TemplateInvoker.h

Go to the documentation of this file.

// -*- lsst-c++ -*-
/*
 * LSST Data Management System
 * See COPYRIGHT file at the top of the source tree.
 *
 * This product includes software developed by the
 * LSST Project (http://www.lsst.org/).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the LSST License Statement and
 * the GNU General Public License along with this program.  If not,
 * see <http://www.lsstcorp.org/LegalNotices/>.
 */

#ifndef LSST_UTILS_PYTHON_TEMPLATEINVOKER_H
#define LSST_UTILS_PYTHON_TEMPLATEINVOKER_H

#include "pybind11/pybind11.h"
#include "pybind11/numpy.h"

#include <iostream>

namespace lsst { namespace utils { namespace python {

class TemplateInvoker {
public:

    template <typename ...Types>
    struct Tag {};

    using OnErrorCallback = std::function<pybind11::object(pybind11::dtype const & dtype)>;

    static pybind11::object handleErrorDefault(pybind11::dtype const & dtype) {
        PyErr_Format(PyExc_TypeError, "dtype '%R' not supported.", dtype.ptr());
        throw pybind11::error_already_set();
    }

    explicit TemplateInvoker(OnErrorCallback onError) : _onError(std::move(onError)) {}

    TemplateInvoker() : TemplateInvoker(handleErrorDefault) {}

    template <typename Function, typename ...TypesToTry>
    pybind11::object apply(
        Function function,
        pybind11::dtype const & dtype,
        Tag<TypesToTry...> typesToTry
    ) const {
        return _apply(function, dtype, typesToTry);
    }

private:

    template <typename Function>
    pybind11::object _apply(Function & function, pybind11::dtype const & dtype, Tag<>) const {
        return _onError(dtype);
    }

    template <typename Function, typename T, typename ...A>
    pybind11::object _apply(Function & function, pybind11::dtype const & dtype, Tag<T, A...>) const {
        if (pybind11::detail::npy_api::get().PyArray_EquivTypes_(dtype.ptr(),
                                                                 pybind11::dtype::of<T>().ptr())) {
            return pybind11::cast(function(static_cast<T>(0)));
        }
        return _apply(function, dtype, Tag<A...>());
    }

    OnErrorCallback _onError;
};

}}}  // namespace lsst::utils::python

#endif