145 lines
3.7 KiB
C++
145 lines
3.7 KiB
C++
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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef __UTIL_INTROSPECTION_HPP
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#define __UTIL_INTROSPECTION_HPP
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#include "variadic.hpp"
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#include <cstddef>
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#include <string>
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#include <tuple>
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namespace util {
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///////////////////////////////////////////////////////////////////////////
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/// Describes a single member variable in a type availabe for introspection
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///
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/// K: target class
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/// R: member type
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/// M: pointer-to-member
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template <
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class K,
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typename R,
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R K::*M
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>
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struct field
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{
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typedef K klass;
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typedef R type;
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static const std::string name;
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static const R& get (const K &k) { return k.*M; }
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static R get (K &k) { return k.*M; }
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};
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///////////////////////////////////////////////////////////////////////////
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/// Holds the fields of a type available for introspection
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///
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/// Specialise the following type struct with a 'fields' tuple of the
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/// members that should be accessed like below:
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///
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/// struct foo { int a; int b; };
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///
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/// template <> struct type<foo>
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/// {
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/// typedef std::tuple<
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/// field<foo,int,&foo::a>,
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/// field<foo,int,&foo::b>
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/// > fields;
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/// };
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///
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/// template <> const std::string field<foo,int,&foo::a>::name = "a";
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/// template <> const std::string field<foo,int,&foo::b>::name = "b";
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template <class K>
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struct type { };
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///////////////////////////////////////////////////////////////////////////
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/// traits class which converts an introspected type to a tuple
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///
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/// K: target class
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template <
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typename K,
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typename I = typename make_indices<
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std::tuple_size<
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typename type<K>::fields
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>::value
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>::type
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>
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struct type_tuple;
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template <
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typename K,
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size_t ...I
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>
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struct type_tuple<
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K,
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indices<I...>
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>
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{
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typedef std::tuple<
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typename std::tuple_element<
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I,
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typename type<K>::fields
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>::type::type...
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> type;
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};
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///////////////////////////////////////////////////////////////////////////
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namespace detail {
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template <
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typename K,
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typename I = typename make_indices<
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std::tuple_size<
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typename type<K>::fields
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>::value
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>::type
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>
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struct _as_tuple;
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template <
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typename K,
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size_t ...I
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>
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struct _as_tuple <
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K,
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indices<I...>
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>
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{
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static typename type_tuple<K>::type
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make (const K &k)
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{
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return std::make_tuple (
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std::tuple_element<I, typename type<K>::fields>::type::get (k)...
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);
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}
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};
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}
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/// Convert an introspection capable class instance into a tuple instance
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///
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/// K: source class
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template <typename K>
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auto
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as_tuple (const K &k)
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{
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return detail::_as_tuple<K>::make (k);
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}
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}
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#endif
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