Class python_access

src/python/histogram.cpp:39–111

namespace boost {
namespace histogram {
class python_access {
public:
  using mp_int = detail::mp_int;
  using wcount = detail::wcount;

  struct dtype_visitor {
    template <typename T, typename Buffer>
    bp::str operator()(T*, const Buffer&, bp::list&, bp::list& strides) {
      strides.append(sizeof(T));
      return bp::dtype_typestr<T>();
    }
    template <typename Buffer>
    bp::str operator()(void*, const Buffer&, bp::list&, bp::list& strides) {
      strides.append(sizeof(uint8_t));
      return bp::dtype_typestr<uint8_t>();
    }
    template <typename Buffer>
    bp::str operator()(mp_int*, const Buffer&, bp::list&, bp::list& strides) {
      strides.append(sizeof(double));
      return bp::dtype_typestr<double>();
    }
    template <typename Buffer>
    bp::str operator()(wcount*, const Buffer&, bp::list& shapes, bp::list& strides) {
      strides.append(sizeof(double));
      strides.append(strides[-1] * 2);
      shapes.append(2);
      return bp::dtype_typestr<double>();
    }
  };

  struct data_visitor {
    template <typename T, typename Buffer>
    bp::object operator()(T* tp, const Buffer&, const bp::list&, const bp::list&) const {
      return bp::make_tuple(reinterpret_cast<uintptr_t>(tp), true);
    }
    template <typename Buffer>
    bp::object operator()(void*, const Buffer&, const bp::list& shapes,
                          const bp::list&) const {
      // cannot pass non-existent memory to numpy; make new
      // zero-initialized uint8 array, and pass it
      return np::zeros(bp::tuple(shapes), np::dtype::get_builtin<uint8_t>());
    }
    template <typename Buffer>
    bp::object operator()(mp_int* tp, const Buffer& b, const bp::list& shapes,
                          const bp::list& strides) const {
      // cannot pass cpp_int to numpy; make new
      // double array, fill it and pass it
      auto a = np::empty(bp::tuple(shapes), np::dtype::get_builtin<double>());
      for (std::size_t i = 0, n = bp::len(shapes); i < n; ++i)
        const_cast<Py_intptr_t*>(a.get_strides())[i] = bp::extract<int>(strides[i]);
      auto* buf = (double*)a.get_data();
      for (std::size_t i = 0; i < b.size; ++i) { buf[i] = static_cast<double>(tp[i]); }
      return a;
    }
  };

  static bp::object array_interface(const pyhistogram& self) {
    bp::dict d;