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.
crc32.go crc32_amd64.go crc32_generic.go
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
IEEETable is the table for the IEEE polynomial.
var IEEETable = simpleMakeTable(IEEE)
func Checksum(data []byte, tab *Table) uint32
Checksum returns the CRC-32 checksum of data using the polynomial represented by the Table.
func ChecksumIEEE(data []byte) uint32
ChecksumIEEE returns the CRC-32 checksum of data using the IEEE polynomial.
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() 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(crc uint32, tab *Table, p []byte) uint32
Update returns the result of adding the bytes in p to the crc.
Table is a 256-word table representing the polynomial for efficient processing.
type Table [256]uint32
func MakeTable(poly uint32) *Table
MakeTable returns a Table constructed from the specified polynomial. The contents of this Table must not be modified.
package main
import (
"fmt"
"hash/crc32"
)
func main() {
// In this package, the CRC polynomial is represented in reversed notation,
// or LSB-first representation.
//
// LSB-first representation is a hexadecimal number with n bits, in which the
// most significant bit represents the coefficient of x⁰ and the least significant
// bit represents the coefficient of xⁿ⁻¹ (the coefficient for xⁿ is implicit).
//
// For example, CRC32-Q, as defined by the following polynomial,
// x³²+ x³¹+ x²⁴+ x²²+ x¹⁶+ x¹⁴+ x⁸+ x⁷+ x⁵+ x³+ x¹+ x⁰
// has the reversed notation 0b11010101100000101000001010000001, so the value
// that should be passed to MakeTable is 0xD5828281.
crc32q := crc32.MakeTable(0xD5828281)
fmt.Printf("%08x\n", crc32.Checksum([]byte("Hello world"), crc32q))
}
© Google, Inc.
Licensed under the Creative Commons Attribution License 3.0.
https://golang.org/pkg/hash/crc32/