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_ITER_H 10 #define _LIBCPP___ALGORITHM_UNWRAP_ITER_H 11 12 #include <__config> 13 #include <__iterator/iterator_traits.h> 14 #include <__memory/pointer_traits.h> 15 #include <__type_traits/enable_if.h> 16 #include <__type_traits/is_copy_constructible.h> 17 #include <__utility/declval.h> 18 #include <__utility/move.h> 19 20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 21 # pragma GCC system_header 22 #endif 23 24 _LIBCPP_PUSH_MACROS 25 #include <__undef_macros> 26 27 _LIBCPP_BEGIN_NAMESPACE_STD 28 29 // TODO: Change the name of __unwrap_iter_impl to something more appropriate 30 // The job of __unwrap_iter is to remove iterator wrappers (like reverse_iterator or __wrap_iter), 31 // to reduce the number of template instantiations and to enable pointer-based optimizations e.g. in std::copy. 32 // 33 // Some algorithms (e.g. std::copy, but not std::sort) need to convert an 34 // "unwrapped" result back into the original iterator type. Doing that is the job of __rewrap_iter. 35 36 // Default case - we can't unwrap anything 37 template <class _Iter, bool = __libcpp_is_contiguous_iterator<_Iter>::value> 38 struct __unwrap_iter_impl { 39 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter, _Iter __iter) { return __iter; } 40 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __unwrap(_Iter __i) _NOEXCEPT { return __i; } 41 }; 42 43 // TODO(hardening): make sure that the following unwrapping doesn't unexpectedly turn hardened iterators into raw 44 // pointers. 45 46 // It's a contiguous iterator, so we can use a raw pointer instead 47 template <class _Iter> 48 struct __unwrap_iter_impl<_Iter, true> { 49 using _ToAddressT = decltype(std::__to_address(std::declval<_Iter>())); 50 51 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter __orig_iter, _ToAddressT __unwrapped_iter) { 52 return __orig_iter + (__unwrapped_iter - std::__to_address(__orig_iter)); 53 } 54 55 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ToAddressT __unwrap(_Iter __i) _NOEXCEPT { 56 return std::__to_address(__i); 57 } 58 }; 59 60 template<class _Iter, 61 class _Impl = __unwrap_iter_impl<_Iter>, 62 __enable_if_t<is_copy_constructible<_Iter>::value, int> = 0> 63 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 64 decltype(_Impl::__unwrap(std::declval<_Iter>())) __unwrap_iter(_Iter __i) _NOEXCEPT { 65 return _Impl::__unwrap(__i); 66 } 67 68 // Allow input_iterators to be passed to __unwrap_iter (but not __rewrap_iter) 69 #if _LIBCPP_STD_VER >= 20 70 template <class _Iter, __enable_if_t<!is_copy_constructible<_Iter>::value, int> = 0> 71 inline _LIBCPP_HIDE_FROM_ABI constexpr _Iter __unwrap_iter(_Iter __i) noexcept { 72 return __i; 73 } 74 #endif 75 76 template <class _OrigIter, class _Iter, class _Impl = __unwrap_iter_impl<_OrigIter> > 77 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _OrigIter __rewrap_iter(_OrigIter __orig_iter, _Iter __iter) _NOEXCEPT { 78 return _Impl::__rewrap(std::move(__orig_iter), std::move(__iter)); 79 } 80 81 _LIBCPP_END_NAMESPACE_STD 82 83 _LIBCPP_PUSH_MACROS 84 85 #endif // _LIBCPP___ALGORITHM_UNWRAP_ITER_H 86