crc32

Documentation

Overview

Package crc32 implements the 32-bit cyclic redundancy check, or CRC-32, checksum. See http://en.wikipedia.org/wiki/Cyclic_redundancy_check for information.

Index

• Constants
• Variables
• func Checksum(data []byte, tab *Table) uint32
• func ChecksumIEEE(data []byte) uint32
• func New(tab *Table) hash.Hash32
• func NewIEEE() hash.Hash32
• func Update(crc uint32, tab *Table, p []byte) uint32
• type Table
  • func MakeTable(poly uint32) *Table

Constants

const (
	// Far and away the most common CRC-32 polynomial.
	// Used by ethernet (IEEE 802.3), v.42, fddi, gzip, zip, png, mpeg-2, ...
	IEEE = 0xedb88320

	// Castagnoli's polynomial, used in iSCSI.
	// Has better error detection characteristics than IEEE.
	// http://dx.doi.org/10.1109/26.231911
	Castagnoli = 0x82f63b78

	// Koopman's polynomial.
	// Also has better error detection characteristics than IEEE.
	// http://dx.doi.org/10.1109/DSN.2002.1028931
	Koopman = 0xeb31d82e
)

Predefined polynomials.

const Size = 4

The size of a CRC-32 checksum in bytes.

Variables

var IEEETable = makeTable(IEEE)

IEEETable is the table for the IEEE polynomial.

Functions

func Checksum

func Checksum(data []byte, tab *Table) uint32

Checksum returns the CRC-32 checksum of data using the polynomial represented by the Table.

func ChecksumIEEE

func ChecksumIEEE(data []byte) uint32

ChecksumIEEE returns the CRC-32 checksum of data using the IEEE polynomial.

func New

func New(tab *Table) hash.Hash32

New creates a new hash.Hash32 computing the CRC-32 checksum using the polynomial represented by the Table.

func NewIEEE

func NewIEEE() hash.Hash32

NewIEEE creates a new hash.Hash32 computing the CRC-32 checksum using the IEEE polynomial.

func Update

func Update(crc uint32, tab *Table, p []byte) uint32

Update returns the result of adding the bytes in p to the crc.

Types

type Table

type Table [256]uint32

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

func MakeTable

func MakeTable(poly uint32) *Table

MakeTable returns the Table constructed from the specified polynomial.