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 //
 // Copyright (c) 2009-2011 Artyom Beilis (Tonkikh)
 // Copyright (c) 2022-2023 Alexander Grund
 //
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
 #ifndef BOOST_LOCALE_UTIL_HPP
 #define BOOST_LOCALE_UTIL_HPP
 
 #include <boost/locale/generator.hpp>
 #include <boost/locale/utf.hpp>
 #include <boost/assert.hpp>
 #include <cstdint>
 #include <locale>
 #include <memory>
 #include <typeinfo>
 
 namespace boost { namespace locale {
     /// \brief This namespace provides various utility function useful for Boost.Locale's backends
     /// implementations
     namespace util {
 
         /// \brief Return default system locale name in POSIX format.
         ///
         /// This function tries to detect the locale using LC_ALL, LC_CTYPE and LANG environment
         /// variables in this order and if all of them are unset, on POSIX platforms it returns "C".
         /// On Windows additionally to the above environment variables, this function
         /// tries to create the locale name from ISO-639 and ISO-3166 country codes defined
         /// for the users default locale.
         /// If \a use_utf8_on_windows is true it sets the encoding to UTF-8,
         /// otherwise, if the system locale supports ANSI codepages it defines the ANSI encoding, e.g. windows-1252,
         /// otherwise (if ANSI codepage is not available) it uses UTF-8 encoding.
         BOOST_LOCALE_DECL
         std::string get_system_locale(bool use_utf8_on_windows = false);
 
         /// \brief Installs information facet to locale \a in based on locale name \a name
         ///
         /// This function installs boost::locale::info facet into the locale \a in and returns
         /// newly created locale.
         ///
         /// Note: all information is based only on parsing of string \a name;
         ///
         /// The name has following format: language[_COUNTRY][.encoding][\@variant]
         /// Where language is ISO-639 language code like "en" or "ru", COUNTRY is ISO-3166
         /// country identifier like "US" or "RU". the Encoding is a character set name
         /// like UTF-8 or ISO-8859-1. Variant is backend specific variant like \c euro or
         /// calendar=hebrew.
         ///
         /// If some parameters are missing they are specified as blanks, default encoding
         /// is assumed to be US-ASCII and missing language is assumed to be "C"
         BOOST_LOCALE_DECL
         std::locale create_info(const std::locale& in, const std::string& name);
 
         /// \brief This class represent a simple stateless converter from UCS-4 and to UCS-4 for
         ///  each single code point
         ///
         /// This class is used for creation of std::codecvt facet for converting utf-16/utf-32 encoding
         /// to encoding supported by this converter
         ///
         /// Please note, this converter should be fully stateless. Fully stateless means it should
         /// never assume that it is called in any specific order on the text. Even if the
         /// encoding itself seems to be stateless like windows-1255 or shift-jis, some
         /// encoders (most notably iconv) can actually compose several code-point into one or
         /// decompose them in case composite characters are found. So be very careful when implementing
         /// these converters for certain character set.
         class BOOST_LOCALE_DECL base_converter {
         public:
             /// This value should be returned when an illegal input sequence or code-point is observed:
             /// For example if a UCS-32 code-point is in the range reserved for UTF-16 surrogates
             /// or an invalid UTF-8 sequence is found
             static constexpr utf::code_point illegal = utf::illegal;
 
             /// This value is returned in following cases: An incomplete input sequence was found or
             /// insufficient output buffer was provided so complete output could not be written.
             static constexpr utf::code_point incomplete = utf::incomplete;
 
             virtual ~base_converter();
 
             /// Return the maximal length that one Unicode code-point can be converted to, for example
             /// for UTF-8 it is 4, for Shift-JIS it is 2 and ISO-8859-1 is 1
             virtual int max_len() const { return 1; }
 
             /// Returns true if calling the functions from_unicode, to_unicode, and max_len is thread safe.
             ///
             /// Rule of thumb: if this class' implementation uses simple tables that are unchanged
             /// or is purely algorithmic like UTF-8 - so it does not share any mutable bit for
             /// independent to_unicode, from_unicode calls, you may set it to true, otherwise,
             /// for example if you use iconv_t descriptor or UConverter as conversion object return false,
             /// and this object will be cloned for each use.
             virtual bool is_thread_safe() const { return false; }
 
             /// Create a polymorphic copy of this object, usually called only if is_thread_safe() return false
             virtual base_converter* clone() const
             {
                 BOOST_ASSERT(typeid(*this) == typeid(base_converter));
                 return new base_converter();
             }
 
