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llvm-project/libcxx/include/__iterator/iterator_traits.h

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// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___ITERATOR_ITERATOR_TRAITS_H
#define _LIBCPP___ITERATOR_ITERATOR_TRAITS_H
#include <__config>
#include <__iterator/incrementable_traits.h>
#include <__iterator/readable_traits.h>
#include <concepts>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17
template <class _Tp>
using __with_reference = _Tp&;
template <class _Tp>
concept __can_reference = requires {
typename __with_reference<_Tp>;
};
template <class _Tp>
concept __dereferenceable = requires(_Tp& __t) {
{ *__t } -> __can_reference; // not required to be equality-preserving
};
// [iterator.traits]
template<__dereferenceable _Tp>
using iter_reference_t = decltype(*declval<_Tp&>());
#endif // _LIBCPP_STD_VER > 17
template <class _Iter>
struct _LIBCPP_TEMPLATE_VIS iterator_traits;
struct _LIBCPP_TEMPLATE_VIS input_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS output_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS forward_iterator_tag : public input_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS bidirectional_iterator_tag : public forward_iterator_tag {};
struct _LIBCPP_TEMPLATE_VIS random_access_iterator_tag : public bidirectional_iterator_tag {};
#if _LIBCPP_STD_VER > 17
struct _LIBCPP_TEMPLATE_VIS contiguous_iterator_tag : public random_access_iterator_tag {};
#endif
template <class _Iter>
struct __iter_traits_cache {
using type = _If<
__is_primary_template<iterator_traits<_Iter> >::value,
_Iter,
iterator_traits<_Iter>
>;
};
template <class _Iter>
using _ITER_TRAITS = typename __iter_traits_cache<_Iter>::type;
struct __iter_concept_concept_test {
template <class _Iter>
using _Apply = typename _ITER_TRAITS<_Iter>::iterator_concept;
};
struct __iter_concept_category_test {
template <class _Iter>
using _Apply = typename _ITER_TRAITS<_Iter>::iterator_category;
};
struct __iter_concept_random_fallback {
template <class _Iter>
using _Apply = __enable_if_t<
__is_primary_template<iterator_traits<_Iter> >::value,
random_access_iterator_tag
>;
};
template <class _Iter, class _Tester> struct __test_iter_concept
: _IsValidExpansion<_Tester::template _Apply, _Iter>,
_Tester
{
};
template <class _Iter>
struct __iter_concept_cache {
using type = _Or<
__test_iter_concept<_Iter, __iter_concept_concept_test>,
__test_iter_concept<_Iter, __iter_concept_category_test>,
__test_iter_concept<_Iter, __iter_concept_random_fallback>
>;
};
template <class _Iter>
using _ITER_CONCEPT = typename __iter_concept_cache<_Iter>::type::template _Apply<_Iter>;
template <class _Tp>
struct __has_iterator_typedefs
{
private:
struct __two {char __lx; char __lxx;};
template <class _Up> static __two __test(...);
template <class _Up> static char __test(typename __void_t<typename _Up::iterator_category>::type* = 0,
typename __void_t<typename _Up::difference_type>::type* = 0,
typename __void_t<typename _Up::value_type>::type* = 0,
typename __void_t<typename _Up::reference>::type* = 0,
typename __void_t<typename _Up::pointer>::type* = 0);
public:
static const bool value = sizeof(__test<_Tp>(0,0,0,0,0)) == 1;
};
template <class _Tp>
struct __has_iterator_category
{
private:
struct __two {char __lx; char __lxx;};
template <class _Up> static __two __test(...);
template <class _Up> static char __test(typename _Up::iterator_category* = nullptr);
public:
static const bool value = sizeof(__test<_Tp>(nullptr)) == 1;
};
template <class _Tp>
struct __has_iterator_concept
{
private:
struct __two {char __lx; char __lxx;};
template <class _Up> static __two __test(...);
template <class _Up> static char __test(typename _Up::iterator_concept* = nullptr);
public:
static const bool value = sizeof(__test<_Tp>(nullptr)) == 1;
};
#if _LIBCPP_STD_VER > 17
// The `cpp17-*-iterator` exposition-only concepts have very similar names to the `Cpp17*Iterator` named requirements
// from `[iterator.cpp17]`. To avoid confusion between the two, the exposition-only concepts have been banished to
// a "detail" namespace indicating they have a niche use-case.
