node_modules/crc/crc1.js

import { Buffer } from 'buffer';
import createBuffer from './create_buffer';
import defineCrc from './define_crc';

const crc1 = defineCrc('crc1', function(buf, previous) {
  if (!Buffer.isBuffer(buf)) buf = createBuffer(buf);

  let crc = ~~previous;
  let accum = 0;

  for (let index = 0; index < buf.length; index++) {
    const byte = buf[index];
    accum += byte;
  }

  crc += accum % 256;
  return crc % 256;
});

export default crc1;