locale_conv.h

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// wstring_convert implementation -*- C++ -*-

// Copyright (C) 2015-2026 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library 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 for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file bits/locale_conv.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{locale}
 */

#ifndef _LOCALE_CONV_H
#define _LOCALE_CONV_H 1

#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else

#include <streambuf>
#include <bits/stringfwd.h>
#include <bits/allocator.h>
#include <bits/codecvt.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   * @addtogroup locales
   * @{
   */

  template<typename _OutStr, typename _InChar, typename _Codecvt,
           typename _State, typename _Fn>
    bool
    __do_str_codecvt(const _InChar* __first, const _InChar* __last,
                     _OutStr& __outstr, const _Codecvt& __cvt, _State& __state,
                     size_t& __count, _Fn __fn)
    {
      if (__first == __last)
        {
          __outstr.clear();
          __count = 0;
          return true;
        }

      size_t __outchars = 0;
      auto __next = __first;
      const auto __maxlen = __cvt.max_length() + 1;

      codecvt_base::result __result;
      do
        {
          __outstr.resize(__outstr.size() + (__last - __next) * __maxlen);
          auto __outnext = &__outstr.front() + __outchars;
          auto const __outlast = &__outstr.back() + 1;
          __result = (__cvt.*__fn)(__state, __next, __last, __next,
                                        __outnext, __outlast, __outnext);
          __outchars = __outnext - &__outstr.front();
        }
      while (__result == codecvt_base::partial && __next != __last
             && ptrdiff_t(__outstr.size() - __outchars) < __maxlen);

      if (__result == codecvt_base::error)
        {
          __count = __next - __first;
          return false;
        }

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
      // The codecvt facet will only return noconv when the types are
      // the same, so avoid instantiating basic_string::assign otherwise
      if constexpr (is_same<typename _Codecvt::intern_type,
                            typename _Codecvt::extern_type>::value)
        if (__result == codecvt_base::noconv)
          {
            __outstr.assign(__first, __last);
            __count = __last - __first;
            return true;
          }
#pragma GCC diagnostic pop

      __outstr.resize(__outchars);
      __count = __next - __first;
      return true;
    }

  // Convert narrow character string to wide.
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_in(const char* __first, const char* __last,
                     basic_string<_CharT, _Traits, _Alloc>& __outstr,
                     const codecvt<_CharT, char, _State>& __cvt,
                     _State& __state, size_t& __count)
    {
      using _Codecvt = codecvt<_CharT, char, _State>;
      using _ConvFn
        = codecvt_base::result
          (_Codecvt::*)(_State&, const char*, const char*, const char*&,
                        _CharT*, _CharT*, _CharT*&) const;
      _ConvFn __fn = &codecvt<_CharT, char, _State>::in;
      return __do_str_codecvt(__first, __last, __outstr, __cvt, __state,
                              __count, __fn);
    }

  // As above, but with no __count parameter
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_in(const char* __first, const char* __last,
                     basic_string<_CharT, _Traits, _Alloc>& __outstr,
                     const codecvt<_CharT, char, _State>& __cvt)
    {
      _State __state = {};
      size_t __n;
      return __str_codecvt_in(__first, __last, __outstr, __cvt, __state, __n);
    }

  // As above, but returns false for partial conversion
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_in_all(const char* __first, const char* __last,
                         basic_string<_CharT, _Traits, _Alloc>& __outstr,
                         const codecvt<_CharT, char, _State>& __cvt)
    {
      _State __state = {};
      size_t __n;
      return __str_codecvt_in(__first, __last, __outstr, __cvt, __state, __n)
        && (__n == size_t(__last - __first));
    }

