code: function (a) {
      var l = a.length, x;
      if (l === 0) { return 0; }
      x = a[l - 1];
      return (l-1) * 32 + sjcl.bitArray.getPartial(x);
    }
docs: Find the length of an array of bits.
  @param {bitArray} a The array.
  @return {Number} The length of a, in bits.