namespace __iterator_traits_detail {
template<class _Ip>
concept __cpp17_iterator =
requires(_Ip __i) {
{ *__i } -> __can_reference;
{ ++__i } -> same_as<_Ip&>;
{ *__i++ } -> __can_reference;
} &&
copyable<_Ip>;
template<class _Ip>
concept __cpp17_input_iterator =
__cpp17_iterator<_Ip> &&
equality_comparable<_Ip> &&
requires(_Ip __i) {
typename incrementable_traits<_Ip>::difference_type;
typename indirectly_readable_traits<_Ip>::value_type;
typename common_reference_t<iter_reference_t<_Ip>&&,
typename indirectly_readable_traits<_Ip>::value_type&>;
typename common_reference_t<decltype(*__i++)&&,
typename indirectly_readable_traits<_Ip>::value_type&>;
requires signed_integral<typename incrementable_traits<_Ip>::difference_type>;
};
template<class _Ip>
concept __cpp17_forward_iterator =
__cpp17_input_iterator<_Ip> &&
constructible_from<_Ip> &&
is_lvalue_reference_v<iter_reference_t<_Ip>> &&
same_as<remove_cvref_t<iter_reference_t<_Ip>>,
typename indirectly_readable_traits<_Ip>::value_type> &&
requires(_Ip __i) {
{ __i++ } -> convertible_to<_Ip const&>;
{ *__i++ } -> same_as<iter_reference_t<_Ip>>;
};
template<class _Ip>
concept __cpp17_bidirectional_iterator =
__cpp17_forward_iterator<_Ip> &&
requires(_Ip __i) {
{ --__i } -> same_as<_Ip&>;
{ __i-- } -> convertible_to<_Ip const&>;
{ *__i-- } -> same_as<iter_reference_t<_Ip>>;
};
template<class _Ip>
concept __cpp17_random_access_iterator =
__cpp17_bidirectional_iterator<_Ip> &&
totally_ordered<_Ip> &&
requires(_Ip __i, typename incrementable_traits<_Ip>::difference_type __n) {
{ __i += __n } -> same_as<_Ip&>;
{ __i -= __n } -> same_as<_Ip&>;
{ __i + __n } -> same_as<_Ip>;
{ __n + __i } -> same_as<_Ip>;
{ __i - __n } -> same_as<_Ip>;
{ __i - __i } -> same_as<decltype(__n)>; // NOLINT(misc-redundant-expression) ; This is llvm.org/PR54114
{ __i[__n] } -> convertible_to<iter_reference_t<_Ip>>;
};
} // namespace __iterator_traits_detail
template<class _Ip>
concept __has_member_reference = requires { typename _Ip::reference; };
template<class _Ip>
concept __has_member_pointer = requires { typename _Ip::pointer; };
template<class _Ip>
concept __has_member_iterator_category = requires { typename _Ip::iterator_category; };
template<class _Ip>
concept __specifies_members = requires {
typename _Ip::value_type;
typename _Ip::difference_type;
requires __has_member_reference<_Ip>;
requires __has_member_iterator_category<_Ip>;
};
template<class>
struct __iterator_traits_member_pointer_or_void {
using type = void;
};
template<__has_member_pointer _Tp>
struct __iterator_traits_member_pointer_or_void<_Tp> {
using type = typename _Tp::pointer;
};
template<class _Tp>
concept __cpp17_iterator_missing_members =
!__specifies_members<_Tp> &&
__iterator_traits_detail::__cpp17_iterator<_Tp>;
template<class _Tp>
concept __cpp17_input_iterator_missing_members =
__cpp17_iterator_missing_members<_Tp> &&
__iterator_traits_detail::__cpp17_input_iterator<_Tp>;
// Otherwise, `pointer` names `void`.
template<class>
struct __iterator_traits_member_pointer_or_arrow_or_void { using type = void; };
// [iterator.traits]/3.2.1
// If the qualified-id `I::pointer` is valid and denotes a type, `pointer` names that type.
template<__has_member_pointer _Ip>
struct __iterator_traits_member_pointer_or_arrow_or_void<_Ip> { using type = typename _Ip::pointer; };
// Otherwise, if `decltype(declval<I&>().operator->())` is well-formed, then `pointer` names that
// type.
template<class _Ip>
requires requires(_Ip& __i) { __i.operator->(); } && (!__has_member_pointer<_Ip>)
struct __iterator_traits_member_pointer_or_arrow_or_void<_Ip> {
using type = decltype(declval<_Ip&>().operator->());
};
// Otherwise, `reference` names `iter-reference-t<I>`.
