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crc16.go
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crc16.go
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// Package crc16 implements the 16-bit cyclic redundancy check, or CRC-16, checksum.
//
// It provides parameters for the majority of well-known CRC-16 algorithms.
package crc16
import "math/bits"
// Params represents parameters of CRC-16 algorithms.
// More information about algorithms parametrization and parameter descriptions
// can be found here - http://www.zlib.net/crc_v3.txt
type Params struct {
Poly uint16
Init uint16
RefIn bool
RefOut bool
XorOut uint16
Check uint16
Name string
}
// Predefined CRC-16 algorithms.
// List of algorithms with their parameters borrowed from here - http://reveng.sourceforge.net/crc-catalogue/16.htm
//
// The variables can be used to create Table for the selected algorithm.
var (
CRC16_ARC = Params{0x8005, 0x0000, true, true, 0x0000, 0xBB3D, "CRC-16/ARC"}
CRC16_AUG_CCITT = Params{0x1021, 0x1D0F, false, false, 0x0000, 0xE5CC, "CRC-16/AUG-CCITT"}
CRC16_BUYPASS = Params{0x8005, 0x0000, false, false, 0x0000, 0xFEE8, "CRC-16/BUYPASS"}
CRC16_CCITT_FALSE = Params{0x1021, 0xFFFF, false, false, 0x0000, 0x29B1, "CRC-16/CCITT-FALSE"}
CRC16_CDMA2000 = Params{0xC867, 0xFFFF, false, false, 0x0000, 0x4C06, "CRC-16/CDMA2000"}
CRC16_DDS_110 = Params{0x8005, 0x800D, false, false, 0x0000, 0x9ECF, "CRC-16/DDS-110"}
CRC16_DECT_R = Params{0x0589, 0x0000, false, false, 0x0001, 0x007E, "CRC-16/DECT-R"}
CRC16_DECT_X = Params{0x0589, 0x0000, false, false, 0x0000, 0x007F, "CRC-16/DECT-X"}
CRC16_DNP = Params{0x3D65, 0x0000, true, true, 0xFFFF, 0xEA82, "CRC-16/DNP"}
CRC16_EN_13757 = Params{0x3D65, 0x0000, false, false, 0xFFFF, 0xC2B7, "CRC-16/EN-13757"}
CRC16_GENIBUS = Params{0x1021, 0xFFFF, false, false, 0xFFFF, 0xD64E, "CRC-16/GENIBUS"}
CRC16_MAXIM = Params{0x8005, 0x0000, true, true, 0xFFFF, 0x44C2, "CRC-16/MAXIM"}
CRC16_MCRF4XX = Params{0x1021, 0xFFFF, true, true, 0x0000, 0x6F91, "CRC-16/MCRF4XX"}
CRC16_RIELLO = Params{0x1021, 0xB2AA, true, true, 0x0000, 0x63D0, "CRC-16/RIELLO"}
CRC16_T10_DIF = Params{0x8BB7, 0x0000, false, false, 0x0000, 0xD0DB, "CRC-16/T10-DIF"}
CRC16_TELEDISK = Params{0xA097, 0x0000, false, false, 0x0000, 0x0FB3, "CRC-16/TELEDISK"}
CRC16_TMS37157 = Params{0x1021, 0x89EC, true, true, 0x0000, 0x26B1, "CRC-16/TMS37157"}
CRC16_USB = Params{0x8005, 0xFFFF, true, true, 0xFFFF, 0xB4C8, "CRC-16/USB"}
CRC16_CRC_A = Params{0x1021, 0xC6C6, true, true, 0x0000, 0xBF05, "CRC-16/CRC-A"}
CRC16_KERMIT = Params{0x1021, 0x0000, true, true, 0x0000, 0x2189, "CRC-16/KERMIT"}
CRC16_MODBUS = Params{0x8005, 0xFFFF, true, true, 0x0000, 0x4B37, "CRC-16/MODBUS"}
CRC16_X_25 = Params{0x1021, 0xFFFF, true, true, 0xFFFF, 0x906E, "CRC-16/X-25"}
CRC16_XMODEM = Params{0x1021, 0x0000, false, false, 0x0000, 0x31C3, "CRC-16/XMODEM"}
)
// Table is a 256-word table representing polinomial and algorithm settings for efficient processing.
type Table struct {
params Params
data [256]uint16
}
// MakeTable returns the Table constructed from the specified algorithm.
func MakeTable(params Params) *Table {
table := new(Table)
table.params = params
for n := 0; n < 256; n++ {
crc := uint16(n) << 8
for i := 0; i < 8; i++ {
bit := (crc & 0x8000) != 0
crc <<= 1
if bit {
crc ^= params.Poly
}
}
table.data[n] = crc
}
return table
}
// Init returns the initial value for CRC register corresponding to the specified algorithm.
func Init(table *Table) uint16 {
return table.params.Init
}
// Update returns the result of adding the bytes in data to the crc.
func Update(crc uint16, data []byte, table *Table) uint16 {
for _, d := range data {
if table.params.RefIn {
d = bits.Reverse8(d)
}
crc = crc<<8 ^ table.data[byte(crc>>8)^d]
}
return crc
}
// Complete returns the result of CRC calculation and post-calculation processing of the crc.
func Complete(crc uint16, table *Table) uint16 {
if table.params.RefOut {
return bits.Reverse16(crc) ^ table.params.XorOut
}
return crc ^ table.params.XorOut
}
// Checksum returns CRC checksum of data using scpecified algorithm represented by the Table.
func Checksum(data []byte, table *Table) uint16 {
crc := Init(table)
crc = Update(crc, data, table)
return Complete(crc, table)
}