473 lines
21 KiB
C++
473 lines
21 KiB
C++
//
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// Copyright (c) 2015 Artyom Beilis (Tonkikh)
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// Copyright (c) 2021-2023 Alexander Grund
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//
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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#ifndef BOOST_LOCALE_GENERIC_CODECVT_HPP
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#define BOOST_LOCALE_GENERIC_CODECVT_HPP
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#include <boost/locale/utf.hpp>
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#include <cstdint>
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#include <locale>
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namespace boost { namespace locale {
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static_assert(sizeof(std::mbstate_t) >= 2, "std::mbstate_t is to small to store an UTF-16 codepoint");
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namespace detail {
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// Avoid including cstring for std::memcpy
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inline void copy_uint16_t(void* dst, const void* src)
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{
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unsigned char* cdst = static_cast<unsigned char*>(dst);
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const unsigned char* csrc = static_cast<const unsigned char*>(src);
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cdst[0] = csrc[0];
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cdst[1] = csrc[1];
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}
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inline uint16_t read_state(const std::mbstate_t& src)
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{
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uint16_t dst;
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copy_uint16_t(&dst, &src);
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return dst;
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}
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inline void write_state(std::mbstate_t& dst, const uint16_t src)
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{
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copy_uint16_t(&dst, &src);
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}
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} // namespace detail
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/// \brief A base class that used to define constants for generic_codecvt
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class generic_codecvt_base {
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public:
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/// Initial state for converting to or from Unicode code points, used by initial_state in derived classes
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enum initial_convertion_state {
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to_unicode_state, ///< The state would be used by to_unicode functions
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from_unicode_state ///< The state would be used by from_unicode functions
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};
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};
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/// \brief Generic codecvt facet for various stateless encodings to UTF-16 and UTF-32 using wchar_t, char32_t
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/// and char16_t
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///
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/// Implementations should derive from this class defining itself as CodecvtImpl and provide following members
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///
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/// - `state_type` - a type of special object that allows to store intermediate cached data, for example `iconv_t`
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/// descriptor
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/// - `state_type initial_state(generic_codecvt_base::initial_convertion_state direction) const` - member function
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/// that creates initial state
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/// - `int max_encoding_length() const` - a maximal length that one Unicode code point is represented, for UTF-8 for
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/// example it is 4 from ISO-8859-1 it is 1
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/// - `utf::code_point to_unicode(state_type& state, const char*& begin, const char* end)` - extract first code
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/// point from the text in range [begin,end), in case of success begin would point to the next character sequence to
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/// be encoded to next code point, in case of incomplete sequence - utf::incomplete shell be returned, and in case
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/// of invalid input sequence utf::illegal shell be returned and begin would remain unmodified
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/// - `utf::len_or_error from_unicode(state_type &state, utf::code_point u, char* begin, const char* end)` - convert
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/// a Unicode code point `u` into a character sequence at [begin,end). Return the length of the sequence in case of
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/// success, utf::incomplete in case of not enough room to encode the code point, or utf::illegal in case conversion
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/// can not be performed
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///
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///
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/// For example implementation of codecvt for latin1/ISO-8859-1 character set
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///
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/// \code
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///
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/// template<typename CharType>
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/// class latin1_codecvt: boost::locale::generic_codecvt<CharType,latin1_codecvt<CharType> >
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/// {
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/// public:
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///
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/// /* Standard codecvt constructor */
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/// latin1_codecvt(size_t refs = 0): boost::locale::generic_codecvt<CharType,latin1_codecvt<CharType> >(refs)
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/// {
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/// }
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///
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/// /* State is unused but required by generic_codecvt */
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/// struct state_type {};
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///
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/// state_type initial_state(generic_codecvt_base::initial_convertion_state /*unused*/) const
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/// {
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/// return state_type();
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/// }
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///
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/// int max_encoding_length() const
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/// {
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/// return 1;
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/// }
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///
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/// boost::locale::utf::code_point to_unicode(state_type&, const char*& begin, const char* end) const
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/// {
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/// if(begin == end)
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/// return boost::locale::utf::incomplete;
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/// return *begin++;
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/// }
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///
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/// boost::locale::utf::len_or_error from_unicode(state_type&, boost::locale::utf::code_point u,
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/// char* begin, const char* end) const
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/// {
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/// if(u >= 256)
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/// return boost::locale::utf::illegal;
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/// if(begin == end)
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/// return boost::locale::utf::incomplete;
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/// *begin = u;
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/// return 1;
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/// }
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/// };
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///
