core: add helpers in Register

include/eigenpy/register.hpp

@@ -20,6 +20,25 @@ namespace eigenpy {
 struct EIGENPY_DLLAPI Register {
   static PyArray_Descr *getPyArrayDescr(PyTypeObject *py_type_ptr);
 
+  static PyArray_Descr *getPyArrayDescrFromTypeNum(const int type_num);
+
+  template <typename Scalar>
+  static PyArray_Descr *getPyArrayDescrFromScalarType() {
+    if (!isNumpyNativeType<Scalar>()) {
+      const std::type_info &info = typeid(Scalar);
+      if (instance().type_to_py_type_bindings.find(&info) !=
+          instance().type_to_py_type_bindings.end()) {
+        PyTypeObject *py_type = instance().type_to_py_type_bindings[&info];
+        return instance().py_array_descr_bindings[py_type];
+      } else
+        return nullptr;
+    } else {
+      PyArray_Descr *new_descr =
+          call_PyArray_DescrFromType(NumpyEquivalentType<Scalar>::type_code);
+      return new_descr;
+    }
+  }
+
   template <typename Scalar>
   static bool isRegistered() {
     return isRegistered(Register::getPyType<Scalar>());

src/register.cpp

@@ -14,6 +14,17 @@ PyArray_Descr* Register::getPyArrayDescr(PyTypeObject* py_type_ptr) {
     return NULL;
 }
 
+PyArray_Descr* Register::getPyArrayDescrFromTypeNum(const int type_num) {
+  if (type_num >= NPY_USERDEF) {
+    for (const auto& elt : instance().py_array_code_bindings) {
+      if (elt.second == type_num)
+        return instance().py_array_descr_bindings[elt.first];
+    }
+    return nullptr;
+  } else
+    return PyArray_DescrFromType(type_num);
+}
+
 bool Register::isRegistered(PyTypeObject* py_type_ptr) {
   if (getPyArrayDescr(py_type_ptr) != NULL)
     return true;