| //===----------------------------------------------------------------------===// |
| // |
| // 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 <__type_traits/is_constant_evaluated.h> |
| #include <__type_traits/is_equality_comparable.h> |
| #include <__type_traits/is_same.h> |
| #include <__type_traits/is_trivially_lexicographically_comparable.h> |
| #include <__type_traits/remove_cv.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)); |
| } |
| } |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| #endif // _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H |