[libcxx][ranges] Add `counted_iterator`.
Differential Revision: https://reviews.llvm.org/D106205
NOKEYCHECK=True
GitOrigin-RevId: 8a48e6dda9f7fb9c7ae7207dcb9570d2c11255ad
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index dd4b812..5fba760 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -135,6 +135,7 @@
__iterator/back_insert_iterator.h
__iterator/common_iterator.h
__iterator/concepts.h
+ __iterator/counted_iterator.h
__iterator/data.h
__iterator/default_sentinel.h
__iterator/distance.h
diff --git a/include/__iterator/counted_iterator.h b/include/__iterator/counted_iterator.h
new file mode 100644
index 0000000..7136aaf
--- /dev/null
+++ b/include/__iterator/counted_iterator.h
@@ -0,0 +1,306 @@
+// -*- 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_COUNTED_ITERATOR_H
+#define _LIBCPP___ITERATOR_COUNTED_ITERATOR_H
+
+#include <__config>
+#include <__debug>
+#include <__iterator/concepts.h>
+#include <__iterator/default_sentinel.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iter_swap.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/readable_traits.h>
+#include <__memory/pointer_traits.h>
+#include <concepts>
+#include <type_traits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if !defined(_LIBCPP_HAS_NO_RANGES)
+
+template<class>
+struct __counted_iterator_concept {};
+
+template<class _Iter>
+ requires requires { typename _Iter::iterator_concept; }
+struct __counted_iterator_concept<_Iter> {
+ using iterator_concept = typename _Iter::iterator_concept;
+};
+
+template<class>
+struct __counted_iterator_category {};
+
+template<class _Iter>
+ requires requires { typename _Iter::iterator_category; }
+struct __counted_iterator_category<_Iter> {
+ using iterator_category = typename _Iter::iterator_category;
+};
+
+template<class>
+struct __counted_iterator_value_type {};
+
+template<indirectly_readable _Iter>
+struct __counted_iterator_value_type<_Iter> {
+ using value_type = iter_value_t<_Iter>;
+};
+
+template<input_or_output_iterator _Iter>
+class counted_iterator
+ : public __counted_iterator_concept<_Iter>
+ , public __counted_iterator_category<_Iter>
+ , public __counted_iterator_value_type<_Iter>
+{
+public:
+ [[no_unique_address]] _Iter __current_ = _Iter();
+ iter_difference_t<_Iter> __count_ = 0;
+
+ using iterator_type = _Iter;
+ using difference_type = iter_difference_t<_Iter>;
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator() requires default_initializable<_Iter> = default;
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator(_Iter __iter, iter_difference_t<_Iter> __n)
+ : __current_(_VSTD::move(__iter)), __count_(__n) {
+ _LIBCPP_ASSERT(__n >= 0, "__n must not be negative.");
+ }
+
+ template<class _I2>
+ requires convertible_to<const _I2&, _Iter>
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator(const counted_iterator<_I2>& __other)
+ : __current_(__other.__current_), __count_(__other.__count_) {}
+
+ template<class _I2>
+ requires assignable_from<_Iter&, const _I2&>
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator& operator=(const counted_iterator<_I2>& __other) {
+ __current_ = __other.__current_;
+ __count_ = __other.__count_;
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr const _Iter& base() const& { return __current_; }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr _Iter base() && { return _VSTD::move(__current_); }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr iter_difference_t<_Iter> count() const noexcept { return __count_; }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr decltype(auto) operator*() {
+ _LIBCPP_ASSERT(__count_ > 0, "Iterator is equal to or past end.");
+ return *__current_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr decltype(auto) operator*() const
+ requires __dereferenceable<const _Iter>
+ {
+ _LIBCPP_ASSERT(__count_ > 0, "Iterator is equal to or past end.");
+ return *__current_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr auto operator->() const noexcept
+ requires contiguous_iterator<_Iter>
+ {
+ return _VSTD::to_address(__current_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator& operator++() {
+ _LIBCPP_ASSERT(__count_ > 0, "Iterator already at or past end.");
+ ++__current_;
+ --__count_;
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ decltype(auto) operator++(int) {
+ _LIBCPP_ASSERT(__count_ > 0, "Iterator already at or past end.");
+ --__count_;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+ try { return __current_++; }
+ catch(...) { ++__count_; throw; }
+#else
+ return __current_++;
+#endif // _LIBCPP_NO_EXCEPTIONS
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator operator++(int)
+ requires forward_iterator<_Iter>
+ {
+ _LIBCPP_ASSERT(__count_ > 0, "Iterator already at or past end.");
+ counted_iterator __tmp = *this;
+ ++*this;
+ return __tmp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator& operator--()
+ requires bidirectional_iterator<_Iter>
+ {
+ --__current_;
+ ++__count_;
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator operator--(int)
+ requires bidirectional_iterator<_Iter>
+ {
+ counted_iterator __tmp = *this;
+ --*this;
+ return __tmp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator operator+(iter_difference_t<_Iter> __n) const
+ requires random_access_iterator<_Iter>
+ {
