path: root/boost/beast/core/detail/type_traits.hpp

//
// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/beast
//

#ifndef BOOST_BEAST_DETAIL_TYPE_TRAITS_HPP
#define BOOST_BEAST_DETAIL_TYPE_TRAITS_HPP

#include <boost/beast/core/error.hpp>
#include <boost/asio/buffer.hpp>
#include <boost/type_traits.hpp>
#include <iterator>
#include <tuple>
#include <type_traits>
#include <string>
#include <utility>

namespace boost {
namespace beast {
namespace detail {

template<class U>
inline
std::size_t constexpr
max_sizeof()
{
    return sizeof(U);
}

template<class U0, class U1, class... Us>
inline
std::size_t constexpr
max_sizeof()
{
    return
        max_sizeof<U0>() > max_sizeof<U1, Us...>() ?
        max_sizeof<U0>() : max_sizeof<U1, Us...>();
}

template<class U>
inline
std::size_t constexpr
max_alignof()
{
    return alignof(U);
}

template<class U0, class U1, class... Us>
std::size_t constexpr
max_alignof()
{
    return
        max_alignof<U0>() > max_alignof<U1, Us...>() ?
        max_alignof<U0>() : max_alignof<U1, Us...>();
}

// (since C++17)
template<class... Ts>
using make_void = boost::make_void<Ts...>;
template<class... Ts>
using void_t = boost::void_t<Ts...>;

// (since C++11) missing from g++4.8
template<std::size_t Len, class... Ts>
struct aligned_union
{
    static
    std::size_t constexpr alignment_value =
        max_alignof<Ts...>();

    using type = typename std::aligned_storage<
        (Len > max_sizeof<Ts...>()) ? Len : (max_sizeof<Ts...>()),
            alignment_value>::type;
};

template<std::size_t Len, class... Ts>
using aligned_union_t =
    typename aligned_union<Len, Ts...>::type;

//------------------------------------------------------------------------------

template<class T>
inline
void
accept_rv(T){}

//------------------------------------------------------------------------------

template<unsigned N, class T, class... Tn>
struct repeat_tuple_impl
{
    using type = typename repeat_tuple_impl<
        N - 1, T, T, Tn...>::type;
};

template<class T, class... Tn>
struct repeat_tuple_impl<0, T, Tn...>
{
    using type = std::tuple<T, Tn...>;
};

template<unsigned N, class T>
struct repeat_tuple
{
    using type =
        typename repeat_tuple_impl<N-1, T>::type;
};

template<class T>
struct repeat_tuple<0, T>
{
    using type = std::tuple<>;
};

//------------------------------------------------------------------------------

template<class R, class C, class ...A>
auto
is_invocable_test(C&& c, int, A&& ...a)
    -> decltype(std::is_convertible<
        decltype(c(std::forward<A>(a)...)), R>::value ||
            std::is_same<R, void>::value,
                std::true_type());

template<class R, class C, class ...A>
std::false_type
is_invocable_test(C&& c, long, A&& ...a);

/** Metafunction returns `true` if F callable as R(A...)

    Example:

    @code
        is_invocable<T, void(std::string)>
    @endcode
*/
/** @{ */
template<class C, class F>
struct is_invocable : std::false_type
{
};

template<class C, class R, class ...A>
struct is_invocable<C, R(A...)>
    : decltype(is_invocable_test<R>(
        std::declval<C>(), 1, std::declval<A>()...))
{
};
/** @} */

//------------------------------------------------------------------------------

// for span
template<class T, class E, class = void>
struct is_contiguous_container: std::false_type {};

template<class T, class E>
struct is_contiguous_container<T, E, void_t<
    decltype(
        std::declval<std::size_t&>() = std::declval<T const&>().size(),
        std::declval<E*&>() = std::declval<T&>().data()),
    typename std::enable_if<
        std::is_same<
            typename std::remove_cv<E>::type,
            typename std::remove_cv<
                typename std::remove_pointer<
                    decltype(std::declval<T&>().data())
                >::type
            >::type
        >::value
    >::type>>: std::true_type
{};

//------------------------------------------------------------------------------

template<class...>
struct unwidest_unsigned;

template<class U0>
struct unwidest_unsigned<U0>
{
    using type = U0;
};

template<class U0, class... UN>
struct unwidest_unsigned<U0, UN...>
{
    BOOST_STATIC_ASSERT(std::is_unsigned<U0>::value);
    using type = typename std::conditional<
        (sizeof(U0) < sizeof(typename unwidest_unsigned<UN...>::type)),
        U0, typename unwidest_unsigned<UN...>::type>::type;
};

template<class...>
struct widest_unsigned;

template<class U0>
struct widest_unsigned<U0>
{
    using type = U0;
};

template<class U0, class... UN>
struct widest_unsigned<U0, UN...>
{
    BOOST_STATIC_ASSERT(std::is_unsigned<U0>::value);
    using type = typename std::conditional<
        (sizeof(U0) > sizeof(typename widest_unsigned<UN...>::type)),
        U0, typename widest_unsigned<UN...>::type>::type;
};

template<class U>
inline
constexpr
U
min_all(U u)
{
    BOOST_STATIC_ASSERT(std::is_unsigned<U>::value);
    return u;
}

template<class U0, class U1, class... UN>
inline
constexpr
typename unwidest_unsigned<U0, U1, UN...>::type
min_all(U0 u0, U1 u1, UN... un)
{
    using type =
        typename unwidest_unsigned<U0, U1, UN...>::type;
    return u0 < u1 ?
        static_cast<type>(min_all(u0, un...)) :
        static_cast<type>(min_all(u1, un...));
}

template<class U>
inline
constexpr
U
max_all(U u)
{
    BOOST_STATIC_ASSERT(std::is_unsigned<U>::value);
    return u;
}

template<class U0, class U1, class... UN>
inline
constexpr
typename widest_unsigned<U0, U1, UN...>::type
max_all(U0 u0, U1 u1, UN... un)
{
    return u0 > u1? max_all(u0, un...) : max_all(u1, un...);
}

