llvm-project/libcxx/include/cstring

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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_CSTRING
#define _LIBCPP_CSTRING

/*
    cstring synopsis

Macros:

    NULL

namespace std
{

Types:

    size_t

void* memcpy(void* restrict s1, const void* restrict s2, size_t n);
void* memmove(void* s1, const void* s2, size_t n);
char* strcpy (char* restrict s1, const char* restrict s2);
char* strncpy(char* restrict s1, const char* restrict s2, size_t n);
char* strcat (char* restrict s1, const char* restrict s2);
char* strncat(char* restrict s1, const char* restrict s2, size_t n);
int memcmp(const void* s1, const void* s2, size_t n);
int strcmp (const char* s1, const char* s2);
int strncmp(const char* s1, const char* s2, size_t n);
int strcoll(const char* s1, const char* s2);
size_t strxfrm(char* restrict s1, const char* restrict s2, size_t n);
const void* memchr(const void* s, int c, size_t n);
      void* memchr(      void* s, int c, size_t n);
const char* strchr(const char* s, int c);
      char* strchr(      char* s, int c);
size_t strcspn(const char* s1, const char* s2);
const char* strpbrk(const char* s1, const char* s2);
      char* strpbrk(      char* s1, const char* s2);
const char* strrchr(const char* s, int c);
      char* strrchr(      char* s, int c);
size_t strspn(const char* s1, const char* s2);
const char* strstr(const char* s1, const char* s2);
      char* strstr(      char* s1, const char* s2);
char* strtok(char* restrict s1, const char* restrict s2);
void* memset(void* s, int c, size_t n);
char* strerror(int errnum);
size_t strlen(const char* s);

}  // std

*/

#include <__assert> // all public C++ headers provide the assertion handler
#include <__config>
#include <__type_traits/is_constant_evaluated.h>

#include <string.h>

#ifndef _LIBCPP_STRING_H
#   error <cstring> tried including <string.h> but didn't find libc++'s <string.h> header. \
          This usually means that your header search paths are not configured properly. \
          The header search paths should contain the C++ Standard Library headers before \
          any C Standard Library, and you are probably using compiler flags that make that \
          not be the case.
#endif

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

_LIBCPP_BEGIN_NAMESPACE_STD

using ::size_t _LIBCPP_USING_IF_EXISTS;
using ::memcpy _LIBCPP_USING_IF_EXISTS;
using ::memmove _LIBCPP_USING_IF_EXISTS;
using ::strcpy _LIBCPP_USING_IF_EXISTS;
using ::strncpy _LIBCPP_USING_IF_EXISTS;
using ::strcat _LIBCPP_USING_IF_EXISTS;
using ::strncat _LIBCPP_USING_IF_EXISTS;
using ::memcmp _LIBCPP_USING_IF_EXISTS;
using ::strcmp _LIBCPP_USING_IF_EXISTS;
using ::strncmp _LIBCPP_USING_IF_EXISTS;
using ::strcoll _LIBCPP_USING_IF_EXISTS;
using ::strxfrm _LIBCPP_USING_IF_EXISTS;
using ::memchr _LIBCPP_USING_IF_EXISTS;
using ::strchr _LIBCPP_USING_IF_EXISTS;
using ::strcspn _LIBCPP_USING_IF_EXISTS;
using ::strpbrk _LIBCPP_USING_IF_EXISTS;
using ::strrchr _LIBCPP_USING_IF_EXISTS;
using ::strspn _LIBCPP_USING_IF_EXISTS;
using ::strstr _LIBCPP_USING_IF_EXISTS;
using ::strtok _LIBCPP_USING_IF_EXISTS;
using ::memset _LIBCPP_USING_IF_EXISTS;
using ::strerror _LIBCPP_USING_IF_EXISTS;
using ::strlen _LIBCPP_USING_IF_EXISTS;

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);
}

template <class _Tp>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
__constexpr_memcmp(const _Tp* __lhs, const _Tp* __rhs, size_t __count) {
#ifdef _LIBCPP_COMPILER_GCC
  if (__libcpp_is_constant_evaluated()) {
    for (; __count; --__count, ++__lhs, ++__rhs) {
      if (*__lhs < *__rhs)
        return -1;
      if (*__rhs < *__lhs)
        return 1;
    }
    return 0;
  }
#endif
  return __builtin_memcmp(__lhs, __rhs, __count);
}

inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const char*
__constexpr_char_memchr(const char* __str, int __char, size_t __count) {
#if __has_builtin(__builtin_char_memchr)
  return __builtin_char_memchr(__str, __char, __count);
#else
  if (!__libcpp_is_constant_evaluated())
    return static_cast<const char*>(std::memchr(__str, __char, __count));
  for (; __count; --__count) {
    if (*__str == __char)
      return __str;
    ++__str;
  }
  return nullptr;
#endif
}

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_CSTRING