in lib/src/int64.dart [615:627]
Int64 toUnsigned(int width) {
if (width < 0 || width > 64) throw RangeError.range(width, 0, 64);
if (width > _BITS01) {
int h = _h.toUnsigned(width - _BITS01);
return Int64._masked(_l, _m, h);
} else if (width > _BITS) {
int m = _m.toUnsigned(width - _BITS);
return Int64._masked(_l, m, 0);
} else {
int l = _l.toUnsigned(width);
return Int64._masked(l, 0, 0);
}
}