Implement P1885R12: <text_encoding> header

libcxx/docs/FeatureTestMacroTable.rst

@@ -500,7 +500,7 @@ Status
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_submdspan``                                    *unimplemented*
     ---------------------------------------------------------- -----------------
-    ``__cpp_lib_text_encoding``                                *unimplemented*
+    ``__cpp_lib_text_encoding``                                ``202306L``
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_to_chars``                                     *unimplemented*
     ---------------------------------------------------------- -----------------

libcxx/docs/Status/Cxx2cPapers.csv

@@ -13,7 +13,7 @@
 "`P2013R5 <https://wg21.link/P2013R5>`__","Freestanding Language: Optional ``::operator new``","2023-06 (Varna)","","",""
 "`P2363R5 <https://wg21.link/P2363R5>`__","Extending associative containers with the remaining heterogeneous overloads","2023-06 (Varna)","","",""
 "`P1901R2 <https://wg21.link/P1901R2>`__","Enabling the Use of ``weak_ptr`` as Keys in Unordered Associative Containers","2023-06 (Varna)","","",""
-"`P1885R12 <https://wg21.link/P1885R12>`__","Naming Text Encodings to Demystify Them","2023-06 (Varna)","","",""
+"`P1885R12 <https://wg21.link/P1885R12>`__","Naming Text Encodings to Demystify Them","2023-06 (Varna)","|Complete|","21",""
 "`P0792R14 <https://wg21.link/P0792R14>`__","``function_ref``: a type-erased callable reference","2023-06 (Varna)","","",""
 "`P2874R2 <https://wg21.link/P2874R2>`__","P2874R2: Mandating Annex D Require No More","2023-06 (Varna)","|Complete|","12",""
 "`P2757R3 <https://wg21.link/P2757R3>`__","Type-checking format args","2023-06 (Varna)","","",""
@@ -79,7 +79,7 @@
 "`P3136R1 <https://wg21.link/P3136R1>`__","Retiring niebloids","2024-11 (Wrocław)","|Complete|","14",""
 "`P3138R5 <https://wg21.link/P3138R5>`__","``views::cache_latest``","2024-11 (Wrocław)","","",""
 "`P3379R0 <https://wg21.link/P3379R0>`__","Constrain ``std::expected`` equality operators","2024-11 (Wrocław)","|Complete|","21",""
-"`P2862R1 <https://wg21.link/P2862R1>`__","``text_encoding::name()`` should never return null values","2024-11 (Wrocław)","","",""
+"`P2862R1 <https://wg21.link/P2862R1>`__","``text_encoding::name()`` should never return null values","2024-11 (Wrocław)","|Complete|","21",""
 "`P2897R7 <https://wg21.link/P2897R7>`__","``aligned_accessor``: An ``mdspan`` accessor expressing pointer over-alignment","2024-11 (Wrocław)","|Complete|","21",""
 "`P3355R1 <https://wg21.link/P3355R1>`__","Fix ``submdspan`` for C++26","2024-11 (Wrocław)","","",""
 "`P3222R0 <https://wg21.link/P3222R0>`__","Fix C++26 by adding transposed special cases for P2642 layouts","2024-11 (Wrocław)","","",""

libcxx/include/CMakeLists.txt

@@ -751,6 +751,8 @@ set(files
   __system_error/error_condition.h
   __system_error/system_error.h
   __system_error/throw_system_error.h
+  __text_encoding/get_locale_encoding.h
+  __text_encoding/text_encoding.h
   __thread/formatter.h
   __thread/id.h
   __thread/jthread.h
@@ -1062,6 +1064,7 @@ set(files
   strstream
   syncstream
   system_error
+  text_encoding
   tgmath.h
   thread
   tuple

libcxx/include/__locale

@@ -31,6 +31,10 @@
 #  include <cstddef>
 #  include <cstring>
 
+#  if _LIBCPP_STD_VER >= 26
+#    include <__text_encoding/text_encoding.h>
+#  endif
+
 #  if _LIBCPP_HAS_WIDE_CHARACTERS
 #    include <cwchar>
 #  else
@@ -99,6 +103,30 @@ public:
 
   // locale operations:
   string name() const;
+
+#  if _LIBCPP_STD_VER >= 26
+  _LIBCPP_HIDE_FROM_ABI text_encoding encoding() const {
+    std::string __name = this->name();
+    if (__name.size() == 1) {
+      if (__name[0] == 'C')
+        return std::text_encoding(text_encoding::id::ASCII);
+      if (__name[0] == '*')
+        return std::text_encoding();
+    }
+
+    auto __encoding_divider = __name.find('.'), __modifier_at = __name.find('@');
+    if (__encoding_divider == std::string::npos) {
+      return std::text_encoding();
+    }
+
+    if (__modifier_at == std::string::npos) {
+      return std::text_encoding(__name.c_str() + __encoding_divider + 1);
+    }
+
+    return std::text_encoding({__name.c_str() + __encoding_divider + 1, __modifier_at - 1 - __encoding_divider});
+  }
+#  endif // _LIBCPP_STD_VER >= 26
+
   bool operator==(const locale&) const;
 #  if _LIBCPP_STD_VER <= 17
   _LIBCPP_HIDE_FROM_ABI bool operator!=(const locale& __y) const { return !(*this == __y); }

