ts-crc16

A direct TypeScript port of the CRC-16 family from libcrc (5 variants: IBM/ARC, MODBUS, XMODEM, CCITT-FALSE, CCITT-1D0F).

If you find this project useful, you can support this and further ports at ko-fi.com/scottmoore0.

Upstream provenance

This package is a TypeScript port of lammertb/libcrc (src/crc16.c, src/crcccitt.c) by Lammert Bies, MIT License.

The translated output is validated against the canonical "123456789" check value for each of the five CRC-16 variants (0xBB3D, 0x4B37, 0x31C3, 0x29B1, 0xE5CC).

Why this exists

CRC-16 is the most-deployed 16-bit checksum family. Different variants are required by different protocols:

• IBM (ARC) — USB, Bisync, original IBM SDLC. The "plain" CRC-16.
• MODBUS — Modbus RTU over serial. Same polynomial as IBM, init 0xFFFF.
• XMODEM — the XMODEM/YMODEM file-transfer protocols (1977).
• CCITT-FALSE — most-used "CRC-CCITT". Bluetooth, SD card command layer, HDLC, KISS framing.
• CCITT-1D0F — older modem standards.

You almost certainly need to pick exactly the right variant: same polynomial families produce wildly different results based on the init value.

ts-crc16 is a direct mechanical translation from libcrc via the cpp-to-ts translator, so its relationship to the algorithms is inspectable.

Install

npm install ts-crc16

Usage

import { crc16ibm, crc16modbus, crc16xmodem, crc16ccitt, crc16ccitt1d0f, toHex } from 'ts-crc16';

crc16ibm('123456789');         // 47933 (= 0xBB3D)
crc16modbus('123456789');      // 19255 (= 0x4B37)
crc16xmodem('123456789');      // 12739 (= 0x31C3)
crc16ccitt('123456789');       // 10673 (= 0x29B1) ← CCITT-FALSE, the common one
crc16ccitt1d0f('123456789');   // 58828 (= 0xE5CC)

toHex(crc16ccitt('123456789'));// '29b1'

// Raw bytes also accepted
crc16ibm(new Uint8Array([0xde, 0xad, 0xbe, 0xef]));

API surface

• crc16ibm(input): number — CRC-16/IBM (a.k.a. ARC, ANSI, USB). poly 0xA001 reflected, init 0x0000.
• crc16modbus(input): number — CRC-16/MODBUS. poly 0xA001 reflected, init 0xFFFF.
• crc16xmodem(input): number — CRC-16/XMODEM. poly 0x1021, init 0x0000.
• crc16ccitt(input): number — CRC-16/CCITT-FALSE. poly 0x1021, init 0xFFFF.
• crc16ccitt1d0f(input): number — CRC-16/CCITT-1D0F. poly 0x1021, init 0x1D0F.
• toHex(n: number): string — 4-char lowercase hex.
• update_crc_16(crc, byte), update_crc_ccitt(crc, byte) — incremental byte-at-a-time updates.

All functions return a uint16 in [0, 65535]. Strings are encoded UTF-8 before hashing.

Reference values (CRC catalogue)

| Variant | "123456789" check value | |---|---| | CRC-16/IBM (ARC) | 0xBB3D | | CRC-16/MODBUS | 0x4B37 | | CRC-16/XMODEM | 0x31C3 | | CRC-16/CCITT-FALSE | 0x29B1 | | CRC-16/CCITT-1D0F | 0xE5CC |

Run:

npm test

Caveats

• Not cryptographic. All CRC variants are easily forgeable. For adversarial integrity use SHA-256 (ts-sha2).
• Pick the right variant. CRC-16 has dozens of catalogued variants. This package covers the five most common; if your protocol specifies "Modbus CRC" use crc16modbus, if it says "CRC-CCITT" almost always use crc16ccitt (FALSE variant), etc. The CRC RevEng catalogue is the authoritative reference.

License

MIT. Original C by Lammert Bies under MIT.

See also

• ts-crc32 — CRC-32 (IEEE 802.3)
• ts-adler32 — Adler-32 (zlib/PNG/deflate)
• ts-sha2 — SHA-256 for cryptographic integrity
• cpp-to-ts — the translator that produced this package