code: function _readVarint(data, off) {
    let num = 0;
    let ch = 0x80;
    let size = 0;
  
    while (ch & 0x80) {
      if (off >= data.length) {
        num = 0;
        break;
      }
  
      ch = data[off++];
  
      // Optimization for javascript insanity.
      switch (size) {
        case 0:
        case 1:
        case 2:
        case 3:
          num += (ch & 0x7f) << (7 * size);
          break;
        case 4:
          num += (ch & 0x7f) * (1 << (7 * size));
          break;
        default:
          num += (ch & 0x7f) * Math.pow(2, 7 * size);
          break;
      }
  
      size++;
  
      assert(size < 7, 'Number exceeds 2^53-1.');
    }
  
    return new Varint(size, num);
  }
docs: /*
  Encoding