com.unister.semweb.drums.file
Class AbstractHeaderFile

java.lang.Object
  com.unister.semweb.drums.file.AbstractHeaderFile

Direct Known Subclasses:

HeaderIndexFile

public abstract class AbstractHeaderFile
extends java.lang.Object

Header structure:

+-----------+--------------+---------------+---------------+
| FILE SIZE | FILLED UP TO | ............. | ............. |
| 8 bytes . | 8 bytes .... | ............. | ............. |
+-----------+--------------+---------------+---------------+
= 1024 bytes (to have enough space for more values)

To use this class correctly, have a look at the following methods:

read(long offset, ByteBuffer destBuffer)

write(long offset, ByteBuffer sourceBuffer)

append(ByteBuffer sourceBuffer)

dbfile.getFilledUpToExclHeader()

Author:

Martin Nettling

Nested Class Summary

static class

AbstractHeaderFile.AccessMode The possible AccessModes.

Field Summary

int	DEFAULT_SIZE the Default size of a file. (16MB)
static int	HEADER_SIZE the size of the header
java.io.File	osFile the file to access
int	RETRY_CONNECT_WAITTIME the time to wait for a retry if a file is locked

Constructor Summary

AbstractHeaderFile()

Method Summary

abstract long	append(byte[] sourceBuffer) appends the given sourceBuffer to the file and returns the file position of the appended entry
abstract long	append(java.nio.ByteBuffer sourceBuffer) appends the given sourceBuffer to the file and returns the file position of the appended entry
void	clear() sets the start of the content to zero
void	close() closes all open channels and the file
void	delete() tries to delete the file
abstract void	enlargeFile(long size) enlarges the file by the given size
long	getFilledUpFromContentStart()
long	getFilledUpTo()
long	getFreeSpace()
java.lang.String	getName()
long	getRemainingBytes(long offset) returns the remaining bytes between filledUpTo and the given offset
boolean	isOpen()
void	lock() tries to lock the file
void	openChannel() opens the RandomAccessFile and the corresponding FileChannel.
abstract int	read(long offset, byte[] destBuffer) Reads x bytes from the file to the given byte array, where x is the minimum of the size of the given byte array and the remaining written bytes in the file.
abstract int	read(long offset, java.nio.ByteBuffer destBuffer) Reads x bytes from the file to the given ByteBuffer, where x is the minimum of the capacity of the buffer and the remaining written bytes in the file.
void	unlock() tries to unlock the file
abstract void	write(long offset, byte[] sourceBuffer) writes the bytes from the given Byte-array to the file beginning at offset.
abstract void	write(long offset, java.nio.ByteBuffer sourceBuffer) writes the bytes from the given ByteBuffer to the file beginning at offset.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_SIZE

public final int DEFAULT_SIZE

the Default size of a file. (16MB)

See Also:

Constant Field Values

RETRY_CONNECT_WAITTIME

public final int RETRY_CONNECT_WAITTIME

the time to wait for a retry if a file is locked

See Also:

Constant Field Values

HEADER_SIZE

public static final int HEADER_SIZE

the size of the header

See Also:

Constant Field Values

osFile

public java.io.File osFile

the file to access

Constructor Detail

AbstractHeaderFile

public AbstractHeaderFile()

Method Detail

enlargeFile

public abstract void enlargeFile(long size)
                          throws java.io.IOException

enlarges the file by the given size

Parameters:

size -

Throws:

java.io.IOException

write

public abstract void write(long offset,
                           java.nio.ByteBuffer sourceBuffer)
                    throws java.io.IOException

writes the bytes from the given ByteBuffer to the file beginning at offset.

Parameters:

offset -

sourceBuffer -

Throws:

java.io.IOException

write

public abstract void write(long offset,
                           byte[] sourceBuffer)
                    throws java.io.IOException

writes the bytes from the given Byte-array to the file beginning at offset.

Parameters:

offset -

sourceBuffer -

Throws:

java.io.IOException

append

public abstract long append(byte[] sourceBuffer)
                     throws java.io.IOException

appends the given sourceBuffer to the file and returns the file position of the appended entry

Parameters:

sourceBuffer -

Returns:

the position in the file after inserting the given sourceBuffer

Throws:

java.io.IOException

append

public abstract long append(java.nio.ByteBuffer sourceBuffer)
                     throws java.io.IOException

appends the given sourceBuffer to the file and returns the file position of the appended entry

Parameters:

sourceBuffer -

Returns:

the position in the file after inserting the given sourceBuffer

Throws:

java.io.IOException

read

public abstract int read(long offset,
                         java.nio.ByteBuffer destBuffer)
                  throws java.io.IOException

Reads x bytes from the file to the given ByteBuffer, where x is the minimum of the capacity of the buffer and the remaining written bytes in the file.

Parameters:

offset -

destBuffer -

Returns:

the number of bytes read

Throws:

java.io.IOException

read

public abstract int read(long offset,
                         byte[] destBuffer)
                  throws java.io.IOException

Reads x bytes from the file to the given byte array, where x is the minimum of the size of the given byte array and the remaining written bytes in the file.

Parameters:

offset -

destBuffer -

Returns:

the number of bytes read

Throws:

java.io.IOException

getRemainingBytes

public long getRemainingBytes(long offset)

returns the remaining bytes between filledUpTo and the given offset

Parameters:

offset -

Returns:

long

clear

public void clear()

sets the start of the content to zero

getFilledUpFromContentStart

public long getFilledUpFromContentStart()

Returns:

the offset in bytes, to where the file is filled

getFilledUpTo

public long getFilledUpTo()

Returns:

the offset in bytes, to where the file is filled

getFreeSpace

public long getFreeSpace()

Returns:

the number of available bytes

openChannel

public void openChannel()
                 throws FileLockException,
                        java.io.IOException

opens the RandomAccessFile and the corresponding FileChannel. Reads the header.

Throws:

FileLockException

java.io.IOException

unlock

public void unlock()
            throws java.io.IOException

tries to unlock the file

Throws:

java.io.IOException

lock

public void lock()
          throws FileLockException,
                 java.io.IOException

tries to lock the file

Throws:

FileLockException

java.io.IOException

isOpen

public boolean isOpen()

Returns:

true, if there is access to the file

close

public void close()

closes all open channels and the file

delete

public void delete()
            throws java.io.IOException

tries to delete the file

Throws:

java.io.IOException

getName

public java.lang.String getName()

Returns:

the name of the underlying OS-File