NanoBindConverter.h

//////////////////////////////////////////////////////////////////////////
//
//  Copyright (c) 2025, Alex Fuller. All rights reserved.
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#ifndef IECOREPYTHON_NANOBINDCONVERTER_H
#define IECOREPYTHON_NANOBINDCONVERTER_H

#include "boost/python.hpp"

#include "nanobind/nanobind.h"

namespace IECorePython
{

// Registers `boost::python` converters for types
// wrapped using nanobind.
template<typename T>
struct NanoBindConverter
{

	static void registerConverters()
	{
		boost::python::to_python_converter<T, ToNanoBind>();
		boost::python::converter::registry::push_back(
			&FromNanoBind::convertible,
			&FromNanoBind::construct,
			boost::python::type_id<T>()
		);
	}

	private :

		struct ToNanoBind
		{
			static PyObject *convert( const T &t )
			{
				nanobind::object o = nanobind::cast( t );
				Py_INCREF( o.ptr() );
				return o.ptr();
			}
		};

		struct FromNanoBind
		{

			static void *convertible( PyObject *object )
			{
				nanobind::handle handle( object );
				return nanobind::cast<T>( handle ) ? object : nullptr;
			}

			static void construct( PyObject *object, boost::python::converter::rvalue_from_python_stage1_data *data )
			{
				void *storage = ( ( boost::python::converter::rvalue_from_python_storage<T> * ) data )->storage.bytes;
				T *t = new( storage ) T;
				data->convertible = storage;

				nanobind::handle handle( object );
				*t = nanobind::cast<T>( handle );
			}

		};

};

} // namespace IECorePython

#endif // IECOREPYTHON_NANOBINDCONVERTER_H