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std::wctomb

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< cpp‎ | string‎ | multibyte
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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.

Contents

[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

#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

converts the next multibyte character to wide character
(function) [edit]
converts a wide character to its multibyte representation, given state
(function) [edit]
[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