std::fwide
From cppreference.com
Defined in header <cwchar>
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int fwide(
std::FILE
* stream, int mode )
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If mode > 0, attempts to make stream wide-oriented. If mode < 0, attempts to make stream byte-oriented. If mode == 0
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 '" << static_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
| opens a file (function) | |
C documentation for fwide
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