| //===----------------------------------------------------------------------===// |
| // |
| // 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 {}; |
| |
| inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const char* __str) { |
| // GCC currently doesn't support __builtin_strlen for heap-allocated memory during constant evaluation. |
| // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70816 |
| #ifdef _LIBCPP_COMPILER_GCC |
| if (__libcpp_is_constant_evaluated()) { |
| size_t __i = 0; |
| for (; __str[__i] != '\0'; ++__i) |
| ; |
| return __i; |
| } |
| #endif |
| return __builtin_strlen(__str); |
| } |
| |
| // Because of __libcpp_is_trivially_lexicographically_comparable 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) { |
| static_assert(__libcpp_is_trivially_lexicographically_comparable<_Tp, _Up>::value, |
| "_Tp and _Up have to be trivially lexicographically comparable"); |
| |
| auto __count = static_cast<size_t>(__n); |
| |
| if (__libcpp_is_constant_evaluated()) { |
| #ifdef _LIBCPP_COMPILER_CLANG_BASED |
| if (sizeof(_Tp) == 1 && !is_same<_Tp, bool>::value) |
| return __builtin_memcmp(__lhs, __rhs, __count * sizeof(_Tp)); |
| #endif |
| |
| while (__count != 0) { |
| if (*__lhs < *__rhs) |
| return -1; |
| if (*__rhs < *__lhs) |
| return 1; |
| |
| --__count; |
| ++__lhs; |
| ++__rhs; |
| } |
| return 0; |
| } else { |
| return __builtin_memcmp(__lhs, __rhs, __count * sizeof(_Tp)); |
| } |
| } |
| |
| // 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) { |
| static_assert(__libcpp_is_trivially_equality_comparable<_Tp, _Up>::value, |
| "_Tp and _Up have to be trivially equality comparable"); |
| |
| auto __count = static_cast<size_t>(__n); |
| |
| if (__libcpp_is_constant_evaluated()) { |
| #ifdef _LIBCPP_COMPILER_CLANG_BASED |
| if (sizeof(_Tp) == 1 && is_integral<_Tp>::value && !is_same<_Tp, bool>::value) |
| return __builtin_memcmp(__lhs, __rhs, __count * sizeof(_Tp)) == 0; |
| #endif |
| while (__count != 0) { |
| if (*__lhs != *__rhs) |
| return false; |
| |
| --__count; |
| ++__lhs; |
| ++__rhs; |
| } |
| return true; |
| } else { |
| return __builtin_memcmp(__lhs, __rhs, __count * sizeof(_Tp)) == 0; |
| } |
| } |
| |
| template <class _Tp, class _Up> |
| _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __constexpr_memchr(_Tp* __str, _Up __value, size_t __count) { |
| static_assert(sizeof(_Tp) == 1 && __libcpp_is_trivially_equality_comparable<_Tp, _Up>::value, |
| "Calling memchr on non-trivially equality comparable types is unsafe."); |
| |
| if (__libcpp_is_constant_evaluated()) { |
| // use __builtin_char_memchr to optimize constexpr evaluation if we can |
| #if _LIBCPP_STD_VER >= 17 && __has_builtin(__builtin_char_memchr) |
| if constexpr (is_same_v<remove_cv_t<_Tp>, char> && is_same_v<remove_cv_t<_Up>, char>) |
| return __builtin_char_memchr(__str, __value, __count); |
| #endif |
| |
| for (; __count; --__count) { |
| if (*__str == __value) |
| return __str; |
| ++__str; |
| } |
| return nullptr; |
| } else { |
| char __value_buffer = 0; |
| __builtin_memcpy(&__value_buffer, &__value, sizeof(char)); |
| return static_cast<_Tp*>(__builtin_memchr(__str, __value_buffer, __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) { |
| __dest = __src; |
| return __dest; |
| } |
| |
| // 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) { |
| __dest = |
| static_cast<_Up&&>(__src); // this is safe, we're not actually moving anything since the assignment is trivial |
| return __dest; |
| } |
| |
| // 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) { |
| // _Tp is trivially destructible, so we don't need to call its destructor to end the lifetime of the object |
| // that was there previously |
| std::__construct_at(std::addressof(__dest), __src); |
| return __dest; |
| } |
| |
| // 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) { |
| // _Tp is trivially destructible, so we don't need to call its destructor to end the lifetime of the object |
| // that was there previously |
| std::__construct_at( |
| std::addressof(__dest), |
| static_cast<_Up&&>(__src)); // this is safe, we're not actually moving anything since the constructor is trivial |
| return __dest; |
| } |
| |
| 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) { |
| size_t __count = static_cast<size_t>(__n); |
| if (__libcpp_is_constant_evaluated()) { |
| #ifdef _LIBCPP_COMPILER_CLANG_BASED |
| if (is_same<__remove_cv_t<_Tp>, __remove_cv_t<_Up> >::value) { |
| ::__builtin_memmove(__dest, __src, __count * sizeof(_Tp)); |
| return __dest; |
| } |
| #endif |
| if (std::__is_pointer_in_range(__src, __src + __count, __dest)) { |
| for (; __count > 0; --__count) |
| std::__assign_trivially_copyable(__dest[__count - 1], __src[__count - 1]); |
| } else { |
| for (size_t __i = 0; __i != __count; ++__i) |
| std::__assign_trivially_copyable(__dest[__i], __src[__i]); |
| } |
| } else if (__count > 0) { |
| ::__builtin_memmove(__dest, __src, (__count - 1) * sizeof(_Tp) + __libcpp_datasizeof<_Tp>::value); |
| } |
| return __dest; |
| } |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H |