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/// \endcode
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///
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/// When external tools used for encoding conversion, the `state_type` is useful to save objects used for
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/// conversions. For example, icu::UConverter can be saved in such a state for an efficient use:
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///
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/// \code
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/// template<typename CharType>
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/// class icu_codecvt: boost::locale::generic_codecvt<CharType,icu_codecvt<CharType>>
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/// {
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/// public:
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///
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/// /* Standard codecvt constructor */
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/// icu_codecvt(std::string const &name,refs = 0):
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/// boost::locale::generic_codecvt<CharType,icu_codecvt<CharType>>(refs)
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/// { ... }
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///
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/// using state_type = std::unique_ptr<UConverter,void (*)(UConverter*)>;
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///
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/// state_type initial_state(generic_codecvt_base::initial_convertion_state /*unused*/) const
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/// {
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/// UErrorCode err = U_ZERO_ERROR;
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/// return state_type(ucnv_safeClone(converter_,0,0,&err),ucnv_close);
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/// }
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///
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/// boost::locale::utf::code_point to_unicode(state_type &ptr,char const *&begin,char const *end) const
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/// {
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/// UErrorCode err = U_ZERO_ERROR;
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/// boost::locale::utf::code_point cp = ucnv_getNextUChar(ptr.get(),&begin,end,&err);
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/// ...
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/// }
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/// ...
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/// };
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/// \endcode
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///
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template<typename CharType, typename CodecvtImpl, int CharSize = sizeof(CharType)>
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class generic_codecvt;
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/// \brief UTF-16 to/from narrow char codecvt facet to use with char16_t or wchar_t on Windows
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///
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/// Note in order to fit the requirements of usability by std::wfstream it uses mbstate_t
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/// to handle intermediate states in handling of variable length UTF-16 sequences
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///
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/// Its member functions implement standard virtual functions of basic codecvt
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template<typename CharType, typename CodecvtImpl>
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class generic_codecvt<CharType, CodecvtImpl, 2> : public std::codecvt<CharType, char, std::mbstate_t>,
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public generic_codecvt_base {
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public:
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typedef CharType uchar;
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generic_codecvt(size_t refs = 0) : std::codecvt<CharType, char, std::mbstate_t>(refs) {}
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const CodecvtImpl& implementation() const { return *static_cast<const CodecvtImpl*>(this); }
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protected:
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std::codecvt_base::result do_unshift(std::mbstate_t& s, char* from, char* /*to*/, char*& next) const override
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{
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if(*reinterpret_cast<char*>(&s) != 0)
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return std::codecvt_base::error;
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next = from;
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return std::codecvt_base::ok;
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}
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int do_encoding() const noexcept override { return 0; }
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int do_max_length() const noexcept override { return implementation().max_encoding_length(); }
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bool do_always_noconv() const noexcept override { return false; }
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int do_length(std::mbstate_t& std_state, const char* from, const char* from_end, size_t max) const override
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{
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bool state = *reinterpret_cast<char*>(&std_state) != 0;
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const char* save_from = from;
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auto cvt_state = implementation().initial_state(to_unicode_state);
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while(max > 0 && from < from_end) {
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const char* prev_from = from;
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const utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
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if(ch == boost::locale::utf::incomplete || ch == boost::locale::utf::illegal) {
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from = prev_from;
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break;
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}
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max--;
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if(ch > 0xFFFF) {
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if(!state)
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from = prev_from;
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state = !state;
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}
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}
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*reinterpret_cast<char*>(&std_state) = state;
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return static_cast<int>(from - save_from);
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}
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std::codecvt_base::result do_in(std::mbstate_t& std_state,
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const char* from,
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const char* from_end,
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const char*& from_next,
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uchar* to,
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uchar* to_end,
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uchar*& to_next) const override
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{
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std::codecvt_base::result r = std::codecvt_base::ok;
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// mbstate_t is POD type and should be initialized to 0 (i.a. state = stateT())
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// according to standard. We use it to keep a flag 0/1 for surrogate pair writing
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//
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// if 0/false no codepoint above >0xFFFF observed, else a codepoint above 0xFFFF was observed
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// and first pair is written, but no input consumed
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bool state = *reinterpret_cast<char*>(&std_state) != 0;
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auto cvt_state = implementation().initial_state(to_unicode_state);
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while(to < to_end && from < from_end) {
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const char* from_saved = from;
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utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
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if(ch == boost::locale::utf::illegal) {
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from = from_saved;
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r = std::codecvt_base::error;
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break;
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}
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if(ch == boost::locale::utf::incomplete) {
