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#pragma once
#include <utility>
#include <cstddef>
namespace mbgl {
// Using structs instead of constexpr templates because GCC 4.9 doesn't support these yet.
template <char... Cs>
struct string_literal {
static constexpr const char chars[] = { Cs..., 0 };
static constexpr const char* value() {
return chars;
}
};
template <char... Cs>
constexpr const char string_literal<Cs...>::chars[];
namespace detail {
using string_fn = const char* (*)();
template <string_fn name, std::size_t... Is>
string_literal<name()[Is]...> to_string_literal(std::index_sequence<Is...>);
constexpr std::size_t string_length(const char* const str, std::size_t len = 0) {
return str[0] ? string_length(str + 1, len + 1) : len;
}
template <class...>
struct concat_literals;
template <>
struct concat_literals<> {
static constexpr auto value() {
return "";
}
};
template <char... As, char... Bs, class... Rest>
struct concat_literals<string_literal<As...>, string_literal<Bs...>, Rest...> {
static constexpr auto value() {
return concat_literals<string_literal<As..., Bs...>, Rest...>::value();
}
};
template <char... Cs>
struct concat_literals<string_literal<Cs...>> {
static constexpr auto value() {
return string_literal<Cs...>::value();
}
};
} // namespace detail
template <detail::string_fn... str>
struct concat_literals {
static constexpr auto value() {
return detail::concat_literals<decltype(detail::to_string_literal<str>(
std::make_index_sequence<detail::string_length(str())>()))...>::value();
}
};
} // namespace mbgl
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