Package org.apache.commons.codec.digest

Class Crc16

java.lang.Object

org.apache.commons.codec.digest.Crc16

All Implemented Interfaces:

Checksum

public final class Crc16
extends Object
implements Checksum

CRC-16 checksum implementations you can customize with a table and init value.

Since there are so many CRC-16 variants, we do not pick a default.

For example, to create a create a custom variant of CRC16-MODBUS with an init value of 0x0000, use:

 Checksum crc16 = CRC16.builder().setTable(CRC16.getModbusTable()).setInit(0x0000).get();
 

Since:

1.20.0

See Also:

• Cyclic redundancy check
• Catalogue of parametrised CRC algorithms with 16 bits
• On-line CRC calculation and free library
• crccalc

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	Crc16.Builder	Builds Crc16 instances.

Field Summary

Fields

Modifier and Type	Field	Description
private static final int[]	ARC
private static final int	ARC_INIT
private static final int[]	CCITT
private static final int	CCITT_INIT
private int	crc	CRC.
private static final int[]	DNP
private static final int	DNP_INIT
private static final int	DNP_XOROUT
private static final int[]	IBM_SDLC
private static final int	IBM_SDLC_INIT
private static final int	IBM_SDLC_XOROUT
private final int	init
private static final int[]	MAXIM
private static final int	MAXIM_INIT
private static final int	MAXIM_XOROUT
private static final int[]	MCRF4XX
private static final int	MCRF4XX_INIT
private static final int[]	MODBUS
private static final int	MODBUS_INIT
private static final int[]	NRSC5
private static final int	NRSC5_INIT
private final int[]	table
private static final int[]	USB
private static final int	USB_INIT
private static final int	USB_XOROUT
private final int	xorOut

Constructor Summary

Constructors

Modifier	Constructor	Description
private	Crc16(Crc16.Builder builder)	Constructs a new instance.

Method Summary

Modifier and Type	Method	Description
static Crc16	arc()	Creates a new CRC16-CCITT Checksum.
static Crc16.Builder	builder()	Creates a new builder.
static Crc16	ccitt()	Creates a new CRC16-CCITT Checksum.
static Crc16	dnp()	Creates a new CRC16-DNP Checksum.
static int[]	getArcTable()	Gets a copy of the CRC16-CCITT table.
static int[]	getCcittTable()	Gets a copy of the CRC16-CCITT table.
static int[]	getDnpTable()	Gets a copy of the CRC16-DNP table.
static int[]	getIbmSdlcTable()	Gets a copy of the CRC16-IBM-SDLC table.
static int[]	getMaximTable()	Gets a copy of the CRC16-MAXIM table.
static int[]	getMcrf4xxTable()	Gets a copy of the CRC16-MCRF4XX table.
static int[]	getModbusTable()	Gets a copy of the CRC16-MODBUS table.
static int[]	getNrsc5Table()	Gets a copy of the CRC16-NRSC-5 table.
long	getValue()
static Crc16	ibmSdlc()	Creates a new CRC16-IBM-SDLC Checksum.
static Crc16	maxim()	Creates a new instance for CRC16-MAXIM Checksum.
static Crc16	mcrf4xx()	Creates a new instance for CRC16-MCRF4XX Checksum.
static Crc16	modbus()	Creates a new instance for CRC16-MODBUS Checksum.
static Crc16	nrsc5()	Creates a new instance for CRC16-NRSC-5 Checksum.
void	reset()
String	toString()
void	update(byte[] b, int off, int len)
void	update(int b)
static Crc16	usb()	Creates a new instance for CRC16-USB Checksum.

Methods inherited from class java.lang.Object

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

Field Details

ARC

private static final int[] ARC

ARC_INIT

private static final int ARC_INIT

See Also:

• Constant Field Values

CCITT

private static final int[] CCITT

CCITT_INIT

private static final int CCITT_INIT

See Also:

• Constant Field Values

DNP

private static final int[] DNP

DNP_INIT

private static final int DNP_INIT

See Also:

• Constant Field Values

DNP_XOROUT

private static final int DNP_XOROUT

See Also:

• Constant Field Values

IBM_SDLC

private static final int[] IBM_SDLC

IBM_SDLC_INIT

private static final int IBM_SDLC_INIT

See Also:

• Constant Field Values

IBM_SDLC_XOROUT

private static final int IBM_SDLC_XOROUT

See Also:

• Constant Field Values

MAXIM

private static final int[] MAXIM

MAXIM_INIT

private static final int MAXIM_INIT

See Also:

• Constant Field Values

MAXIM_XOROUT

private static final int MAXIM_XOROUT

See Also:

• Constant Field Values

MCRF4XX

private static final int[] MCRF4XX

MCRF4XX_INIT

private static final int MCRF4XX_INIT

See Also:

• Constant Field Values

MODBUS

private static final int[] MODBUS

MODBUS_INIT

private static final int MODBUS_INIT

See Also:

• Constant Field Values

NRSC5

private static final int[] NRSC5

NRSC5_INIT

private static final int NRSC5_INIT

See Also:

• Constant Field Values

USB

private static final int[] USB

USB_INIT

private static final int USB_INIT

See Also:

• Constant Field Values

USB_XOROUT

private static final int USB_XOROUT

See Also:

• Constant Field Values

crc

private int crc

CRC.

init

private final int init

table

private final int[] table

xorOut

private final int xorOut

Constructor Details

Crc16

private Crc16(Crc16.Builder builder)

Constructs a new instance.

