Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__iterator/distance.h

@@ -0,0 +1,108 @@
+// -*- 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_DISTANCE_H
+#define _LIBCPP___ITERATOR_DISTANCE_H
+
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iterator_traits.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/size.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/remove_cvref.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _InputIter>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
+typename iterator_traits<_InputIter>::difference_type
+__distance(_InputIter __first, _InputIter __last, input_iterator_tag)
+{
+    typename iterator_traits<_InputIter>::difference_type __r(0);
+    for (; __first != __last; ++__first)
+        ++__r;
+    return __r;
+}
+
+template <class _RandIter>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
+typename iterator_traits<_RandIter>::difference_type
+__distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
+{
+    return __last - __first;
+}
+
+template <class _InputIter>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX17
+typename iterator_traits<_InputIter>::difference_type
+distance(_InputIter __first, _InputIter __last)
+{
+    return _VSTD::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
+}
+
+#if _LIBCPP_STD_VER >= 20
+
+// [range.iter.op.distance]
+
+namespace ranges {
+namespace __distance {
+
+struct __fn {
+  template<class _Ip, sentinel_for<_Ip> _Sp>
+    requires (!sized_sentinel_for<_Sp, _Ip>)
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const {
+    iter_difference_t<_Ip> __n = 0;
+    while (__first != __last) {
+      ++__first;
+      ++__n;
+    }
+    return __n;
+  }
+
+  template<class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr iter_difference_t<_Ip> operator()(_Ip&& __first, _Sp __last) const {
+    if constexpr (sized_sentinel_for<_Sp, __remove_cvref_t<_Ip>>) {
+      return __last - __first;
+    } else {
+      return __last - decay_t<_Ip>(__first);
+    }
+  }
+
+  template<range _Rp>
+  _LIBCPP_HIDE_FROM_ABI
+  constexpr range_difference_t<_Rp> operator()(_Rp&& __r) const {
+    if constexpr (sized_range<_Rp>) {
+      return static_cast<range_difference_t<_Rp>>(ranges::size(__r));
+    } else {
+      return operator()(ranges::begin(__r), ranges::end(__r));
+    }
+  }
+};
+
+} // namespace __distance
+
+inline namespace __cpo {
+  inline constexpr auto distance = __distance::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___ITERATOR_DISTANCE_H