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//
// 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_INTEGER_SEQUENCE_HPP
#define BOOST_BEAST_DETAIL_INTEGER_SEQUENCE_HPP
#include <boost/config.hpp>
#include <cstddef>
#include <type_traits>
#include <utility>
namespace boost {
namespace beast {
namespace detail {
template<class T, T... Ints>
struct integer_sequence
{
using value_type = T;
BOOST_STATIC_ASSERT(std::is_integral<T>::value);
static std::size_t constexpr static_size = sizeof...(Ints);
static std::size_t constexpr size()
{
return sizeof...(Ints);
}
};
template<std::size_t... Ints>
using index_sequence = integer_sequence<std::size_t, Ints...>;
// This workaround is needed for broken sizeof...
template<class... Args>
struct sizeof_workaround
{
static std::size_t constexpr size = sizeof... (Args);
};
#ifdef BOOST_MSVC
// This implementation compiles on real MSVC and clang but not gcc
template<class T, unsigned long long N, class Seq>
struct make_integer_sequence_unchecked;
template<class T, unsigned long long N, unsigned long long ...Indices>
struct make_integer_sequence_unchecked<
T, N, integer_sequence<T, Indices...>>
{
using type = typename make_integer_sequence_unchecked<
T, N-1, integer_sequence<T, N-1, Indices...>>::type;
};
template<class T, unsigned long long ...Indices>
struct make_integer_sequence_unchecked<
T, 0, integer_sequence<T, Indices...>>
{
using type = integer_sequence<T, Indices...>;
};
template<class T, T N>
struct make_integer_sequence_checked
{
BOOST_STATIC_ASSERT(std::is_integral<T>::value);
BOOST_STATIC_ASSERT(N >= 0);
using type = typename make_integer_sequence_unchecked<
T, N, integer_sequence<T>>::type;
};
template<class T, T N>
using make_integer_sequence =
typename make_integer_sequence_checked<T, N>::type;
template<std::size_t N>
using make_index_sequence = make_integer_sequence<std::size_t, N>;
template<class... Args>
using index_sequence_for =
make_index_sequence<sizeof_workaround<Args...>::size>;
#else
// This implementation compiles on gcc but not MSVC
template<std::size_t... Ints>
struct index_tuple
{
using next = index_tuple<Ints..., sizeof... (Ints)>;
};
template<std::size_t N>
struct build_index_tuple
{
using type = typename build_index_tuple<N-1>::type::next;
};
template<>
struct build_index_tuple<0>
{
using type = index_tuple<>;
};
template<class T, T N,
class Seq = typename build_index_tuple<N>::type
>
struct integer_sequence_helper;
template<class T, T N, std::size_t... Ints>
struct integer_sequence_helper<T, N, index_tuple<Ints...>>
{
BOOST_STATIC_ASSERT(std::is_integral<T>::value);
BOOST_STATIC_ASSERT(N >= 0);
using type = integer_sequence<T, static_cast<T> (Ints)...>;
};
template<class T, T N>
using make_integer_sequence =
typename integer_sequence_helper<T, N>::type;
template<std::size_t N>
using make_index_sequence = make_integer_sequence<std::size_t, N>;
template<class... Args>
using index_sequence_for =
make_index_sequence<sizeof_workaround<Args...>::size>;
#endif
} // detail
} // beast
} // boost
#endif
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