cpp11chat/check_policy.hpp

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#pragma once
#include <type_traits>
#include "chat_messages.hpp"
/* SFINAE compile-type checker for receive policies (as defined in chat_networking.hpp)
* it checks whether PolicyCandidate supplies all of the following methods:
* - static void message_do_what(chat_message)
* - static void handshake_do_what(chat_message)
* - static void serverdirection_do_what(chat_message)
* - static void login_do_what(chat_message)
* - static void logout_do_what(chat_message) */
template <class PolicyCandidate, typename = void>
struct is_valid_receive_policy : std::false_type {};
template <class PolicyCandidate>
struct is_valid_receive_policy<
PolicyCandidate,
typename
std::enable_if<
std::is_same<
decltype(PolicyCandidate
::message_do_what(std::declval<chat::chat_message>())),
void
>::value
&&
std::is_same<
decltype(PolicyCandidate
::handshake_do_what(std::declval<chat::chat_message>())),
void
>::value
&&
std::is_same<
decltype(PolicyCandidate
::serverdirection_do_what(std::declval<chat::chat_message>())),
void
>::value
&&
std::is_same<
decltype(PolicyCandidate
::login_do_what(std::declval<chat::chat_message>())),
void
>::value
&&
std::is_same<
decltype(PolicyCandidate
::logout_do_what(std::declval<chat::chat_message>())),
void
>::value
>::type>
: std::true_type {};
/* SFINAE compile-type checker for send policies (as defined in chat_networking.hpp)
* it checks whether PolicyCandidate supplies all of the following methods:
* - static bool check_msg_length(chat_message) */
template <class PolicyCandidate, typename = void>
struct is_valid_send_policy : std::false_type {};
template <class PolicyCandidate>
struct is_valid_send_policy<
PolicyCandidate,
typename
std::enable_if<
std::is_same<
decltype(PolicyCandidate
::check_msg_length(std::declval<chat::chat_message>())),
bool
>::value
>::type>
: std::true_type {};