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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___ITERATOR_ALIASING_ITERATOR_H10#define _LIBCPP___ITERATOR_ALIASING_ITERATOR_H11 12#include <__config>13#include <__cstddef/ptrdiff_t.h>14#include <__iterator/iterator_traits.h>15#include <__memory/addressof.h>16#include <__memory/pointer_traits.h>17#include <__type_traits/is_trivially_constructible.h>18#include <__type_traits/is_trivially_copyable.h>19 20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)21# pragma GCC system_header22#endif23 24// This iterator wrapper is used to type-pun an iterator to return a different type. This is done without UB by not25// actually punning the type, but instead inspecting the object representation of the base type and copying that into26// an instance of the alias type. For that reason the alias type has to be trivial. The alias is returned as a prvalue27// when derferencing the iterator, since it is temporary storage. This wrapper is used to vectorize some algorithms.28 29_LIBCPP_BEGIN_NAMESPACE_STD30 31template <class _BaseIter, class _Alias>32struct __aliasing_iterator_wrapper {33 class __iterator {34 _BaseIter __base_ = nullptr;35 36 using __iter_traits _LIBCPP_NODEBUG = iterator_traits<_BaseIter>;37 using __base_value_type _LIBCPP_NODEBUG = typename __iter_traits::value_type;38 39 static_assert(__has_random_access_iterator_category<_BaseIter>::value,40 "The base iterator has to be a random access iterator!");41 42 public:43 using iterator_category = random_access_iterator_tag;44 using value_type = _Alias;45 using difference_type = ptrdiff_t;46 using reference = value_type&;47 using pointer = value_type*;48 49 static_assert(is_trivially_default_constructible<value_type>::value);50 static_assert(is_trivially_copyable<value_type>::value);51 static_assert(sizeof(__base_value_type) == sizeof(value_type));52 53 _LIBCPP_HIDE_FROM_ABI __iterator() = default;54 _LIBCPP_HIDE_FROM_ABI __iterator(_BaseIter __base) _NOEXCEPT : __base_(__base) {}55 56 _LIBCPP_HIDE_FROM_ABI __iterator& operator++() _NOEXCEPT {57 ++__base_;58 return *this;59 }60 61 _LIBCPP_HIDE_FROM_ABI __iterator operator++(int) _NOEXCEPT {62 __iterator __tmp(*this);63 ++__base_;64 return __tmp;65 }66 67 _LIBCPP_HIDE_FROM_ABI __iterator& operator--() _NOEXCEPT {68 --__base_;69 return *this;70 }71 72 _LIBCPP_HIDE_FROM_ABI __iterator operator--(int) _NOEXCEPT {73 __iterator __tmp(*this);74 --__base_;75 return __tmp;76 }77 78 _LIBCPP_HIDE_FROM_ABI friend __iterator operator+(__iterator __iter, difference_type __n) _NOEXCEPT {79 return __iterator(__iter.__base_ + __n);80 }81 82 _LIBCPP_HIDE_FROM_ABI friend __iterator operator+(difference_type __n, __iterator __iter) _NOEXCEPT {83 return __iterator(__n + __iter.__base_);84 }85 86 _LIBCPP_HIDE_FROM_ABI __iterator& operator+=(difference_type __n) _NOEXCEPT {87 __base_ += __n;88 return *this;89 }90 91 _LIBCPP_HIDE_FROM_ABI friend __iterator operator-(__iterator __iter, difference_type __n) _NOEXCEPT {92 return __iterator(__iter.__base_ - __n);93 }94 95 _LIBCPP_HIDE_FROM_ABI friend difference_type operator-(__iterator __lhs, __iterator __rhs) _NOEXCEPT {96 return __lhs.__base_ - __rhs.__base_;97 }98 99 _LIBCPP_HIDE_FROM_ABI __iterator& operator-=(difference_type __n) _NOEXCEPT {100 __base_ -= __n;101 return *this;102 }103 104 _LIBCPP_HIDE_FROM_ABI _BaseIter __base() const _NOEXCEPT { return __base_; }105 106 _LIBCPP_HIDE_FROM_ABI _Alias operator*() const _NOEXCEPT {107 _Alias __val;108 __builtin_memcpy(std::addressof(__val), std::__to_address(__base_), sizeof(value_type));109 return __val;110 }111 112 _LIBCPP_HIDE_FROM_ABI value_type operator[](difference_type __n) const _NOEXCEPT { return *(*this + __n); }113 114 _LIBCPP_HIDE_FROM_ABI friend bool operator==(const __iterator& __lhs, const __iterator& __rhs) _NOEXCEPT {115 return __lhs.__base_ == __rhs.__base_;116 }117 118 _LIBCPP_HIDE_FROM_ABI friend bool operator!=(const __iterator& __lhs, const __iterator& __rhs) _NOEXCEPT {119 return __lhs.__base_ != __rhs.__base_;120 }121 };122};123 124// This is required to avoid ADL instantiations on _BaseT125template <class _BaseT, class _Alias>126using __aliasing_iterator _LIBCPP_NODEBUG = typename __aliasing_iterator_wrapper<_BaseT, _Alias>::__iterator;127 128_LIBCPP_END_NAMESPACE_STD129 130#endif // _LIBCPP___ITERATOR_ALIASING_ITERATOR_H131