zkteco-terminal/src/lib/checksum.js

A useful utility library

const USHRT_MAX = 65535;

export default function calculateChecksum(buf) {
  let chksum = 0;
  for (let i = 0; i < buf.length; i += 2) {
    if (i == buf.length - 1) {
      chksum += buf[i];
    } else {
      chksum += buf.readUInt16LE(i);
    }
    chksum %= USHRT_MAX;
  }
  chksum = USHRT_MAX - chksum - 1;

  return chksum;
}