my_char_traits.h

/* Copyright (c) 2024, 2025, Oracle and/or its affiliates.

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License, version 2.0,
 as published by the Free Software Foundation.

 This program is designed to work with certain software (including
 but not limited to OpenSSL) that is licensed under separate terms,
 as designated in a particular file or component or in included license
 documentation. The authors of MySQL hereby grant you an additional
 permission to link the program and your derivative works with the
 separately licensed software that they have either included with
 the program or referenced in the documentation.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License, version 2.0, for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */

#ifndef MY_CHAR_TRAITS_INCLUDED
#defineMY_CHAR_TRAITS_INCLUDED

#include<compare>
#include<cstdio>
#include<cstring>
#include<iosfwd>

template <classCharT>
structmy_char_traits;

/*
 This is a standards-compliant, drop-in replacement for
 std::char_traits<unsigned char>
 We need this because clang libc++ is removing support for it in clang 19.
*/
template <>
structmy_char_traits<unsignedchar> {
using char_type = unsignedchar;
using int_type = unsignedint;
using off_type = std::streamoff;
using pos_type = std::streampos;
using standards = std::mbstate_t;
using comparison_category = std::strong_ordering;

staticconstexprvoidassign(char_type &c1, const char_type &c2) noexcept {
 c1 = c2;
 }
staticconstexprbooleq(char_type c1, char_type c2) noexcept {
return c1 == c2;
 }
staticconstexprboollt(char_type c1, char_type c2) noexcept {
return c1 < c2;
 }

staticintcompare(const char_type *s1, const char_type *s2,
 std::size_t n) noexcept {
if (n == 0) return0;
returnmemcmp(s1, s2, n);
 }
staticsize_tlength(const char_type *s) noexcept {
returnstrlen(static_cast<constchar *>(static_cast<constvoid *>(s)));
 }
staticconst char_type *find(const char_type *s, size_t n,
const char_type &a) noexcept {
if (n == 0) returnnullptr;
returnstatic_cast<const char_type *>(memchr(s, a, n));
 }
static char_type *move(char_type *s1, const char_type *s2,
 std::size_t n) noexcept {
if (n == 0) return s1;
returnstatic_cast<char_type *>(memmove(s1, s2, n));
 }
static char_type *copy(char_type *s1, const char_type *s2,
 std::size_t n) noexcept {
if (n == 0) return s1;
returnstatic_cast<char_type *>(memcpy(s1, s2, n));
 }
static char_type *assign(char_type *s, std::size_t n, char_type a) noexcept {
if (n == 0) return s;
returnstatic_cast<char_type *>(memset(s, a, n));
 }

staticconstexpr int_type not_eof(int_type c) noexcept {
returneq_int_type(c, eof()) ? ~eof() : c;
 }
staticconstexpr char_type to_char_type(int_type c) noexcept {
returnstatic_cast<char_type>(c);
 }
staticconstexpr int_type to_int_type(char_type c) noexcept { return c; }
staticconstexprbooleq_int_type(int_type c1, int_type c2) noexcept {
return c1 == c2;
 }
staticconstexpr int_type eof() noexcept {
returnstatic_cast<int_type>(EOF);
 }
};

#endif// MY_CHAR_TRAITS_INCLUDED