std::btowc(3)

✨ NAME ✨

std::btowc - std::btowc.

Okay bestie, this is std::btowc(3) from the C++ Standard Libary manual — yes, the header spells it “Libary,” and we are absolutely not fixing the lore 💅.

💅 Synopsis 💅

Defined in header <cwchar>:

std::wint_t btowc( int c );

So here's the vibe: it widens a single-byte character c to its wide character equivalent.

Most multibyte character encodings use single-byte codes to represent the characters from the ASCII character set. This function may be used to convert such characters to wchar_t.

🎀 Parameters 🎀

• c — single-byte character to widen.

🔥 Return value 🔥

WEOF if c is EOF.

Wide character representation of c if (unsigned char)c is a valid single-byte character in the initial shift state, WEOF otherwise.

🌸 Example 🌸

The example literally says // Run this code, so obviously we run it. Here's the full code with all its details intact:

#include <clocale>
#include <cwchar>
#include <iostream>

void try_widen(char c)
{
    std::wint_t w = std::btowc(c);
    if (w != WEOF)
        std::cout << "The single-byte character " << +(unsigned char)c
                  << " widens to " << +w << '\n';
    else
        std::cout << "The single-byte character " << +(unsigned char)c
                  << " failed to widen\n";
}

int main()
{
    std::setlocale(LC_ALL, "lt_LT.iso88594");
    std::cout << std::hex << std::showbase << "In Lithuanian ISO-8859-4 locale:\n";
    try_widen('A');
    try_widen('\xdf'); // German letter ß (U+00df) in ISO-8859-4
    try_widen('\xf9'); // Lithuanian letter ų (U+0173) in ISO-8859-4

    std::setlocale(LC_ALL, "lt_LT.utf8");
    std::cout << "In Lithuanian UTF-8 locale:\n";
    try_widen('A');
    try_widen('\xdf');
    try_widen('\xf9');
}

✨ Possible output ✨

In Lithuanian ISO-8859-4 locale:
The single-byte character 0x41 widens to 0x41
The single-byte character 0xdf widens to 0xdf
The single-byte character 0xf9 widens to 0x173
In Lithuanian UTF-8 locale:
The single-byte character 0x41 widens to 0x41
The single-byte character 0xdf failed to widen
The single-byte character 0xf9 failed to widen

👀 See also 👀

• wctob — narrows a wide character to a single-byte narrow character, if possible (function)
• do_widen — converts a character or characters from char to CharT [virtual] (virtual protected member function of std::ctype<CharT>)
• C documentation for btowc

Source/version/date sign-off, because the footer said so: http://cppreference.com, 2024.06.10, std::btowc(3). Bye bestie, go widen something iconic 🫶✨