MBSRTOWCS(3)

NAME
mbsrtowcs - converts a multibyte character string to a wide-character string (restartable)

SYNOPSIS
#include <wchar.h>
size_t
mbsrtowcs(wchar_t * restrict pwcs, const char ** restrict s, size_t n, mbstate_t * restrict ps);

DESCRIPTION
The mbsrtowcs() converts the multibyte character string indirectly pointed to by s to the corresponding wide-character string, and stores it in the array pointed to by pwcs. The conversion stops due to the following reasons:

•   The conversion reaches a null byte. In this case, the null byte is also converted.

•   The mbsrtowcs() has already stored n wide characters.

•   The conversion encounters an invalid character.

Each character is converted as if mbrtowc(3) is continuously called.

After conversion, if pwcs is not a NULL pointer, the pointer object pointed to by s is a NULL pointer (if the conversion is stopped due to reaching a null byte) or the first byte of the character just after the last character converted.

If pwcs is not a null pointer and the conversion is stopped due to reaching a null byte, the mbsrtowcs() places the state object pointed to by ps to an initial state after the conversion has taken place.

The behaviour of the mbsrtowcs() is affected by the LC_CTYPE category of the current locale.

These are the special cases:

s == NULL || *s == NULL
    Undefined (may cause the program to crash).

pwcs == NULL
    The conversion has taken place, but the resultant wide-character string was discarded. In this case, the pointer object pointed to by s is not modified and n is ignored.

ps == NULL
    The mbsrtowcs() uses its own internal state object to keep the conversion state, instead of ps mentioned in this manual page.

    Calling any other functions in libc never change the internal state of mbsrtowcs(), which is initialized at startup time of the program.

RETURN VALUES
mbsrtowcs() returns:

0 or positive
    The value returned is the number of elements stored in the array pointed to by pwcs, except for a terminating null wide character (if any). If pwcs is not null and the value returned is equal to n, the wide-character string pointed to by pwcs is not null terminated. If pwcs is a null pointer, the value returned is the number of elements to contain the whole string converted, except for a terminating null wide character.

(size_t)-1
    The array indirectly pointed to by s contains a byte sequence forming invalid character. In this case, mbsrtowcs() sets errno to indicate the error.

ERRORS
mbsrtowcs() may cause an error in the following cases:

[EILSEQ]
    The pointer pointed to by s points to an invalid or incomplete multibyte character.

[EINVAL]
    ps points to an invalid or uninitialized mbstate_t object.

SEE ALSO
mbrtowc(3), mbstowcs(3), setlocale(3)

STANDARDS
The mbsrtowcs() function conforms to ISO/IEC 9899/AMD1:1995 (“ISO C90, Amendment 1”). The restrict qualifier is added at ISO/IEC 9899/1999 “(ISO C99)”.