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146 lines
3.4 KiB
C++
146 lines
3.4 KiB
C++
//
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// Copyright (c) 2013-2016 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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#ifndef BEAST_DETAIL_INTEGER_SEQUENCE_H_INCLUDED
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#define BEAST_DETAIL_INTEGER_SEQUENCE_H_INCLUDED
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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namespace beast {
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namespace detail {
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template<class T, T... Ints>
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struct integer_sequence
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{
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using value_type = T;
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static_assert (std::is_integral<T>::value,
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"std::integer_sequence can only be instantiated with an integral type" );
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static std::size_t constexpr static_size = sizeof...(Ints);
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static std::size_t constexpr size()
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{
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return sizeof...(Ints);
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}
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};
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template<std::size_t... Ints>
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using index_sequence = integer_sequence<std::size_t, Ints...>;
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// This workaround is needed for broken sizeof...
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template<class... Args>
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struct sizeof_workaround
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{
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static std::size_t constexpr size = sizeof... (Args);
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};
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#ifdef _MSC_VER
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// This implementation compiles on MSVC and clang but not gcc
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template<class T, unsigned long long N, class Seq>
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struct make_integer_sequence_unchecked;
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template<class T, unsigned long long N, unsigned long long ...Indices>
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struct make_integer_sequence_unchecked<
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T, N, integer_sequence<T, Indices...>>
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{
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using type = typename make_integer_sequence_unchecked<
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T, N-1, integer_sequence<T, N-1, Indices...>>::type;
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};
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template<class T, unsigned long long ...Indices>
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struct make_integer_sequence_unchecked<
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T, 0, integer_sequence<T, Indices...>>
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{
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using type = integer_sequence<T, Indices...>;
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};
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template<class T, T N>
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struct make_integer_sequence_checked
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{
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static_assert (std::is_integral<T>::value,
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"T must be an integral type");
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static_assert (N >= 0,
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"N must be non-negative");
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using type = typename make_integer_sequence_unchecked<
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T, N, integer_sequence<T>>::type;
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};
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template<class T, T N>
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using make_integer_sequence =
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typename make_integer_sequence_checked<T, N>::type;
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template<std::size_t N>
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using make_index_sequence = make_integer_sequence<std::size_t, N>;
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template<class... Args>
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using index_sequence_for =
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make_index_sequence<sizeof_workaround<Args...>::size>;
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#else
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// This implementation compiles on gcc but not MSVC
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template<std::size_t... Ints>
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struct index_tuple
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{
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using next = index_tuple<Ints..., sizeof... (Ints)>;
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};
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template<std::size_t N>
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struct build_index_tuple
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{
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using type = typename build_index_tuple<N-1>::type::next;
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};
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template<>
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struct build_index_tuple<0>
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{
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using type = index_tuple<>;
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};
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template<class T, T N,
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class Seq = typename build_index_tuple<N>::type
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>
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struct integer_sequence_helper;
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template<class T, T N, std::size_t... Ints>
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struct integer_sequence_helper<T, N, index_tuple<Ints...>>
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{
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static_assert (std::is_integral<T>::value,
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"T must be an integral type");
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static_assert (N >= 0,
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"N must be non-negative");
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using type = integer_sequence<T, static_cast<T> (Ints)...>;
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};
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template<class T, T N>
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using make_integer_sequence =
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typename integer_sequence_helper<T, N>::type;
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template<std::size_t N>
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using make_index_sequence = make_integer_sequence<std::size_t, N>;
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template<class... Args>
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using index_sequence_for =
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make_index_sequence<sizeof_workaround<Args...>::size>;
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#endif
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} // detail
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} // beast
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#endif
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