  // Convert wide character string to narrow.
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_out(const _CharT* __first, const _CharT* __last,
                      basic_string<char, _Traits, _Alloc>& __outstr,
                      const codecvt<_CharT, char, _State>& __cvt,
                      _State& __state, size_t& __count)
    {
      using _Codecvt = codecvt<_CharT, char, _State>;
      using _ConvFn
        = codecvt_base::result
          (_Codecvt::*)(_State&, const _CharT*, const _CharT*, const _CharT*&,
                        char*, char*, char*&) const;
      _ConvFn __fn = &codecvt<_CharT, char, _State>::out;
      return __do_str_codecvt(__first, __last, __outstr, __cvt, __state,
                              __count, __fn);
    }

  // As above, but with no __count parameter
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_out(const _CharT* __first, const _CharT* __last,
                      basic_string<char, _Traits, _Alloc>& __outstr,
                      const codecvt<_CharT, char, _State>& __cvt)
    {
      _State __state = {};
      size_t __n;
      return __str_codecvt_out(__first, __last, __outstr, __cvt, __state, __n);
    }

  // As above, but returns false for partial conversions
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_out_all(const _CharT* __first, const _CharT* __last,
                          basic_string<char, _Traits, _Alloc>& __outstr,
                          const codecvt<_CharT, char, _State>& __cvt)
    {
      _State __state = {};
      size_t __n;
      return __str_codecvt_out(__first, __last, __outstr, __cvt, __state, __n)
        && (__n == size_t(__last - __first));
    }

#ifdef _GLIBCXX_USE_CHAR8_T

  // Convert wide character string to narrow.
  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_out(const _CharT* __first, const _CharT* __last,
                      basic_string<char8_t, _Traits, _Alloc>& __outstr,
                      const codecvt<_CharT, char8_t, _State>& __cvt,
                      _State& __state, size_t& __count)
    {
      using _Codecvt = codecvt<_CharT, char8_t, _State>;
      using _ConvFn
        = codecvt_base::result
          (_Codecvt::*)(_State&, const _CharT*, const _CharT*, const _CharT*&,
                        char8_t*, char8_t*, char8_t*&) const;
      _ConvFn __fn = &codecvt<_CharT, char8_t, _State>::out;
      return __do_str_codecvt(__first, __last, __outstr, __cvt, __state,
                              __count, __fn);
    }

  template<typename _CharT, typename _Traits, typename _Alloc, typename _State>
    inline bool
    __str_codecvt_out(const _CharT* __first, const _CharT* __last,
                      basic_string<char8_t, _Traits, _Alloc>& __outstr,
                      const codecvt<_CharT, char8_t, _State>& __cvt)
    {
      _State __state = {};
      size_t __n;
      return __str_codecvt_out(__first, __last, __outstr, __cvt, __state, __n);
    }

#endif  // _GLIBCXX_USE_CHAR8_T

  namespace __detail
  {
    template<typename _Tp>
      struct _Scoped_ptr
      {
        __attribute__((__nonnull__(2)))
        explicit
        _Scoped_ptr(_Tp* __ptr) noexcept
        : _M_ptr(__ptr)
        { }

        _Scoped_ptr(_Tp* __ptr, const char* __msg)
        : _M_ptr(__ptr)
        {
          if (!__ptr)
            __throw_logic_error(__msg);
        }

        ~_Scoped_ptr() { delete _M_ptr; }

        _Scoped_ptr(const _Scoped_ptr&) = delete;
        _Scoped_ptr& operator=(const _Scoped_ptr&) = delete;

        __attribute__((__returns_nonnull__))
        _Tp* operator->() const noexcept { return _M_ptr; }

        _Tp& operator*() const noexcept { return *_M_ptr; }

      private:
        _Tp* _M_ptr;
      };
  }

_GLIBCXX_BEGIN_NAMESPACE_CXX11

  /// String conversions
  template<typename _Codecvt, typename _Elem = wchar_t,
           typename _Wide_alloc = allocator<_Elem>,
           typename _Byte_alloc = allocator<char>>
    class _GLIBCXX17_DEPRECATED wstring_convert
    {
    public:
      typedef basic_string<char, char_traits<char>, _Byte_alloc>   byte_string;
      typedef basic_string<_Elem, char_traits<_Elem>, _Wide_alloc> wide_string;
      typedef typename _Codecvt::state_type                        state_type;
      typedef typename wide_string::traits_type::int_type          int_type;

