// File based streams -*- C++ -*-

// Copyright (C) 1997-2025 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 include/fstream
 *  This is a Standard C++ Library header.
 */

//
// ISO C++ 14882: 27.8  File-based streams
//

#ifndef _GLIBCXX_FSTREAM
#define _GLIBCXX_FSTREAM 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/requires_hosted.h> // iostreams

#include <istream>
#include <ostream>
#include <bits/codecvt.h>
#include <cstdio>             // For BUFSIZ
#include <bits/basic_file.h>  // For __basic_file, __c_lock
#if __cplusplus >= 201103L
#include <string>             // For std::string overloads.
#endif

#define __glibcxx_want_fstream_native_handle
#include <bits/version.h>

// This can be overridden by the target's os_defines.h
#ifndef _GLIBCXX_BUFSIZ
# define _GLIBCXX_BUFSIZ BUFSIZ
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

#if __cplusplus >= 201703L
  // Enable if _Path is a filesystem::path or experimental::filesystem::path
  template<typename _Path, typename _Result = _Path, typename _Path2
	   = decltype(std::declval<_Path&>().make_preferred().filename())>
    using _If_fs_path = enable_if_t<is_same_v<_Path, _Path2>, _Result>;
#endif // C++17


  // [27.8.1.1] template class basic_filebuf
  /**
   *  @brief  The actual work of input and output (for files).
   *  @ingroup io
   *
   *  @tparam _CharT  Type of character stream.
   *  @tparam _Traits  Traits for character type, defaults to
   *                   char_traits<_CharT>.
   *
   *  This class associates both its input and output sequence with an
   *  external disk file, and maintains a joint file position for both
   *  sequences.  Many of its semantics are described in terms of similar
   *  behavior in the Standard C Library's @c FILE streams.
   *
   *  Requirements on traits_type, specific to this class:
   *  - traits_type::pos_type must be fpos<traits_type::state_type>
   *  - traits_type::off_type must be streamoff
   *  - traits_type::state_type must be Assignable and DefaultConstructible,
   *  - traits_type::state_type() must be the initial state for codecvt.
   */
  template<typename _CharT, typename _Traits>
    class basic_filebuf : public basic_streambuf<_CharT, _Traits>
    {
#if __cplusplus >= 201103L
      template<typename _Tp>
	using __chk_state = __and_<is_copy_assignable<_Tp>,
				   is_copy_constructible<_Tp>,
				   is_default_constructible<_Tp>>;

      static_assert(__chk_state<typename _Traits::state_type>::value,
		    "state_type must be CopyAssignable, CopyConstructible"
		    " and DefaultConstructible");

      static_assert(is_same<typename _Traits::pos_type,
			    fpos<typename _Traits::state_type>>::value,
		    "pos_type must be fpos<state_type>");
#endif
    public:
      // Types:
      typedef _CharT                     	        char_type;
      typedef _Traits                    	        traits_type;
      typedef typename traits_type::int_type 		int_type;
      typedef typename traits_type::pos_type 		pos_type;
      typedef typename traits_type::off_type 		off_type;

      typedef basic_streambuf<char_type, traits_type>  	__streambuf_type;
      typedef basic_filebuf<char_type, traits_type>     __filebuf_type;
      typedef __basic_file<char>		        __file_type;
      typedef typename traits_type::state_type          __state_type;
      typedef codecvt<char_type, char, __state_type>    __codecvt_type;

      friend class ios_base; // For sync_with_stdio.

    protected:
      // Data Members:
      // MT lock inherited from libio or other low-level io library.
      __c_lock          	_M_lock;

      // External buffer.
      __file_type 		_M_file;

      /// Place to stash in || out || in | out settings for current filebuf.
      ios_base::openmode 	_M_mode;

      // Beginning state type for codecvt.
      __state_type 		_M_state_beg;

      // During output, the state that corresponds to pptr(),
      // during input, the state that corresponds to egptr() and
      // _M_ext_next.
      __state_type		_M_state_cur;

      // Not used for output. During input, the state that corresponds
      // to eback() and _M_ext_buf.
      __state_type		_M_state_last;

      /// Pointer to the beginning of internal buffer.
      char_type*		_M_buf;

      /**
       *  Actual size of internal buffer. This number is equal to the size
       *  of the put area + 1 position, reserved for the overflow char of
       *  a full area.
       */
      size_t			_M_buf_size;

      // Set iff _M_buf is allocated memory from _M_allocate_internal_buffer.
      bool			_M_buf_allocated;

      /**
       *  _M_reading == false && _M_writing == false for @b uncommitted mode;
       *  _M_reading == true for @b read mode;
       *  _M_writing == true for @b write mode;
       *
       *  NB: _M_reading == true && _M_writing == true is unused.
       */
      bool                      _M_reading;
      bool                      _M_writing;

      ///@{
      /**
       *  Necessary bits for putback buffer management.
       *
       *  @note pbacks of over one character are not currently supported.
       */
      char_type			_M_pback;
      char_type*		_M_pback_cur_save;
      char_type*		_M_pback_end_save;
      bool			_M_pback_init;
      ///@}

      // Cached codecvt facet.
      const __codecvt_type* 	_M_codecvt;

      /**
       *  Buffer for external characters. Used for input when
       *  codecvt::always_noconv() == false. When valid, this corresponds
       *  to eback().
       */
      char*			_M_ext_buf;

      /**
       *  Size of buffer held by _M_ext_buf.
       */
      streamsize		_M_ext_buf_size                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             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