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//===----------------------------------------------------------------------===//
//
// 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_ALIASING_ITERATOR_H
#define _LIBCPP___ITERATOR_ALIASING_ITERATOR_H
#include <__config>
#include <__iterator/iterator_traits.h>
#include <__memory/pointer_traits.h>
#include <__type_traits/is_trivial.h>
#include <cstddef>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
// This iterator wrapper is used to type-pun an iterator to return a different type. This is done without UB by not
// actually punning the type, but instead inspecting the object representation of the base type and copying that into
// an instance of the alias type. For that reason the alias type has to be trivial. The alias is returned as a prvalue
// when derferencing the iterator, since it is temporary storage. This wrapper is used to vectorize some algorithms.
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _BaseIter, class _Alias>
struct __aliasing_iterator_wrapper {
class __iterator {
_BaseIter __base_ = nullptr;
using __iter_traits = iterator_traits<_BaseIter>;
using __base_value_type = typename __iter_traits::value_type;
static_assert(__has_random_access_iterator_category<_BaseIter>::value,
"The base iterator has to be a random access iterator!");
public:
using iterator_category = random_access_iterator_tag;
using value_type = _Alias;
using difference_type = ptrdiff_t;
using reference = value_type&;
using pointer = value_type*;
static_assert(is_trivial<value_type>::value);
static_assert(sizeof(__base_value_type) == sizeof(value_type));
_LIBCPP_HIDE_FROM_ABI __iterator() = default;
_LIBCPP_HIDE_FROM_ABI __iterator(_BaseIter __base) _NOEXCEPT : __base_(__base) {}
_LIBCPP_HIDE_FROM_ABI __iterator& operator++() _NOEXCEPT {
++__base_;
return *this;
}
_LIBCPP_HIDE_FROM_ABI __iterator operator++(int) _NOEXCEPT {
__iterator __tmp(*this);
++__base_;
return __tmp;
}
_LIBCPP_HIDE_FROM_ABI __iterator& operator--() _NOEXCEPT {
--__base_;
return *this;
}
_LIBCPP_HIDE_FROM_ABI __iterator operator--(int) _NOEXCEPT {
__iterator __tmp(*this);
--__base_;
return __tmp;
}
_LIBCPP_HIDE_FROM_ABI friend __iterator operator+(__iterator __iter, difference_type __n) _NOEXCEPT {
return __iterator(__iter.__base_ + __n);
}
_LIBCPP_HIDE_FROM_ABI friend __iterator operator+(difference_type __n, __iterator __iter) _NOEXCEPT {
return __iterator(__n + __iter.__base_);
}
_LIBCPP_HIDE_FROM_ABI __iterator& operator+=(difference_type __n) _NOEXCEPT {
__base_ += __n;
return *this;
}
_LIBCPP_HIDE_FROM_ABI friend __iterator operator-(__iterator __iter, difference_type __n) _NOEXCEPT {
return __iterator(__iter.__base_ - __n);
}
_LIBCPP_HIDE_FROM_ABI friend difference_type operator-(__iterator __lhs, __iterator __rhs) _NOEXCEPT {
return __lhs.__base_ - __rhs.__base_;
}
_LIBCPP_HIDE_FROM_ABI __iterator& operator-=(difference_type __n) _NOEXCEPT {
__base_ -= __n;
return *this;
}
_LIBCPP_HIDE_FROM_ABI _BaseIter __base() const _NOEXCEPT { return __base_; }
_LIBCPP_HIDE_FROM_ABI _Alias operator*() const _NOEXCEPT {
_Alias __val;
__builtin_memcpy(&__val, std::__to_address(__base_), sizeof(value_type));
return __val;
}
_LIBCPP_HIDE_FROM_ABI value_type operator[](difference_type __n) const _NOEXCEPT { return *(*this + __n); }
_LIBCPP_HIDE_FROM_ABI friend bool operator==(const __iterator& __lhs, const __iterator& __rhs) _NOEXCEPT {
return __lhs.__base_ == __rhs.__base_;
}
_LIBCPP_HIDE_FROM_ABI friend bool operator!=(const __iterator& __lhs, const __iterator& __rhs) _NOEXCEPT {
return __lhs.__base_ != __rhs.__base_;
}
};
};
// This is required to avoid ADL instantiations on _BaseT
template <class _BaseT, class _Alias>
using __aliasing_iterator = typename __aliasing_iterator_wrapper<_BaseT, _Alias>::__iterator;
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ITERATOR_ALIASING_ITERATOR_H
|