      /// Default constructor.
      wstring_convert() : _M_cvt(new _Codecvt()) { }

      /** Constructor.
       *
       * @param  __pcvt The facet to use for conversions.
       *
       * Takes ownership of @p __pcvt and will delete it in the destructor.
       */
      explicit
      wstring_convert(_Codecvt* __pcvt) : _M_cvt(__pcvt, "wstring_convert")
      { }

      /** Construct with an initial converstion state.
       *
       * @param  __pcvt The facet to use for conversions.
       * @param  __state Initial conversion state.
       *
       * Takes ownership of @p __pcvt and will delete it in the destructor.
       * The object's conversion state will persist between conversions.
       */
      wstring_convert(_Codecvt* __pcvt, state_type __state)
      : _M_cvt(__pcvt, "std::wstring_convert"),
        _M_state(__state), _M_with_cvtstate(true)
      { }

      /** Construct with error strings.
       *
       * @param  __byte_err A string to return on failed conversions.
       * @param  __wide_err A wide string to return on failed conversions.
       */
      explicit
      wstring_convert(const byte_string& __byte_err,
                      const wide_string& __wide_err = wide_string())
      : _M_cvt(new _Codecvt),
        _M_byte_err_string(__byte_err), _M_wide_err_string(__wide_err),
        _M_with_strings(true)
      { }

      ~wstring_convert() = default;

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2176. Special members for wstring_convert and wbuffer_convert
      wstring_convert(const wstring_convert&) = delete;
      wstring_convert& operator=(const wstring_convert&) = delete;

      /// @{ Convert from bytes.
      wide_string
      from_bytes(char __byte)
      {
        char __bytes[2] = { __byte };
        return from_bytes(__bytes, __bytes+1);
      }

      wide_string
      from_bytes(const char* __ptr)
      { return from_bytes(__ptr, __ptr+char_traits<char>::length(__ptr)); }

      wide_string
      from_bytes(const byte_string& __str)
      {
        auto __ptr = __str.data();
        return from_bytes(__ptr, __ptr + __str.size());
      }

      wide_string
      from_bytes(const char* __first, const char* __last)
      {
        if (!_M_with_cvtstate)
          _M_state = state_type();
        wide_string __out{ _M_wide_err_string.get_allocator() };
        if (__str_codecvt_in(__first, __last, __out, *_M_cvt, _M_state,
                             _M_count))
          return __out;
        if (_M_with_strings)
          return _M_wide_err_string;
        __throw_range_error("wstring_convert::from_bytes");
      }
      /// @}

      /// @{ Convert to bytes.
      byte_string
      to_bytes(_Elem __wchar)
      {
        _Elem __wchars[2] = { __wchar };
        return to_bytes(__wchars, __wchars+1);
      }

      byte_string
      to_bytes(const _Elem* __ptr)
      {
        return to_bytes(__ptr, __ptr+wide_string::traits_type::length(__ptr));
      }

      byte_string
      to_bytes(const wide_string& __wstr)
      {
        auto __ptr = __wstr.data();
        return to_bytes(__ptr, __ptr + __wstr.size());
      }

      byte_string
      to_bytes(const _Elem* __first, const _Elem* __last)
      {
        if (!_M_with_cvtstate)
          _M_state = state_type();
        byte_string __out{ _M_byte_err_string.get_allocator() };
        if (__str_codecvt_out(__first, __last, __out, *_M_cvt, _M_state,
                              _M_count))
          return __out;
        if (_M_with_strings)
          return _M_byte_err_string;
        __throw_range_error("wstring_convert::to_bytes");
      }
      /// @}

