home | help 
std::fwide(3)		       C++ Standard Libary		   std::fwide(3)

NAME
     std::fwide - std::fwide

Synopsis
	Defined in header <cwchar>
	int fwide( std::FILE* stream, int mode );

	If  mode  >  0,  attempts to make stream wide-oriented. If mode < 0, at-
     tempts to make
	stream byte-oriented. If mode == 0, only queries the current orientation
     of the
	stream.

	If the orientation of the stream has already been decided (by  executing
     output or by
	an earlier call to fwide), this function does nothing.

Parameters
	stream - pointer to the C I/O stream to modify or query
	mode	-  integer  value greater than zero to set the stream wide, less
     than zero to
		 set the stream narrow, or zero to query only

Return value
	An integer greater than zero if the stream is wide-oriented  after  this
     call, less
	than  zero  if	the stream is byte-oriented after this call, and zero if
     the stream has
	no orientation.

Example
	The following code sets and resets the stream orientation.

     // Run this code

      #include <cstdio>
      #include <cstdlib>
      #include <cwchar>
      #include <iostream>

      void show_orientation(int n)
      {
	  n < 0 ? std::wcout << "\tnarrow orientation\n" :
	  n > 0 ? std::wcout << "\twide orientation\n" :
		  std::wcout << "\tno orientation\n";
      }

      void try_read(FILE* fp)
      {
	  if (const int c = std::fgetc(fp); c == EOF)
	      std::wcout << "\tnarrow character read failed\n";
	  else
	      std::wcout << "\tnarrow character read '" <<  static_cast<char>(c)
     << "'\n";

	  if (const wint_t wc = std::fgetwc(fp); wc == WEOF)
	      std::wcout << "\twide character read failed\n";
	  else
	      std::wcout    <<	  "\twide    character	  read	  '"   <<   sta-
     tic_cast<wchar_t>(wc) << "'\n";
      }

      int main()
      {
	  enum fwide_orientation : int { narrow = -1, query, wide };

	  FILE* fp = std::fopen("main.cpp", "r");
	  if (!fp)
	  {
	      std::wcerr << "fopen() failed\n";
	      return EXIT_FAILURE;
	  }

	  std::wcout << "1) A newly opened stream has no orientation.\n";
	  show_orientation(std::fwide(fp, fwide_orientation::query));

	  std::wcout << "2) Establish byte orientation.\n";
	  show_orientation(std::fwide(fp, fwide_orientation::narrow));
	  try_read(fp);

	  std::wcout << "3) Only freopen() can reset stream orientation.\n";
	  if (std::freopen("main.cpp", "r", fp) == NULL)
	  {
	      std::wcerr << "freopen() failed\n";
	      return EXIT_FAILURE;
	  }

	  std::wcout << "4) A reopened stream has no orientation.\n";
	  show_orientation(std::fwide(fp, fwide_orientation::query));

	  std::wcout << "5) Establish wide orientation.\n";
	  show_orientation(std::fwide(fp, fwide_orientation::wide));
	  try_read(fp);

	  std::fclose(fp);
      }

Possible output:
      1) A newly opened stream has no orientation.
	      no orientation
      2) Establish byte orientation.
	      narrow orientation
	      narrow character read '#'
	      wide character read failed
      3) Only freopen() can reset stream orientation.
      4) A reopened stream has no orientation.
	      no orientation
      5) Establish wide orientation.
	      wide orientation
	      narrow character read failed
	      wide character read '#'

See also
	fopen opens a file
	      (function)
	C documentation for
	fwide

http://cppreference.com 	   2024.06.10			   std::fwide(3)
home | help