github.com/igggame/nebulas-go@v2.1.0+incompatible/nbre/3rd_party/fflib/include/ff/util/function_traits.h

/***********************************************
The MIT License (MIT)

Copyright (c) 2012 Athrun Arthur <athrunarthur@gmail.com>

Permission is hereby granted, free of charge, to any person obtaining a copy
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The above copyright notice and this permission notice shall be included in
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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*************************************************/
#pragma once
#include "ff/util/func_type_checker.h"
#include "ff/util/is_callable.h"
#include <functional>
#include <type_traits>

namespace ff {
namespace util {
template <class F>
struct deduce_function {};

template <class Ret, class C, class... Args>
struct deduce_function<Ret (C::*)(Args...) const> {
  typedef std::function<Ret(Args...)> type;
  typedef Ret ret_type;
};

template <class Ret, class C, class... Args>
struct deduce_function<Ret (C::*)(Args...)> {
  typedef std::function<Ret(Args...)> type;
  typedef Ret ret_type;
};

template <class Ret, class... Args>
struct deduce_function<Ret(Args...)> {
  typedef std::function<Ret(Args...)> type;
  typedef Ret ret_type;
};

template <class F>
struct is_no_args_function {
  const static bool value = false;
};

template <class Ret, class C>
struct is_no_args_function<Ret (C::*)(void) const> {
  const static bool value = true;
};

template <class Ret, class C>
struct is_no_args_function<Ret (C::*)(void)> {
  const static bool value = true;
};

template <class Ret>
struct is_no_args_function<Ret(void)> {
  const static bool value = true;
};
template <class Ret>
struct is_no_args_function<Ret (*)(void)> {
  const static bool value = true;
};

template <class F, bool flag>
struct functor_res_traits {
  typedef typename deduce_function<decltype(
      &std::remove_reference<F>::type::operator())>::ret_type ret_type;
};

template <class F>
struct functor_res_traits<F, false> {
  typedef void ret_type;
};

template <class F, bool flag>
struct bind_res_traits {
  typedef typename F::result_type ret_type;
};

template <class F>
struct bind_res_traits<F, false> {
  typedef void ret_type;
};

namespace internal {
template <class F, bool flag>
struct function_res_traits_impl {
  typedef typename deduce_function<F>::ret_type ret_type;
};
template <class F>
struct function_res_traits_impl<F, false> {
  typedef void ret_type;
};

template <class F>
struct function_res_traits_impl<F *, true> {
  typedef typename deduce_function<F>::ret_type ret_type;
};
template <class F>
struct function_res_traits_impl<F &, true> {
  typedef typename deduce_function<F>::ret_type ret_type;
};
} // namespace internal

template <class F>
struct function_res_traits {
  typedef typename std::remove_reference<F>::type FT;
  const static bool s_is_class = std::is_class<FT>::value;
  const static bool s_is_bind_expr = std::is_bind_expression<FT>::value;

  typedef typename std::conditional<
      s_is_class,
      typename std::conditional<
          s_is_bind_expr,
          typename bind_res_traits<FT, s_is_bind_expr>::ret_type,
          typename functor_res_traits<FT, !s_is_bind_expr &&
                                              s_is_class>::ret_type>::type,
      typename internal::function_res_traits_impl<FT, !s_is_class>::ret_type>::
      type ret_type;
};

template <class F, bool flag>
struct functor_args_traits {
  const static bool is_no_args = is_no_args_function<decltype(
      &std::remove_reference<F>::type::operator())>::value;
};

template <class F>
struct functor_args_traits<F, false> {
  const static bool is_no_args = false;
};

namespace internal {
template <class F, bool flag>
struct function_args_traits_impl {
  const static bool is_no_args = is_no_args_function<F>::value;
};

template <class F>
struct function_args_traits_impl<F, false> {
  const static bool is_no_args = false;
};

template <class F>
struct function_args_traits_impl<F *, true> {
  const static bool is_no_args = is_no_args_function<F>::value;
};
template <class F>
struct function_args_traits_impl<F &, true> {
  const static bool is_no_args = is_no_args_function<F>::value;
};
} // namespace internal

template <class F>
struct function_args_traits {
  typedef typename std::remove_reference<F>::type FT;
  const static bool s_is_class = std::is_class<FT>::value;

  const static bool is_no_args =
      functor_args_traits<FT, s_is_class>::is_no_args ||
      internal::function_args_traits_impl<FT, !s_is_class>::is_no_args;
};

} // end namespace util
};  // end namespace ff