This module provides fast calculation of CRC ([Cyclic redundancy check][Wiki]) with custom parameters: * width - any number 1 ... 32 * polynom * XOR in * XOR out * reflect Calculation is table-based. Tables are dynamically generated once per CRC model. There are prebuilt models for CRC-6, CRC-8, CRC-10, CRC-16, CRC-24, CRC-32, CRC-32C. Motivation for this module were checksums (CRC-6 and CRC-10) used in IuUP (3GPP TS 25.415). It seems to be no other universal and fast CRC module in npm registry. CRC mathematics are mostly ported from https://pycrc.org/ ## Installation `npm install polycrc` ## API Where available, this library supports: * Standard ECMAScript TypedArrays, DataView, ArrayBuffer * Legacy Node.js Buffers #### crc6(buffer) #### crc8(buffer) #### crc10(buffer) #### crc16(buffer) #### crc24(buffer) #### crc32(buffer) #### crc32c(buffer) Calculates checksum. Returns number. #### crc(width, poly, xor_in, xor_out, reflect) Generates new CRC function with custom parameters. Returns function. #### new CRC(width, poly, xor_in, xor_out, reflect) Generates new CRC model with custom parameters. Returns class. Mostly for internal purposes. For creating new CRC checksum functions use generator function *crc()*. #### models `module.exports.models` object holds prebuilt classes, which can be used for pretty-printing generated CRC tables: `console.log(polycrc.models.crc8.print_table())` ### Example ``` let crypto = require('crypto') let polycrc = require('polycrc') let crc10 = polycrc.crc10 let result = crc10(crypto.randomBytes(1024)) console.log(result) let crc5 = polycrc.crc(5, 0x5, 0x1f, 0x1f, true) console.log(crc5('Input is usually a buffer, but string is ok')) console.log(polycrc.models.crc8.print_table()) ``` ### Prebuilt models ``` const models = { crc1: new CRC(1, 0x01, 0x00, 0x00, false), crc6: new CRC(6, 0x2F, 0x00, 0x00, false), crc8: new CRC(8, 0x07, 0x00, 0x00, false), crc10: new CRC(10, 0x233, 0x0000, 0x0000, false), crc16: new CRC(16, 0x8005, 0x0000, 0x0000, true), crc24: new CRC(24, 0x864CFB, 0xB704CE, 0x000000, false), crc32: new CRC(32, 0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true), crc32c: new CRC(32, 0x1EDC6F41, 0xFFFFFFFF, 0xFFFFFFFF, true) } ``` ## Module comparison Here are benchmarks for several npm modules, compared to polycrc. Benchmarking tool located in examples dir. Binary modules marked * #### 100 Mb of data in 300 byte chunks algorythm module value calc/sec crc1 polycrc 1 742093 crc1 crc 172 1588754 crc6 polycrc 8 776724 crc8 polycrc 115 1398104 crc8 crc 115 1065628 crc8 node-crc * 115 452168 crc10 polycrc 451 771580 crc16 polycrc 18086 960236 crc16 crc 18086 1046485 crc16 node-crc * 18086 484779 crc24 polycrc 3554611 775002 crc24 crc 3554611 604716 crc32 polycrc 1459514028 976329 crc32 crc 1459514028 1149756 crc32 node-crc * 1459514028 466034 crc32 polycrc 1459514028 970905 crc32 crc 1459514028 1165086 crc32 node-crc 1459514028 458094 crc32 crc-32 1459514028 1127503 crc32 buffer-crc32 1459514028 992971 crc32 cyclic-32 1459514028 1157370 crc32c polycrc 4240566998 865163 crc32c fast-crc32c(js) 4240566998 1019026 crc32c fast-crc32c * 4240566998 2818758 crc32c sse4_crc32 * 4240566998 2410524 #### 100 Mb of data in 100 kb chunks algorythm module value calc/sec crc1 polycrc 0 1572 crc1 crc 193 5919 crc6 polycrc 33 1651 crc8 polycrc 27 4231 crc8 crc 27 3250 crc8 node-crc * 27 3683 crc10 polycrc 119 1670 crc16 polycrc 17776 2976 crc16 crc 17776 3240 crc16 node-crc * 17776 3592 crc24 polycrc 14484065 2438 crc24 crc 14484065 1738 crc32 polycrc 61412246 2942 crc32 crc 61412246 3518 crc32 node-crc * 61412246 3567 crc32 polycrc 61412246 2934 crc32 crc 61412246 3592 crc32 node-crc 61412246 3631 crc32 crc-32 61412246 3580 crc32 buffer-crc32 61412246 3555 crc32 cyclic-32 61412246 3567 crc32c polycrc 587481699 3011 crc32c fast-crc32c(js) 587481699 3240 crc32c fast-crc32c * 587481699 53894 crc32c sse4_crc32 * 587481699 56888 [wiki]: https://en.wikipedia.org/wiki/Cyclic_redundancy_check ## Author Copyright (c) 2018 Vladimir Latyshev License: MIT