code: function _writeVarint(data, num, off) {
    assert(Number.isSafeInteger(num), 'Number exceeds 2^53-1.');
  
    do {
      assert(off < data.length);
      let ch = num & 0x7f;
      num -= num % 0x80;
      num /= 0x80;
      if (num !== 0)
        ch |= 0x80;
      data[off] = ch;
      off++;
    } while (num > 0);
  
    return off;
  }
docs: /*
  Encoding