//
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// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/beast
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//
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#ifndef BOOST_BEAST_DETAIL_STREAM_TRAITS_HPP
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#define BOOST_BEAST_DETAIL_STREAM_TRAITS_HPP
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#include <boost/beast/core/error.hpp>
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#include <boost/asio/buffer.hpp>
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#include <boost/type_traits/make_void.hpp>
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#include <type_traits>
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namespace boost {
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namespace beast {
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namespace detail {
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//------------------------------------------------------------------------------
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//
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// get_lowest_layer
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// lowest_layer_type
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// detail::has_next_layer
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//
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template <class T>
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std::false_type has_next_layer_impl(void*);
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template <class T>
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auto has_next_layer_impl(decltype(nullptr)) ->
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decltype(std::declval<T&>().next_layer(), std::true_type{});
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template <class T>
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using has_next_layer = decltype(has_next_layer_impl<T>(nullptr));
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template<class T, bool = has_next_layer<T>::value>
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struct lowest_layer_type_impl
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{
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using type = typename std::remove_reference<T>::type;
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};
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template<class T>
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struct lowest_layer_type_impl<T, true>
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{
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using type = typename lowest_layer_type_impl<
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decltype(std::declval<T&>().next_layer())>::type;
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};
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template<class T>
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using lowest_layer_type = typename
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lowest_layer_type_impl<T>::type;
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template<class T>
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T&
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get_lowest_layer_impl(
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T& t, std::false_type) noexcept
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{
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return t;
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}
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template<class T>
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lowest_layer_type<T>&
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get_lowest_layer_impl(
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T& t, std::true_type) noexcept
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{
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return get_lowest_layer_impl(t.next_layer(),
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has_next_layer<typename std::decay<
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decltype(t.next_layer())>::type>{});
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}
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//------------------------------------------------------------------------------
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// Types that meet the requirements,
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// for use with std::declval only.
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template<class BufferType>
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struct BufferSequence
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{
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using value_type = BufferType;
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using const_iterator = BufferType const*;
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~BufferSequence() = default;
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BufferSequence(BufferSequence const&) = default;
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const_iterator begin() const noexcept { return {}; }
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const_iterator end() const noexcept { return {}; }
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};
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using ConstBufferSequence =
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BufferSequence<net::const_buffer>;
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using MutableBufferSequence =
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BufferSequence<net::mutable_buffer>;
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//
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// Types that meet the requirements,
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// for use with std::declval only.
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struct StreamHandler
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{
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StreamHandler(StreamHandler const&) = default;
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void operator()(error_code, std::size_t) {}
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};
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using ReadHandler = StreamHandler;
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using WriteHandler = StreamHandler;
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//------------------------------------------------------------------------------
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} // detail
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} // beast
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} // boost
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#endif
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