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2174. wstring_convert::converted() should be noexcept
      /// The number of elements successfully converted in the last conversion.
      size_t converted() const noexcept { return _M_count; }

      /// The final conversion state of the last conversion.
      state_type state() const { return _M_state; }

    private:
      __detail::_Scoped_ptr<_Codecvt>   _M_cvt;
      byte_string               _M_byte_err_string;
      wide_string               _M_wide_err_string;
      state_type                _M_state = state_type();
      size_t                    _M_count = 0;
      bool                      _M_with_cvtstate = false;
      bool                      _M_with_strings = false;
    };

_GLIBCXX_END_NAMESPACE_CXX11

  /// Buffer conversions
  template<typename _Codecvt, typename _Elem = wchar_t,
           typename _Tr = char_traits<_Elem>>
    class _GLIBCXX17_DEPRECATED wbuffer_convert
    : public basic_streambuf<_Elem, _Tr>
    {
      typedef basic_streambuf<_Elem, _Tr> _Wide_streambuf;

    public:
      typedef typename _Codecvt::state_type state_type;

      /// Default constructor.
      wbuffer_convert() : wbuffer_convert(nullptr) { }

      /** Constructor.
       *
       * @param  __bytebuf The underlying byte stream buffer.
       * @param  __pcvt    The facet to use for conversions.
       * @param  __state   Initial conversion state.
       *
       * Takes ownership of @p __pcvt and will delete it in the destructor.
       */
      explicit
      wbuffer_convert(streambuf* __bytebuf, _Codecvt* __pcvt = new _Codecvt,
                      state_type __state = state_type())
      : _M_buf(__bytebuf), _M_cvt(__pcvt, "std::wbuffer_convert"),
        _M_state(__state), _M_always_noconv(_M_cvt->always_noconv())
      {
        if (_M_buf)
          {
            this->setp(_M_put_area, _M_put_area + _S_buffer_length);
            this->setg(_M_get_area + _S_putback_length,
                       _M_get_area + _S_putback_length,
                       _M_get_area + _S_putback_length);
          }
      }

      ~wbuffer_convert() = default;

      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2176. Special members for wstring_convert and wbuffer_convert
      wbuffer_convert(const wbuffer_convert&) = delete;
      wbuffer_convert& operator=(const wbuffer_convert&) = delete;

      streambuf* rdbuf() const noexcept { return _M_buf; }

      streambuf*
      rdbuf(streambuf *__bytebuf) noexcept
      {
        auto __prev = _M_buf;
        _M_buf = __bytebuf;
        return __prev;
      }

      /// The conversion state following the last conversion.
      state_type state() const noexcept { return _M_state; }

    protected:
      int
      sync()
      { return _M_buf && _M_conv_put() && !_M_buf->pubsync() ? 0 : -1; }

      typename _Wide_streambuf::int_type
      overflow(typename _Wide_streambuf::int_type __out)
      {
        if (!_M_buf || !_M_conv_put())
          return _Tr::eof();
        else if (!_Tr::eq_int_type(__out, _Tr::eof()))
          return this->sputc(__out);
        return _Tr::not_eof(__out);
      }

      typename _Wide_streambuf::int_type
      underflow()
      {
        if (!_M_buf)
          return _Tr::eof();

        if (this->gptr() < this->egptr() || (_M_buf && _M_conv_get()))
          return _Tr::to_int_type(*this->gptr());
        else
          return _Tr::eof();
      }

      streamsize
      xsputn(const typename _Wide_streambuf::char_type* __s, streamsize __n)
      {
        if (!_M_buf || __n == 0)
          return 0;
        streamsize __done = 0;
        do
        {
          auto __nn = std::min<streamsize>(this->epptr() - this->pptr(),
                                           __n - __done);
          _Tr::copy(this->pptr(), __s + __done, __nn);
          this->pbump(__nn);
          __done += __nn;
        } while (__done < __n && _M_conv_put());
        return __done;
      }

    private:
      // fill the get area from converted contents of the byte stream buffer
      bool
      _M_conv_get()
      {
        const streamsize __pb1 = this->gptr() - this->eback();
        const streamsize __pb2 = _S_putback_length;
        const streamsize __npb = std::min(__pb1, __pb2);

