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Package crc32

import "hash/crc32"
Overview
Index
Examples

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.

Polynomials are represented in LSB-first form also known as reversed representation.

See http://en.wikipedia.org/wiki/Mathematics_of_cyclic_redundancy_checks#Reversed_representations_and_reciprocal_polynomials for information.

Constants

Predefined polynomials.

const (
    // IEEE is by far and away the most common CRC-32 polynomial.
    // Used by ethernet (IEEE 802.3), v.42, fddi, gzip, zip, png, ...
    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
)

The size of a CRC-32 checksum in bytes.

const Size = 4

Variables

IEEETable is the table for the IEEE polynomial.

var IEEETable = simpleMakeTable(IEEE)

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. Its Sum method will lay the value out in big-endian byte order.

func NewIEEE

func NewIEEE() hash.Hash32

NewIEEE creates a new hash.Hash32 computing the CRC-32 checksum using the IEEE polynomial. Its Sum method will lay the value out in big-endian byte order.

func Update

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

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

type Table

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

type Table [256]uint32

func MakeTable

func MakeTable(poly uint32) *Table

MakeTable returns a Table constructed from the specified polynomial. The contents of this Table must not be modified.

Example

2964d064