crc32a

README

CRC32A

A pure Go implementation of CRC32A (ITU I.363.5) checksum missing from Golang standard library. Largely based on C implementation found in PHP source files.

Usage

package main

import (
	"fmt"
	
	"github.com/boguslaw-wojcik/crc32a"
)

func main() {
	b := []byte("123456789")
	sum := crc32a.Checksum(b)
	sumHex := crc32a.ChecksumHex(b)

	fmt.Println(sum)    // 404326908
	fmt.Println(sumHex) // 181989fc
}

Background

There are four popular implementations of CRC32 of which three are included in Golang standard library. This package provides missing implementation of CRC32A (ITU I.363.5) popularized by bzip2 and PHP. If you're unsure what CRC32 algorithm you're using, calculate checksum for string 123456789 and compare results with the table below.

Variant	Performance	Standard Library	Data	Hex	Sum
CRC32A (ITU I.363.5)	31.4 ns/op	no	123456789	181989fc	404326908
CRC32B (ITU V.42 / IEEE 802.3)	24.0 ns/op	yes	123456789	cbf43926	3421780262
CRC32C (Castagnoli)	15.2 ns/op	yes	123456789	e3069283	3808858755
CRC32K (Koopman)	4534 ns/op	yes	123456789	2d3dd0ae	759025838

Note: Unless you're required to use CRC32A for legacy reasons, in general you should choose CRC32B as the most popular and widely implemented CRC32 variation.

References

• CRC32 Demystified by Michael Pohoreski
• PHP CRC32 source by PHP Group

Documentation

Index

• func Checksum(data []byte) uint32
• func ChecksumHex(data []byte) string

Functions

func Checksum

func Checksum(data []byte) uint32

Checksum calculates CRC32A (ITU I.363.5 algorithm, popularized by BZIP2) checksum. This function will produce the same results as following PHP code:

hexdec(hash('crc32', $data))

func ChecksumHex

func ChecksumHex(data []byte) string

ChecksumHex is a convenience function that outputs CRC32A (ITU I.363.5 algorithm, popularized by BZIP2) checksum as a hex string. This function will produce the same results as following PHP code:

hash('crc32', $data)