template<class _Ip>
struct __iterator_traits_member_reference { using type = iter_reference_t<_Ip>; };
// [iterator.traits]/3.2.2
// If the qualified-id `I::reference` is valid and denotes a type, `reference` names that type.
template<__has_member_reference _Ip>
struct __iterator_traits_member_reference<_Ip> { using type = typename _Ip::reference; };
// [iterator.traits]/3.2.3.4
// input_iterator_tag
template<class _Ip>
struct __deduce_iterator_category {
using type = input_iterator_tag;
};
// [iterator.traits]/3.2.3.1
// `random_access_iterator_tag` if `I` satisfies `cpp17-random-access-iterator`, or otherwise
template<__iterator_traits_detail::__cpp17_random_access_iterator _Ip>
struct __deduce_iterator_category<_Ip> {
using type = random_access_iterator_tag;
};
// [iterator.traits]/3.2.3.2
// `bidirectional_iterator_tag` if `I` satisfies `cpp17-bidirectional-iterator`, or otherwise
template<__iterator_traits_detail::__cpp17_bidirectional_iterator _Ip>
struct __deduce_iterator_category<_Ip> {
using type = bidirectional_iterator_tag;
};
// [iterator.traits]/3.2.3.3
// `forward_iterator_tag` if `I` satisfies `cpp17-forward-iterator`, or otherwise
template<__iterator_traits_detail::__cpp17_forward_iterator _Ip>
struct __deduce_iterator_category<_Ip> {
using type = forward_iterator_tag;
};
template<class _Ip>
struct __iterator_traits_iterator_category : __deduce_iterator_category<_Ip> {};
// [iterator.traits]/3.2.3
// If the qualified-id `I::iterator-category` is valid and denotes a type, `iterator-category` names
// that type.
template<__has_member_iterator_category _Ip>
struct __iterator_traits_iterator_category<_Ip> {
using type = typename _Ip::iterator_category;
};
// otherwise, it names void.
template<class>
struct __iterator_traits_difference_type { using type = void; };
// If the qualified-id `incrementable_traits<I>::difference_type` is valid and denotes a type, then
// `difference_type` names that type;
template<class _Ip>
requires requires { typename incrementable_traits<_Ip>::difference_type; }
struct __iterator_traits_difference_type<_Ip> {
using type = typename incrementable_traits<_Ip>::difference_type;
};
// [iterator.traits]/3.4
// Otherwise, `iterator_traits<I>` has no members by any of the above names.
template<class>
struct __iterator_traits {};
// [iterator.traits]/3.1
// If `I` has valid ([temp.deduct]) member types `difference-type`, `value-type`, `reference`, and
// `iterator-category`, then `iterator-traits<I>` has the following publicly accessible members:
template<__specifies_members _Ip>
struct __iterator_traits<_Ip> {
using iterator_category = typename _Ip::iterator_category;
using value_type = typename _Ip::value_type;
using difference_type = typename _Ip::difference_type;
using pointer = typename __iterator_traits_member_pointer_or_void<_Ip>::type;
using reference = typename _Ip::reference;
};
// [iterator.traits]/3.2
// Otherwise, if `I` satisfies the exposition-only concept `cpp17-input-iterator`,
// `iterator-traits<I>` has the following publicly accessible members:
template<__cpp17_input_iterator_missing_members _Ip>
struct __iterator_traits<_Ip> {
using iterator_category = typename __iterator_traits_iterator_category<_Ip>::type;
using value_type = typename indirectly_readable_traits<_Ip>::value_type;
using difference_type = typename incrementable_traits<_Ip>::difference_type;
using pointer = typename __iterator_traits_member_pointer_or_arrow_or_void<_Ip>::type;
using reference = typename __iterator_traits_member_reference<_Ip>::type;
};
// Otherwise, if `I` satisfies the exposition-only concept `cpp17-iterator`, then
// `iterator_traits<I>` has the following publicly accessible members:
template<__cpp17_iterator_missing_members _Ip>
struct __iterator_traits<_Ip> {
using iterator_category = output_iterator_tag;
using value_type = void;
using difference_type = typename __iterator_traits_difference_type<_Ip>::type;
using pointer = void;
using reference = void;
};
template<class _Ip>
struct iterator_traits : __iterator_traits<_Ip> {
using __primary_template = iterator_traits;
};
#else // _LIBCPP_STD_VER > 17
template <class _Iter, bool> struct __iterator_traits {};
template <class _Iter, bool> struct __iterator_traits_impl {};
template <class _Iter>
struct __iterator_traits_impl<_Iter, true>
{
typedef typename _Iter::difference_type difference_type;
typedef typename _Iter::value_type value_type;
typedef typename _Iter::pointer pointer;
typedef typename _Iter::reference reference;
typedef typename _Iter::iterator_category iterator_category;
};
template <class _Iter>
struct __iterator_traits<_Iter, true>
: __iterator_traits_impl
<
_Iter,
is_convertible<typename _Iter::iterator_category, input_iterator_tag>::value ||
is_convertible<typename _Iter::iterator_category, output_iterator_tag>::value
>
{};
// iterator_traits<Iterator> will only have the nested types if Iterator::iterator_category
// exists. Else iterator_traits<Iterator> will be an empty class. This is a
// conforming extension which allows some programs to compile and behave as
// the client expects instead of failing at compile time.