        _Tr::move(_M_get_area + _S_putback_length - __npb,
                  this->gptr() - __npb, __npb);

        streamsize __nbytes = sizeof(_M_get_buf) - _M_unconv;
        __nbytes = std::min(__nbytes, _M_buf->in_avail());
        if (__nbytes < 1)
          __nbytes = 1;
        __nbytes = _M_buf->sgetn(_M_get_buf + _M_unconv, __nbytes);
        if (__nbytes < 1)
          return false;
        __nbytes += _M_unconv;

        // convert _M_get_buf into _M_get_area

        _Elem* __outbuf = _M_get_area + _S_putback_length;
        _Elem* __outnext = __outbuf;
        const char* __bnext = _M_get_buf;

        codecvt_base::result __result;
        if (_M_always_noconv)
          __result = codecvt_base::noconv;
        else
          {
            _Elem* __outend = _M_get_area + _S_buffer_length;

            __result = _M_cvt->in(_M_state,
                                  __bnext, __bnext + __nbytes, __bnext,
                                  __outbuf, __outend, __outnext);
          }

        if (__result == codecvt_base::noconv)
          {
            // cast is safe because noconv means _Elem is same type as char
            auto __get_buf = reinterpret_cast<const _Elem*>(_M_get_buf);
            _Tr::copy(__outbuf, __get_buf, __nbytes);
            _M_unconv = 0;
            return true;
          }

        if ((_M_unconv = _M_get_buf + __nbytes - __bnext))
          char_traits<char>::move(_M_get_buf, __bnext, _M_unconv);

        this->setg(__outbuf, __outbuf, __outnext);

        return __result != codecvt_base::error;
      }

      // unused
      bool
      _M_put(...)
      { return false; }

      bool
      _M_put(const char* __p, streamsize __n)
      {
        if (_M_buf->sputn(__p, __n) < __n)
          return false;
        return true;
      }

      // convert the put area and write to the byte stream buffer
      bool
      _M_conv_put()
      {
        _Elem* const __first = this->pbase();
        const _Elem* const __last = this->pptr();
        const streamsize __pending = __last - __first;

        if (_M_always_noconv)
          return _M_put(__first, __pending);

        char __outbuf[2 * _S_buffer_length];

        const _Elem* __next = __first;
        const _Elem* __start;
        do
          {
            __start = __next;
            char* __outnext = __outbuf;
            char* const __outlast = __outbuf + sizeof(__outbuf);
            auto __result = _M_cvt->out(_M_state, __next, __last, __next,
                                        __outnext, __outlast, __outnext);
            if (__result == codecvt_base::error)
              return false;
            else if (__result == codecvt_base::noconv)
              return _M_put(__next, __pending);

            if (!_M_put(__outbuf, __outnext - __outbuf))
              return false;
          }
        while (__next != __last && __next != __start);

        if (__next != __last)
          _Tr::move(__first, __next, __last - __next);

        this->pbump(__first - __next);
        return __next != __first;
      }

      streambuf*                        _M_buf;
      __detail::_Scoped_ptr<_Codecvt>   _M_cvt;
      state_type                        _M_state;

      static const streamsize   _S_buffer_length = 32;
      static const streamsize   _S_putback_length = 3;
      _Elem                     _M_put_area[_S_buffer_length];
      _Elem                     _M_get_area[_S_buffer_length];
      streamsize                _M_unconv = 0;
      char                      _M_get_buf[_S_buffer_length-_S_putback_length];
      bool                      _M_always_noconv;
    };

  /// @} group locales

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif // __cplusplus

#endif /* _LOCALE_CONV_H */