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_BEGIN_NAMESPACE_STD 25 26 // TODO: Change the name of __unwrap_iter_impl to something more appropriate 27 // The job of __unwrap_iter is to remove iterator wrappers (like reverse_iterator or __wrap_iter), 28 // to reduce the number of template instantiations and to enable pointer-based optimizations e.g. in std::copy. 29 // In debug mode, we don't do this. 30 // 31 // Some algorithms (e.g. std::copy, but not std::sort) need to convert an 32 // "unwrapped" result back into the original iterator type. Doing that is the job of __rewrap_iter. 33 34 // Default case - we can't unwrap anything 35 template <class _Iter, bool = __is_cpp17_contiguous_iterator<_Iter>::value> 36 struct __unwrap_iter_impl { 37 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter, _Iter __iter) { return __iter; } 38 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __unwrap(_Iter __i) _NOEXCEPT { return __i; } 39 }; 40 41 #ifndef _LIBCPP_ENABLE_DEBUG_MODE 42 43 // It's a contiguous iterator, so we can use a raw pointer instead 44 template <class _Iter> 45 struct __unwrap_iter_impl<_Iter, true> { 46 using _ToAddressT = decltype(std::__to_address(std::declval<_Iter>())); 47 48 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter __orig_iter, _ToAddressT __unwrapped_iter) { 49 return __orig_iter + (__unwrapped_iter - std::__to_address(__orig_iter)); 50 } 51 52 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ToAddressT __unwrap(_Iter __i) _NOEXCEPT { 53 return std::__to_address(__i); 54 } 55 }; 56 57 #endif // !_LIBCPP_ENABLE_DEBUG_MODE 58 59 template<class _Iter, 60 class _Impl = __unwrap_iter_impl<_Iter>, 61 __enable_if_t<is_copy_constructible<_Iter>::value, int> = 0> 62 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 63 decltype(_Impl::__unwrap(std::declval<_Iter>())) __unwrap_iter(_Iter __i) _NOEXCEPT { 64 return _Impl::__unwrap(__i); 65 } 66 67 template <class _OrigIter, class _Iter, class _Impl = __unwrap_iter_impl<_OrigIter> > 68 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _OrigIter __rewrap_iter(_OrigIter __orig_iter, _Iter __iter) _NOEXCEPT { 69 return _Impl::__rewrap(std::move(__orig_iter), std::move(__iter)); 70 } 71 72 _LIBCPP_END_NAMESPACE_STD 73 74 #endif // _LIBCPP___ALGORITHM_UNWRAP_ITER_H 75