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MBSRTOWCS(3)               Library Functions Manual               MBSRTOWCS(3)

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <wchar.h>

     size_t
     mbsrtowcs(wchar_t * restrict pwcs, const char ** restrict s, size_t n,
         mbstate_t * restrict ps);

     size_t
     mbsnrtowcs(wchar_t * restrict pwcs, const char ** restrict s, size_t nmc,
         size_t n, mbstate_t * restrict ps);

DESCRIPTION
     The mbsrtowcs() function 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 NUL byte.  In this case, the NUL byte is
         also converted.

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

     ⊕   The conversion encounters an invalid character.

     Each character will be 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 NUL 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 NUL byte, the mbsrtowcs() places the state object pointed to
     by ps to an initial state after the conversion has taken place.

     The behaviour of 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 resulting 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 Standard C Library
                       (libc, -lc) never changes the internal state of
                       mbsrtowcs(), which is initialized at startup time of
                       the program.

     The mbsnrtowcs() function behaves identically to mbsrtowcs(), except that
     the conversion stops after reading at most nmc characters from the buffer
     pointed to by s.

RETURN VALUES
     The mbsrtowcs() and mbsnrtowcs() functions return:

     0, or positive    The value returned is the number of elements stored in
                       the array pointed to by pwcs, except for a terminating
                       NUL 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 NUL-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 NUL 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
     The mbsrtowcs() and mbsnrtowcs() functions may fail with the following
     errors:

     [EILSEQ]           s points to a string containing 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 was added by ISO/IEC 9899:1999
     ("ISO C99").

     The mbsnrtowcs() function conforms to IEEE Std 1003.1-2008 ("POSIX.1").

NetBSD 11.99                   September 9, 2024                  NetBSD 11.99