template <class _Iter>
struct _LIBCPP_TEMPLATE_VIS iterator_traits
: __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> {
using __primary_template = iterator_traits;
};
#endif // _LIBCPP_STD_VER > 17
template<class _Tp>
#if _LIBCPP_STD_VER > 17
requires is_object_v<_Tp>
#endif
struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
{
typedef ptrdiff_t difference_type;
typedef typename remove_cv<_Tp>::type value_type;
typedef _Tp* pointer;
typedef _Tp& reference;
typedef random_access_iterator_tag iterator_category;
#if _LIBCPP_STD_VER > 17
typedef contiguous_iterator_tag iterator_concept;
#endif
};
template <class _Tp, class _Up, bool = __has_iterator_category<iterator_traits<_Tp> >::value>
struct __has_iterator_category_convertible_to
: is_convertible<typename iterator_traits<_Tp>::iterator_category, _Up>
{};
template <class _Tp, class _Up>
struct __has_iterator_category_convertible_to<_Tp, _Up, false> : false_type {};
template <class _Tp, class _Up, bool = __has_iterator_concept<_Tp>::value>
struct __has_iterator_concept_convertible_to
: is_convertible<typename _Tp::iterator_concept, _Up>
{};
template <class _Tp, class _Up>
struct __has_iterator_concept_convertible_to<_Tp, _Up, false> : false_type {};
template <class _Tp>
struct __is_cpp17_input_iterator : public __has_iterator_category_convertible_to<_Tp, input_iterator_tag> {};
template <class _Tp>
struct __is_cpp17_forward_iterator : public __has_iterator_category_convertible_to<_Tp, forward_iterator_tag> {};
template <class _Tp>
struct __is_cpp17_bidirectional_iterator : public __has_iterator_category_convertible_to<_Tp, bidirectional_iterator_tag> {};
template <class _Tp>
struct __is_cpp17_random_access_iterator : public __has_iterator_category_convertible_to<_Tp, random_access_iterator_tag> {};
// __is_cpp17_contiguous_iterator determines if an iterator is known by
// libc++ to be contiguous, either because it advertises itself as such
// (in C++20) or because it is a pointer type or a known trivial wrapper
// around a (possibly fancy) pointer type, such as __wrap_iter<T*>.
// Such iterators receive special "contiguous" optimizations in
// std::copy and std::sort.
//
#if _LIBCPP_STD_VER > 17
template <class _Tp>
struct __is_cpp17_contiguous_iterator : _Or<
__has_iterator_category_convertible_to<_Tp, contiguous_iterator_tag>,
__has_iterator_concept_convertible_to<_Tp, contiguous_iterator_tag>
> {};
#else
template <class _Tp>
struct __is_cpp17_contiguous_iterator : false_type {};
#endif
// Any native pointer which is an iterator is also a contiguous iterator.
template <class _Up>
struct __is_cpp17_contiguous_iterator<_Up*> : true_type {};
template <class _Tp>
struct __is_exactly_cpp17_input_iterator
: public integral_constant<bool,
__has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value &&
!__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {};
#if _LIBCPP_STD_VER >= 17
template<class _InputIterator>
using __iter_value_type = typename iterator_traits<_InputIterator>::value_type;
template<class _InputIterator>
using __iter_key_type = remove_const_t<typename iterator_traits<_InputIterator>::value_type::first_type>;
template<class _InputIterator>
using __iter_mapped_type = typename iterator_traits<_InputIterator>::value_type::second_type;
template<class _InputIterator>
using __iter_to_alloc_type = pair<
add_const_t<typename iterator_traits<_InputIterator>::value_type::first_type>,
typename iterator_traits<_InputIterator>::value_type::second_type>;
#endif // _LIBCPP_STD_VER >= 17
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ITERATOR_ITERATOR_TRAITS_H
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