libcxx/include/__locale_dir/locale_base_api.h

@@ -149,6 +149,9 @@
 #    if _LIBCPP_HAS_WIDE_CHARACTERS
 #      include <wctype.h>
 #    endif
+#    if __has_include(<langinfo.h>)
+#      include <langinfo.h>
+#    endif
 _LIBCPP_BEGIN_NAMESPACE_STD
 namespace __locale {
 //
@@ -179,6 +182,12 @@ inline _LIBCPP_HIDE_FROM_ABI char* __setlocale(int __category, char const* __loc
 inline _LIBCPP_HIDE_FROM_ABI void __freelocale(__locale_t __loc) { freelocale(__loc); }
 
 inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t& __loc) { return __libcpp_localeconv_l(__loc); }
+
+#      if __has_include(<langinfo.h>)
+inline _LIBCPP_HIDE_FROM_ABI char* __nl_langinfo_l(int __category_mask, __locale_t __l) {
+  return ::nl_langinfo_l(__category_mask, __l);
+}
+#      endif
 #    endif // _LIBCPP_BUILDING_LIBRARY
 
 //

libcxx/include/__locale_dir/locale_base_api/ibm.h

@@ -18,6 +18,10 @@
 #include <stdarg.h>
 #include <stdio.h>
 
+#if __has_include(<langinfo.h>)
+#  include <langinfo.h>
+#endif
+
 #include "cstdlib"
 
 #if defined(__MVS__)
@@ -105,4 +109,10 @@ _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 2, 0) int vasprintf(char** strp, const char
   return str_size;
 }
 
+#if __has_include(<langinfo.h>)
+inline _LIBCPP_HIDE_FROM_ABI char* __nl_langinfo_l(int __category_mask, __locale_t __l) {
+  return ::nl_langinfo_l(__category_mask, __l);
+}
+#endif
+
 #endif // _LIBCPP___LOCALE_DIR_LOCALE_BASE_API_IBM_H

libcxx/include/__locale_dir/support/bsd_like.h

@@ -23,7 +23,9 @@
 #  include <wchar.h>
 #  include <wctype.h>
 #endif
-
+#if __has_include(<langinfo.h>)
+#  include <langinfo.h>
+#endif
 #include <xlocale.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -60,6 +62,13 @@ inline _LIBCPP_HIDE_FROM_ABI char* __setlocale(int __category, char const* __loc
 }
 
 inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t& __loc) { return ::localeconv_l(__loc); }
+
+#  if __has_include(<langinfo.h>)
+inline _LIBCPP_HIDE_FROM_ABI char* __nl_langinfo_l(int __category_mask, __locale_t __l) {
+  return ::nl_langinfo_l(__category_mask, __l);
+}
+#  endif
+
 #endif // _LIBCPP_BUILDING_LIBRARY
 
 //

libcxx/include/__locale_dir/support/fuchsia.h

@@ -16,6 +16,10 @@
 #include <cstdlib>
 #include <cwchar>
 
+#if __has_include(<langinfo.h>)
+#  include <langinfo.h>
+#endif
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
@@ -69,6 +73,12 @@ inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t& __loc) {
   return std::localeconv();
 }
 
+#  if __has_include(<langinfo.h>)
+inline _LIBCPP_HIDE_FROM_ABI char* __nl_langinfo_l(int __category_mask, __locale_t __l) {
+  return ::nl_langinfo_l(__category_mask, __l);
+}
+#  endif
+
 //
 // Other functions
 //

libcxx/include/__locale_dir/support/linux.h

@@ -24,6 +24,9 @@
 #  include <cwchar>
 #  include <wctype.h>
 #endif
+#if __has_include(<langinfo.h>)
+#  include <langinfo.h>
+#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -77,6 +80,13 @@ inline _LIBCPP_HIDE_FROM_ABI __lconv_t* __localeconv(__locale_t& __loc) {
   __locale_guard __current(__loc);
   return std::localeconv();
 }
+
+#  if __has_include(<langinfo.h>)
+inline _LIBCPP_HIDE_FROM_ABI char* __nl_langinfo_l(int __category_mask, __locale_t __l) {
+  return ::nl_langinfo_l(__category_mask, __l);
+}
+#  endif
+
 #endif // _LIBCPP_BUILDING_LIBRARY
 
 //

libcxx/include/__text_encoding/get_locale_encoding.h

@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___GET_LOCALE_ENCODING_H
+#define _LIBCPP___GET_LOCALE_ENCODING_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_HAS_LOCALIZATION
+
+#  include <string_view>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+string_view _LIBCPP_EXPORTED_FROM_ABI __get_locale_encoding(const char* __name);
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_HAS_LOCALIZATION
+
+#endif // _LIBCPP___GET_LOCALE_ENCODING_H