Method Details

arc

public static Crc16 arc()

Creates a new CRC16-CCITT Checksum.

• The init value is 0x0000.
• The XorOut value is 0x0000.

Also known as:

• CRC-16/ARC
• ARC
• CRC-16
• CRC-16/LHA
• CRC-IBM

Returns:

a new CRC16-CCITT Checksum.

builder

public static Crc16.Builder builder()

Creates a new builder.

Since there are so many CRC-16 variants, we do not pick a default.

Returns:

a new builder.

ccitt

public static Crc16 ccitt()

Creates a new CRC16-CCITT Checksum.

• The init value is 0x0000.
• The XorOut value is 0x0000.

Also known as:

• CRC-16/KERMIT
• CRC-16/BLUETOOTH
• CRC-16/CCITT
• CRC-16/CCITT-TRUE
• CRC-16/V-41-LSB
• CRC-CCITT
• KERMIT

Returns:

a new CRC16-CCITT Checksum.

dnp

public static Crc16 dnp()

Creates a new CRC16-DNP Checksum.

• The init value is 0x0000.
• The XorOut value is 0xFFFF.

Returns:

a new CRC16-DNP Checksum.

getArcTable

public static int[] getArcTable()

Gets a copy of the CRC16-CCITT table.

Returns:

a copy of the CCRC16-CITT table.

getCcittTable

public static int[] getCcittTable()

Gets a copy of the CRC16-CCITT table.

Returns:

a copy of the CCRC16-CITT table.

getDnpTable

public static int[] getDnpTable()

Gets a copy of the CRC16-DNP table.

Returns:

a copy of the CCRC16-DNP table.

getIbmSdlcTable

public static int[] getIbmSdlcTable()

Gets a copy of the CRC16-IBM-SDLC table.

Returns:

a copy of the CRC16-IBM-SDLC table.

getMaximTable

public static int[] getMaximTable()

Gets a copy of the CRC16-MAXIM table.

Returns:

a copy of the CRC16-MAXIM table.

getMcrf4xxTable

public static int[] getMcrf4xxTable()

Gets a copy of the CRC16-MCRF4XX table.

Returns:

a copy of the CRC16-MCRF4XX table.

getModbusTable

public static int[] getModbusTable()

Gets a copy of the CRC16-MODBUS table.

Returns:

a copy of the CRC16-MODBUS table.

getNrsc5Table

public static int[] getNrsc5Table()

Gets a copy of the CRC16-NRSC-5 table.

Returns:

a copy of the CRC16-NRSC-5 table.

ibmSdlc

public static Crc16 ibmSdlc()

Creates a new CRC16-IBM-SDLC Checksum.

• The init value is 0xFFFF.
• The XorOut value is 0xFFFF.

Also known as:

• CRC-16/IBM-SDLC
• CRC-16/ISO-HDLC
• CRC-16/ISO-IEC-14443-3-B
• CRC-16/X-25
• CRC-B
• X-25

Returns:

a new CRC16-IBM-SDLC Checksum.

maxim

public static Crc16 maxim()

Creates a new instance for CRC16-MAXIM Checksum.

CRC-16 checksum implementation based on polynomial x<sup>16</spu> + x^15 + x^2 + 1 (0x8005).

• The init value is 0xFFFF.
• The XorOut value is 0xFFFF.

Also known as:

• CRC-16/MAXIM-DOW

Returns:

a new CRC16-MAXIM Checksum.

mcrf4xx

public static Crc16 mcrf4xx()

Creates a new instance for CRC16-MCRF4XX Checksum.

• The init value is 0xFFFF.
• The XorOut value is 0x0000.

Returns:

a new CRC16-MCRF4XX Checksum.

modbus

public static Crc16 modbus()

Creates a new instance for CRC16-MODBUS Checksum.

CRC-16 checksum implementation based on polynomial x<sup>16</spu> + x^15 + x^2 + 1 (0x8005).

• The init value is 0xFFFF.
• The XorOut value is 0x0000.

Also known as:

• CRC-16/MODBUST
• MODBUST

Returns:

a new CRC16-MODBUS Checksum.

nrsc5

public static Crc16 nrsc5()

Creates a new instance for CRC16-NRSC-5 Checksum.

• The init value is 0xFFFF.
• The XorOut value is 0x0000.

Returns:

a new CRC16-NRSC-5 Checksum.

usb

public static Crc16 usb()

Creates a new instance for CRC16-USB Checksum.

• The init value is 0xFFFF.
• The XorOut value is 0xFFFF.

Returns:

a new CRC16-USB Checksum.

getValue

public long getValue()

Specified by:

getValue in interface Checksum

reset

public void reset()

Specified by:

reset in interface Checksum

toString

public String toString()

Overrides:

toString in class Object

update

public void update(byte[] b,
 int off,
 int len)

Specified by:

update in interface Checksum

update

public void update(int b)

Specified by:

update in interface Checksum