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from = from_saved;
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r = std::codecvt_base::partial;
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break;
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}
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// Normal codepoints go directly to stream
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if(ch <= 0xFFFF)
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*to++ = static_cast<uchar>(ch);
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else {
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// For other codepoints we do the following
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//
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// 1. We can't consume our input as we may find ourselves
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// in state where all input consumed but not all output written,i.e. only
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// 1st pair is written
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// 2. We only write first pair and mark this in the state, we also revert back
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// the from pointer in order to make sure this codepoint would be read
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// once again and then we would consume our input together with writing
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// second surrogate pair
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ch -= 0x10000;
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std::uint16_t w1 = static_cast<std::uint16_t>(0xD800 | (ch >> 10));
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std::uint16_t w2 = static_cast<std::uint16_t>(0xDC00 | (ch & 0x3FF));
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if(!state) {
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from = from_saved;
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*to++ = w1;
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} else
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*to++ = w2;
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state = !state;
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}
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}
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from_next = from;
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to_next = to;
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if(r == std::codecvt_base::ok && (from != from_end || state))
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r = std::codecvt_base::partial;
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*reinterpret_cast<char*>(&std_state) = state;
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return r;
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}
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std::codecvt_base::result do_out(std::mbstate_t& std_state,
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const uchar* from,
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const uchar* from_end,
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const uchar*& from_next,
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char* to,
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char* to_end,
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char*& to_next) const override
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{
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std::codecvt_base::result r = std::codecvt_base::ok;
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// mbstate_t is POD type and should be initialized to 0 (i.a. state = stateT())
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// according to standard. We assume that sizeof(mbstate_t) >=2 in order
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// to be able to store first observed surrogate pair
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//
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// State: state!=0 - a first surrogate pair was observed (state = first pair),
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// we expect the second one to come and then zero the state
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std::uint16_t state = detail::read_state(std_state);
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auto cvt_state = implementation().initial_state(from_unicode_state);
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while(to < to_end && from < from_end) {
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utf::code_point ch = 0;
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if(state != 0) {
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// if the state indicates that 1st surrogate pair was written
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// we should make sure that the second one that comes is actually
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// second surrogate
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std::uint16_t w1 = state;
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std::uint16_t w2 = *from;
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// we don't forward from as writing may fail to incomplete or
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// partial conversion
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if(0xDC00 <= w2 && w2 <= 0xDFFF) {
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std::uint16_t vh = w1 - 0xD800;
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std::uint16_t vl = w2 - 0xDC00;
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ch = ((uint32_t(vh) << 10) | vl) + 0x10000;
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} else {
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// Invalid surrogate
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r = std::codecvt_base::error;
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break;
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}
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} else {
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ch = *from;
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if(0xD800 <= ch && ch <= 0xDBFF) {
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// if this is a first surrogate pair we put
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// it into the state and consume it, note we don't
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// go forward as it should be illegal so we increase
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// the from pointer manually
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state = static_cast<uint16_t>(ch);
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from++;
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continue;
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} else if(0xDC00 <= ch && ch <= 0xDFFF) {
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// if we observe second surrogate pair and
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// first only may be expected we should break from the loop with error
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// as it is illegal input
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r = std::codecvt_base::error;
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break;
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}
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}
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if(!boost::locale::utf::is_valid_codepoint(ch)) {
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r = std::codecvt_base::error;
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break;
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}
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const utf::code_point len = implementation().from_unicode(cvt_state, ch, to, to_end);
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if(len == boost::locale::utf::incomplete) {
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r = std::codecvt_base::partial;
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break;
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} else if(len == boost::locale::utf::illegal) {
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r = std::codecvt_base::error;
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break;
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} else
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to += len;
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state = 0;
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from++;
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}
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from_next = from;
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to_next = to;
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if(r == std::codecvt_base::ok && (from != from_end || state != 0))
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r = std::codecvt_base::partial;
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detail::write_state(std_state, state);
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return r;
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}
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};
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/// \brief UTF-32 to/from narrow char codecvt facet to use with char32_t or wchar_t on POSIX platforms
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///
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/// Its member functions implement standard virtual functions of basic codecvt.