//------------------------------------------------------------------------------

template<class T, class = void>
struct get_lowest_layer_helper
{
    using type = T;
};

template<class T>
struct get_lowest_layer_helper<T,
    void_t<typename T::lowest_layer_type>>
{
    using type = typename T::lowest_layer_type;
};

//------------------------------------------------------------------------------

//
// buffer concepts
//

// Types that meet the requirements,
// for use with std::declval only.
template<class BufferType>
struct BufferSequence
{
    using value_type = BufferType;
    using const_iterator = BufferType const*;
    ~BufferSequence();
    BufferSequence(BufferSequence const&) = default;
    const_iterator begin() const noexcept;
    const_iterator end() const noexcept;
};
using ConstBufferSequence =
    BufferSequence<boost::asio::const_buffer>;
using MutableBufferSequence =
    BufferSequence<boost::asio::mutable_buffer>;

template<class B1, class... Bn>
struct is_all_const_buffer_sequence
    : std::integral_constant<bool,
        boost::asio::is_const_buffer_sequence<B1>::value &&
        is_all_const_buffer_sequence<Bn...>::value>
{
};

template<class B>
struct is_all_const_buffer_sequence<B>
    : boost::asio::is_const_buffer_sequence<B>
{
};

template<class... Bn>
struct common_buffers_type
{
    using type = typename std::conditional<
        boost::is_convertible<std::tuple<Bn...>,
            typename repeat_tuple<sizeof...(Bn),
                boost::asio::mutable_buffer>::type>::value,
                    boost::asio::mutable_buffer,
                        boost::asio::const_buffer>::type;
};

template<class B>
struct buffer_sequence_iterator
{
    using type = decltype(
        boost::asio::buffer_sequence_begin(
            std::declval<B const&>()));
};

// Types that meet the requirements,
// for use with std::declval only.
struct StreamHandler
{
    StreamHandler(StreamHandler const&) = default;
    void operator()(error_code ec, std::size_t);
};
using ReadHandler = StreamHandler;
using WriteHandler = StreamHandler;

template<class Buffers>
class buffers_range_adaptor
{
    Buffers const& b_;

public:
    using value_type = typename std::conditional<
        boost::is_convertible<
            typename std::iterator_traits<
                typename buffer_sequence_iterator<
                    Buffers>::type>::value_type,
                boost::asio::mutable_buffer>::value,
            boost::asio::mutable_buffer,
            boost::asio::const_buffer>::type;

    class const_iterator
    {
        friend class buffers_range_adaptor;

        using iter_type = typename
            buffer_sequence_iterator<Buffers>::type;

        iter_type it_;

        const_iterator(iter_type const& it)
            : it_(it)
        {
        }

    public:
        using value_type = typename
            buffers_range_adaptor::value_type;
        using pointer = value_type const*;
        using reference = value_type;
        using difference_type = std::ptrdiff_t;
        using iterator_category =
            std::bidirectional_iterator_tag;
        
        bool
        operator==(const_iterator const& other) const
        {
            return it_ == other.it_;
        }

        bool
        operator!=(const_iterator const& other) const
        {
            return ! (*this == other);
        }

        reference
        operator*() const
        {
            return *it_;
        }

        pointer
        operator->() const = delete;

        const_iterator&
        operator++()
        {
            ++it_;
            return *this;
        }

        const_iterator
        operator++(int)
        {
            auto temp = *this;
            ++(*this);
            return temp;
        }

        // deprecated
        const_iterator&
        operator--()
        {
            --it_;
            return *this;
        }

        // deprecated
        const_iterator
        operator--(int)
        {
            auto temp = *this;
            --(*this);
            return temp;
        }
    };

    explicit
    buffers_range_adaptor(Buffers const& b)
        : b_(b)
    {
    }

    const_iterator
    begin() const noexcept
    {
        return boost::asio::buffer_sequence_begin(b_);
    }

    const_iterator
    end() const noexcept
    {
        return boost::asio::buffer_sequence_end(b_);
    }
};

template<class Buffers>
buffers_range_adaptor<Buffers>
buffers_range(Buffers const& buffers)
{
    return buffers_range_adaptor<Buffers>{buffers};
}

/*  If this static assert goes off, it means that the completion
    handler you provided to an asynchronous initiating function did
    not have the right signature. Check the parameter types for your
    completion handler and make sure they match the list of types
    expected by the initiating function,
*/
#define BOOST_BEAST_HANDLER_INIT(type, sig) \
    static_assert(boost::beast::is_completion_handler< \
    BOOST_ASIO_HANDLER_TYPE(type, sig), sig>::value, \
    "CompletionHandler signature requirements not met"); \
    boost::asio::async_completion<type, sig> init{handler}

} // detail
} // beast
} // boost

#endif