MBRTOWC(3) BSD Library Functions Manual MBRTOWC(3)
mbrtowc -- converts a multibyte character to a wide character (restartable)
Standard C Library (libc, -lc)
mbrtowc(wchar_t * restrict pwc, const char * restrict s, size_t n, mbstate_t * restrict ps);
The mbrtowc() usually converts the multibyte character pointed to by s to a wide character,
and stores the wide character to the wchar_t object pointed to by pwc if pwc is non-NULL and
s points to a valid character. The conversion happens in accordance with, and changes the
conversion state described in the mbstate_t object pointed to by ps. This function may
examine at most n bytes of the array beginning from s.
If s points to a valid character and the character corresponds to a nul wide character, then
the mbrtowc() places the mbstate_t object pointed to by ps to an initial conversion state.
Unlike mbtowc(3), the mbrtowc() may accept the byte sequence pointed to by s not forming a
complete multibyte character but which may be part of a valid character. In this case, this
function will accept all such bytes and save them into the conversion state object pointed
to by ps. They will be used at subsequent calls of this function to restart the conversion
The behaviour of mbrtowc() is affected by the LC_CTYPE category of the current locale.
These are the special cases:
s == NULL mbrtowc() sets the conversion state object pointed to by ps to an initial
state and always returns 0. Unlike mbtowc(3), the value returned does not
indicate whether the current encoding of the locale is state-dependent.
In this case, mbrtowc() ignores pwc and n, and is equivalent to the following
mbrtowc(NULL, "", 1, ps);
pwc == NULL The conversion from a multibyte character to a wide character has taken place
and the conversion state may be affected, but the resulting wide character is
ps == NULL mbrtowc() 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 mbrtowc(), which is initialized at startup time of the
In the usual cases, mbrtowc() returns:
0 The next bytes pointed to by s form a nul character.
positive If s points to a valid character, mbrtowc() returns the number of bytes in the
(size_t)-2 s points to a byte sequence which possibly contains part of a valid multibyte
character, but which is incomplete. When n is at least MB_CUR_MAX, this case
can only occur if the array pointed to by s contains a redundant shift
(size_t)-1 s points to an illegal byte sequence which does not form a valid multibyte
character. In this case, mbrtowc() sets errno to indicate the error.
mbrtowc() may cause an error in the following case:
[EILSEQ] s points to an invalid or incomplete multibyte character.
[EINVAL] ps points to an invalid or uninitialized mbstate_t object.
mbrlen(3), mbtowc(3), setlocale(3)
The mbrtowc() function conforms to ISO/IEC 9899/AMD1:1995 (``ISO C90, Amendment 1''). The
restrict qualifier is added at ISO/IEC 9899:1999 (``ISO C99'').
BSD February 4, 2002 BSD