std:: wcsrtombs

Converts a sequence of wide characters from the array whose first element is pointed to by * src to its narrow multibyte representation that begins in the conversion state described by * ps . If dst is not null, converted characters are stored in the successive elements of the char array pointed to by dst . No more than len bytes are written to the destination array.

Each character is converted as if by a call to std::wcrtomb . The conversion stops if:

• The null character was converted and stored. src is set to a null pointer and * ps represents the initial shift state.
• A wchar_t was found that does not correspond to a valid character in the current C locale. src is set to point at the first unconverted wide character.
• The next multibyte character to be stored would exceed len . src is set to point at the first unconverted wide character. This condition is not checked if dst is a null pointer.

Parameters

Return value

On success, returns the number of bytes (including any shift sequences, but excluding the terminating ' \0 ' ) written to the character array whose first element is pointed to by dst . If dst is a null pointer, returns the number of bytes that would have been written (again, excluding the terminating null character ' \0 ' ).

On conversion error (if invalid wide character was encountered), returns static_cast < std:: size_t > ( - 1 ) , stores EILSEQ in errno , and leaves * ps in unspecified state.

Example

#include <clocale>
#include <cwchar>
#include <iostream>
#include <string>
#include <vector>
 
void print_wide(const wchar_t* wstr)
{
    std::mbstate_t state = std::mbstate_t();
    std::size_t len = 1 + std::wcsrtombs(nullptr, &wstr, 0, &state);
    std::vector<char> mbstr(len);
    std::wcsrtombs(&mbstr[0], &wstr, mbstr.size(), &state);
    std::cout << "multibyte string: " << &mbstr[0] << '\n'
              << "Length, including '\\0': " << mbstr.size() << '\n';
}
 
int main()
{
    std::setlocale(LC_ALL, "en_US.utf8");
    // UTF-8 narrow multibyte encoding
    const wchar_t* wstr = L"z\u00df\u6c34\U0001d10b"; // or L"zß水𝄋"
    print_wide(wstr);
}

multibyte string: zß水𝄋
Length, including '\0': 11

See also