org.basex.util
Class Num

java.lang.Object
  org.basex.util.Num

public final class Num
extends java.lang.Object

This class provides operations to compress and decompress integer values in byte arrays to save memory. The first four bytes of the array store the array length. more() and next() can be called to iterate through the stored values.

Author:

Workgroup DBIS, University of Konstanz 2005-07, ISC License, Christian Gruen

Constructor Summary

Num(byte[] array, boolean w)
Constructor for iterating a Num instance.

Method Summary

static byte[]	add(byte[] array, byte[] v) Adds a byte array to the specified array.
static byte[]	add(byte[] array, int val) Compresses and writes an integer value to the specified byte array.
static byte[]	finish(byte[] array) Finishes compressed id array.
int	id() Returns next id.
static int	len(byte[] array, int val) Returns integer length.
boolean	more() Checks if more numbers are to be iterated.
static byte[]	newNum() Returns an empty number array.
static byte[]	newNum(int val) Creates a new num array.
void	next() Jumps to next id.
int	pos() Returns next word position.
static int	read(byte[] array, int pos) Reads and decompresses an integer value from the specified byte array.
static int	size(byte[] array) Returns length of the specified array.

Methods inherited from class java.lang.Object

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

Constructor Detail

Num

public Num(byte[] array,
           boolean w)

Constructor for iterating a Num instance.

Parameters:

array - array to be iterated

w - flag stating if word positions are stored in the array

Method Detail

add

public static byte[] add(byte[] array,
                         byte[] v)

Adds a byte array to the specified array.

Parameters:

array - array to be mofified

v - array to be added

Returns:

modified array

add

public static byte[] add(byte[] array,
                         int val)

Compresses and writes an integer value to the specified byte array.

Parameters:

array - array

val - value to be written

Returns:

new array

finish

public static byte[] finish(byte[] array)

Finishes compressed id array.

Parameters:

array - to be finished

Returns:

byte array

id

public int id()

Returns next id.

Returns:

next id

len

public static int len(byte[] array,
                      int val)

Returns integer length.

Parameters:

array - array

val - integer value

Returns:

value length

more

public boolean more()

Checks if more numbers are to be iterated.

Returns:

true if more numbers are found

newNum

public static byte[] newNum()

Returns an empty number array.

Returns:

new array

newNum

public static byte[] newNum(int val)

Creates a new num array.

Parameters:

val - initial value to be written

Returns:

new array

next

public void next()

Jumps to next id.

pos

public int pos()

Returns next word position.

Returns:

next word position

read

public static int read(byte[] array,
                       int pos)

Reads and decompresses an integer value from the specified byte array.

Parameters:

array - array

pos - position to parse

Returns:

decompressed value

size

public static int size(byte[] array)

Returns length of the specified array.

Parameters:

array - array to be evaluated

Returns:

array length