std::btowc

 

C++

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Technical Specifications

 

Strings library

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Classes

basic_string

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Null-terminated multibyte strings

Wide/multibyte conversions
mbsinit
mbtowc mbstowcs btowc mbrtowc mbsrtowcs mbrtoc16 (C++11) mbrtoc32 (C++11) mblen	wctomb wcstombs wctob wcrtomb wcsrtombs c16rtomb (C++11) c32rtomb (C++11) mbrlen
Types
mbstate_t

 

Defined in header <cwchar>
std::wint_t btowc( int c );

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

Run this code

#include <iostream>
#include <cwchar>
#include <clocale>
 
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');
}

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 [virtual]	converts a character or characters from char to charT (virtual protected member function of std::ctype)
C documentation for btowc