             /// Convert a single character starting at begin and ending at most at end to Unicode code-point.
             ///
             /// if valid input sequence found in [\a begin,\a code_point_end) such as \a begin < \a code_point_end && \a
             /// code_point_end <= \a end it is converted to its Unicode code point equivalent, \a begin is set to \a
             /// code_point_end
             ///
             /// if incomplete input sequence found in [\a begin,\a end), i.e. there my be such \a code_point_end that \a
             /// code_point_end > \a end and [\a begin, \a code_point_end) would be valid input sequence, then \a
             /// incomplete is returned begin stays unchanged, for example for UTF-8 conversion a *begin = 0xc2, \a begin
             /// +1 = \a end is such situation.
             ///
             /// if invalid input sequence found, i.e. there is a sequence [\a begin, \a code_point_end) such as \a
             /// code_point_end <= \a end that is illegal for this encoding, \a illegal is returned and begin stays
             /// unchanged. For example if *begin = 0xFF and begin < end for UTF-8, then \a illegal is returned.
             virtual utf::code_point to_unicode(const char*& begin, const char* end)
             {
                 if(begin == end)
                     return incomplete; // LCOV_EXCL_LINE
                 unsigned char cp = *begin;
                 if(cp <= 0x7F) {
                     begin++;
                     return cp;
                 }
                 return illegal;
             }
 
             /// Convert a single code-point \a u into encoding and store it in [begin,end) range.
             ///
             /// If u is invalid Unicode code-point, or it can not be mapped correctly to represented character set,
             /// \a illegal should be returned
             ///
             /// If u can be converted to a sequence of bytes c1, ... , cN (1<= N <= max_len() ) then
             ///
             /// -# If end - begin >= N, c1, ... cN are written starting at begin and N is returned
             /// -# If end - begin < N, incomplete is returned, it is unspecified what would be
             ///    stored in bytes in range [begin,end)
             virtual utf::len_or_error from_unicode(utf::code_point u, char* begin, const char* end)
             {
                 if(begin == end)
                     return incomplete; // LCOV_EXCL_LINE
                 if(u >= 0x80)
                     return illegal;
                 *begin = static_cast<char>(u);
                 return 1;
             }
         };
 
         /// This function creates a \a base_converter that can be used for conversion between UTF-8 and
         /// Unicode code points
         BOOST_LOCALE_DECL std::unique_ptr<base_converter> create_utf8_converter();
 
         BOOST_DEPRECATED("This function is deprecated, use 'create_utf8_converter()'")
         inline std::unique_ptr<base_converter> create_utf8_converter_unique_ptr()
         {
             return create_utf8_converter();
         }
 
         /// This function creates a \a base_converter that can be used for conversion between single byte
         /// character encodings like ISO-8859-1, koi8-r, windows-1255 and Unicode code points,
         ///
         /// If \a encoding is not supported, empty pointer is returned.
         /// So you should check whether the returned pointer is valid/non-NULL
         BOOST_LOCALE_DECL std::unique_ptr<base_converter> create_simple_converter(const std::string& encoding);
 
         BOOST_DEPRECATED("This function is deprecated, use 'create_simple_converter()'")
         inline std::unique_ptr<base_converter> create_simple_converter_unique_ptr(const std::string& encoding)
         {
             return create_simple_converter(encoding);
         }
 
         /// Install codecvt facet into locale \a in and return new locale that is based on \a in and uses new
         /// facet.
         ///
         /// codecvt facet would convert between narrow and wide/char16_t/char32_t encodings using \a cvt converter.
         /// If \a cvt is null pointer, always failure conversion would be used that fails on every first input or
         /// output.
         ///
         /// Note: the codecvt facet handles both UTF-16 and UTF-32 wide encodings, it knows to break and join
         /// Unicode code-points above 0xFFFF to and from surrogate pairs correctly. \a cvt should be unaware
         /// of wide encoding type
         BOOST_LOCALE_DECL
         std::locale create_codecvt(const std::locale& in, std::unique_ptr<base_converter> cvt, char_facet_t type);
 
         BOOST_DEPRECATED("This function is deprecated, use 'create_codecvt()'")
         inline std::locale create_codecvt_from_pointer(const std::locale& in, base_converter* cvt, char_facet_t type)
         {
             return create_codecvt(in, std::unique_ptr<base_converter>(cvt), type);
         }
 
         BOOST_DEPRECATED("This function is deprecated, use 'create_utf8_converter()'")
         BOOST_LOCALE_DECL base_converter* create_utf8_converter_new_ptr();
 
         BOOST_DEPRECATED("This function is deprecated, use 'create_simple_converter()'")
         BOOST_LOCALE_DECL base_converter* create_simple_converter_new_ptr(const std::string& encoding);
 
         /// Install utf8 codecvt to UTF-16 or UTF-32 into locale \a in and return
         /// new locale that is based on \a in and uses new facet.
         BOOST_LOCALE_DECL
         std::locale create_utf8_codecvt(const std::locale& in, char_facet_t type);
 
         /// This function installs codecvt that can be used for conversion between single byte
         /// character encodings like ISO-8859-1, koi8-r, windows-1255 and Unicode code points,
         ///
         /// \throws boost::locale::conv::invalid_charset_error: Character set is not supported or isn't a single
         /// byte character set
         BOOST_LOCALE_DECL
         std::locale create_simple_codecvt(const std::locale& in, const std::string& encoding, char_facet_t type);
     } // namespace util
 }}    // namespace boost::locale
 
 #endif

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