README
¶
crc32
CRC32 hash with x64 optimizations
This package is a drop-in replacement for the standard library hash/crc32 package, that features SSE 4.2 optimizations on x64 platforms, for a 10x speedup.
usage
Install using go get github.com/klauspost/crc32. This library is based on Go 1.4.2 code and requires Go 1.3 or newer.
Replace import "hash/crc32" with import "github.com/klauspost/crc32" and you are good to go.
performance
For IEEE tables (the most common), there is approximately a factor 10 speedup with SSE 4.2:
benchmark old ns/op new ns/op delta
BenchmarkCrc32KB 99955 10258 -89.74%
benchmark old MB/s new MB/s speedup
BenchmarkCrc32KB 327.83 3194.20 9.74x
For other tables and non-SSE 4.2 the peformance is the same as the standard library.
license
Standard Go license. Changes are Copyright (c) 2015 Klaus Post under same conditions.
Documentation
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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.
Index ¶
Examples ¶
Constants ¶
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 )
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 ¶
Checksum returns the CRC-32 checksum of data using the polynomial represented by the Table.
func ChecksumIEEE ¶
ChecksumIEEE returns the CRC-32 checksum of data using the IEEE polynomial.
func New ¶
New creates a new hash.Hash32 computing the CRC-32 checksum using the polynomial represented by the Table.
Types ¶
type Table ¶
type Table [256]uint32
Table is a 256-word table representing the polynomial for efficient processing.
func MakeTable ¶
MakeTable returns the Table constructed from the specified polynomial.
Example ¶
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))
}
Output: 2964d064
Source Files