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# std::wcsrtombs

From cppreference.com
< cpp‎ | string‎ | multibyte

Defined in header `<cwchar>` |  |
std::size_t wcsrtombs( char* dst, const wchar_t** src, std::size_t len, std::mbstate_t* ps ); |  |

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 NULL 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==NULL.

### [edit] Parameters

dst | - | pointer to narrow character array where the multibyte characters will be stored
src | - | pointer to pointer to the first element of a null-terminated wide string
len | - | number of bytes available in the array pointed to by dst
ps | - | pointer to the conversion state object

### [edit] 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==NULL, 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.

### [edit] Example

Run this code

    #include <iostream>
    #include <vector>
    #include <clocale>
    #include <string>
    #include <cwchar>

    void print_wide(const wchar_t* wstr)
    {
        std::mbstate_t state = std::mbstate_t();
        int 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);
    }

Output:

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

### [edit] See also

wcrtomb | converts a wide character to its multibyte representation, given state (function) [edit]
mbsrtowcs | converts a narrow multibyte character string to wide string, 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 wcsrtombs

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