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80 lines
1.8 KiB
C++
80 lines
1.8 KiB
C++
/**
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* @file libimp/countof.h
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* @author mutouyun (orz@orzz.org)
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* @brief Returns the size of the given range
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* @date 2022-03-01
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*/
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#pragma once
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#include <type_traits> // std::declval, std::true_type, std::false_type
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#include <cstddef> // std::size_t
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#include "libimp/def.h"
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#include "libimp/generic.h"
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LIBIMP_NAMESPACE_BEG_
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/**
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* @see https://en.cppreference.com/w/cpp/iterator/size
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*/
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namespace detail_countof {
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template <typename T>
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struct trait_has_size {
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private:
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template <typename Type>
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static std::true_type check(decltype(std::declval<Type>().size())*);
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template <typename Type>
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static std::false_type check(...);
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public:
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using type = decltype(check<T>(nullptr));
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constexpr static auto value = type::value;
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};
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template <typename T>
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struct trait_has_Size {
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private:
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template <typename Type>
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static std::true_type check(decltype(std::declval<Type>().Size())*);
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template <typename Type>
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static std::false_type check(...);
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public:
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using type = decltype(check<T>(nullptr));
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constexpr static auto value = type::value;
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};
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template <typename C, bool = trait_has_size<C>::value
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, bool = trait_has_Size<C>::value>
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struct trait;
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template <typename T, std::size_t N>
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struct trait<T[N], false, false> {
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constexpr static auto countof(T const (&)[N]) noexcept {
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return N;
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}
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};
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template <typename C, bool B>
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struct trait<C, true, B> {
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constexpr static auto countof(C const &c) noexcept(noexcept(c.size())) {
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return c.size();
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}
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};
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template <typename C>
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struct trait<C, false, true> {
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constexpr static auto countof(C const &c) noexcept(noexcept(c.Size())) {
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return c.Size();
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}
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};
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} // namespace detail_countof
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template <typename C, typename R = detail_countof::trait<C>>
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constexpr auto countof(C const &c) noexcept(noexcept(R::countof(c))) {
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return R::countof(c);
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}
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LIBIMP_NAMESPACE_END_
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