tdesktop/Telegram/SourceFiles/rpl/details/callable.h

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/*
This file is part of Telegram Desktop,
the official desktop application for the Telegram messaging service.
For license and copyright information please follow this link:
https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
*/
#pragma once
#include "base/build_config.h"
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#include <tuple>
namespace rpl {
namespace details {
template <typename Arg>
const Arg &const_ref_val() noexcept;
template <typename Arg>
Arg &lvalue_ref_val() noexcept;
using false_t = char;
struct true_t {
false_t data[2];
};
static_assert(sizeof(false_t) != sizeof(true_t), "I can't work :(");
template <
typename Method,
typename ...Args,
typename = decltype(std::declval<Method>()(
std::declval<Args>()...))>
true_t test_callable_plain(Method &&, Args &&...) noexcept;
false_t test_callable_plain(...) noexcept;
template <typename Method, typename ...Args>
struct is_callable_plain
: std::bool_constant<(
sizeof(test_callable_plain(
std::declval<Method>(),
std::declval<Args>()...
)) == sizeof(true_t))> {
};
template <typename Method, typename ...Args>
constexpr bool is_callable_plain_v = is_callable_plain<Method, Args...>::value;
template <
typename Method,
typename ...Types,
typename = decltype(std::declval<Method>()(
std::declval<Types>()...))>
true_t test_callable_tuple(
Method &&,
std::tuple<Types...> &&) noexcept;
template <
typename Method,
typename ...Types,
typename = decltype(std::declval<Method>()(
const_ref_val<Types>()...))>
true_t test_callable_tuple(
Method &&,
const std::tuple<Types...> &) noexcept;
false_t test_callable_tuple(...) noexcept;
template <typename Method, typename Arg>
constexpr bool is_callable_tuple_v = (sizeof(test_callable_tuple(
std::declval<Method>(),
std::declval<Arg>())) == sizeof(true_t));
template <typename Method, typename Arg>
struct is_callable_tuple
: std::bool_constant<
is_callable_tuple_v<Method, Arg>> {
};
template <typename Method, typename ...Args>
struct is_callable;
template <typename Method>
struct is_callable<Method>
: std::bool_constant<
is_callable_plain_v<Method>> {
};
template <typename Method, typename Arg>
struct is_callable<Method, Arg>
: std::bool_constant<
is_callable_plain_v<Method, Arg> ||
is_callable_tuple_v<Method, Arg> ||
is_callable_plain_v<Method>> {
};
template <typename Method, typename ...Args>
constexpr bool is_callable_v = is_callable<Method, Args...>::value;
template <typename Method, typename Arg>
inline decltype(auto) callable_invoke(Method &&method, Arg &&arg) {
if constexpr (is_callable_plain_v<Method, Arg>) {
return std::forward<Method>(method)(std::forward<Arg>(arg));
} else if constexpr (is_callable_tuple_v<Method, Arg>) {
return std::apply(
std::forward<Method>(method),
std::forward<Arg>(arg));
} else if constexpr (is_callable_v<Method>) {
return std::forward<Method>(method)();
} else {
static_assert(false_(method, arg), "Bad callable_invoke() call.");
}
}
template <typename Method, typename Arg>
using callable_result = decltype(callable_invoke(
std::declval<Method>(),
std::declval<Arg>()));
template <
typename Method,
typename Arg,
typename = decltype(std::declval<Method>()(
const_ref_val<std::decay_t<Arg>>()))>
true_t test_allows_const_ref(Method &&, Arg &&) noexcept;
false_t test_allows_const_ref(...) noexcept;
template <typename Method, typename Arg>
constexpr bool allows_const_ref_v = (sizeof(test_allows_const_ref(
std::declval<Method>(),
std::declval<Arg>())) == sizeof(true_t));
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template <typename Method, typename Arg>
inline decltype(auto) const_ref_call_invoke(
Method &&method,
const Arg &arg) {
if constexpr (allows_const_ref_v<Method, Arg>) {
return callable_invoke(std::forward<Method>(method), arg);
} else {
auto copy = arg;
return callable_invoke(
std::forward<Method>(method),
std::move(copy));
}
}
} // namespace details
} // namespace rpl