core: add std::pair converter support

Author: jcarpent

CMakeLists.txt

@@ -164,6 +164,7 @@ set(${PROJECT_NAME}_HEADERS
     include/eigenpy/register.hpp
     include/eigenpy/std-array.hpp
     include/eigenpy/std-map.hpp
+    include/eigenpy/std-pair.hpp
     include/eigenpy/std-vector.hpp
     include/eigenpy/optional.hpp
     include/eigenpy/pickle-vector.hpp

include/eigenpy/std-pair.hpp

@@ -0,0 +1,69 @@
+//
+// Copyright (c) 2023 INRIA
+//
+
+#ifndef __eigenpy_utils_std_pair_hpp__
+#define __eigenpy_utils_std_pair_hpp__
+
+#include <boost/python.hpp>
+#include <utility>
+
+namespace eigenpy {
+
+template <typename pair_type>
+struct StdPairConverter {
+  typedef typename pair_type::first_type T1;
+  typedef typename pair_type::second_type T2;
+
+  static PyObject* convert(const pair_type& pair) {
+    return boost::python::incref(
+        boost::python::make_tuple(pair.first, pair.second).ptr());
+  }
+
+  static void* convertible(PyObject* obj) {
+    if (!PyTuple_CheckExact(obj)) return 0;
+    if (PyTuple_Size(obj) != 2) return 0;
+    {
+      boost::python::tuple tuple(boost::python::borrowed(obj));
+      boost::python::extract<T1> elt1(tuple[0]);
+      if (!elt1.check()) return 0;
+      boost::python::extract<T2> elt2(tuple[1]);
+      if (!elt2.check()) return 0;
+    }
+    return obj;
+  }
+
+  static void construct(
+      PyObject* obj,
+      boost::python::converter::rvalue_from_python_stage1_data* memory) {
+    boost::python::tuple tuple(boost::python::borrowed(obj));
+    void* storage =
+        reinterpret_cast<
+            boost::python::converter::rvalue_from_python_storage<pair_type>*>(
+            reinterpret_cast<void*>(memory))
+            ->storage.bytes;
+    new (storage) pair_type(boost::python::extract<T1>(tuple[0]),
+                            boost::python::extract<T2>(tuple[1]));
+    memory->convertible = storage;
+  }
+
+  static PyTypeObject const* get_pytype() {
+    PyTypeObject const* py_type = &PyTuple_Type;
+    return py_type;
+  }
+
+  static void registration() {
+    boost::python::converter::registry::push_back(
+        reinterpret_cast<void* (*)(_object*)>(&convertible), &construct,
+        boost::python::type_id<pair_type>()
+#ifndef BOOST_PYTHON_NO_PY_SIGNATURES
+            ,
+        get_pytype
+#endif
+    );
+  }
+};
+
+}  // namespace eigenpy
+
+#endif  // ifndef __eigenpy_utils_std_pair_hpp__