chromium/third_party/libc++/src/include/__string/constexpr_c_functions.h

//===----------------------------------------------------------------------===//
//
// 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___STRING_CONSTEXPR_C_FUNCTIONS_H
#define _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H

#include <__config>
#include <__memory/addressof.h>
#include <__memory/construct_at.h>
#include <__type_traits/datasizeof.h>
#include <__type_traits/is_always_bitcastable.h>
#include <__type_traits/is_assignable.h>
#include <__type_traits/is_constant_evaluated.h>
#include <__type_traits/is_constructible.h>
#include <__type_traits/is_equality_comparable.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_trivially_copyable.h>
#include <__type_traits/is_trivially_lexicographically_comparable.h>
#include <__type_traits/remove_cv.h>
#include <__utility/is_pointer_in_range.h>
#include <cstddef>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

// Type used to encode that a function takes an integer that represents a number
// of elements as opposed to a number of bytes.
enum class __element_count : size_t { … };

__is_char_type;

__is_char_type;

#ifndef _LIBCPP_HAS_NO_CHAR8_T
__is_char_type;
#endif

template <class _Tp>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const _Tp* __str) _NOEXCEPT { … }

// Because of __is_trivially_lexicographically_comparable_v we know that comparing the object representations is
// equivalent to a std::memcmp. Since we have multiple objects contiguously in memory, we can call memcmp once instead
// of invoking it on every object individually.
template <class _Tp, class _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
__constexpr_memcmp(const _Tp* __lhs, const _Up* __rhs, __element_count __n) { … }

// Because of __libcpp_is_trivially_equality_comparable we know that comparing the object representations is equivalent
// to a std::memcmp(...) == 0. Since we have multiple objects contiguously in memory, we can call memcmp once instead
// of invoking it on every object individually.
template <class _Tp, class _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
__constexpr_memcmp_equal(const _Tp* __lhs, const _Up* __rhs, __element_count __n) { … }

template <class _Tp, class _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __constexpr_memchr(_Tp* __str, _Up __value, size_t __count) { … }

// This function performs an assignment to an existing, already alive TriviallyCopyable object
// from another TriviallyCopyable object.
//
// It basically works around the fact that TriviallyCopyable objects are not required to be
// syntactically copy/move constructible or copy/move assignable. Technically, only one of the
// four operations is required to be syntactically valid -- but at least one definitely has to
// be valid.
//
// This is necessary in order to implement __constexpr_memmove below in a way that mirrors as
// closely as possible what the compiler's __builtin_memmove is able to do.
template <class _Tp, class _Up, __enable_if_t<is_assignable<_Tp&, _Up const&>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp& __assign_trivially_copyable(_Tp& __dest, _Up const& __src) { … }

// clang-format off
template <class _Tp, class _Up, __enable_if_t<!is_assignable<_Tp&, _Up const&>::value &&
                                               is_assignable<_Tp&, _Up&&>::value, int> = 0>
// clang-format on
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp& __assign_trivially_copyable(_Tp& __dest, _Up& __src) { … }

// clang-format off
template <class _Tp, class _Up, __enable_if_t<!is_assignable<_Tp&, _Up const&>::value &&
                                              !is_assignable<_Tp&, _Up&&>::value &&
                                               is_constructible<_Tp, _Up const&>::value, int> = 0>
// clang-format on
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& __assign_trivially_copyable(_Tp& __dest, _Up const& __src) { … }

// clang-format off
template <class _Tp, class _Up, __enable_if_t<!is_assignable<_Tp&, _Up const&>::value &&
                                              !is_assignable<_Tp&, _Up&&>::value &&
                                              !is_constructible<_Tp, _Up const&>::value &&
                                               is_constructible<_Tp, _Up&&>::value, int> = 0>
// clang-format on
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Tp& __assign_trivially_copyable(_Tp& __dest, _Up& __src) { … }

template <class _Tp, class _Up, __enable_if_t<__is_always_bitcastable<_Up, _Tp>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp*
__constexpr_memmove(_Tp* __dest, _Up* __src, __element_count __n) { … }

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H