libcxx/include/__algorithm/unwrap_range.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___ALGORITHM_UNWRAP_RANGE_H
  10 #define _LIBCPP___ALGORITHM_UNWRAP_RANGE_H
  11
  12 #include <__algorithm/unwrap_iter.h>
  13 #include <__concepts/constructible.h>
  14 #include <__config>
  15 #include <__iterator/concepts.h>
  16 #include <__iterator/next.h>
  17 #include <__utility/declval.h>
  18 #include <__utility/move.h>
  19 #include <__utility/pair.h>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_BEGIN_NAMESPACE_STD
  26
  27 // __unwrap_range and __rewrap_range are used to unwrap ranges which may have different iterator and sentinel types.
  28 // __unwrap_iter and __rewrap_iter don't work for this, because they assume that the iterator and sentinel have
  29 // the same type. __unwrap_range tries to get two iterators and then forward to __unwrap_iter.
  30
  31 #if _LIBCPP_STD_VER >= 20
  32 template <class _Iter, class _Sent>
  33 struct __unwrap_range_impl {
  34   _LIBCPP_HIDE_FROM_ABI static constexpr auto __unwrap(_Iter __first, _Sent __sent)
  35     requires random_access_iterator<_Iter> && sized_sentinel_for<_Sent, _Iter>
  36   {
  37     auto __last = ranges::next(__first, __sent);
  38     return pair{std::__unwrap_iter(std::move(__first)), std::__unwrap_iter(std::move(__last))};
  39   }
  40
  41   _LIBCPP_HIDE_FROM_ABI static constexpr auto __unwrap(_Iter __first, _Sent __last) {
  42     return pair{std::move(__first), std::move(__last)};
  43   }
  44
  45   _LIBCPP_HIDE_FROM_ABI static constexpr auto
  46   __rewrap(_Iter __orig_iter, decltype(std::__unwrap_iter(std::move(__orig_iter))) __iter)
  47     requires random_access_iterator<_Iter> && sized_sentinel_for<_Sent, _Iter>
  48   {
  49     return std::__rewrap_iter(std::move(__orig_iter), std::move(__iter));
  50   }
  51
  52   _LIBCPP_HIDE_FROM_ABI static constexpr auto __rewrap(const _Iter&, _Iter __iter)
  53     requires(!(random_access_iterator<_Iter> && sized_sentinel_for<_Sent, _Iter>))
  54   {
  55     return __iter;
  56   }
  57 };
  58
  59 template <class _Iter>
  60 struct __unwrap_range_impl<_Iter, _Iter> {
  61   _LIBCPP_HIDE_FROM_ABI static constexpr auto __unwrap(_Iter __first, _Iter __last) {
  62     return pair{std::__unwrap_iter(std::move(__first)), std::__unwrap_iter(std::move(__last))};
  63   }
  64
  65   _LIBCPP_HIDE_FROM_ABI static constexpr auto
  66   __rewrap(_Iter __orig_iter, decltype(std::__unwrap_iter(__orig_iter)) __iter) {
  67     return std::__rewrap_iter(std::move(__orig_iter), std::move(__iter));
  68   }
  69 };
  70
  71 template <class _Iter, class _Sent>
  72 _LIBCPP_HIDE_FROM_ABI constexpr auto __unwrap_range(_Iter __first, _Sent __last) {
  73   return __unwrap_range_impl<_Iter, _Sent>::__unwrap(std::move(__first), std::move(__last));
  74 }
  75
  76 template < class _Sent, class _Iter, class _Unwrapped>
  77 _LIBCPP_HIDE_FROM_ABI constexpr _Iter __rewrap_range(_Iter __orig_iter, _Unwrapped __iter) {
  78   return __unwrap_range_impl<_Iter, _Sent>::__rewrap(std::move(__orig_iter), std::move(__iter));
  79 }
  80 #else  // _LIBCPP_STD_VER >= 20
  81 template <class _Iter, class _Unwrapped = decltype(std::__unwrap_iter(std::declval<_Iter>()))>
  82 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR pair<_Unwrapped, _Unwrapped> __unwrap_range(_Iter __first, _Iter __last) {
  83   return std::make_pair(std::__unwrap_iter(std::move(__first)), std::__unwrap_iter(std::move(__last)));
  84 }
  85
  86 template <class _Iter, class _Unwrapped>
  87 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap_range(_Iter __orig_iter, _Unwrapped __iter) {
  88   return std::__rewrap_iter(std::move(__orig_iter), std::move(__iter));
  89 }
  90 #endif // _LIBCPP_STD_VER >= 20
  91
  92 _LIBCPP_END_NAMESPACE_STD
  93
  94 #endif // _LIBCPP___ALGORITHM_UNWRAP_RANGE_H