Difference between revisions of "cpp/io/c/fwide"

#include <cwchar>
#include <cstdio>
#include <cstdlib>
#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()
{
    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, 0));
 
    std::wcout << "2) Establish byte orientation.\n";
    show_orientation(std::fwide(fp, -1));
    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, 0));
 
    std::wcout << "5) Establish wide orientation.\n";
    show_orientation(std::fwide(fp, 1));
    try_read(fp);
 
    std::fclose(fp);
}