mirror of https://github.com/AxioDL/logvisor.git
95 lines
3.5 KiB
C++
95 lines
3.5 KiB
C++
//
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// Copyright (c) 2020 Alexander Grund
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef NOWIDE_DETAIL_IS_STRING_CONTAINER_HPP_INCLUDED
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#define NOWIDE_DETAIL_IS_STRING_CONTAINER_HPP_INCLUDED
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#include <cstddef>
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#include <type_traits>
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namespace nowide {
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namespace detail {
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template<class...>
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struct make_void
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{
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typedef void type;
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};
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template<class... Ts>
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using void_t = typename make_void<Ts...>::type;
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template<typename T>
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struct is_char_type : std::false_type
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{};
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template<>
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struct is_char_type<char> : std::true_type
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{};
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template<>
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struct is_char_type<wchar_t> : std::true_type
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{};
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template<>
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struct is_char_type<char16_t> : std::true_type
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{};
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template<>
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struct is_char_type<char32_t> : std::true_type
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{};
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#ifdef __cpp_char8_t
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template<>
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struct is_char_type<char8_t> : std::true_type
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{};
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#endif
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template<typename T>
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struct is_c_string : std::false_type
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{};
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template<typename T>
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struct is_c_string<const T*> : is_char_type<T>
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{};
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template<typename T>
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using const_data_result = decltype(std::declval<const T>().data());
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/// Return the size of the char type returned by the data() member function
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template<typename T>
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using get_data_width =
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std::integral_constant<std::size_t, sizeof(typename std::remove_pointer<const_data_result<T>>::type)>;
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template<typename T>
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using size_result = decltype(std::declval<T>().size());
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/// Return true if the data() member function returns a pointer to a type of size 1
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template<typename T>
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using has_narrow_data = std::integral_constant<bool, (get_data_width<T>::value == 1)>;
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/// Return true if T is a string container, e.g. std::basic_string, std::basic_string_view
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/// Requires a static value `npos`, a member function `size()` returning an integral,
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/// and a member function `data()` returning a C string
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template<typename T, bool isNarrow, typename = void>
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struct is_string_container : std::false_type
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{};
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// clang-format off
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template<typename T, bool isNarrow>
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struct is_string_container<T, isNarrow, void_t<decltype(T::npos), size_result<T>, const_data_result<T>>>
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: std::integral_constant<bool,
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std::is_integral<decltype(T::npos)>::value
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&& std::is_integral<size_result<T>>::value
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&& is_c_string<const_data_result<T>>::value
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&& isNarrow == has_narrow_data<T>::value>
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{};
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// clang-format on
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template<typename T>
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using requires_narrow_string_container = typename std::enable_if<is_string_container<T, true>::value>::type;
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template<typename T>
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using requires_wide_string_container = typename std::enable_if<is_string_container<T, false>::value>::type;
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template<typename T>
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using requires_narrow_char = typename std::enable_if<sizeof(T) == 1 && is_char_type<T>::value>::type;
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template<typename T>
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using requires_wide_char = typename std::enable_if<(sizeof(T) > 1) && is_char_type<T>::value>::type;
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} // namespace detail
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} // namespace nowide
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#endif
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