:

IOException

checkAccess

protected void checkAccess()
                    throws IOException

Checks that the instance has read access. Called on methods that attempt to read from the channel. The base implementation does nothing.

Subclasses overriding this method should ensure that if an instance has write access (checkWriteAccess() does not throw an exception), then it also has read access.

Throws:

IOException - thrown if the instance does not have read access