crc16

package module

v0.0.0-...-4128ccb Latest Latest Go to latest Published: Oct 13, 2016 License: BSD-2-Clause Imports: 2 Imported by: 14

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Repository

github.com/npat-efault/crc16

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Open Source Insights

README ¶

crc16

Package crc16 implements the 16-bit Cyclic Redundancy Check

Download:

go get github.com/npat-efault/crc16

Package crc16 is a Golang implementation of the 16-bit Cyclic Redundancy Check, or CRC-16 checksum.

The package's API is almost identical to the standard-library's hash/crc32 and hash/crc64 packages.

Package crc16 supports CRC calculation in all possible configurations: Polynomial, bit-order, byte-order, initial value, and final value can all be selected. Predefined configurations are supplied for the most common uses (e.g. PPP, X25, Modbus, etc).

(See also)

Documentation ¶

Overview ¶

Package crc16 implements the 16-bit cyclic redundancy check, or CRC-16, checksum. See http://en.wikipedia.org/wiki/Cyclic_redundancy_check for information.

Index ¶

Constants
Variables
func Checksum(c *Conf, data []byte) uint16
func Update(crc uint16, tab *Table, p []byte) uint16
func UpdateNBR(crc uint16, tab *Table, p []byte) uint16
type Conf
type Hash16
- func New(c *Conf) Hash16
type Table
- func MakeTable(poly uint16) *Table
- func MakeTableNBR(poly uint16) *Table

Constants ¶

View Source

const Size = 2

The size of a CRC-16 checksum in bytes.

Variables ¶

View Source

var (
	X25 = &Conf{
		Poly: 0x1021, BitRev: true,
		IniVal: 0xffff, FinVal: 0xffff,
		BigEnd: false,
	}
	PPP    = X25
	Modbus = &Conf{
		Poly: 0x8005, BitRev: true,
		IniVal: 0xffff, FinVal: 0x0,
		BigEnd: false,
	}
	XModem = &Conf{
		Poly: 0x1021, BitRev: false,
		IniVal: 0x0000, FinVal: 0x0,
		BigEnd: true,
	}
	Kermit = &Conf{
		Poly: 0x1021, BitRev: true,
		IniVal: 0x0, FinVal: 0x0,
		BigEnd: false,
	}
)

Typical CRC-16 configurations. Mostly used are the CCITT (0x1021) and the IBM/ANSI (0x8005) polynomials, either bit-reversed or not. For more configurations see: http://reveng.sourceforge.net/crc-catalogue/

Functions ¶

func Checksum ¶

func Checksum(c *Conf, data []byte) uint16

Checksum returns the CRC-16 checksum of data using the configuration c.

func Update ¶

func Update(crc uint16, tab *Table, p []byte) uint16

Update returns the CRC-16 checksum of p using the polynomial table tab constructed by MakeTable (bit-reversed order). The resulting CRC is in bit-reversed order (bit-15 corresponds to the X^0 term). Argument crc is the initial value of the CRC register.

func UpdateNBR ¶

func UpdateNBR(crc uint16, tab *Table, p []byte) uint16

UpdateNBR returns the CRC-16 checksum of p using the polynomial table tab constructed by MakeTableNBR (non-bit-reversed order). The resulting CRC is in non-bit-reversed order (bit-0 corresponds to the X^0 term). Argument CRC is the initial value of the CRC register.

Types ¶

type Conf ¶

type Conf struct {
	Poly   uint16 // Polynomial to use.
	BitRev bool   // Bit reversed CRC (bit-15 is X^0)?
	IniVal uint16 // Initial value of CRC register.
	FinVal uint16 // XOR CRC with this at the end.
	BigEnd bool   // Emit *bytes* most significant first (see Hash.Sum)?
	// contains filtered or unexported fields
}

Conf is a CRC configuration. It is passed to functions New and Checksum and specifies the parameters of the calculated checksum. The first time New or Checksum are called with a configuration structure c, they calculate the polynomial table for this configuration; subsequent calls with the same c use the table already calculated. A few commonly used configurations are defined as global variables (X25, PPP, Modbus, etc.)

type Hash16 ¶

type Hash16 interface {
	hash.Hash
	Sum16() uint16
}

Hash16 is the common interface implemented by all 16-bit hash functions.

func New ¶

func New(c *Conf) Hash16

New creates a new hash.Hash16 computing the CRC-16 checksum using the configuration c.

type Table ¶

type Table [256]uint16

Table is a 256-word table representing the polynomial for efficient processing.

func MakeTable ¶

func MakeTable(poly uint16) *Table

MakeTable returns the Table constructed from the specified polynomial. The table is calcuated in bit-reversed order (bit-15 corresponds to the X^0 term). Argument poly must be given bit-reversed (e.g. 0xA001 for the 0x8005 polynomial).

func MakeTableNBR ¶

func MakeTableNBR(poly uint16) *Table

MakeTableNBR returns the Table constructed from the specified polynomial. The table is calculated in non-bit-reversed order (bit-0 corresponds to the X^0 term).

Source Files ¶

View all Source files

crc16.go

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