org.apache.derbyTesting.unitTests.util

Class BitUtil

java.lang.Object

org.apache.derbyTesting.unitTests.util.BitUtil

public class BitUtil
extends java.lang.Object

This class provides utility methods for converting byte arrays to hexidecimal Strings and manipulating BIT/BIT VARYING values as a packed vector of booleans.

The BIT/BIT VARYING methods are modeled after some methods in the java.util.BitSet class. An alternative to using a SQL BIT (VARYING) column in conjunction with the methods provided herein to provide bit manipulation would be to use a serialized java.util.BitSet column instead.

This class contains the following static methods:

• void set(byte[] bytes, int position) to set a bit
• void clear(byte[] bytes, int position) to clear a bit
• boolean get(byte[] bytes, int position) to get the bit status

Since these methods effectively allow a SQL BIT to be considered as an array of booleans, all offsets (position parameters) are zero based. So if you want to set the first bit of a BIT type, you would use set(MyBitColumn, 0) .

Examples:

• SELECT BitUtil::get(bitcol, 2) FROM mytab
• UPDATE mytab SET bitcol = BitUtil::set(bitcol, 2)
• UPDATE mytab SET bitcol = BitUtil::clear(bitcol, 2)

Field Summary

Fields

Modifier and Type	Field and Description
private static char[]	hex_table

Constructor Summary

Constructors

Constructor and Description
BitUtil()

Method Summary

Modifier and Type	Method and Description
static byte[]	clear(byte[] bytes, int position) Clear the bit at the specified position
static boolean	get(byte[] bytes, int position) Check to see if the specified bit is set
static java.lang.String	hexDump(byte[] data) Convert a byte array to a human-readable String for debugging purposes.
static byte[]	set(byte[] bytes, int position) Set the bit at the specified position

Methods inherited from class java.lang.Object

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

Field Detail

hex_table

private static char[] hex_table

Constructor Detail

BitUtil

public BitUtil()

Method Detail

set

public static byte[] set(byte[] bytes,
                         int position)

Set the bit at the specified position

Parameters:

bytes - the byte array

position - the bit to set, starting from zero

Returns:

the byte array with the set bit

Throws:

java.lang.IndexOutOfBoundsException - on bad position

clear

public static byte[] clear(byte[] bytes,
                           int position)

Clear the bit at the specified position

Parameters:

bytes - the byte array

position - the bit to clear, starting from zero

Returns:

the byte array with the cleared bit

Throws:

java.lang.IndexOutOfBoundsException - on bad position

get

public static boolean get(byte[] bytes,
                          int position)

Check to see if the specified bit is set

Parameters:

bytes - the byte array

position - the bit to check, starting from zero

Returns:

true/false

Throws:

java.lang.IndexOutOfBoundsException - on bad position

hexDump

public static java.lang.String hexDump(byte[] data)

Convert a byte array to a human-readable String for debugging purposes.