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Reintroduce back_insert_iterator detection

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This commit is contained in:
Victor Zverovich 2024-01-07 17:44:40 -08:00
parent df67df7b4c
commit f348d1a211
1 changed files with 32 additions and 21 deletions
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53
include/fmt/core.h
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@ -478,6 +478,25 @@ FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, std::size_t n)
}
return 0;
}
template <typename It, typename Enable = std::true_type>
struct is_back_insert_iterator : std::false_type {};
template <typename It>
struct is_back_insert_iterator<
It,
bool_constant<std::is_same<
decltype(back_inserter(std::declval<typename It::container_type&>())),
It>::value>> : std::true_type {};
// Extracts a reference to the container from *insert_iterator.
template <typename OutputIt>
inline auto get_container(OutputIt it) -> typename OutputIt::container_type& {
struct accessor : OutputIt {
accessor(OutputIt base) : OutputIt(base) {}
using OutputIt::container;
};
return *accessor(it).container;
}
} // namespace detail
template <typename Char>
@ -1034,14 +1053,17 @@ template <typename T> class iterator_buffer<T*, T> : public buffer<T> {
};
// A buffer that writes to a container with the contiguous storage.
template <typename Container>
class iterator_buffer<back_insert_iterator<Container>,
enable_if_t<is_contiguous<Container>::value,
typename Container::value_type>>
: public buffer<typename Container::value_type> {
template <typename OutputIt>
class iterator_buffer<
OutputIt,
enable_if_t<detail::is_back_insert_iterator<OutputIt>::value &&
is_contiguous<typename OutputIt::container_type>::value,
typename OutputIt::container_type::value_type>>
: public buffer<typename OutputIt::container_type::value_type> {
private:
using value_type = typename Container::value_type;
Container& container_;
using container_type = typename OutputIt::container_type;
using value_type = typename container_type::value_type;
container_type& container_;
static FMT_CONSTEXPR20 void grow(buffer<value_type>& buf, size_t capacity) {
auto& self = static_cast<iterator_buffer&>(buf);
@ -1050,14 +1072,12 @@ class iterator_buffer<back_insert_iterator<Container>,
}
public:
explicit iterator_buffer(Container& c)
explicit iterator_buffer(container_type& c)
: buffer<value_type>(grow, c.size()), container_(c) {}
explicit iterator_buffer(back_insert_iterator<Container> out, size_t = 0)
explicit iterator_buffer(OutputIt out, size_t = 0)
: iterator_buffer(get_container(out)) {}
auto out() -> back_insert_iterator<Container> {
return back_inserter(container_);
}
auto out() -> OutputIt { return back_inserter(container_); }
};
// A buffer that counts the number of code units written discarding the output.
@ -1557,15 +1577,6 @@ struct is_output_iterator<
It, T, void_t<decltype(*std::declval<It&>()++ = std::declval<T>())>>
: std::true_type {};
template <typename It, typename Enable = std::true_type>
struct is_back_insert_iterator : std::false_type {};
template <typename It>
struct is_back_insert_iterator<
It, bool_constant<std::is_same<
decltype(back_inserter(
std::declval<typename It::container_type&>())),
It>::value>> : std::true_type {};
// A type-erased reference to an std::locale to avoid a heavy <locale> include.
class locale_ref {
private: