adapted_slice::adapted_slice(boost::python::slice const& sl, std::size_t sz)
:
step(1),
size(0)
{
static const boost::python::slice_nil slice_nil = boost::python::slice_nil();
long signed_sz = static_cast<long>(sz);
if (sl.step() != slice_nil) {
step = boost::python::extract<long>(sl.step());
}
if (sl.start() == slice_nil) {
start = step < 0 ? signed_sz-1 : 0;
}
else {
start = boost::python::extract<long>(sl.start());
if (start < 0) start += signed_sz;
}
if (sl.stop() == slice_nil) {
stop = step < 0 ? -1 : signed_sz;
}
else {
stop = boost::python::extract<long>(sl.stop());
if (stop < 0) stop += signed_sz;
}
if (start > signed_sz-1) start = signed_sz;
if (start < 0) start = 0;
if (stop < -1) stop = -1;
else if (stop > signed_sz) stop = signed_sz;
SCITBX_ASSERT(step != 0 || stop == start);
long signed_size = stop - start + step;
if (step < 0) signed_size++;
else if (step > 0) signed_size--;
else {
signed_size = 0;
step = 1;
}
signed_size /= step;
if (signed_size < 0) signed_size = 0;
size = static_cast<std::size_t>(signed_size);
stop = start + step * size;
}
static ImmutableTreeVector<T> slice(ImmutableTreeVector<T>& in, boost::python::slice s)
{
int32_t start = boost::python::extract<int32_t>(s.start());
if (start < 0)
start = in.size() - start;
int32_t stop = boost::python::extract<int32_t>(s.stop());
if (stop < 0)
stop = in.size() - stop;
return in.slice(start, stop);
}