TemplateInvoker.h

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// -*- 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
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 *
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 * GNU General Public License for more details.
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 * see <http://www.lsstcorp.org/LegalNotices/>.
 */
 
#ifndef LSST_CPPUTILS_PYTHON_TEMPLATEINVOKER_H
#define LSST_CPPUTILS_PYTHON_TEMPLATEINVOKER_H
 
#include "pybind11/pybind11.h"
#include "pybind11/numpy.h"
 
#include <iostream>
 
namespace lsst { namespace cpputils { 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::cpputils::python
 
#endif