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/// mbstate_t is not used for UTF-32 handling due to fixed length encoding
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template<typename CharType, typename CodecvtImpl>
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class generic_codecvt<CharType, CodecvtImpl, 4> : public std::codecvt<CharType, char, std::mbstate_t>,
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public generic_codecvt_base {
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public:
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typedef CharType uchar;
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generic_codecvt(size_t refs = 0) : std::codecvt<CharType, char, std::mbstate_t>(refs) {}
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const CodecvtImpl& implementation() const { return *static_cast<const CodecvtImpl*>(this); }
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protected:
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std::codecvt_base::result
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do_unshift(std::mbstate_t& /*s*/, char* from, char* /*to*/, char*& next) const override
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{
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next = from;
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return std::codecvt_base::ok;
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}
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int do_encoding() const noexcept override { return 0; }
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int do_max_length() const noexcept override { return implementation().max_encoding_length(); }
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bool do_always_noconv() const noexcept override { return false; }
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int do_length(std::mbstate_t& /*state*/, const char* from, const char* from_end, size_t max) const override
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{
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const char* start_from = from;
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auto cvt_state = implementation().initial_state(to_unicode_state);
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while(max > 0 && from < from_end) {
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const char* save_from = from;
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const utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
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if(ch == boost::locale::utf::incomplete || ch == boost::locale::utf::illegal) {
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from = save_from;
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break;
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}
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max--;
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}
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return static_cast<int>(from - start_from);
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}
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std::codecvt_base::result do_in(std::mbstate_t& /*state*/,
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const char* from,
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const char* from_end,
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const char*& from_next,
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uchar* to,
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uchar* to_end,
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uchar*& to_next) const override
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{
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std::codecvt_base::result r = std::codecvt_base::ok;
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auto cvt_state = implementation().initial_state(to_unicode_state);
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while(to < to_end && from < from_end) {
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const char* from_saved = from;
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const utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
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if(ch == boost::locale::utf::illegal) {
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r = std::codecvt_base::error;
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from = from_saved;
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break;
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}
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if(ch == boost::locale::utf::incomplete) {
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r = std::codecvt_base::partial;
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from = from_saved;
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break;
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}
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*to++ = ch;
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}
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from_next = from;
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to_next = to;
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if(r == std::codecvt_base::ok && from != from_end)
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r = std::codecvt_base::partial;
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return r;
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}
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std::codecvt_base::result do_out(std::mbstate_t& /*std_state*/,
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const uchar* from,
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const uchar* from_end,
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const uchar*& from_next,
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char* to,
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char* to_end,
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char*& to_next) const override
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{
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std::codecvt_base::result r = std::codecvt_base::ok;
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auto cvt_state = implementation().initial_state(from_unicode_state);
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while(to < to_end && from < from_end) {
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const std::uint32_t ch = *from;
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if(!boost::locale::utf::is_valid_codepoint(ch)) {
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r = std::codecvt_base::error;
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break;
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}
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const utf::code_point len = implementation().from_unicode(cvt_state, ch, to, to_end);
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if(len == boost::locale::utf::incomplete) {
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r = std::codecvt_base::partial;
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break;
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} else if(len == boost::locale::utf::illegal) {
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r = std::codecvt_base::error;
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break;
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}
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to += len;
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from++;
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}
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from_next = from;
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to_next = to;
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if(r == std::codecvt_base::ok && from != from_end)
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r = std::codecvt_base::partial;
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return r;
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}
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};
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template<typename CodecvtImpl>
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class generic_codecvt<char, CodecvtImpl, 1> : public std::codecvt<char, char, std::mbstate_t>,
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public generic_codecvt_base {
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public:
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typedef char uchar;
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const CodecvtImpl& implementation() const { return *static_cast<const CodecvtImpl*>(this); }
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generic_codecvt(size_t refs = 0) : std::codecvt<char, char, std::mbstate_t>(refs) {}
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};
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}} // namespace boost::locale
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#endif
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