org.basex.io
Class DataAccess

java.lang.Object
  org.basex.io.DataAccess

public final class DataAccess
extends Object

This class allows positional read and write access to a database file.

Author:

Workgroup DBIS, University of Konstanz 2005-10, ISC License, Christian Gruen

Constructor Summary

DataAccess(File f)
Constructor, initializing the file reader.

Method Summary

void	close() Closes the data access.
org.basex.io.Buffer	cursor(long p) Sets the disk cursor.
void	flush() Flushes the buffered data.
long	length() Returns file length.
boolean	more() Checks if more bytes can be read.
long	pos() Returns the current file position.
byte	read1() Reads a byte value.
int	read4() Reads an integer value.
int	read4(long p) Reads an integer value from the specified position.
long	read5() Reads a 5-byte value.
long	read5(long p) Reads a 5-byte value from the specified file offset.
byte[]	readBytes(long from, long to) Reads a number of bytes in range from -> to and returns them as array.
int	readNum() Reads the next compressed number and returns it as integer.
int	readNum(long p) Reads a Num value from disk.
byte[]	readToken(long p) Reads a token from disk.
void	writeBytes(long p, byte[] v) Appends a value to the file and return it's offset.
void	writeInt(int v) Writes an integer value to the specified output stream.

Methods inherited from class java.lang.Object

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

Constructor Detail

DataAccess

public DataAccess(File f)
           throws IOException

Constructor, initializing the file reader.

Parameters:

f - the file to be read

Throws:

IOException - IO Exception

Method Detail

flush

public void flush()
           throws IOException

Flushes the buffered data.

Throws:

IOException - I/O exception

close

public void close()
           throws IOException

Closes the data access.

Throws:

IOException - I/O exception

pos

public long pos()

Returns the current file position.

Returns:

text as byte array

length

public long length()

Returns file length.

Returns:

file length

more

public boolean more()

Checks if more bytes can be read.

Returns:

result of check

read1

public byte read1()

Reads a byte value.

Returns:

integer value

read4

public int read4()

Reads an integer value.

Returns:

integer value

read4

public int read4(long p)

Reads an integer value from the specified position.

Parameters:

p - position

Returns:

integer value

read5

public long read5(long p)

Reads a 5-byte value from the specified file offset.

Parameters:

p - position

Returns:

long value

read5

public long read5()

Reads a 5-byte value.

Returns:

long value

readNum

public int readNum(long p)

Reads a Num value from disk.

Parameters:

p - text position

Returns:

read num

readToken

public byte[] readToken(long p)

Reads a token from disk.

Parameters:

p - text position

Returns:

text as byte array

readBytes

public byte[] readBytes(long from,
                        long to)

Reads a number of bytes in range from -> to and returns them as array.

Parameters:

from - starting position for reading

to - ending position for reading

Returns:

byte array

writeBytes

public void writeBytes(long p,
                       byte[] v)

Appends a value to the file and return it's offset.

Parameters:

p - write position

v - byte array to be appended

cursor

public org.basex.io.Buffer cursor(long p)

Sets the disk cursor.

Parameters:

p - read position

Returns:

buffer

readNum

public int readNum()

Reads the next compressed number and returns it as integer.

Returns:

next integer

writeInt

public void writeInt(int v)

Writes an integer value to the specified output stream.

Parameters:

v - value to be written