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# std::wctomb

From cppreference.com
< cpp‎ | string‎ | multibyte

Defined in header `<cstdlib>` |  |
int wctomb( char *s, wchar_t wc ); |  |

Converts a wide character `wc` to multibyte encoding and stores it (including any shift sequences) in the char array whose first element is pointed to by `s`. No more than MB_CUR_MAX characters are stored.

If `wc` is the null character, the null byte is written to `s`, preceded by any shift sequences necessary to restore the initial shift state.

If `s` is a null pointer, resets the global conversion state and determines whether shift sequences are used.

### [edit] Parameters

s | - | pointer to the character array for output
wc | - | wide character to convert

### [edit] Return value

If `s` is not a null pointer, returns the number of bytes that are contained in the multibyte representation of `wc` or -1 if `wc` is not a valid character.

If `s` is a null pointer, resets its internal conversion state to represent the initial shift state and returns ​0​ if the current multibyte encoding is not state-dependent (does not use shift sequences) or a non-zero value if the current multibyte encoding is state-dependent (uses shift sequences).

### [edit] Notes

Each call to `wctomb` updates the internal global conversion state (a static object of type std::mbstate_t, only known to this function). If the multibyte encoding uses shift states, this function is not reentrant. In any case, multiple threads should not call `wctomb` without synchronization: std::wcrtomb may be used instead.

### [edit] Example

Run this code

    #include <iostream>
    #include <clocale>
    #include <string>
    #include <cstdlib>

    void print_wide(const std::wstring& wstr)
    {
        bool shifts = std::wctomb(NULL, 0); // reset the conversion state
        std::cout << "shift sequences " << (shifts ? "are" : "not" ) << " used\n";
        for (wchar_t wc : wstr) {
            std::string mb(MB_CUR_MAX, '\0');
            int ret = std::wctomb(&mb[0], wc);
            std::cout << "multibyte char " << mb << " is " << ret << " bytes\n";
        }
    }

    int main()
    {
        std::setlocale(LC_ALL, "en_US.utf8");
        // UTF-8 narrow multibyte encoding
        std::wstring wstr = L"z\u00df\u6c34\U0001d10b"; // or L"zß水𝄋"
        print_wide(wstr);
    }

Output:

    shift sequences not used
    multibyte char z is 1 bytes
    multibyte char ß is 2 bytes
    multibyte char 水 is 3 bytes
    multibyte char 𝄋 is 4 bytes

### [edit] See also

mbtowc | converts the next multibyte character to wide character (function) [edit]
wcrtomb | converts a wide character to its multibyte representation, given state (function) [edit]
do_out [virtual] | converts a string from internT to externT, such as when writing to file (virtual protected member function of `std::codecvt`) [edit]
C documentation for wctomb

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