+ return counted_iterator(__current_ + __n, __count_ - __n);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr counted_iterator operator+(
+ iter_difference_t<_Iter> __n, const counted_iterator& __x)
+ requires random_access_iterator<_Iter>
+ {
+ return __x + __n;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator& operator+=(iter_difference_t<_Iter> __n)
+ requires random_access_iterator<_Iter>
+ {
+ _LIBCPP_ASSERT(__n <= __count_, "Cannot advance iterator past end.");
+ __current_ += __n;
+ __count_ -= __n;
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator operator-(iter_difference_t<_Iter> __n) const
+ requires random_access_iterator<_Iter>
+ {
+ return counted_iterator(__current_ - __n, __count_ + __n);
+ }
+
+ template<common_with<_Iter> _I2>
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr iter_difference_t<_I2> operator-(
+ const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs)
+ {
+ return __rhs.__count_ - __lhs.__count_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr iter_difference_t<_Iter> operator-(
+ const counted_iterator& __lhs, default_sentinel_t)
+ {
+ return -__lhs.__count_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr iter_difference_t<_Iter> operator-(
+ default_sentinel_t, const counted_iterator& __rhs)
+ {
+ return __rhs.__count_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr counted_iterator& operator-=(iter_difference_t<_Iter> __n)
+ requires random_access_iterator<_Iter>
+ {
+ _LIBCPP_ASSERT(-__n <= __count_, "Attempt to subtract too large of a size: "
+ "counted_iterator would be decremented before the "
+ "first element of its range.");
+ __current_ -= __n;
+ __count_ += __n;
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ constexpr decltype(auto) operator[](iter_difference_t<_Iter> __n) const
+ requires random_access_iterator<_Iter>
+ {
+ _LIBCPP_ASSERT(__n < __count_, "Subscript argument must be less than size.");
+ return __current_[__n];
+ }
+
+ template<common_with<_Iter> _I2>
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr bool operator==(
+ const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs)
+ {
+ return __lhs.__count_ == __rhs.__count_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr bool operator==(
+ const counted_iterator& __lhs, default_sentinel_t)
+ {
+ return __lhs.__count_ == 0;
+ }
+
+ template<common_with<_Iter> _I2>
+ friend constexpr strong_ordering operator<=>(
+ const counted_iterator& __lhs, const counted_iterator<_I2>& __rhs)
+ {
+ return __rhs.__count_ <=> __lhs.__count_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr iter_rvalue_reference_t<_Iter> iter_move(const counted_iterator& __i)
+ noexcept(noexcept(ranges::iter_move(__i.__current_)))
+ requires input_iterator<_Iter>
+ {
+ _LIBCPP_ASSERT(__i.__count_ > 0, "Iterator must not be past end of range.");
+ return ranges::iter_move(__i.__current_);
+ }
+
+ template<indirectly_swappable<_Iter> _I2>
+ _LIBCPP_HIDE_FROM_ABI
+ friend constexpr void iter_swap(const counted_iterator& __x, const counted_iterator<_I2>& __y)
+ noexcept(noexcept(ranges::iter_swap(__x.__current_, __y.__current_)))
+ {
+ _LIBCPP_ASSERT(__x.__count_ > 0 && __y.__count_ > 0,
+ "Iterators must not be past end of range.");
+ return ranges::iter_swap(__x.__current_, __y.__current_);
+ }
+};
+
+template<input_iterator _Iter>
+ requires same_as<_ITER_TRAITS<_Iter>, iterator_traits<_Iter>>
+struct iterator_traits<counted_iterator<_Iter>> : iterator_traits<_Iter> {
+ using pointer = conditional_t<contiguous_iterator<_Iter>,
+ add_pointer_t<iter_reference_t<_Iter>>, void>;
+};
+
+#endif // !defined(_LIBCPP_HAS_NO_RANGES)
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ITERATOR_COUNTED_ITERATOR_H
diff --git a/include/iterator b/include/iterator
index a9f794c..e0b2520 100644
--- a/include/iterator
+++ b/include/iterator
@@ -403,6 +403,13 @@
struct default_sentinel_t;
inline constexpr default_sentinel_t default_sentinel{};
+// [iterators.counted], counted iterators
+template<input_or_output_iterator I> class counted_iterator;
+
+template<input_iterator I>
+ requires see below
+ struct iterator_traits<counted_iterator<I>>;
+
template <class T, class charT = char, class traits = char_traits<charT>, class Distance = ptrdiff_t>
class istream_iterator
: public iterator<input_iterator_tag, T, Distance, const T*, const T&> // until C++17
@@ -574,6 +581,7 @@
#include <__iterator/back_insert_iterator.h>
#include <__iterator/common_iterator.h>
#include <__iterator/concepts.h>
+#include <__iterator/counted_iterator.h>
#include <__iterator/data.h>
#include <__iterator/default_sentinel.h>
#include <__iterator/distance.h>
diff --git a/include/module.modulemap b/include/module.modulemap
index 11cabad..b5781b0 100644
--- a/include/module.modulemap
+++ b/include/module.modulemap
@@ -485,6 +485,7 @@
module back_insert_iterator { private header "__iterator/back_insert_iterator.h" }
module common_iterator { private header "__iterator/common_iterator.h" }
module concepts { private header "__iterator/concepts.h" }
+ module counted_iterator { private header "__iterator/counted_iterator.h" }
module data { private header "__iterator/data.h" }
module default_sentinel { private header "__iterator/default_sentinel.h" }
module distance { private header "__iterator/distance.h" }