code: function bnpLShiftTo(n,r) {
    var this_array = this.array;
    var r_array = r.array;
    var bs = n%BI_DB;
    var cbs = BI_DB-bs;
    var bm = (1<<cbs)-1;
    var ds = Math.floor(n/BI_DB), c = (this.s<<bs)&BI_DM, i;
    for(i = this.t-1; i >= 0; --i) {
      r_array[i+ds+1] = (this_array[i]>>cbs)|c;
      c = (this_array[i]&bm)<<bs;
    }
    for(i = ds-1; i >= 0; --i) r_array[i] = 0;
    r_array[ds] = c;
    r.t = this.t+ds+1;
    r.s = this.s;
    r.clamp();
  }
docs: (protected) r = this << n